Bio

Clinical Focus


  • Oncologic Imaging
  • Gynecologic Imaging
  • Urogenital imaging
  • Diagnostic Radiology
  • Hepatobiliary and pancreatic imaging
  • Ultrasound
  • Thyroid ultrasound

Academic Appointments


Administrative Appointments


  • Associate Fellowship Director, Body Imaging Fellowship (2007 - Present)

Honors & Awards


  • Fellow, Society of Radiologists in Ultrasound (2013-)
  • Fellow, Society of Abdominal Radiology (2013-)
  • Department of Radiology Angel Funding Grant, Stanford Department of Radiology (2012)
  • Developmental Cancer Research Award, Stanford Cancer Center (2011-2013)
  • Wylie J. Dodds Research Award, The Society of Gastrointestinal Radiologists (2011-2013)
  • 2011 Research Award, The Society of Uroradiology (2011-2012)
  • Certificate of Merit - Research Exhibit, American Roentgen Ray Society (2010)
  • New Investigator Finalist, American Institute of Ultrasound in Medicine (2010)
  • Certificate of Merit - Research Exhibit, American Roentgen Ray Society (2009)
  • Teacher of the Year Award, Stanford University Department of Radiology (2006-2007)
  • Teacher of the Year Award, Stanford University Department of Radiology (2005-2006)
  • 2003 Laurence A. Mack Research Award, Society of Radiologists in Ultrasound (2003)
  • 2002 Executive Council Research Paper Award, American Roentgen Ray Society (2002)
  • Outstanding Scientific Paper Award, University of Michigan Health System (2002)
  • Utah State Finalist Clinical Vignette Competition, American College of Physicians (2000)
  • Summa cum Laude, Dartmouth College (-)
  • Presidential Scholar, Dartmouth College (-)
  • Tau Beta Pi, Dartmouth College (-)
  • Phi Beta Kappa, Dartmouth College (-)

Professional Education


  • Board Certification: Diagnostic Radiology, American Board of Radiology (2004)
  • Fellowship, Stanford University, Body Imaging (2005)
  • Residency:University of Michigan Health System (2004) MI
  • Internship:LDS Hospital (2000) UT
  • Medical Education:University of Utah School of Medicine (1999) UT
  • A.B., Dartmouth College, Engineering Sciences (1995)

Community and International Work


  • Asian Health Services, Oakland

    Location

    International

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    No

Research & Scholarship

Current Research and Scholarly Interests


Novel ultrasound technologies
Perfusion CT imaging of abdominal tumors

Clinical Trials


  • Combination SBRT (Stereotactic Body Radiotherapy) With TACE (Transarterial Chemoembolization) for Unresectable Hepatocellular Carcinoma Not Recruiting

    To establish the efficacy and toxicity of TACE combined with SBRT

    Stanford is currently not accepting patients for this trial. For more information, please contact Laurie Ann Columbo, 650-736-0792.

    View full details

  • A Phase 2b Study of Modified Vaccinia Virus to Treat Patients Advanced Liver Cancer Who Failed Sorafenib Not Recruiting

    This study is to determine whether JX-594 (Pexa-Vec) plus best supportive care is more effective in improving survival than best supportive care in patients with advanced Hepatocellular Carcinoma (HCC) who have failed sorafenib.

    Stanford is currently not accepting patients for this trial. For more information, please contact Fizaa Ahmed, (650) 725 - 6409.

    View full details

  • Perfusion CT as a Predictor of Treatment Response in Patients With Rectal Cancer Recruiting

    Recent advances in computed tomography (CT) technology have made CT perfusion imaging feasible for the assessment of tumor perfusion in solid tumors of the abdomen. CT perfusion has shown promising results in serving as a noninvasive method of predicting response to therapy in cancer patients. CT perfusion parameters have also been found to correlate with immunohistologic markers of angiogenesis in a number of solid tumors, suggesting a possible role for CT perfusion as a noninvasive biomarker of tumor angiogenesis. The goals of the investigators study are twofold: first, to determine the relationship between baseline CT perfusion characteristics of rectal cancers and their response to treatment, and second, to determine if perfusion CT can be used to subsequently monitor tumor response to treatment. The investigators hope to enroll those patients with locally advanced rectal cancer undergoing standard CT for pre-treatment planning, integrating CT perfusion imaging into the current abdomen/pelvis imaging protocol with close clinical and radiologic follow-up after treatment to determine response to therapy and time to disease progression.

    View full details

  • Ultrasound Elastography in Diagnosing Patients With Kidney or Liver Solid Focal Lesions Recruiting

    This clinical trial studies ultrasound elastography in diagnosing patients with kidney or liver solid focal lesions. New diagnostic procedures, such as ultrasound elastography, may be a less invasive way to check for kidney or liver solid focal lesions.

    View full details

  • Perfusion CT as a Predictor of Treatment Response in Patients With Hepatic Malignancies Recruiting

    The purpose of this study is to determine whether baseline CT perfusion characteristics (measurements of blood-flow using CT) of hepatic cancers can predict tumor response to treatment and whether perfusion CT after treatment can be used as a biomarker for response to treatment. Treatment may consist of chemotherapy or stereotactic body radiotherapy (SBRT)or embolization therapy.

    View full details

  • 3D Dynamic Contrast-Enhanced Ultrasound Imaging in Predicting Treatment Response in Patients With Liver Metastases From Colon Cancer Recruiting

    Patients are invited to participate in a research study of liver perfusion (how blood flows to the liver over time). Researchers hope to learn whether perfusion characteristics of liver metastases may be predictive of response to treatment and whether liver perfusion characteristics can be used to follow response to treatment. Patients were selected as a possible participant in this study because they are identified as having liver metastases

    View full details

  • Phase I Pilot Study to Evaluate the Prognostic Value of Perfusion CT for Primary Cervical Cancer Not Recruiting

    The investigators hope to learn whether perfusion CT is a useful way to assess primary cervical tumor microenvironment and whether there is a relationship between pretreatment perfusion CT measurements and primary cervical tumor size, lymph node involvement (as assessed by standard of care pretreatment fludeoxyglucose Positron emission tomography/CT (FDG-PET/CT)), and treatment response (as assessed by standard of care 3-month post-therapy FDG-PET/CT).

    Stanford is currently not accepting patients for this trial. For more information, please contact Jacob Wynne, 650-723-8843.

    View full details

  • Capecitabine, Temozolomide and Bevacizumab for Metastatic or Unresectable Pancreatic Neuroendocrine Tumors Recruiting

    This phase II trial studies the side effects and how well giving bevacizumab together with capecitabine and temozolomide works in treating patients with pancreatic neuroendocrine tumors that are metastatic or cannot be removed by surgery. Monoclonal antibodies, such as bevacizumab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. Drugs used in chemotherapy, such as capecitabine and temozolomide, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving bevacizumab together with combination chemotherapy may kill more tumor cells.

    View full details

Teaching

2013-14 Courses


Publications

Journal Articles


  • A multicenter phase II study of pazopanib in patients with advanced gastrointestinal stromal tumors (GIST) following failure of at least imatinib and sunitinib. Annals of oncology Ganjoo, K. N., Villalobos, V. M., Kamaya, A., Fisher, G. A., Butrynski, J. E., Morgan, J. A., Wagner, A. J., D'adamo, D., McMillan, A., Demetri, G. D., George, S. 2014; 25 (1): 236-240

    Abstract

    Advanced GISTs are incurable, but often treatable for years with tyrosine kinase inhibitors (TKIs). The majority of GISTs harbor an oncogenic activating mutation in KIT or PDGFRA. Inhibition of this activating mutation with TKIs most often leads to durable disease control for many patients. However, almost all patients develop resistance to these TKIs, typically due to the development of secondary mutations, heralding the need for new therapeutic options. We conducted a phase II study evaluating the efficacy and toxicity of pazopanib, a broad spectrum TKI inhibiting KIT, VEGFRs (-1, -2, and -3), and PDGFR (-α and-β) in patients with advanced GIST following failure of at least imatinib and sunitinib.Patients received pazopanib 800 mg orally once daily. All patients were assessed for efficacy with CT scans every 8 weeks (two cycles). Patients continued pazopanib until progression or unacceptable toxicity. The primary end point was the 24-week nonprogression [complete response+partial response+stable disease (SD)] rate (NPR) per RECIST 1.1. Secondary end points included PFS, OS, and toxicity.Between August 2011 and September 2012, a total of 25 patients were treated at two institutions. Median number of prior therapy was 3 (range 2-7). A total of 90 cycles of pazopanib were administered, with a median of two cycles (range 1 to 17+) per patient. Best response of SD at any time was observed in 12 (48%) patients. The NPR was 17% [95% confidence interval (CI) 4.5-37]. All but one patient discontinued protocol either due to PD (n = 19) or intolerance (n = 4). One patient with succinate dehydrogenase (SDH)-deficient GIST exhibited continuing disease control after 17 cycles. The median PFS for the entire cohort was 1.9 months (95% CI 1.6-5.2), and the median OS was 10.7 months (95% CI 3.9-NR).Pazopanib was reasonably well tolerated with no unexpected toxicities. Pazopanib as a single agent has marginal activity in unselected heavily pretreated patients with advanced GIST.

    View details for DOI 10.1093/annonc/mdt484

    View details for PubMedID 24356634

  • The elusive parathyroid adenoma: techniques for detection. Ultrasound quarterly Devcic, Z., Jeffrey, R. B., Kamaya, A., Desser, T. S. 2013; 29 (3): 179-187

    Abstract

    The success of minimally invasive surgery for hyperparathyroidism depends on accurate preoperative localization of the hyperfunctioning adenoma with imaging. Ultrasound is an excellent initial modality because it has a high positive predictive value, sensitivity, and specificity, while being inexpensive and noninvasive without use of ionizing radiation. Determining the exact location and number of adenomas is essential, because these factors guide the surgical approach. The goal of this review article was to discuss specific sonographic techniques that can be applied to find even the elusive adenoma, which include (1) compression scanning, (2) color Doppler, (3) scanning regions where ectopic glands may be located, and (4) evaluating intrathyroidal adenomas.

    View details for DOI 10.1097/RUQ.0b013e3182a1ba6f

    View details for PubMedID 23975046

  • New technologies in clinical ultrasound. Seminars in roentgenology Kamaya, A., Machtaler, S., Safari Sanjani, S., Nikoozadeh, A., Graham Sommer, F., Pierre Khuri-Yakub, B. T., Willmann, J. K., Desser, T. S. 2013; 48 (3): 214-223

    View details for DOI 10.1053/j.ro.2013.03.009

    View details for PubMedID 23796372

  • Photoacoustic imaging of the bladder: a pilot study. Journal of ultrasound in medicine Kamaya, A., Vaithilingam, S., Chung, B. I., Oralkan, O., Khuri-Yakub, B. T. 2013; 32 (7): 1245-1250

    Abstract

    Photoacoustic imaging is a promising new technology that combines tissue optical characteristics with ultrasound transmission and can potentially visualize tumor depth in bladder cancer. We imaged simulated tumors in 5 fresh porcine bladders with conventional pulse-echo sonography and photoacoustic imaging. Isoechoic biomaterials of different optical qualities were used. In all 5 of the bladder specimens, photoacoustic imaging showed injected biomaterials, containing varying degrees of pigment, better than control pulse-echo sonography. Photoacoustic imaging may be complementary to diagnostic information obtained by cystoscopy and urine cytologic analysis and could potentially obviate the need for biopsy in some tumors before definitive treatment.

    View details for DOI 10.7863/ultra.32.7.1245

    View details for PubMedID 23804347

  • Pitfalls in sonographic evaluation of thyroid abnormalities. Seminars in ultrasound, CT, and MR Patel, B. N., Kamaya, A., Desser, T. S. 2013; 34 (3): 226-235

    Abstract

    Ultrasound of the thyroid has become increasingly common, with evaluation of thyroid nodules representing the main indication for its use. While detection of thyroid nodules with modern high-resolution sonographic equipment is generally not a challenge, pitfalls may occur by which normal structures or pathology in neighboring organs are mistaken for thyroid nodules. Numerous reports in the literature describe various sonographic features of nodules in an attempt to stratify lesions into benign or malignant categories. While neither nodule size nor number is reliable, echogenicity, microcalcifcation, shape, and composition have been reported to be helpful in classifying thyroid nodules. No single feature should be used in isolation, and consensus guidelines have been established as to when fine-needle aspiration is indicated. Pitfalls remain in the evaluation of thyroid nodules demonstrating atypical features, such as cystic papillary carcinomas. Focal presentation of typically diffuse processes, such as Graves' disease and Hashimoto thyroiditis, may mimic malignant nodules, but carcinomas occur in these settings as well as in a background of normal thyroid parenchyma. Finally, because ultrasound is commonly used for surveillance of patients with thyroid carcinoma after thyroidectomy, sonographers should be familiar with the ultrasound appearance of disease recurrence and its mimics.

    View details for DOI 10.1053/j.sult.2012.11.001

    View details for PubMedID 23768889

  • Physiologic, histologic, and imaging features of retained products of conception. Radiographics Sellmyer, M. A., Desser, T. S., Maturen, K. E., Jeffrey, R. B., Kamaya, A. 2013; 33 (3): 781-796

    Abstract

    Retained products of conception (RPOC) are a common and treatable complication after delivery or termination of pregnancy. The pathologic diagnosis of RPOC is made based on the presence of chorionic villi, which indicates persistent placental or trophoblastic tissue. In the setting of postpartum hemorrhage, however, distinguishing RPOC from bleeding related to normal postpartum lochia or uterine atony can be clinically challenging. Ultrasonographic (US) evaluation can be particularly helpful in these patients, and a thickened endometrial echo complex (EEC) or a discrete mass in the uterine cavity is a helpful gray-scale US finding that suggests RPOC. However, gray-scale US findings alone are inadequate for accurate diagnosis. Detection of vascularity in a thickened EEC or an endometrial mass at color or power Doppler US increases the positive predictive value for the diagnosis of RPOC. Computed tomography or magnetic resonance imaging may be helpful when US findings are equivocal and typically demonstrates an enhancing intracavitary mass in patients with RPOC. Diagnostic pitfalls are rare but may include highly vascular RPOC, which can be mistaken for a uterine arteriovenous malformation; true arteriovenous malformations of the uterus; invasive moles; blood clot; and subinvolution of the placental implantation site. © RSNA, 2013.

    View details for DOI 10.1148/rg.333125177

    View details for PubMedID 23674774

  • Aortoenteric fistulas: spectrum of CT findings ABDOMINAL IMAGING Raman, S. P., Kamaya, A., Federle, M., Fishman, E. K. 2013; 38 (2): 367-375

    Abstract

    This article reviews the causes of aortoenteric fistulas, diagnostic options, and important CT findings.Aortoenteric fistula, a rare but potentially fatal entity, presents a significant challenge to radiologists in diagnosis, largely because of its subtle and nonspecific imaging findings. These fistulas can be divided into primary and secondary forms, depending on the presence or absence of prior aortic reconstructive surgery, but the secondary form is more common. Typical CT findings, which can overlap with those seen in perigraft infection, aortitis, infected/mycotic aneurysms, perianeurysmal fibrosis, and the immediate post-operative period after placement of a graft, include: Effacement of the fat planes around the aorta, perigraft fluid/soft tissue thickening, ectopic gas, tethering of adjacent thickened bowel loops towards the aortic graft, and in rare cases, extravasation of contrast from the aorta into the involved segment of bowel.

    View details for DOI 10.1007/s00261-012-9873-7

    View details for Web of Science ID 000316144100019

    View details for PubMedID 22366854

  • Quantitatively Defining Washout in Hepatocellular Carcinoma AMERICAN JOURNAL OF ROENTGENOLOGY Liu, Y. I., Shin, L. K., Jeffrey, R. B., Kamaya, A. 2013; 200 (1): 84-89

    Abstract

    Washout on delayed phase (or equilibrium phase) imaging of an arterially hyperenhancing lesion is an excellent predictor of hepatocellular carcinoma (HCC). The purpose of our study was to quantitatively define washout in pathologically proven HCC. A quantitative definition of HCC may minimize interobserver variability and facilitate more accurate diagnosis.We identified 47 liver lesions that were hyperenhancing in the arterial phase from 24 patients who underwent triphasic MDCT as part of preoperative evaluation for liver transplantation. All HCCs were pathologically proven. Regions of interest were obtained of lesions and areas of adjacent liver on arterial, portal venous, and delayed phase images. Enhancement profiles were assessed by three radiologists.Of the 47 hypervascular lesions, 14 HCCs were identified. There was a statistically significant difference in percentage attenuation ratio (defined as 100 × ratio of attenuation of adjacent liver to that of the lesion) between lesions that were HCC (median percentage attenuation ratio, 121) and those that were not (median percentage attenuation ratio, 101) on delayed phase. Percentage attenuation ratio ? 107 on delayed phase imaging achieved maximal sensitivity (100%) with good specificity (75.8%), positive predictive value (PPV) (63.6%), and negative predictive value (NPV) (100%) in HCC detection. Percentage attenuation ratio also correlated well with radiologists' assessments of enhancement profiles of lesions (multinomial logistic regression McFadden R(2), 0.72; chi-square p, < 0.01).Our analysis of simple CT attenuation measurements indicates that percentage attenuation ratio offers excellent sensitivity, specificity, PPV, and NPV for HCC detection and very good correlation with radiologists' assessments of washout.

    View details for DOI 10.2214/AJR.11.7171

    View details for Web of Science ID 000312772200027

    View details for PubMedID 23255745

  • Multidetector Computed Tomography Triphasic Evaluation of the Liver Before Transplantation: Importance of Equilibrium Phase Washout and Morphology for Characterizing Hypervascular Lesions JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY Liu, Y. I., Kamaya, A., Jeffrey, R. B., Shin, L. K. 2012; 36 (2): 213-219

    Abstract

    We aim to identify the sensitivity and positive predictive value (PPV) of arterial phase imaging in detecting hepatocellular carcinoma (HCC) and determine the added value of portal venous and equilibrium phase imaging and lesion morphology characterization.We reviewed all patients who underwent liver transplantation at our institution that had a triphasic multidetector computed tomography examination within 6 months of transplantation. Forty-seven hypervascular lesions were identified in 24 patients. Imaging findings were correlated with explant pathologic correlation.Hypervascularity in the arterial phase resulted in sensitivity of 87.5% and PPV of 29.8%. The presence of washout in the equilibrium phase increased the PPV to 92.9% with a slight decrease in sensitivity (81.3%). The negative predictive value of hypervascular lesions without washout in the equilibrium phase was 97.1%. There was significant correlation between larger lesions and HCC and between round lesions and HCC.The presence of washout in the equilibrium phase is a better indicator of malignancy.

    View details for DOI 10.1097/RCT.0b013e318247c8f0

    View details for Web of Science ID 000302141800011

    View details for PubMedID 22446362

  • Photoacoustic Imaging Using a 9F MicroLinear CMUT ICE Catheter 2012 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS) Nikoozadeh, A., Choe, J. W., Kothapalli, S., Moini, A., Sanjani, S. S., Kamaya, A., Oralkan, O., Gambhir, S. S., Khuri-Yakub, P. T. 2012: 24-27
  • Ultrasound Imaging of Bowel Pathology: Technique and Keys to Diagnosis in the Acute Abdomen AMERICAN JOURNAL OF ROENTGENOLOGY Maturen, K. E., Wasnik, A. P., Kamaya, A., Dillman, J. R., Kaza, R. K., Pandya, A., Maheshwary, R. K. 2011; 197 (6): W1067-W1075

    Abstract

    This article illustrates the normal and pathologic sonographic appearances of bowel, with an emphasis on diagnostic ultrasound techniques.The current role of ultrasound for adult bowel evaluation is limited in the United States, with CT emerging as the primary modality for evaluation of the acute abdomen. However, mounting concerns regarding diagnostic radiation and health care costs may affect practice patterns and shift utilization back toward sonography, which is widely available and relatively inexpensive.

    View details for DOI 10.2214/AJR.11.6594

    View details for Web of Science ID 000297369900014

    View details for PubMedID 22109321

  • Imaging Manifestations of Abdominal Fat Necrosis and Its Mimics RADIOGRAPHICS Kamaya, A., Federle, M. P., Desser, T. S. 2011; 31 (7): 2021-2034

    Abstract

    Intraabdominal fat is a metabolically active tissue that may undergo necrosis through a number of mechanisms. Fat necrosis is a common finding at abdominal cross-sectional imaging, and it may cause abdominal pain, mimic findings of acute abdomen, or be asymptomatic and accompany other pathophysiologic processes. Common processes that are present in fat necrosis include torsion of an epiploic appendage, infarction of the greater omentum, and fat necrosis related to trauma or pancreatitis. In addition, other pathologic processes that involve fat may be visualized at computed tomography, including focal lipohypertrophy, pathologic fat paucity (lipodystrophies), and malignancies such as liposarcoma, which may mimic benign causes of fat stranding. Because fat necrosis and malignant processes such as liposarcoma and peritoneal carcinomatosis may mimic one another, knowledge of a patient's clinical history and prior imaging studies is essential for accurate diagnosis.

    View details for DOI 10.1148/rg.317115046

    View details for Web of Science ID 000297047000019

    View details for PubMedID 22084185

  • A Bayesian Network for Differentiating Benign From Malignant Thyroid Nodules Using Sonographic and Demographic Features AMERICAN JOURNAL OF ROENTGENOLOGY Liu, Y. I., Kamaya, A., Desser, T. S., Rubin, D. L. 2011; 196 (5): W598-W605

    Abstract

    The objective of our study was to create a Bayesian network (BN) that incorporates a multitude of imaging features and patient demographic characteristics to guide radiologists in assessing the likelihood of malignancy in suspicious-appearing thyroid nodules.We built a BN to combine multiple indicators of the malignant potential of thyroid nodules including both imaging and demographic factors. The imaging features and conditional probabilities relating those features to diagnoses were compiled from an extensive literature review. To evaluate our network, we randomly selected 54 benign and 45 malignant nodules from 93 adult patients who underwent ultrasound-guided biopsy. The final diagnosis in each case was pathologically established. We compared the performance of our network with that of two radiologists who independently evaluated each case on a 5-point scale of suspicion for malignancy. Probability estimates of malignancy from the BN and radiologists were compared using receiver operating characteristic (ROC) analysis.The network performed comparably to the two expert radiologists. Using each radiologist's assessment of the imaging features as input to the network, the differences between the area under the ROC curve (A(z)) for the BN and for the radiologists were -0.03 (BN vs radiologist 1, 0.85 vs 0.88) and -0.01 (BN vs radiologist 2, 0.76 vs 0.77).We created a BN that incorporates a range of sonographic and demographic features and provides a probability about whether a thyroid nodule is benign or malignant. The BN distinguished between benign and malignant thyroid nodules as well as the expert radiologists did.

    View details for DOI 10.2214/AJR.09.4037

    View details for Web of Science ID 000289769000015

    View details for PubMedID 21512051

  • Hepatic Epithelioid Hemangioendothelioma DIGESTIVE DISEASES AND SCIENCES Liu, Y. I., Brown, S. S., Elihu, A., Bonham, C. A., Concepcion, W., Longacre, T. A., Kamaya, A. 2011; 56 (2): 303-306

    View details for DOI 10.1007/s10620-010-1470-4

    View details for Web of Science ID 000286664900006

    View details for PubMedID 21053076

  • Recurrence in the Thyroidectomy Bed: Sonographic Findings AMERICAN JOURNAL OF ROENTGENOLOGY Kamaya, A., Gross, M., Akatsu, H., Jeffrey, R. B. 2011; 196 (1): 66-70

    Abstract

    The purpose of this article is to characterize sonographic features of differentiated thyroid cancer recurrence in the thyroidectomy bed.Patients referred for biopsy of thyroidectomy bed lesions between February 2006 and December 2009 were identified. Patient data and gray-scale and color Doppler features were recorded.Results of ultrasound-guided biopsies of 30 nodules in 27 patients were reviewed. Twenty-five lesions yielded diagnostic findings, including 22 recurrences in 19 patients and three benign lesions in three patients. Five biopsies were nondiagnostic. Among the 22 recurrences, 21 (95%) were hypoechoic and one (5%) was mixed hypoechoic and hyperechoic on gray-scale imaging. On Doppler imaging, 100% of recurrences had detectable vascularity. Eight lesions (36%) had microcalcifications, and five (23%) had coarse calcifications; the average long-axis dimension was 1.5 cm. Of the five nondiagnostic lesions, four (80%) were hypoechoic, one (20%) was isoechoic, one (20%) had microcalcifications, none had coarse calcifications, and two (40%) had vascularity; the average long-axis dimension was 0.6 cm. Of the negative lesions, three (100%) were hypoechoic, two (66%) had vascularity, and two (66%) had coarse calcifications. No microcalcifications were seen, and the average long-axis dimension was 2 cm. Serum thyroglobulin (Tg) or anti-Tg antibodies were elevated in 12 (63%) of 19 patients with recurrence (eight [42%] with elevated Tg levels and four [21%] with elevated anti-Tg antibody levels).An ultrasound finding of a hypoechoic thyroidectomy bed lesion with internal vascularity and size greater than 6 mm is highly sensitive in predicting recurrence. Serum Tg levels were less sensitive than ultrasound in detection of recurrence in the thyroidectomy bed.

    View details for DOI 10.2214/AJR.10.4474

    View details for Web of Science ID 000286018800009

    View details for PubMedID 21178048

  • Informatics in Radiology RADTF: A Semantic Search-enabled, Natural Language Processor-generated Radiology Teaching File RADIOGRAPHICS Do, B. H., Wu, A., Biswal, S., Kamaya, A., Rubin, D. L. 2010; 30 (7): 2039-2048

    Abstract

    Storing and retrieving radiology cases is an important activity for education and clinical research, but this process can be time-consuming. In the process of structuring reports and images into organized teaching files, incidental pathologic conditions not pertinent to the primary teaching point can be omitted, as when a user saves images of an aortic dissection case but disregards the incidental osteoid osteoma. An alternate strategy for identifying teaching cases is text search of reports in radiology information systems (RIS), but retrieved reports are unstructured, teaching-related content is not highlighted, and patient identifying information is not removed. Furthermore, searching unstructured reports requires sophisticated retrieval methods to achieve useful results. An open-source, RadLex(®)-compatible teaching file solution called RADTF, which uses natural language processing (NLP) methods to process radiology reports, was developed to create a searchable teaching resource from the RIS and the picture archiving and communication system (PACS). The NLP system extracts and de-identifies teaching-relevant statements from full reports to generate a stand-alone database, thus converting existing RIS archives into an on-demand source of teaching material. Using RADTF, the authors generated a semantic search-enabled, Web-based radiology archive containing over 700,000 cases with millions of images. RADTF combines a compact representation of the teaching-relevant content in radiology reports and a versatile search engine with the scale of the entire RIS-PACS collection of case material.

    View details for DOI 10.1148/rg.307105083

    View details for Web of Science ID 000284094200021

    View details for PubMedID 20801868

  • Pathological response after chemoradiation for T3 rectal cancer COLORECTAL DISEASE Chennupati, S. K., Kamaya, A., Fisher, G. A., Ford, J. M., Kunz, P., Itakura, H., Welton, M. L., Shelton, A., Van Dam, J., Koong, A. C., Chang, D. T. 2010; 12 (7): E24-E30
  • Pathological response after chemoradiation for T3 rectal cancer. Colorectal disease Chennupati, S. K., Kamaya, A., Fisher, G. A., Ford, J. M., Kunz, P., Itakura, H., Welton, M. L., Shelton, A., Van Dam, J., Koong, A. C., Chang, D. T. 2010; 12 (7 Online): e24-30

    Abstract

    The aim of this study was to investigate the effect of preoperative chemoradiotherapy (CRT) on nodal disease in locally advanced rectal adenocarcinoma.Thirty-two patients staged uT3N0 and 27 patients staged uT3N1 rectal adenocarcinoma who underwent pre-CRT staging using endoscopic ultrasound or rectal protocol CT were included. The median radiation dose was 50.4 Gy (range: 45-50.4 Gy) at 1.8 Gy per fraction and all patients received concurrent 5-FU or capecitabine-based chemotherapy. Low anterior resection or abdomino-perineal resection occurred at a median of 46 days (range: 27-112 days) after CRT.Eleven of 32 uT3N0 patients (34.4%) and 13 of 26 uT3N1 patients (50.0%) had ypN+ (P = 0.29). For patients with uT3N0, 10 of 20 (50.0%) with ypT2-3 and 1 of 12 (8.3%) with ypT0-1 were ypN+ (P = 0.02). For patients with uT3N1, 12 of 20 (60.0%) with ypT2-3 and 1 of 6 (16.7%) with ypT0-1 were ypN+ (P = 0.16). Overall, the ypN+ rate was 11.1% in the ypT0-yT1 group compared with 55.0% in the ypT2-yT3 group (P = 003). Among patients with uT3N0 disease, the ypN+ rate in patients who had surgery > 46 days vs 46 days vs 46 days vs

    View details for DOI 10.1111/j.1463-1318.2009.02013.x

    View details for PubMedID 19614668

  • 3-D Deep Penetration Photoacoustic Imaging with a 2-D CMUT Array. Proceedings / IEEE ... Ultrasonics Symposium. IEEE Ultrasonics Symposium Ma, T. J., Kothapalli, S. R., Vaithilingam, S., Oralkan, O., Kamaya, A., Wygant, I. O., Zhuang, X., Gambhir, S. S., Jeffrey, R. B., Khuri-Yakub, B. T. 2010; 2010: 375-377

    Abstract

    In this work, we demonstrate 3-D photoacoustic imaging of optically absorbing targets embedded as deep as 5 cm inside a highly scattering background medium using a 2-D capacitive micromachined ultrasonic transducer (CMUT) array with a center frequency of 5.5 MHz. 3-D volumetric images and 2-D maximum intensity projection images are presented to show the objects imaged at different depths. Due to the close proximity of the CMUT to the integrated frontend circuits, the CMUT array imaging system has a low noise floor. This makes the CMUT a promising technology for deep tissue photoacoustic imaging.

    View details for PubMedID 22977296

  • Three-Dimensional Photoacoustic Imaging Using a Two-Dimensional CMUT Array IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Vaithilingam, S., Ma, T., Furukawa, Y., Wygant, I. O., Zhuang, X., de la Zerda, A., Oralkan, O., Kamaya, A., Gambhir, S. S., Jeffrey, R. B., Khuri-Yakub, B. T. 2009; 56 (11): 2411-2419

    Abstract

    In this paper, we describe using a 2-D array of capacitive micromachined ultrasonic transducers (CMUTs) to perform 3-D photoacoustic and acoustic imaging. A tunable optical parametric oscillator laser system that generates nanosecond laser pulses was used to induce the photoacoustic signals. To demonstrate the feasibility of the system, 2 different phantoms were imaged. The first phantom consisted of alternating black and transparent fishing lines of 180 mum and 150 mum diameter, respectively. The second phantom comprised polyethylene tubes, embedded in chicken breast tissue, filled with liquids such as the dye indocyanine green, pig blood, and a mixture of the 2. The tubes were embedded at a depth of 0.8 cm inside the tissue and were at an overall distance of 1.8 cm from the CMUT array. Two-dimensional cross-sectional slices and 3-D volume rendered images of pulse-echo data as well as photoacoustic data are presented. The profile and beamwidths of the fishing line are analyzed and compared with a numerical simulation carried out using the Field II ultrasound simulation software. We investigated using a large aperture (64 x 64 element array) to perform photoacoustic and acoustic imaging by mechanically scanning a smaller CMUT array (16 x 16 elements). Two-dimensional transducer arrays overcome many of the limitations of a mechanically scanned system and enable volumetric imaging. Advantages of CMUT technology for photoacoustic imaging include the ease of integration with electronics, ability to fabricate large, fully populated 2-D arrays with arbitrary geometries, wide-bandwidth arrays and high-frequency arrays. A CMUT based photoacoustic system is proposed as a viable alternative to a piezoelectric transducer based photoacoustic systems.

    View details for DOI 10.1109/TUFFC.2009.1329

    View details for Web of Science ID 000271478600010

    View details for PubMedID 19942528

  • Hypervascular Liver Lesions SEMINARS IN ULTRASOUND CT AND MRI Kamaya, A., Maturen, K. E., Tye, G. A., Liu, Y. I., Parti, N. N., Desser, T. S. 2009; 30 (5): 387-407

    Abstract

    Hypervascular hepatocellular lesions include both benign and malignant etiologies. In the benign category, focal nodular hyperplasia and adenoma are typically hypervascular. In addition, some regenerative nodules in cirrhosis may be hypervascular. Malignant hypervascular primary hepatocellular lesions include hepatocellular carcinoma, fibrolamellar carcinoma, and peripheral cholangiocarcinoma. Vascular liver lesions often appear hypervascular because they tend to follow the enhancement of the blood pool; these include hemangiomas, arteriovenous malformations, angiosarcomas, and peliosis. While most gastrointestinal malignancies that metastasize to the liver will appear hypovascular on arterial and portal-venous phase imaging, certain cancers such as metastatic neuroendocrine tumors (including pancreatic neuroendocrine tumors, carcinoid, and gastrointestinal stromal tumors) tend to produce hypervascular metastases due to the greater recruitment of arterial blood supply. Finally, rare hepatic lesions such as glomus tumor and inflammatory pseudotumor may have a hypervascular appearance.

    View details for DOI 10.1053/j.sult.2009.06.001

    View details for Web of Science ID 000270442900003

    View details for PubMedID 19842564

  • Imaging and Diagnosis of Postpartum Complications Sonography and Other Imaging Modalities ULTRASOUND QUARTERLY Kamaya, A., Ro, K., Benedetti, N. J., Chang, P. L., Desser, T. S. 2009; 25 (3): 151-162

    Abstract

    Postpartum complications can be broadly divided into 4 categories: postpartum hemorrhage, obstetrical trauma, thromboembolic complications, and puerperal infections. Postpartum hemorrhage is most commonly caused by uterine atony, abnormal placentation, or genital tract trauma. Secondary causes of hemorrhage include retained products of conception and, rarely, subinvolution of the placental implantation site. Uterine dehiscence or rupture may be occult on ultrasound examination and may be better visualized on sagittal computed tomography or magnetic resonance imaging. Obstetric trauma during prolonged vaginal or cesarean delivery may lead to fistula formation, ureteral injury, or bowel injury. Later potential complications of cesarean delivery include cesarean delivery scar ectopic, endometrial implants in the cesarean scar, and placenta accreta. Thromboembolic complications can include pulmonary embolism and deep vein thrombosis as well as ovarian vein thrombosis, the latter of which can be difficult to clinically differentiate from appendicitis in the postpartum female.

    View details for Web of Science ID 000208127100008

    View details for PubMedID 19730078

  • Retained Products of Conception Spectrum of Color Doppler Findings JOURNAL OF ULTRASOUND IN MEDICINE Kamaya, A., Petrovitch, I., Chen, B., Frederick, C. E., Jeffrey, R. B. 2009; 28 (8): 1031-1041

    Abstract

    The purpose of this study was to characterize color Doppler imaging features of retained products of conception (RPOC) with gray scale correlation.Clinically suspected cases of RPOC between January 2005 and February 2008 were reviewed. Patient data and relevant color Doppler and gray scale features were recorded.A total of 269 patients referred for sonographic evaluation for RPOC were identified. Thirty-five patients had confirmed pathologic diagnoses, 28 of whom had RPOC. In those with RPOC, 5 (18%) were avascular (type 0); 6 (21%) had minimal vascularity (type 1); 12 (43%) had moderate vascularity (type 2); and 5 (18%) had marked vascularity (type 3). Peak systolic velocities ranged from 10 to 108 cm/s (average, 36.1 cm/s). Resistive indices in arterial waveforms ranged from 0.33 to 0.7 (average, 0.5). Five (45%) of the patients with type 0 vascularity had RPOC; 6 (86%) of those with type 1 had RPOC; and 17 (100%) of those with types 2 and 3 had RPOC. An echogenic mass had a moderate positive predictive value (80%) but low sensitivity (29%) for RPOC.Color Doppler evaluation of the endometrium is helpful in determining the presence of RPOC. Endometrial vascularity is highly correlated with RPOC, whereas the lack of vascularity can be seen in both intrauterine clots and avascular RPOC.

    View details for Web of Science ID 000268556800008

    View details for PubMedID 19643786

  • Laparoscopic radical nephrectomy after shrinkage of a caval tumor thrombus with sunitinib NATURE REVIEWS UROLOGY Harshman, L. C., Srinivas, S., Kamaya, A., Chung, B. I. 2009; 6 (6): 338-343

    Abstract

    A 57-year-old woman presented to the emergency department at a community hospital with a 2-month history of fatigue and right-sided flank and abdominal pain. Noncontrast CT of the abdomen and pelvis revealed a 9.1 cm right renal mass.Contrast CT of the chest, abdomen and pelvis, MRI of the abdomen and pelvis with gadolinium, radionuclide bone scan, lung nodule biopsy, complete blood count, comprehensive metabolic profile, and measurement of serum lactate dehydrogenase.Stage IV, T3bN0M1 clear cell renal cell carcinoma, with an associated tumor thrombus extending into the vena cava.The patient was treated with neoadjuvant sunitinib, which resulted in a marked response in the primary tumor and metastatic lesions as well as regression of the tumor thrombus well into the renal vein. Thus, laparoscopic radical nephrectomy was feasible and was achieved without hemorrhagic or wound healing complications. One month after surgery, she had evidence of disease progression in the lung and a periaortic lymph node. She was restarted on sunitinib with resultant disease stabilization, but discontinued the drug owing to toxicity. Eight months after cessation of sunitinib, she received a dendritic cell vaccine. She remains alive without evidence of disease progression 2 years after her diagnosis.

    View details for DOI 10.1038/nrurol.2009.84

    View details for Web of Science ID 000266773900012

    View details for PubMedID 19498412

  • Intraoperative Ultrasound of the Pancreas ULTRASOUND QUARTERLY Shin, L. K., Brant-Zawadzki, G., Kamaya, A., Jeffrey, R. B. 2009; 25 (1): 39-48

    Abstract

    Intraoperative ultrasound provides spatial resolution of the pancreas superior to computed tomography, magnetic resonance imaging, and transabdominal sonography. This pictorial essay will review common benign and malignant pancreatic processes including the following: pancreatic ductal adenocarcinoma, pancreatitis, endocrine tumors, mucinous cystic neoplasm, intraductal papillary mucinous neoplasm, serous cystadenoma, and solid pseudopapillary tumor. The use of intraoperative ultrasound in specific surgical situations will be discussed, which include the following: (1) identification of insulinoma(s) which are not detectable preoperatively, (2) identification of the pancreatic duct to determine dissection planes for chronic pancreatitis surgery (eg, Puestow procedure) and for tumor resection, and (3) staging purposes for malignant disease.

    View details for Web of Science ID 000208118300005

    View details for PubMedID 19276960

  • Optimal Vascular and Parenchymal Contrast Enhancement: The Current State of the Art RADIOLOGIC CLINICS OF NORTH AMERICA Fleischmann, D., Kamaya, A. 2009; 47 (1): 13-?

    Abstract

    A fundamental understanding of early arterial and parenchymal contrast medium (CM) dynamics is the basis for the design of CT scanning and injection protocols for state-of-the-art cardiovascular and body CT applications. Although normal parenchymal enhancement is primarily controlled by the total iodine dose injected per body weight, arterial enhancement is controlled by the iodine flux, the injection duration, and cardiac output. The technical capabilities of modern CT equipment allow and require precise scan timing to synchronize data acquisition with the desired phase of vascular enhancement (for CTA) and parenchymal enhancement (for liver and pancreatic CT). Automated tube current modulation and weight-based injection protocols allow individual optimization of radiation exposure and reduce interindividual variability of CM enhancement.

    View details for DOI 10.1016/j.rcl.2008.10.009

    View details for Web of Science ID 000263843900003

    View details for PubMedID 19195531

  • A Controlled Vocabulary to Represent Sonographic Features of the Thyroid and its application in a Bayesian Network to Predict Thyroid Nodule Malignancy. Summit on translational bioinformatics Liu, Y. I., Kamaya, A., Desser, T. S., Rubin, D. L. 2009; 2009: 68-72

    Abstract

    It is challenging to distinguish benign from malignant thyroid nodules on high resolution ultrasound. Many ultrasound features have been studied individually as predictors for thyroid malignancy, none with a high degree of accuracy, and there is no consistent vocabulary used to describe the features. Our hypothesis is that a standard vocabulary will advance accuracy. We performed a systemic literature review and identified all the sonographic features that have been well studied in thyroid cancers. We built a controlled vocabulary for describing sonographic features and to enable us to unify data in the literature on the predictive power of each feature. We used this terminology to build a Bayesian network to predict thyroid malignancy. Our Bayesian network performed similar to or slightly better than experienced radiologists. Controlled terminology for describing thyroid radiology findings could be useful to characterize thyroid nodules and could enable decision support applications.

    View details for PubMedID 21347173

  • Emergency Gynecologic Imaging SEMINARS IN ULTRASOUND CT AND MRI Kamaya, A., Shin, L., Chen, B., Desser, T. S. 2008; 29 (5): 353-368

    Abstract

    Acute pelvic pain in the female patient can have myriad presentations and, depending on the diagnosis, profound consequences. In the pregnant patient with pelvic pain or bleeding, an ectopic pregnancy must be first excluded. Ultrasound is important in determining the size and location of the ectopic pregnancy, and presence of bleeding, which in turn helps guide treatment decisions. Subchorionic or subplacental bleeds in an intrauterine pregnancy may also present with vaginal bleeding with consequences dependent on gestational age and size of bleed. In the postpartum female suspected to have retained products of conception, sonographic findings may vary from a thickened endometrial stripe to an echogenic mass with associated marked vascularity, often mimicking an arterial-venous malformation. In the nonpregnant patient, early diagnosis and treatment of ovarian torsion can preserve ovarian function. Other causes of peritoneal irritation may also cause acute pelvic pain including a ruptured hemorrhagic cyst or ruptured endometrioma. When pelvic inflammatory disease is suspected, imaging is used to evaluate for serious associated complications including the presence of a tuboovarian abscess or peritonitis. While leiomyomas of the uterus are largely asymptomatic, a leiomyoma that undergoes necrosis, torsion or prolapse through the cervix may be associated with acute severe pain or bleeding. The imaging features of these and other important clinical entities in the female pelvis will be presented.

    View details for DOI 10.1053/j.sult.2008.06.006

    View details for Web of Science ID 000260064700006

    View details for PubMedID 18853841

  • Fetus in fetu: 11 fetoid forms in a single fetus - Review of the literature and imaging JOURNAL OF ULTRASOUND IN MEDICINE Gerber, R. E., Kamaya, A., Miller, S. S., Cronin, D. M., Dwyer, B., Chueh, J., Conner, K. E., Barth, R. A. 2008; 27 (9): 1381-1387

    View details for Web of Science ID 000258853200015

    View details for PubMedID 18716149

  • Ultrasound of thyroid nodules NEUROIMAGING CLINICS OF NORTH AMERICA Desser, T. S., Kamaya, A. 2008; 18 (3): 463-478

    Abstract

    Thyroid nodules can be detected in 4% to 8% of the adult population by palpation, but in 40% to 50% of the population by ultrasound. The overwhelming majority of these represent benign hyperplastic nodules or adenomas. Approximately 5% of nodules are malignant, with papillary carcinoma representing approximately 75% to 80% of primary thyroid malignancies. Although many sonographic features have been studied as a means of distinguishing benign from malignant nodules, ultrasound-guided fine-needle aspiration with cytologic evaluation remains a mainstay in the management of palpable and incidentally detected nodules. This article reviews the current techniques for sonographic evaluation of the thyroid and the imaging features of the various types of thyroid nodules.

    View details for DOI 10.1016/j.nic.2008.03.005

    View details for Web of Science ID 000258670800004

    View details for PubMedID 18656028

  • An unusual imaging and clinical presentation of papillary thyroid carcinoma JOURNAL OF ULTRASOUND IN MEDICINE Liu, Y. I., Shin, L. K., Kamaya, A., Jeffrey, R. B. 2008; 27 (8): 1241-1244

    View details for Web of Science ID 000258088100015

    View details for PubMedID 18645084

  • Initial evaluation of F-18-fluorothymidine (FLT) PET/CT scanning for primary pancreatic cancer EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING Quon, A., Chang, S. T., Chin, F., Kamaya, A., Dick, D. W., Loo, B. W., Gambhir, S. S., Koong, A. C. 2008; 35 (3): 527-531

    Abstract

    The aim of this study was to evaluate the potential of (18)F-fluorothymidine (FLT) PET/CT for imaging pancreatic adenocarcinoma.This was a pilot study of five patients (four males, one female) with newly diagnosed and previously untreated pancreatic adenocarcinoma. Patients underwent FLT PET/CT, (18)F-fluorodeoxyglucose (FDG) PET/CT, and contrast-enhanced CT scanning before treatment. The presence of cancer was confirmed by histopathological analysis at the time of scanning in all five patients. The degree of FLT and FDG uptake at the primary tumor site was assessed using visual interpretation and semi-quantitative SUV analyses.The primary tumor size ranged from 2.5 x 2.8 cm to 3.5 x 7.0 cm. The SUV of FLT uptake within the primary tumor ranged from 2.1 to 3.1. Using visual interpretation, the primary cancer could be detected from background activity in two of five patients (40%) on FLT PET/CT. By comparison, FDG uptake was higher in each patient with a SUV range of 3.4 to 10.8, and the primary cancer could be detected from background in all five patients (100%).In this pilot study of five patients with primary pancreatic adenocarcinoma, FLT PET/CT scanning showed poor lesion detectability and relatively low levels of radiotracer uptake in the primary tumor.

    View details for DOI 10.1007/s00259-007-0630-z

    View details for Web of Science ID 000254402800010

    View details for PubMedID 17960376

  • Investigating Large 2D Arrays for Photoacoustic and Acoustic Imaging using CMUT Technology 2008 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-4 AND APPENDIX Vaithilingam, S., Ma, T., Furukawa, Y., Oralkan, O., Kamaya, A., Torashima, K., Kupnik, M., Wygant, I. O., Zhuang, X., Jeffrey, R. B., Khuri-Yakub, B. T. 2008: 1238-1241
  • A Bayesian classifier for differentiating benign versus malignant thyroid nodules using sonographic features. AMIA ... Annual Symposium proceedings / AMIA Symposium. AMIA Symposium Liu, Y. I., Kamaya, A., Desser, T. S., Rubin, D. L. 2008: 419-423

    Abstract

    Thyroid nodules are a common, yet challenging clinical problem. The vast majority of these nodules are benign; however, deciding which nodule should undergo biopsy is difficult because the imaging appearance of benign and malignant thyroid nodules overlap. High resolution ultrasound is the primary imaging modality for evaluating thyroid nodules. Many sonographic features have been studied individually as predictors for thyroid malignancy. There has been little work to create predictive models that combine multiple predictors, both imaging features and demographic factors. We have created a Bayesian classifier to predict whether a thyroid nodule is benign or malignant using sonographic and demographic findings. Our classifier performed similar to or slightly better than experienced radiologists when evaluated using 41 thyroid nodules with known pathologic diagnosis. This classifier could be helpful in providing practitioners an objective basis for deciding whether to biopsy suspicious thyroid nodules.

    View details for PubMedID 18999209

  • A co-axial scanning acoustic and. photoacoustic microscope 2007 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1-6 Vaithilingam, S., Ma, T., Furukawa, Y., de la Zerda, A., Oralkan, O., Kamaya, A., Keren, S., Gambhir, S. S., Jeffrey, R. B., Khuri-Yakub, B. T. 2007: 2413-2416
  • Sonography of the abnormal parathyroid gland. Ultrasound quarterly Kamaya, A., Quon, A., Jeffrey, R. B. 2006; 22 (4): 253-262

    Abstract

    In 80% to 90% of patients with primary hyperparathyroidism, a single parathyroid adenoma will be identified as the culprit, whereas the remaining 10% to 20% are caused by multiple adenomas, parathyroid hyperplasia, and rarely, parathyroid carcinoma. At the 2002 National Institute of Health consensus meeting, minimally invasive parathyroidectomy was endorsed as a promising and attractive alternative to total parathyroidectomy. Therefore, preoperative localization of the adenoma is critical in the clinical evaluation of the patient before surgical resection. Although adenomas less than 1 cm may be difficult to visualize sonographically, knowledge of typical imaging characteristics of parathyroid adenomas and use of special sonographic techniques will facilitate identification in most patients. Typical imaging characteristics of parathyroid adenomas include homogeneously hypoechoic echotexture on gray scale with an enlarged feeding artery and peripheral arc of vascularity seen on color and power Doppler. Proper neck extension, unilateral graded compression techniques, and patient swallowing will improve visualization of adenomas.

    View details for PubMedID 17146333

  • Multiple lesions of the spleen: Differential diagnosis of cystic and solid lesions SEMINARS IN ULTRASOUND CT AND MRI Kamaya, A., Weinstein, S., Desser, T. S. 2006; 27 (5): 389-403

    Abstract

    Lesions in the spleen may be encountered in a variety of clinical settings ranging from asymptomatic patients to patients who are critically ill. Etiologies for multifocal splenic lesions include infectious and inflammatory processes, primary vascular and lymphoid neoplasms, metastatic disease, vascular processes, and systemic diseases. There is often overlap in the imaging appearance alone, so the clinical setting is very helpful in differential diagnosis. In the immunocompromised patient, multiple small splenic lesions usually represent disseminated fungal disease and microabscesses. The spleen is a relatively rare site for metastatic disease; patients with metastatic lesions in the spleen usually have disease in other sites as well. Breast, lung, ovary, melanoma, and colon cancer are common primary tumors that metastasize to the spleen. Vascular neoplasms of the spleen represent the majority of the nonhematologic/nonlymphoid neoplasms and commonly produce multifocal lesions. Splenic infarcts may be seen with localized processes such as portal hypertension or pancreatitis, or may arise from an embolic source. Radiologists should be aware of the spectrum of processes that may involve the spleen and the clinical context in which they occur.

    View details for DOI 10.1053/j.sult.2006.06.004

    View details for Web of Science ID 000241312600004

    View details for PubMedID 17048454

  • Characterization of a linear streak artifact with pulse inversion tissue harmonics in musculoskeletal Sonography JOURNAL OF ULTRASOUND IN MEDICINE Kamaya, A., Abate, S., Nan, B., Grover, I., Adler, R. S., Jamadar, D., Rubin, J. M. 2004; 23 (12): 1597-1605

    Abstract

    To understand a linear artifact that projects deep to reflective structures that move rapidly while using tissue harmonic imaging with pulse inversion (PI) sonography. We hypothesize that this artifact is due to a cancellation error between firings in PI imaging, and it is, therefore, similar in generation to the twinkling artifact in color Doppler sonography. This artifact could be studied with the use of surfaces of different roughness to represent different rates of motion, in which roughness corresponds to spatial fluctuations in surface height. Given very slight variations in beam focusing as occurs with sonographic imaging arrays, these spatial fluctuations translate into temporal fluctuations in the received signal as would occur with tissue motion.We scanned 4 different sandpaper grits and a smooth surface through a water path using fundamental and PI mode, 1- and 2-pulse techniques, respectively. The sandpaper and the smooth surface were scanned through a water path at mechanical indices of 0.1 to 0.7. Four independent images were subtracted pairwise to remove nonfluctuating signals. These noise pixels were counted and analyzed.Analysis of variance showed that the noise generated behind the different surfaces was highly significantly different. Two-tailed t tests generally showed significant differences in the quantity of noise between fundamental and harmonic imaging behind the roughest 3 grades of sandpaper. A multiple regression model showed significantly greater slopes for harmonic imaging for all grades of sandpaper and the smooth surface.The noise and, by extension, the linear streak artifact in musculoskeletal imaging are dependent on the mechanical index and are functions of sandpaper roughness. This would be equivalent to a subtraction error between 2 firings due to soft tissue motion, and the artifact may be a way to identify rapid soft tissue motion in PI images.

    View details for Web of Science ID 000225515300006

    View details for PubMedID 15557302

  • Twinkling artifact on color Doppler sonography: Dependence on machine parameters and underlying cause AMERICAN JOURNAL OF ROENTGENOLOGY Kamaya, A., Tuthill, T., Rubin, J. M. 2003; 180 (1): 215-222

    Abstract

    The objective of our study was to evaluate the color Doppler sonographic effect known as twinkling artifact.Struvite (ammonium magnesium phosphate) stone fragments, wire mesh, and a flat surface were scanned in a water bath with a sonography scanner using a high-frequency linear array probe fixed in a ring clamp. Pulse repetition frequency, color-write priority, gray-scale gain, and spectral Doppler gain were varied. Color and spectral Doppler modes were used.Twinkling artifact and spectral broadening were seen most intensely behind struvite stone fragments, and both were seen more strongly behind wire mesh with greater surface roughness than behind wire mesh with less surface roughness or a flat surface. The appearance of the twinkling artifact is highly dependent on machine settings. System noise measured on a flat surface generates a band-limited Doppler shift on spectral displays with a mean frequency shift of 0 Hz and a mean (+/- SD) absolute fluctuation of 86 +/- 10 Hz over a pulse repetition frequency range of 1250-10,000 Hz. Rough surfaces increase the spectral bandwidth.The appearance of the twinkling artifact is highly dependent on machine settings and is likely generated by a narrow-band, intrinsic machine noise called phase (or clock) jitter. Surface roughness secondarily broadens the noise spectrum. With a strongly reflecting, rough surface such as a renal stone, the high amplitude, broadband signal appears as random motion in color Doppler sonography. Understanding of the twinkling artifact may result in better use of its clinical appearance.

    View details for Web of Science ID 000179979400040

    View details for PubMedID 12490508

Conference Proceedings


  • Positron Emission Tomography for Predicting Pathologic Response After Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer Chennupati, S. K., Quon, A., Kamaya, A., Pai, R. K., La, T., Krakow, T. E., Graves, E., Koong, A. C., Chang, D. T. LIPPINCOTT WILLIAMS & WILKINS. 2012: 334-339

    Abstract

    To investigate whether before and after chemoradiotherapy (CRT) positron emission tomography (PET) predict for pathologic response after preoperative CRT in patients with locally advanced rectal adenocarcinoma.Thirty-five patients who underwent pre-CRT and post-CRT PET scans before surgery were included. All patients were staged with endoscopic ultrasound or high resolution CT. CRT was given with 50.4 Gy at 1.8 Gy per fraction and concurrent 5-fluorouracil-based chemotherapy. Surgery occurred at a median of 46 days (range, 27 to 112 d) after completing CRT. The maximum standardized uptake value (SUV(max)) and the metabolic tumor volume (MTV) using various minimum SUV thresholds (2, 2.5, 3) on the PET scans (MTV(2.0), MTV(2.5), MTV(3.0)) were determined. Post-CRT PET scans were done 3 to 5 weeks after completion of CRT. Pathologic response was assessed using the tumor regression grade (TRG) scale. Patients with complete or near-complete response (TRG=0 to 1) were considered pathologic responders. The pre-CRT and post-CRT PET scan SUV(max) and MTV values were correlated with TRG. The ?SUV(max) and ?MTV were correlated with TRG.No correlation was seen with SUV(max) (P=0.99), MTV(2.0) (P=0.73), MTV(2.5) (P=0.73), or MTV(3.0) (P=0.31) on the pre-CRT PET between pathologic responders versus nonresponders. No correlation was noted between SUV(max) (P=0.49), MTV(2.0) (P=0.73), MTV(2.5) (P=0.49), or MTV(3.0) (P=0.31) on the post-CRT PET scan and pathologic response. Finally, the ?SUV(max) (P=0.32), ?MTV(2.0) (P=0.99), ?MTV(2.5) (P=0.31), ?MTV(3.0) (P=0.31) did not correlate with pathologic response.Changes seen on PET have limited value in predicting for pathologic response of rectal cancer after preoperative neoadjuvant therapy.

    View details for DOI 10.1097/COC.0b013e3182118d12

    View details for Web of Science ID 000306599200006

    View details for PubMedID 21422989

Stanford Medicine Resources: