Bio

Bio

Education:
2002 - B.S., Physics, Drohobych State University, Ukraine
2004 - M.S., Physics, Minnesota State University, Mankato, MN
2008 - Ph.D., Applied Physics, University of South Florida (H. Lee Moffitt Cancer Center and Research Institute), Tampa, FL
2010 - Medical Physics Residency, Mayo Clinic, Rochester, MN

Academic Appointments:
2010 - 2015 - Instructor, Harvard Medical School, Massachusetts General Hospital/Boston Medical Center, Department of Radiation Oncology, Boston, MA
2015 - 2019 - Clinical Assistant Professor, Stanford University, Department of Radiation Oncology, Stanford, CA
2019 - present - Clinical Associate Professor, Stanford University, Department of Radiation Oncology, Stanford, CA
2019 - present - Adjunct Associate Professor, MD Anderson Cancer Center/University of Texas, Houston, TX

Academic Appointments

Honors & Awards

  • Medical Physics Teaching Award, Radiation Oncology Department, Stanford, Stanford (2017)
  • ARRO Educator of the Year Award by Harvard Radiation Oncology Residency Program, ARRO (2014)
  • Quality Improvement Award at Boston Medical Center, Boston Medical Center (2013)
  • Resident Travel Grant Award for the 2009 American Brachytherapy Society (ABS) Annual Meeting, ABS (2009)
  • Boutzoukas Radiology Research Award, H. Lee Moffitt, Moffitt Cancer Center (2006)
  • Midwestern Association of Graduate Schools Distinguished Thesis Competition Award, MAGS (2005)
  • MSU Best Thesis of the Year Award, MSU (2004)

Boards, Advisory Committees, Professional Organizations

  • NRG Physics HN committee, liaison (2018 - Present)
  • COG Workgroup on pediatric TBI, member (2018 - Present)
  • AAPM MP3.0 Committee, member (2018 - Present)
  • COG Physics Committee, member (2017 - Present)
  • NRG Physics Committee, member (2017 - Present)
  • ASTRO, member (2010 - Present)
  • AAPM, member (2008 - Present)

Contact

Research & Scholarship

Clinical Trials

  • De-intensified Radiation Therapy With Chemotherapy (Cisplatin) or Immunotherapy (Nivolumab) in Treating Patients With Early-Stage, HPV-Positive, Non-Smoking Associated Oropharyngeal Cancer Recruiting

    This phase II/III trial studies how well a reduced dose of radiation therapy works with nivolumab compared to cisplatin in treating patients with human papillomavirus (HPV)-positive oropharyngeal cancer that is early in its growth and may not have spread to other parts of the body (early-stage), and is not associated with smoking. Radiation therapy uses high-energy x-rays to kill tumor cells and shrink tumors. Chemotherapy drugs, such as cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. This trial is being done to see if a reduced dose of radiation therapy and nivolumab works as well as standard dose radiation therapy and cisplatin in treating patients with oropharyngeal cancer.

    View full details

Publications

All Publications

  • Importance of a Culture Committee for Boosting Morale and Maintaining a Healthy Work Environment in Radiation Oncology. Advances in radiation oncology Gutkin, P. M., Minneci, M. O., Valenton, J., Kovalchuk, N., Chang, D. T., Horst, K. C. 2020

    Abstract

    During the unprecedented workplace disruption from the corona virus disease 2019 (COVID-19) pandemic, health care workers have been particularly vulnerable to increased work-related stress and anxiety. This may have a negative effect on job performance and personal well-being. Personal safety, job security, and childcare needs are essential concerns that must be addressed by health care organizations to ensure stability of its workforce. In addition, workplace morale is also damaged by the many daily changes brought about by social distancing. Thus, opportunities exist for departments to address the loss of social bonding and cohesiveness needed for successful team building. In this report, we describe the efforts of our departmental workplace culture committee during this pandemic.

    View details for DOI 10.1016/j.adro.2020.07.002

    View details for PubMedID 32838068

    View details for PubMedCentralID PMC7368646

  • A preliminary report of gonadal-sparing TBI using a VMAT technique. Practical radiation oncology Blomain, E. S., Kovalchuk, N., Neilsen, E., Skinner, L., Hoppe, R. T., Hiniker, S. M. 2020

    Abstract

    Reproductive toxicity is common following total body irradiation and has major quality of life implications for patients. In that context, this is the first report of gonadal-sparing VMAT TBI, successfully delivered in a boy and a girl with aplastic anemia. Both patients' VMAT TBI plans demonstrated improved gonadal sparing versus simulated conventional 2D approach (mean testes dose 0.45 Gy VMAT versus 0.72 Gy 2D; mean ovary dose 0.64 Gy VMAT versus 1.47 Gy 2D). PTV coverage was also improved for both cases with the VMAT plan versus conventional 2D plan (2 Gy D90% versus 1.9 Gy D90%, respectively). Given these dosimetric advantages, the present study can serve as a proof-of-concept for further prospective studies evaluating this technique for wider applications in populations receiving TBI.

    View details for DOI 10.1016/j.prro.2020.07.006

    View details for PubMedID 32795616

  • Successful Full-term Pregnancies After High-dose Pelvic Radiotherapy for Ewing Sarcoma: A Case Report. Journal of pediatric hematology/oncology Gutkin, P. M., Chen, E. L., Miller, C. J., Donaldson, S. S., Kovalchuk, N., Callejas, M. J., Hiniker, S. M. 2019

    Abstract

    Survivors of childhood cancer are at risk of long-term sequelae that arise as a consequence of cancer treatment. Radiation and chemotherapy treatment in pediatric female patients can have detrimental impacts on fertility, particularly in those with pelvic tumor involvement. We report 2 successful natural full-term pregnancies with vaginal delivery in a woman 12 years after biopsy, irradiation (55.5Gy), and multi-agent chemotherapy for treatment of pelvic Ewing sarcoma. Both children were born healthy, with no complications in pregnancy or delivery. Fertility preservation and risk assessment following chemotherapy/radiation therapy is evolving, providing new data to effectively counsel and treat young women.

    View details for DOI 10.1097/MPH.0000000000001581

    View details for PubMedID 31415018

  • Incorporating dosimetric features into the prediction of 3D VMAT dose distributions using deep convolutional neural network PHYSICS IN MEDICINE AND BIOLOGY Ma, M., Kovalchuk, N., Buyyounouski, M. K., Xing, L., Yang, Y. 2019; 64 (12)

    View details for DOI 10.1088/1361-6560/ab2146

    View details for Web of Science ID 000518929400007

  • Incorporating dosimetric features into the prediction of 3D VMAT dose distributions using deep convolutional neural network. Physics in medicine and biology Ma, M., Kovalchuk, N., Buyyounouski, M. K., Xing, L., Yang, Y. 2019

    Abstract

    An accurate prediction of achievable dose distribution on a patient specific basis would greatly improve IMRT/VMAT planning in both efficiency and quality. Recently machine learning techniques have been proposed for IMRT dose prediction based on patient's contour information from planning CT. In these existing prediction models geometric/anatomic features were learned for building the dose prediction models and few features that characterize the dosimetric properties of the patients were utilized. In this study we propose a method to incorporate the dosimetric features in the construction of a more reliable dose prediction model based on the deep convolutional neural network (CNN). In addition to the contour information, the dose distribution from a PTV-only plan (i.e., the plan with the best PTV coverage by sacrificing the OARs sparing) is also employed as the model input to build a deep learning based dose prediction model. A database of 60 volumetric modulated arc therapy (VMAT) plans for the prostate cancer patients was used for training. The trained prediction model was then tested on a cohort of 10 cases. Dose difference maps, DVHs, dosimetric endpoints and statistical analysis of the sum of absolute residuals (SARs) were used to evaluate the proposed method. Our results showed that the mean SARs for the PTV, bladder and rectum using our method were 0.007±0.003, 0.035±0.032 and 0.067±0.037 respectively, lower than the SARs obtained with the contours-based method, indicating the potential of the proposed approach in accurately predicting dose distribution.

    View details for PubMedID 31082805

  • Attention-aware fully convolutional neural network with convolutional long short-term memory network for ultrasound-based motion tracking MEDICAL PHYSICS Huang, P., Yu, G., Lu, H., Liu, D., Xing, L., Yin, Y., Kovalchuk, N., Xing, L., Li, D. 2019; 46 (5): 2275?85

    View details for DOI 10.1002/mp.13510

    View details for Web of Science ID 000467556800032

  • Attention-aware Fully Convolutional Neural Network with Convolutional Long Short-Term Memory Network for Ultrasound-Based Motion Tracking. Medical physics Huang, P., Yu, G., Lu, H., Liu, D., Xing, L., Yin, Y., Kovalchuk, N., Xing, L., Li, D. 2019

    Abstract

    PURPOSE: One of the promising options for motion management in radiation therapy (RT) is the use of Linac-compatible robotic-arm-mounted ultrasound imaging system due to its high soft tissue contrast, real-time capability, absence of ionizing radiation and low cost. The purpose of this work is to develop a novel deep learning-based real-time motion tracking strategy for ultrasound image-guided RT.METHODS: The proposed tracker combined the attention-aware Fully Convolutional Neural Network (FCNN) and the Convolutional Long Short-Term Memory network (CLSTM) that is end-to-end trainable. The glimpse sensor module was built inside the attention-aware FCNN to discard majority of background by focusing on a region containing the object of interest. FCNN extracted discriminating spatial features of glimpse to facilitate temporal modeling for CLSTM. The saliency mask computed from CLSTM refined the features particular to the tracked landmarks. Moreover, the multi-task loss strategy including bounding box loss, localization loss, saliency loss, and adaptive loss weighting term was utilized to facilitate training convergence and avoid over/under-fitting. The tracker was tested on the databases provided by MICCAI 2015 challenges, and the ground truth data was obtained with the help of brute force-based template matching technology.RESULTS: The mean tracking error of 0.97 ± 0.52 mm and maximum tracking error of 1.94 mm were observed for 85 point-landmarks across 39 ultrasound cases compared to the ground truth annotations. The tracking speed per frame per landmark with the GPU implementation ranged from 66 and 101 frames per second, which largely exceeded the ultrasound imaging rate.CONCLUSION: The results demonstrated the robustness and accuracy of the proposed deep learning-based motion estimation, despite of the existence of some known shortcomings of ultrasound imaging such as speckle noise. The tracking speed of the system was found to be remarkable, sufficiently fast for real-time applications in RT environment. The approach provides a valuable tool to guide RT treatment with beam gating or multi leaf collimator (MLC) tracking in real time. This article is protected by copyright. All rights reserved.

    View details for PubMedID 30912590

  • Dosimetric features-driven machine learning model for DVH prediction in VMAT treatment planning MEDICAL PHYSICS Ma, M., Kovalchuk, N., Buyyounouski, M. K., Xing, L., Yang, Y. 2019; 46 (2): 857?67

    View details for DOI 10.1002/mp.13334

    View details for Web of Science ID 000459616200041

  • Optimizing efficiency and safety in external beam radiotherapy using automated plan check (APC) tool and six sigma methodology. Journal of applied clinical medical physics Liu, S., Bush, K. K., Bertini, J., Fu, Y., Lewis, J. M., Pham, D. J., Yang, Y., Niedermayr, T. R., Skinner, L., Xing, L., Beadle, B. M., Hsu, A., Kovalchuk, N. 2019; 20 (8): 56?64

    Abstract

    To develop and implement an automated plan check (APC) tool using a Six Sigma methodology with the aim of improving safety and efficiency in external beam radiotherapy.The Six Sigma define-measure-analyze-improve-control (DMAIC) framework was used by measuring defects stemming from treatment planning that were reported to the departmental incidence learning system (ILS). The common error pathways observed in the reported data were combined with our departmental physics plan check list, and AAPM TG-275 identified items. Prioritized by risk priority number (RPN) and severity values, the check items were added to the APC tool developed using Varian Eclipse Scripting Application Programming Interface (ESAPI). At 9 months post-APC implementation, the tool encompassed 89 check items, and its effectiveness was evaluated by comparing RPN values and rates of reported errors. To test the efficiency gains, physics plan check time and reported error rate were prospectively compared for 20 treatment plans.The APC tool was successfully implemented for external beam plan checking. FMEA RPN ranking re-evaluation at 9 months post-APC demonstrated a statistically significant average decrease in RPN values from 129.2 to 83.7 (P < .05). After the introduction of APC, the average frequency of reported treatment-planning errors was reduced from 16.1% to 4.1%. For high-severity errors, the reduction was 82.7% for prescription/plan mismatches and 84.4% for incorrect shift note. The process shifted from 4? to 5? quality for isocenter-shift errors. The efficiency study showed a statistically significant decrease in plan check time (10.1 ± 7.3 min, P = .005) and decrease in errors propagating to physics plan check (80%).Incorporation of APC tool has significantly reduced the error rate. The DMAIC framework can provide an iterative and robust workflow to improve the efficiency and quality of treatment planning procedure enabling a safer radiotherapy process.

    View details for DOI 10.1002/acm2.12678

    View details for PubMedID 31423729

  • Dosimetric Features-Driven Machine Learning Model for DVHs Prediction in VMAT Treatment Planning. Medical physics Ma, M., Kovalchuk, N., Buyyounouski, M. K., Xing, L., Yang, Y. 2018

    Abstract

    PURPOSE: Few features characterizing the dosimetric properties of the patients are included in currently available dose-volume histogram (DVH) prediction models, making it intractable to build a correlative relationship between the input and output parameters. Here we use PTV-only treatment plans of the patients (i.e., the achievable dose distribution in the absence of organs-at-risks (OARs) constraints) to estimate the potentially achievable quality of treatment plans and establish a machine learning-based DVH prediction framework with the use of the dosimetric metric as model input parameters.METHODS: A support vector regression (SVR) approach was used as the backbone of our machine learning model. A database containing volumetric modulated arc therapy (VMAT) plans of 63 prostate cancer patients were used. For each patient, the PTV-only plan was generated first. A correlative relationship between the OAR DVH of the PTV-only plan (model input) and the corresponding DVH of the clinical treatment plan (CTP) (model output) was then established with the 53 training cases. The prediction model was tested by the validation cohort of 10 cases.RESULTS: For the training cohort, the checks of dosimetric endpoints (DEs) indicated that 52 out of 53 plans (98%) were within 10% error bound for bladder, and 45 out of 53 plans (85%) were within 10% error bound for rectum. In the validation tests, 92% and 96% of the DEs were within the 10% error bounds for bladder and rectum respectively, and 8 out of 10 validation plans (80%) were within 10% error bound for both bladder and rectum. The sum of absolute residuals (SAR) achieved mean 0.034 ± 0.028 and 0.046 ± 0.021 for the bladder and rectum, respectively.CONCLUSIONS: A novel dosimetric features-driven machine learning model with the use of PTV-only plan has been established for DVH prediction. The framework is capable of efficiently generating best achievable DVHs for VMAT planning. This article is protected by copyright. All rights reserved.

    View details for PubMedID 30536442

  • Machine Learning Applications in Medical Dosimetry Recent Advancements and Applications in Dosimetry Kovalchuk, N., Xing, L. Nova Publishers. 2018
  • Liver Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy Qian, Y., Weiner , J., Moding, E., Kovalchuk, N., Koong, A., Hong, T., Chang, D. Demos Medical. 2018
  • Dosimetry and Physics Quality Assurance Gastrointestinal Malignancies: A Practical Guide on Treatment Techniques Kovalchuk, N., Niedermayr, T., Russo, S., Chang, D. Springer. 2018
  • Stereotactic body radiotherapy for pediatric hepatocellular carcinoma with central biliary obstruction PEDIATRIC BLOOD & CANCER Hiniker, S. M., Rangaswami, A., Lungren, M. P., Thakor, A. S., Concepcion, W., Balazy, K. E., Kovalchuk, N., Donaldson, S. S. 2017; 64 (6)

    Abstract

    Here, we present the case of a pediatric patient with newly diagnosed hepatocellular carcinoma causing central biliary obstruction and persistently elevated bilirubin of 3.0-4.3 mg/dl despite placement of bilateral internal-external biliary drains. The tumor was not resectable, and the patient was not a candidate for liver transplant due to nodal disease, for chemotherapy due to hyperbilirubinemia, or for local therapies aside from stereotactic body radiotherapy (SBRT). In this report, we discuss the successful use of SBRT in the management of this patient, and its role in allowing the patient to become a candidate for additional therapies.

    View details for DOI 10.1002/pbc.26330

    View details for PubMedID 28436210

  • Stereotactic body radiotherapy for pediatric hepatocellular carcinoma with central biliary obstruction PEDIATRIC BLOOD & CANCER Hiniker, S. M., Rangaswami, A., Lungren, M. P., Thakor, A. S., Concepcion, W., Balazy, K. E., Kovalchuk, N., Donaldson, S. S. 2017; 64 (6)

    View details for DOI 10.1002/pbc.26330

    View details for Web of Science ID 000400616500005

  • Postmastectomy Radiotherapy with and without Reconstruction Radiation Therapy Techniques and Treatment Planning for Breast Cancer. Horst, K., Kovalchuk, N., Marquez, C. Springer. 2016
  • Optimizing efficiency and safety in a radiation oncology department through the use of ARIA 11 Visual Care Path PRACTICAL RADIATION ONCOLOGY Kovalchuk, N., Russo, G. A., Shin, J. Y., Kachnic, L. A. 2015; 5 (5): 295?303

    Abstract

    Visual Care Path (VCP) is a workflow tool within the ARIA 11 Record and Verify System. The purpose of this study was to quantify the impact of VCP implementation on the metrics of efficiency, safety, and staff satisfaction.Our multidisciplinary quality improvement team reviewed the entire process of patient care and constructed VCP modules to chart serial and parallel events from consultation to treatment completion. A failure mode and effects analysis was performed to identify high-risk tasks within existing patient care workflow. Data on timeliness of task completion were collected for 612 patients (6560 tasks) in 3 time phases: pre-VCP, transition, and post-VCP. Errors detected during a physics plan check were also monitored. A survey about the VCP was distributed to all staff to evaluate the impact of the VCP on the department. Descriptive statistics were calculated for the metrics of efficiency, safety, and staff satisfaction.Notable improvements in efficiency and safety were observed. Radiation oncologists' compliance with timely completion of the Simulation Preparation VCP tasks increased from 45.9% ± 14.3% during the pre-VCP phase to 85.8% ± 10.9% during the post-VCP phase. Compliance with Treatment Planning VCP tasks also increased from 52.6% ± 9.9% during the pre-VCP phase to 76.0% ± 9.7% during the post-VCP phase. The monthly defect rate (ratio of plans with errors to the total number of plans checked by a physicist) decreased from 19.1% ± 1.3% during the pre-VCP phase to 5.2% ± 4.1% during the post-VCP phase. Ninety-four percent of staff members responded to the VCP survey; more than 80% of respondents found the VCP to have a favorable impact.Implementation of the VCP in our department improved workflow efficiency, reduced the number of errors, and was very well received within the department.

    View details for DOI 10.1016/j.prro.2015.05.001

    View details for Web of Science ID 000422360300012

    View details for PubMedID 26127009

  • Clinical and treatment factors associated with vaginal stenosis after definitive chemoradiation for anal canal cancer PRACTICAL RADIATION ONCOLOGY Mirabeau-Beale, K., Hong, T. S., Niemierko, A., Ancukiewicz, M., Blaszkowsky, L. S., Crowley, E. M., Cusack, J. C., Drapek, L. C., Kovalchuk, N., Markowski, M., Napolitano, B., Nyamwanda, J., Ryan, D. P., Wolfgang, J., Kachnic, L. A., Wo, J. Y. 2015; 5 (3): E113?E118

    Abstract

    We sought to evaluate the incidence of vaginal stenosis (VS) and identify clinical and treatment factors that predict for VS in female patients with anal cancer treated with definitive chemoradiation.The cohort included 95 consecutive women receiving definitive chemoradiation between 2003 and 2012. All but 1 received intensity modulated radiation therapy; median primary tumor dose 50.4 Gy (range, 41.4-60). A modified National Cancer Institute Common Terminology Criteria for Adverse Events version 4 was used to score VS based on the medical record description of dyspareunia, pain with dilator use, vaginal dryness, or difficult pelvic examination. Ordered logistic regression was performed to assess VS predictors.Median age was 60.4 years (range, 19-97). With median follow-up of 2.5 years, 70 women (74%) had adequate information to assess VS. Of these, VS grade distribution was 21.4% grade 0, 14.3% grade 1, 27.1% grade 2, and 37.1% grade 3. By multivariable ordered logistic regression, younger age (P = .02), higher tumor dose (P = .06), and earlier treatment year (P = .04) were associated with higher grade of VS.VS is a common late complication in women treated definitively with chemoradiation for anal canal cancer. Younger age, higher tumor dose, and earlier year of treatment were associated with a higher grade of stenosis. Prospective investigation into patient reported outcomes is warranted, including sexual function and VS prevention strategies to better understand its effect on long-term survivorship.

    View details for DOI 10.1016/j.prro.2014.09.003

    View details for Web of Science ID 000422354000002

    View details for PubMedID 25424587

  • Radiotherapy Planning PET CLINICS Minh Tam Truong, Kovalchuk, N. 2015; 10 (2): 279?96

    Abstract

    Incorporation of PET/computed tomography (CT) in radiotherapy planning plays a critical role in assisting gross tumor volume delineation for radiotherapy planning and delivery. As radiotherapy techniques evolve to become more conformal with the increasing use of intensity-modulated radiotherapy and stereotactic body radiotherapy, whereby sharp dose gradients exist between the target and adjacent normal tissue, accurate contouring of tumor targets is vital for the success of radiotherapy to achieve cure and locoregional control. This article outlines the integration of PET/CT into radiotherapy planning for head and neck, lung, and other solid tumors.

    View details for DOI 10.1016/j.cpet.2014.12.010

    View details for Web of Science ID 000422075500011

    View details for PubMedID 25829092

  • Volumetric tumor burden and its effect on brachial plexus dosimetry in head and neck intensity-modulated radiotherapy MEDICAL DOSIMETRY Romesser, P. B., Qureshi, M. M., Kovalchuk, N., Minh Tam Truong 2014; 39 (2): 169?73

    Abstract

    To determine the effect of gross tumor volume of the primary (GTV-P) and nodal (GTV-N) disease on planned radiation dose to the brachial plexus (BP) in head and neck intensity-modulated radiotherapy (IMRT). Overall, 75 patients underwent definitive IMRT to a median total dose of 69.96Gy in 33 fractions. The right BP and left BP were prospectively contoured as separate organs at risk. The GTV was related to BP dose using the unpaired t-test. Receiver operating characteristics curves were constructed to determine optimized volumetric thresholds of GTV-P and GTV-N corresponding to a maximum BP dose cutoff of > 66Gy. Multivariate analyses were performed to account for factors associated with a higher maximal BP dose. A higher maximum BP dose (> 66 vs ? 66Gy) correlated with a greater mean GTV-P (79.5 vs 30.8cc; p = 0.001) and ipsilateral GTV-N (60.6 vs 19.8cc; p = 0.014). When dichotomized by the optimized nodal volume, patients with an ipsilateral GTV-N ? 4.9 vs < 4.9cc had a significant difference in maximum BP dose (64.2 vs 59.4Gy; p = 0.001). Multivariate analysis confirmed that an ipsilateral GTV-N ? 4.9cc was an independent predictor for the BP to receive a maximal dose of > 66Gy when adjusted individually for BP volume, GTV-P, the use of a low anterior neck field technique, total planned radiation dose, and tumor category. Although both the primary and the nodal tumor volumes affected the BP maximal dose, the ipsilateral nodal tumor volume (GTV-N ? 4.9cc) was an independent predictor for high maximal BP dose constraints in head and neck IMRT.

    View details for DOI 10.1016/j.meddos.2013.12.004

    View details for Web of Science ID 000336465900009

    View details for PubMedID 24480376

    View details for PubMedCentralID PMC5018050

  • Correlating planned radiation dose to the cochlea with primary site and tumor stage in patients with head and neck cancer treated with intensity-modulated radiation therapy MEDICAL DOSIMETRY Zhang, J., Qureshi, M. M., Kovalchuk, N., Truong, M. 2014; 39 (1): 88?92

    Abstract

    The aim of the study was to determine tumor characteristics that predict higher planned radiation (RT) dose to the cochlea in patients with head and neck cancer (HNC) treated with intensity-modulated radiotherapy (IMRT). From 2004 to 2012, 99 patients with HNC underwent definitive IMRT to a median dose of 69.96Gy in 33 fractions, with the right and left cochlea-vestibular apparatus contoured for IMRT optimization as avoidance structures. If disease involvement was adjacent to the cochlea, preference was given to tumor coverage by prescription dose. Descriptive statistics were calculated for dose-volume histogram planning data, and mean planning dose to the cochlea (from left or right cochlea, receiving the greater amount of RT dose) was correlated to primary site and tumor stage. Mean (standard deviation) cochlear volume was 1.0 (0.60)cm(3) with maximum and mean planned doses of 31.9 (17.5)Gy and 22.1 (13.7)Gy, respectively. Mean planned dose (Gy) to cochlea by tumor site was as follows: oral cavity (18.6, 14.4), oropharynx (21.7, 9.1), nasopharynx (36.3, 10.4), hypopharynx (14.9, 7.1), larynx (2.1, 0.62), others including the parotid gland, temporal bone, and paranasal sinus (33.6, 24.0), and unknown primary (25.6, 6.7). Average mean planned dose (Gy) to the cochlea in T0-T2 and T3-T4 disease was 22.0 and 29.2Gy, respectively (p = 0.019). By site, a significant difference was noted for nasopharynx and others (31.6 and 50.7, p = 0.012) but not for oropharynx, oral cavity, and hypopharynx. Advanced T category predicted for higher mean cochlear dose, particularly for nasopharyngeal, parotid gland, temporal bone, and paranasal sinus HNC sites.

    View details for DOI 10.1016/j.meddos.2013.10.004

    View details for Web of Science ID 000330927800017

    View details for PubMedID 24485054

  • A quantitative assessment of volumetric and anatomic changes of the parotid gland during intensity-modulated radiotherapy for head and neck cancer using serial computed tomography MEDICAL DOSIMETRY Ajani, A. A., Qureshi, M. M., Kovalchuk, N., Orlina, L., Sakai, O., Minh Tam Truong 2013; 38 (3): 238?42

    Abstract

    To evaluate the change in volume and movement of the parotid gland measured by serial contrast-enhanced computed tomography scans in patients with head and neck cancer treated with parotid-sparing intensity-modulated radiotherapy (IMRT). A prospective study was performed on 13 patients with head and neck cancer undergoing dose-painted IMRT to 69.96Gy in 33 fractions. Serial computed tomography scans were performed at baseline, weeks 2, 4, and 6 of radiotherapy (RT), and at 6 weeks post-RT. The parotid volume was contoured at each scan, and the movement of the medial and lateral borders was measured. The patient's body weight was recorded at each corresponding week during RT. Regression analyses were performed to ascertain the rate of change during treatment as a percent change per fraction in parotid volume and distance relative to baseline. The mean parotid volume decreased by 37.3% from baseline to week 6 of RT. The overall rate of change in parotid volume during RT was-1.30% per fraction (-1.67% and-0.91% per fraction in?31Gy and<31Gy mean planned parotid dose groups, respectively, p = 0.0004). The movement of parotid borders was greater in the?31Gy mean parotid dose group compared with the<31Gy group (0.22% per fraction and 0.14% per fraction for the lateral border and 0.19% per fraction and 0.06% per fraction for the medial border, respectively). The median change in body weight was-7.4% (range, 0.75% to-17.5%) during RT. A positive correlation was noted between change in body weight and parotid volume during the course of RT (Spearman correlation coefficient, r = 0.66, p<0.01). Head and neck IMRT results in a volume loss of the parotid gland, which is related to the planned parotid dose, and the patient's weight loss during RT.

    View details for DOI 10.1016/j.meddos.2013.01.007

    View details for Web of Science ID 000323025000003

    View details for PubMedID 23558146

  • Cone-beam computed tomography image guided therapy to evaluate lumpectomy cavity variation before and during breast radiotherapy JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS Minh Tam Truong, Hirsch, A. E., Kovalchuk, N., Qureshi, M. M., Damato, A., Schuller, B., Vassilakis, N., Stone, M., Gierga, D., Willins, J., Kachnic, L. A. 2013; 14 (2): 209?19

    View details for DOI 10.1120/jacmp.v14i2.4243

    View details for Web of Science ID 000315898300018

  • Radiosurgery and Radiotherapy for Benign and Malignant Anterior Skull Base Lesions Rhinology and Endoscopic Skull Base Surgery Romesser, P., Kovalchuk, N., Nawaz, A., Truong, M. Springer. 2013
  • Rectal and Anal Cancer Decision Tools for Radiation Oncology Chin, J., Kovalchuk, N., Kachnic, L. Springer. 2013
  • PET/CT of Cancer Patients: Part 2, Deformable Registration Imaging Before and After Chemotherapy for Radiation Treatment Planning in Head and Neck Cancer AMERICAN JOURNAL OF ROENTGENOLOGY Schoenfeld, J. D., Kovalchuk, N., Subramaniam, R. M., Minh Tam Truong 2012; 199 (5): 968?74

    Abstract

    The purpose of this perspective is to discuss the use of deformable registration as a tool for image fusion to integrate information from PET/CT scans obtained before and after chemotherapy to assist definition of radiation targets in the management of head and neck cancer.The consistent method for target delineation described capitalizes on the capability of deformable registration to compensate for changes in position and accurately represent evolving spatial relationships between normal anatomy and areas at risk of disease.

    View details for DOI 10.2214/AJR.12.8562

    View details for Web of Science ID 000310593000027

    View details for PubMedID 23096167

  • Deformable Registration of Preoperative PET/CT with Postoperative Radiation Therapy Planning CT in Head and Neck Cancer RADIOGRAPHICS Kovalchuk, N., Jalisi, S., Subramaniam, R. M., Truong, M. T. 2012; 32 (5): 1329?41

    Abstract

    In intensity-modulated radiation therapy (IMRT), precise target delineation is important to avoid underdosing areas at risk for recurrence and overdosing adjacent normal tissue. In postoperative radiation therapy of patients with head and neck cancer (HNC), surgical extirpation of tumor, anatomic changes resulting from tissue removal, and surgical reconstruction often obscure anatomic detail and may make it difficult to identify high-risk target volumes at postoperative planning computed tomography (CT). Positron emission tomography (PET)/CT can significantly affect CT-based tumor contours by providing information on both biologic and metabolic features of cancer. To incorporate diagnostic PET/CT into target delineation at postoperative CT, an advanced image registration method is required to overcome significant differences in patient position and anatomy between the imaging studies. Rigid registration can account for only linear or uniform transformation between the imaging datasets within six degrees of freedom (three rotations and three translations). However, deformable registration can account for significant temporal and anatomic changes between the corresponding images by computing nonlinear and nonuniform relationships between the volume elements across the imaging datasets. Use of deformable registration to integrate preoperative PET/CT with postoperative treatment planning CT is a powerful tool for target volume delineation in HNC patients undergoing postoperative IMRT.

    View details for DOI 10.1148/rg.325125008

    View details for Web of Science ID 000308632900011

    View details for PubMedID 22977021

  • Radiation dose to the brachial plexus in head-and-neck intensity-modulated radiation therapy and its relationship to tumor and nodal stage. International journal of radiation oncology, biology, physics Truong, M. T., Romesser, P. B., Qureshi, M. M., Kovalchuk, N., Orlina, L., Willins, J. 2012; 84 (1): 158?64

    Abstract

    The purpose of this retrospective study was to determine tumor factors contributing to brachial plexus (BP) dose in head-and-neck cancer (HNC) patients treated with intensity-modulated radiotherapy (IMRT) when the BP is routinely contoured as an organ at risk (OAR) for IMRT optimization.From 2004 to 2011, a total of 114 HNC patients underwent IMRT to a total dose of 69.96 Gy in 33 fractions, with the right and left BP prospectively contoured as separate OARs in 111 patients and the ipsilateral BP contoured in 3 patients (total, 225 BP). Staging category T4 and N2/3 disease were present in 34 (29.8%) and 74 (64.9%) patients, respectively. During IMRT optimization, the intent was to keep the maximum BP dose to ?60 Gy, but prioritizing tumor coverage over achieving the BP constraints. BP dose parameters were compared with tumor and nodal stage.With a median follow-up of 16.2 months, 43 (37.7%) patients had ?24 months of follow-up with no brachial plexopathy reported. Mean BP volume was 8.2 ± 4.5 cm(3). Mean BP maximum dose was 58.1 ± 12.2 Gy, and BP mean dose was 42.2 ± 11.3 Gy. The BP maximum dose was ?60, ?66, and ?70 Gy in 122 (54.2%), 185 (82.2%), and 203 (90.2%) BP, respectively. For oropharynx, hypopharynx, and larynx sites, the mean BP maximum dose was 58.4 Gy and 63.4 Gy in T0-3 and T4 disease, respectively (p = 0.002). Mean BP maximum dose with N0/1 and N2/3 disease was 52.8 Gy and 60.9 Gy, respectively (p < 0.0001).In head-and-neck IMRT, dose constraints for the BP are difficult to achieve to ?60 to 66 Gy with T4 disease of the larynx, hypopharynx, and oropharynx or N2/3 disease. The risk of brachial plexopathy is likely very small in HNC patients undergoing IMRT, although longer follow-up is required.

    View details for DOI 10.1016/j.ijrobp.2011.10.079

    View details for PubMedID 22300574

    View details for PubMedCentralID PMC5014352

  • Statistical Learning Theory Paradigms Adapted to Breast Cancer Diagnosis / Classification Using Image and Non-Image Clinical Data. Int J Funct Inform Personal Med Land, W., Heine, J., Mizaku, A., Raway, T., Kovalchuk, N., Yang, J. 2008
  • Three-dimensional Representation of Breast Cancer Using X-ray Imaging Emerging Technologies in Breast Imaging and Mammography Kallergi, M., Manohar, A., Kovalchuk, N. American Scientific Publishers. 2006

Footer Links:

Stanford Medicine Resources: