Clinical Focus

  • Internal Medicine

Academic Appointments

  • Clinical Assistant Professor, Medicine

Administrative Appointments

  • Medical Director, Quality Documentation and Outcomes Integrity, Stanford Health Care (2018 - Present)
  • Liaison, Division of Hospital Medicine, Stanford Center for Digital Health (2018 - Present)
  • Co-Director, Stanford School of Medicine, Practice of Medicine, Quarter VI (2017 - Present)
  • Co-Course Director, Stanford School of Medicine, SHIELD Program (2017 - Present)
  • Research Lead, Division of Hospital Medicine, University Hospitalist Group (2016 - Present)
  • Co-Investigator/Clinical Team Member, Stanford Center for Undiagnosed Diseases (2015 - Present)
  • Hospitalist, Division of General Medical Disciplines (2014 - Present)
  • Faculty Mentor, Stanford Internal Medicine Residency Core Faculty Program (2014 - Present)
  • Chief Resident, Stanford Internal Medicine Residency Program (2013 - 2014)

Honors & Awards

  • Finalist, Clinical Vignettes Competition, ACP National Meeting (2017)
  • 1st Place Presentation in the Clinical Vignettes Competition, ACP National Meeting (2016)
  • Henry J. Kaiser Family Foundation Award for Excellence in Clinical Teaching, Stanford University School of Medicine (2016)
  • Rathmann Family Foundation Medical Education Fellow, Stanford (2015-2016)
  • General Medical Disciplines - Division Teaching Award, Stanford Department of Medicine (2015)
  • Philips CT NetForum Publication of the Year - Finalist, UCSF Neurocardiovascular Imaging Laboratory (2009)
  • Research Fellow, Doris Duke Clinical Foundation (2008-2009)
  • Medical Education Excellence Award, American Medical Student Association (2006)
  • Summer Research Fellow, American Heart Association (2006)
  • Member, Phi Beta Kappa (2005)
  • The Dean's Award for Academic Accomplishment, Stanford University (2005)
  • Summer Research Fellow, Howard Hughes Medical Institute (2004)
  • Donald Kennedy Public Service Fellow, Stanford Haas Center for Public Service (2003)
  • Outstanding Service Award, Department of Veterans Affairs Central Office (2003)

Professional Education

  • Residency:Stanford University Internal Medicine Residency Training (2013) CA
  • Medical Education:University of California at San Francisco School of Medicine (2010) CA
  • Board Certification: Internal Medicine, American Board of Internal Medicine (2013)
  • MD, University of California, San Francisco School of Medicine, MD with Certificate in Biomedical Research (2010)
  • BS with Distinction, Stanford University, Major in Biological Sciences, Minor in Philosophy (2005)

Research & Scholarship

Current Research and Scholarly Interests

Since 2005, I have worked on a variety of clinical and translational imaging research projects, under the mentorship of Dr. Max Wintermark.

Since 2012, I have worked on a variety of multi-disciplinary high value care research projects, with a focus on studying interventions related to medical education and clinical decision support systems.



All Publications

  • An Electronic Best Practice Alert Based on Choosing Wisely Guidelines Reduces Thrombophilia Testing in the Outpatient Setting. Journal of general internal medicine Jun, T., Kwang, H., Mou, E., Berube, C., Bentley, J., Shieh, L., Hom, J. 2018

    View details for DOI 10.1007/s11606-018-4663-8

    View details for PubMedID 30215176

  • An Evaluation of Clinical Order Patterns Machine-Learned from Clinician Cohorts Stratified by Patient Mortality Outcomes. Journal of biomedical informatics Wang, J. K., Hom, J., Balasubramanian, S., Schuler, A., Shah, N. H., Goldstein, M. K., Baiocchi, M. T., Chen, J. H. 2018


    OBJECTIVE: Evaluate the quality of clinical order practice patterns machine-learned from clinician cohorts stratified by patient mortality outcomes.MATERIALS AND METHODS: Inpatient electronic health records from 2010-2013 were extracted from a tertiary academic hospital. Clinicians (n=1,822) were stratified into low-mortality (21.8%, n=397) and high-mortality (6.0%, n=110) extremes using a two-sided P-value score quantifying deviation of observed vs. expected 30-day patient mortality rates. Three patient cohorts were assembled: patients seen by low-mortality clinicians, high-mortality clinicians, and an unfiltered crowd of all clinicians (n=1,046, 1,046, and 5,230 post-propensity score matching, respectively). Predicted order lists were automatically generated from recommender system algorithms trained on each patient cohort and evaluated against i) real-world practice patterns reflected in patient cases with better-than-expected mortality outcomes and ii) reference standards derived from clinical practice guidelines.RESULTS: Across six common admission diagnoses, order lists learned from the crowd demonstrated the greatest alignment with guideline references (AUROC range=0.86-0.91), performing on par or better than those learned from low-mortality clinicians (0.79-0.84, P<10-5) or manually-authored hospital order sets (0.65-0.77, P<10-3). The same trend was observed in evaluating model predictions against better-than-expected patient cases, with the crowd model (AUROC mean=0.91) outperforming the low-mortality model (0.87, P<10-16) and order set benchmarks (0.78, P<10-35).DISCUSSION: Whether machine-learning models are trained on all clinicians or a subset of experts illustrates a bias-variance tradeoff in data usage. Defining robust metrics to assess quality based on internal (e.g. practice patterns from better-than-expected patient cases) or external reference standards (e.g. clinical practice guidelines) is critical to assess decision support content.CONCLUSION: Learning relevant decision support content from all clinicians is as, if not more, robust than learning from a select subgroup of clinicians favored by patient outcomes.

    View details for DOI 10.1016/j.jbi.2018.09.005

    View details for PubMedID 30195660

  • Lean-Based Redesign of Multidisciplinary Rounds on General Medicine Service. Journal of hospital medicine Kane, M., Rohatgi, N., Heidenreich, P., Thakur, A., Winget, M., Shum, K., Hereford, J., Shieh, L., Lew, T., Horn, J., Chi, J., Weinacker, A., Seay-Morrison, T., Ahuja, N. 2018


    Multidisciplinary rounds (MDR) facilitate timely communication amongst the care team and with patients. We used Lean techniques to redesign MDR on the teaching general medicine service.To examine if our Lean-based new model of MDR was associated with change in the primary outcome of length of stay (LOS) and secondary outcomes of discharges before noon, documentation of estimated discharge date (EDD), and patient satisfaction.This is a pre-post study. The preperiod (in which the old model of MDR was followed) comprised 4000 patients discharged between September 1, 2013, and October 22, 2014. The postperiod (in which the new model of MDR was followed) comprised 2085 patients between October 23, 2014, and April 30, 2015.Lean-based redesign of MDR.LOS, discharges before noon, EDD, and patient satisfaction.There was no change in the mean LOS. Discharges before noon increased from 6.9% to 10.7% (P < .001). Recording of EDD increased from 31.4% to 41.3% (P < .001). There was no change in patient satisfaction.Lean-based redesign of MDR was associated with an increase in discharges before noon and in recording of EDD.

    View details for DOI 10.12788/jhm.2908

    View details for PubMedID 29394300

  • Reducing Telemetry Use is Safe: A Retrospective Analysis of Rapid Response Team and Code Events After a Successful Intervention to Reduce Telemetry Use American Journal of Medical Quality Xie, L., Svec, D., Hom, J., Ahuja, N., Garg, T., Kaimal, R., Barnes, J., Shieh, L. 2018
  • A Patient with Sjogren’s Syndrome and Subsequent Diagnosis of Inclusion Body Myositis and Light-Chain Amyloidosis. Journal of General Internal Medicine Hom, J., Marwaha, S., Postolova, A., Kittle, J., Vasquez, R., Davidson, J., Kohler, J., Dries, A., Betancourt, L., Majcherska, M., Dearlove, J., Undiagnosed Diseases Network, U., Vogel, H., Bernstein, J., Fisher, P., Ashley, E., Sampson, J., Wheeler, M. 2018
  • Predicting Low Information Laboratory Diagnostic Tests. AMIA Joint Summits on Translational Science proceedings. AMIA Joint Summits on Translational Science Roy, S. K., Hom, J., Mackey, L., Shah, N., Chen, J. H. 2018; 2017: 217–26


    Escalating healthcare costs and inconsistent quality is exacerbated by clinical practice variability. Diagnostic testing is the highest volume medical activity, but human intuition is typically unreliable for quantitative inferences on diagnostic performance characteristics. Electronic medical records from a tertiary academic hospital (2008-2014) allow us to systematically predict laboratory pre-test probabilities of being normal under different conditions. We find that low yield laboratory tests are common (e.g., ~90% of blood cultures are normal). Clinical decision support could triage cases based on available data, such as consecutive use (e.g., lactate, potassium, and troponin are >90% normal given two previously normal results) or more complex patterns assimilated through common machine learning methods (nearly 100% precision for the top 1% of several example labs).

    View details for PubMedID 29888076

    View details for PubMedCentralID PMC5961775

  • A high value care curriculum for interns: a description of curricular design, implementation and housestaff feedback. Postgraduate medical journal Hom, J., Kumar, A., Evans, K. H., Svec, D., Richman, I., Fang, D., Smeraglio, A., Holubar, M., Johnson, T., Shah, N., Renault, C., Ahuja, N., Witteles, R., Harman, S., Shieh, L. 2017


    Most residency programmes do not have a formal high value care curriculum. Our goal was to design and implement a multidisciplinary high value care curriculum specifically targeted at interns.Our curriculum was designed with multidisciplinary input from attendings, fellows and residents at Stanford. Curricular topics were inspired by the American Board of Internal Medicine's Choosing Wisely campaign, Alliance for Academic Internal Medicine, American College of Physicians and Society of Hospital Medicine. Our topics were as follows: introduction to value-based care; telemetry utilisation; lab ordering; optimal approach to thrombophilia work-ups and fresh frozen plasma use; optimal approach to palliative care referrals; antibiotic stewardship; and optimal approach to imaging for low back pain. Our curriculum was implemented at the Stanford Internal Medicine residency programme over the course of two academic years (2014 and 2015), during which 100 interns participated in our high value care curriculum. After each high value care session, interns were offered the opportunity to complete surveys regarding feedback on the curriculum, self-reported improvements in knowledge, skills and attitudinal module objectives, and quiz-based knowledge assessments.The overall survey response rate was 67.1%. Overall, the material was rated as highly useful on a 5-point Likert scale (mean 4.4, SD 0.6). On average, interns reported a significant improvement in their self-rated knowledge, skills and attitudes after the six seminars (mean improvement 1.6 points, SD 0.4 (95% CI 1.5 to 1.7), p<0.001).We successfully implemented a novel high value care curriculum that specifically targets intern physicians.

    View details for DOI 10.1136/postgradmedj-2016-134617

    View details for PubMedID 28663352

  • Using Electronic Best Practice Alerts to Improve Thrombophilia Testing Based on ASH Choosing Wisely Guidelines. Blood Jun, T., Kwang, H., Mou, E., Berube, C., Shah, N., Kaimal, R., Bentley, J., Ahuja, N., Shieh, L., Hom, J. 2017; 130 (3355)
  • Magnitude of Potentially Inappropriate Thrombophilia Testing in the Inpatient Hospital Setting. Journal of hospital medicine Mou, E., Kwang, H., Hom, J., Shieh, L., Kumar, A., Richman, I., Berube, C. 2017; 12 (9): 735–38


    Laboratory costs of thrombophilia testing exceed an estimated $650 million (in US dollars) annually. Quantifying the prevalence and financial impact of potentially inappropriate testing in the inpatient hospital setting represents an integral component of the effort to reduce healthcare expenditures. We conducted a retrospective analysis of our electronic medical record to evaluate 2 years' worth of inpatient thrombophilia testing measured against preformulated appropriateness criteria. Cost data were obtained from the Centers for Medicare and Medicaid Services 2016 Clinical Laboratory Fee Schedule. Of the 1817 orders analyzed, 777 (42.7%) were potentially inappropriate, with an associated cost of $40,422. The tests most frequently inappropriately ordered were Factor V Leiden, prothrombin gene mutation, protein C and S activity levels, antithrombin activity levels, and the lupus anticoagulant. Potentially inappropriate thrombophilia testing is common and costly. These data demonstrate a need for institution-wide changes in order to reduce unnecessary expenditures and improve patient care.

    View details for DOI 10.12788/jhm.2819

    View details for PubMedID 28914278

  • The State of Medical Student Performance Evaluations: Improved Transparency or Continued Obfuscation? Academic medicine Hom, J., Richman, I., Hall, P., Ahuja, N., Harman, S., Harrington, R., Witteles, R. 2016; 91 (11): 1534-1539


    The medical student performance evaluation (MSPE), a letter summarizing academic performance, is included in each medical student's residency application. The extent to which medical schools follow Association of American Medical Colleges (AAMC) recommendations for comparative and transparent data is not known. This study's purpose was to describe the content, interpretability, and transparency of MSPEs.This cross-sectional study examined one randomly selected MSPE from every Liaison Committee on Medical Education-accredited U.S. medical school from which at least one student applied to the Stanford University internal medical residency program during the 2013-2014 application cycle. The authors described the number, distribution, and range of key words and clerkship grades used in the MSPEs and the proportions of schools with missing or incomplete data.The sample included MSPEs from 117 (89%) of 131 medical schools. Sixty schools (51%) provided complete information about clerkship grade and key word distributions. Ninety-six (82%) provided comparative data for clerkship grades, and 71 (61%) provided complete key word data. Key words describing overall performance were extremely heterogeneous, with a total of 72 used and great variation in the assignment of the top designation (median: 24% of students; range: 1%-60%). There was also great variation in the proportion of students awarded the top internal medicine clerkship grade (median: 29%; range: 2%-90%).The MSPE is a critical component of residency applications, yet data contained within MSPEs are incomplete and variable. Approximately half of U.S. medical schools do not follow AAMC guidelines for MSPEs.

    View details for PubMedID 26703411

  • R-SCAN: Imaging for Low Back Pain. Journal of the American College of Radiology Hom, J., Smith, C. D., Ahuja, N., Wintermark, M. 2016; 13 (11): 1385-1386 e1

    View details for DOI 10.1016/j.jacr.2016.06.043

    View details for PubMedID 27595195

  • R-SCAN: Imaging for Uncomplicated Acute Rhinosinusitis. Journal of the American College of Radiology Kroll, H., Hom, J., Ahuja, N., Smith, C. D., Wintermark, M. 2016

    View details for DOI 10.1016/j.jacr.2016.08.018

    View details for PubMedID 27744010

  • Patient Outcomes when Housestaff Exceed 80 Hours per Week. American journal of medicine Ouyang, D., Chen, J. H., Krishnan, G., Hom, J., Witteles, R., Chi, J. 2016; 129 (9): 993-999 e1


    It has been posited that high workload and long work hours for trainees could affect the quality and efficiency of patient care. Duty hour restrictions seek to balance patient care and resident education by limiting resident work hours. Through a retrospective cohort study, we investigate whether patient care on an inpatient general medicine service at a large academic medical center is impacted when housestaff work greater than eighty hours per week METHODS: We identified all admissions to a housestaff-run general medicine service between June 25, 2013 and June 29, 2014. Each hospitalization was classified by whether or not the patient was admitted by housestaff who have worked more than eighty hours a week during their hospitalization. Housestaff computer activity and duty hours were calculated by institutional electronic heath record audit, as well as length of stay and a composite of in-hospital mortality, ICU transfer rate, and 30-day readmission rate.We identified 4,767 hospitalizations by 3,450 unique patients; of which 40.9% of hospitalizations were managed by housestaff who worked more than eighty hours that week during their hospitalization. There was a significantly higher rate of the composite outcome (19.2% vs. 16.7%, p = 0.031) for patients admitted by housestaff working more than eighty hours a week during their hospitalization. We found a statistically significant higher length of stay (5.12 vs. 4.66 days, p = 0.048) and rate of ICU transfer (3.18% vs. 2.38%, p = 0.029). There was no statistically significant difference in 30-day readmission rate (13.7% vs. 12.8%, p = 0.395), or in-hospital mortality rate (3.18% vs. 2.42%, p = 0.115).There was no correlation with team census on admission and patient outcomes.Patients taken care of by housestaff working more than eighty hours a week had increased length of stay and number of ICU transfers. There was no association between resident work-hours and patient in-hospital mortality or 30-day readmission rate.

    View details for DOI 10.1016/j.amjmed.2016.03.023

    View details for PubMedID 27103047

  • Effect of opioid prescribing guidelines in primary care. Medicine Chen, J. H., Hom, J., Richman, I., Asch, S. M., Podchiyska, T., Johansen, N. A. 2016; 95 (35)


    Long-term opioid use for noncancer pain is increasingly prevalent yet controversial given the risks of addiction, diversion, and overdose. Prior literature has identified the problem and proposed management guidelines, but limited evidence exists on the actual effectiveness of implementing such guidelines in a primary care setting.A multidisciplinary working group of institutional experts assembled comprehensive guidelines for chronic opioid prescribing, including monitoring and referral recommendations. The guidelines were disseminated in September 2013 to our medical center's primary care clinics via in person and electronic education.We extracted electronic medical records for patients with noncancer pain receiving opioid prescriptions (Rxs) in seasonally matched preintervention (11/1/2012-6/1/2013) and postintervention (11/1/2013-6/1/2014) periods. For patients receiving chronic (3 or more) opioid Rxs, we assessed the rates of drug screening, specialty referrals, clinic visits, emergency room visits, and quantity of opioids prescribed.After disseminating guidelines, the percentage of noncancer clinic patients receiving any opioid Rxs dropped from 3.9% to 3.4% (P = 0.02). The percentage of noncancer patients receiving chronic opioid Rxs decreased from 2.0% to 1.6% (P = 0.03). The rate of urine drug screening increased from 9.2% to 17.3% (P = 0.005) amongst noncancer chronic opioid patients. No significant differences were detected for other metrics or demographics assessed.An educational intervention for primary care opioid prescribing is feasible and was temporally associated with a modest reduction in overall opioid Rx rates. Provider use of routine drug screening increased, but overall rates of screening and specialty referral remained low despite the intervention. Despite national pressures to introduce opioid prescribing guidelines for chronic pain, doing so alone does not necessarily yield substantial changes in clinical practice.

    View details for DOI 10.1097/MD.0000000000004760

    View details for PubMedID 27583928

  • Fulfilling outpatient medicine responsibilities during internal medicine residency: a quantitative study of housestaff participation with between visit tasks BMC MEDICAL EDUCATION Hom, J., Richman, I., Chen, J. H., Singh, B., Crump, C., Chi, J. 2016; 16


    Internal Medicine residents experience conflict between inpatient and outpatient medicine responsibilities. Outpatient "between visit" responsibilities such as reviewing lab and imaging data, responding to medication refill requests and replying to patient inquiries compete for time and attention with inpatient duties. By examining Electronic Health Record (EHR) audits, our study quantitatively describes this balance between competing responsibilities, focusing on housestaff participation with "between visit" outpatient responsibilities.We examined EHR log-in data from 2012-2013 for 41 residents (R1 to R3) assigned to a large academic center's continuity clinic. From the EHR log-in data, we examined housestaff compliance with "between visit" tasks, based on official clinic standards. We used generalized estimating equations to evaluate housestaff compliance with between visit tasks and amount of time spent on tasks. We examined the relationship between compliance with between visit tasks and resident year of training, rotation type (elective or required) and interest in primary care.Housestaff compliance with logging in to complete "between visit" tasks varied significantly depending on rotation, with overall compliance of 45 % during core inpatient rotations compared to 68 % during electives (p = 0.01). Compliance did not significantly vary by interest in primary care or training level. Once logged in, housestaff spent a mean 53 min per week logged in while on electives, compared to 55 min on required rotations (p = 0.90).Our study quantitatively highlights the difficulty of attending to outpatient responsibilities during busy core inpatient rotations, which comprise the bulk of residency at our institution and at others. Our results reinforce the need to continue development and study of innovative systems for coverage of "between visit" responsibilities, including shared coverage models among multiple residents and shared coverage models between residents and clinic attendings, both of which require a balance between clinic efficiency and resident ownership, autonomy and learning.

    View details for DOI 10.1186/s12909-016-0665-6

    View details for Web of Science ID 000375685100002

    View details for PubMedID 27160008

    View details for PubMedCentralID PMC4862079

  • Internal Medicine Resident Computer Usage: An Electronic Audit of an Inpatient Service. JAMA internal medicine Ouyang, D., Chen, J. H., Hom, J., Chi, J. 2016; 176 (2): 252-254

    View details for DOI 10.1001/jamainternmed.2015.6831

    View details for PubMedID 26642261

  • Prevalence and Financial Impact of Inappropriate Thrombophilia Testing in the Inpatient Hospital Setting: A Retrospective Analysis Blood Mou, E., Kwang, H., Hom, J., Shieh, L., Ahuja, N., Harman, S., Johnson, T., Kumar, A., Shah, N., Witteles, R., Berube, C. 2016; 128 (22 2230)
  • R-SCAN: Imaging for Headache. Journal of the American College of Radiology : JACR Hom, J., Ahuja, N., Smith, C. D., Wintermark, M. 2016; 13 (12 Pt A): 1534–35.e1

    View details for DOI 10.1016/j.jacr.2016.08.020

    View details for PubMedID 28341311

  • Hospitalist intervention for appropriate use of telemetry reduces length of stay and cost. Journal of hospital medicine Svec, D., Ahuja, N., Evans, K. H., Hom, J., Garg, T., Loftus, P., Shieh, L. 2015; 10 (9): 627-632


    Telemetry monitoring is a widely used, labor-intensive, and often-limited resource. Little is known of the effectiveness of methods to guide appropriate use.Our intervention for appropriate use included: (1) a hospitalist-led, daily review of bed utilization, (2) hospitalist-driven education module for trainees, (3) quarterly feedback of telemetry usage, and (4) financial incentives.Hospitalists were encouraged to discuss daily telemetry utilization on rounds. A module on appropriate telemetry usage was taught by hospitalists during the intervention period (January 2013-August 2013) on medicine wards. Pre- and post-evaluations measured changes regarding telemetry use. We compared hospital bed-use data between the baseline period (January 2012-December 2012), intervention period, and extension period (September 2014-March 2015). During the intervention period, hospital bed-use data were sent to the hospitalist group quarterly. Financial incentives were provided after a decrease in hospitalist telemetry utilization.Stanford Hospital, a 444-bed, academic medical center in Stanford, California.Hospitalists saw reductions for both length of stay (LOS) (2.75 vs 2.13 days, P = 0.005) and total cost (22.5% reduction) for telemetry bed utilization in the intervention period. Nonhospitalists telemetry bed utilization remained unchanged. We saw significant improvements in trainee knowledge of the most cost-saving action (P = 0.002) and the least cost-saving action (P = 0.003) in the pre- and post-evaluation analyses. Results were sustained in the hospitalist group, with telemetry LOS of 1.93 days in the extension period.A multipronged, hospitalist-driven intervention to improve appropriate use of telemetry reduces LOS and cost, and increases knowledge of cost-saving actions among trainees.

    View details for DOI 10.1002/jhm.2411

    View details for PubMedID 26149105

  • Leakage Effects. MR and CT Perfusion and Pharmacokinetic Imaging Donahue, K., Hom, J., Boxerman, J., Bammer, R. Lippincott. 2014
  • Hemorrhage MR and CT Perfusion and Pharmacokinetic Imaging Wijman, C., Kassner, A., Hom, J. Lippincott. 2014
  • The electronic health record as a healthcare management strategy and implications for obstetrics and gynecologic practice. Current opinion in obstetrics & gynecology Eisenberg, M., Hom, J., Sharp, C. 2013; 25 (6): 476-481


    To review the current trends, utilities, impacts and strategy for electronic health records (EHRs) as related to obstetrics and gynecology.Adoption and utilization of EHRs are increasing rapidly but variably, given pressures of financial incentives, policy and technological advancement. Adoption is outpacing published evidence, but there is a growing body of descriptive literature regarding incentives, benefits, risks and costs of adoption and utilization. Further, there is a rising body of evidence that EHRs can bring benefits to processes and outcomes, and that their implementation can be considered as a healthcare management strategy. Obstetrics and gynecology practices have specific needs, which must be addressed in the adoption of such technology. Specialty specific literature is sparse but should be considered as part of any strategy aimed at achieving quality improvement and practice behavior change.Obstetrics and gynecologic practice presents unique challenges to the effective adoption and use of EHR technologies, but there is promise as the technologies, integration and usability are rapidly improving. This technology will have an increasing impact on the practice of obstetrics and gynecology in the coming years.

    View details for DOI 10.1097/GCO.0000000000000029

    View details for PubMedID 24185005

  • Multiparametric MRI and CT Models of Infarct Core and Favorable Penumbral Imaging Patterns in Acute Ischemic Stroke STROKE Kidwell, C. S., Wintermark, M., De Silva, D. A., Schaewe, T. J., Jahan, R., Starkman, S., Jovin, T., Hom, J., Jumaa, M., Schreier, J., Gornbein, J., Liebeskind, D. S., Alger, J. R., Saver, J. L. 2013; 44 (1): 73-79


    Objective imaging methods to identify optimal candidates for late recanalization therapies are needed. The study goals were (1) to develop magnetic resonance imaging (MRI) and computed tomography (CT) multiparametric, voxel-based predictive models of infarct core and penumbra in acute ischemic stroke patients, and (2) to develop patient-level imaging criteria for favorable penumbral pattern based on good clinical outcome in response to successful recanalization.An analysis of imaging and clinical data was performed on 2 cohorts of patients (one screened with CT, the other with MRI) who underwent successful treatment for large vessel, anterior circulation stroke. Subjects were divided 2:1 into derivation and validation cohorts. Pretreatment imaging parameters independently predicting final tissue infarct and final clinical outcome were identified.The MRI and CT models were developed and validated from 34 and 32 patients, using 943 320 and 1 236 917 voxels, respectively. The derivation MRI and 2-branch CT models had an overall accuracy of 74% and 80%, respectively, and were independently validated with an accuracy of 71% and 79%, respectively. The imaging criteria of (1) predicted infarct core ≤90 mL and (2) ratio of predicted infarct tissue within the at-risk region ≤70% identified patients as having a favorable penumbral pattern with 78% to 100% accuracy.Multiparametric voxel-based MRI and CT models were developed to predict the extent of infarct core and overall penumbral pattern status in patients with acute ischemic stroke who may be candidates for late recanalization therapies. These models provide an alternative approach to mismatch in predicting ultimate tissue fate.

    View details for DOI 10.1161/STROKEAHA.112.670034

    View details for Web of Science ID 000312883800014

    View details for PubMedID 23233383

  • MRI Blood-Brain Barrier Permeability Measurements to Predict Hemorrhagic Transformation in a Rat Model of Ischemic Stroke TRANSLATIONAL STROKE RESEARCH Hoffmann, A., Bredno, J., Wendland, M. F., Derugin, N., Hom, J., Schuster, T., Zimmer, C., Su, H., Ohara, P. T., Young, W. L., Wintermark, M. 2012; 3 (4): 508-516
  • Delay correction for the assessment of blood-brain barrier permeability using first-pass dynamic perfusion CT. AJNR. American journal of neuroradiology Schneider, T., Hom, J., Bredno, J., Dankbaar, J. W., Cheng, S., Wintermark, M. 2011; 32 (7): E134-8


    Hemorrhagic transformation is a serious potential complication of ischemic stroke with damage to the BBB as one of the contributing mechanisms. BBB permeability measurements extracted from PCT by using the Patlak model can provide a valuable assessment of the extent of BBB damage. Unfortunately, Patlak assumptions require extended PCT acquisition, increasing the risk of motion artifacts. A necessary correction is presented for obtaining accurate BBB permeability measurements from first-pass PCT.

    View details for DOI 10.3174/ajnr.A2152

    View details for PubMedID 20538824

  • Dynamic perfusion-CT assessment of early changes in blood brain barrier permeability of acute ischaemic stroke patients JOURNAL OF NEURORADIOLOGY Dankbaar, J. W., Hom, J., Schneider, T., Cheng, S., Bredno, J., LAU, B. C., van der Schaaf, I. C., Wintermark, M. 2011; 38 (3): 161-166


    Damage to the blood brain barrier (BBB) may lead to haemorrhagic transformation after ischaemic stroke. The purpose of this study was to evaluate the effect of patient characteristics and stroke severity on admission BBB permeability (BBBP) values measured with perfusion-CT (PCT) in acute ischaemic stroke patients.We retrospectively identified 65 patients with proven ischaemic stroke admitted within 12 hours after symptom onset. Patients' charts were reviewed for demographic variables and vascular risk factors. The Patlak's model was applied to calculate BBBP values from the PCT data in the infarct core, penumbra and non-ischaemic tissue in the contralateral hemisphere. Mean BBBP values and their 95% confidence intervals (CI) were calculated in the different tissue types. Effects of demographic variables and risk factors on BBBP were analyzed using a multivariate, generalized estimating equations (GEE) model.BBBP values in the infarct core (mean [95%CI]: 2.48 [2.16-2.85]) and penumbra (2.48 [2.21-2.79]) were significantly higher than in non-ischaemic tissue (2.12 [1.88-2.39]). Multivariate analysis demonstrated that collateral filling has effect on BBBP. Less elevated BBBP values were associated with more than 50% collateral filling.BBBP values are increased in ischaemic brain tissue on the admission PCT scan of acute ischaemic stroke patients. Less abnormally elevated BBBP values were observed in patients with more than 50% collateral filling, possibly explaining why there is a relationship between more collateral filling and a lower incidence of haemorrhagic transformation.

    View details for DOI 10.1016/j.neurad.2010.08.001

    View details for Web of Science ID 000293209800005

    View details for PubMedID 20950860

  • Validation of In Vivo Magnetic Resonance Imaging Blood-Brain Barrier Permeability Measurements by Comparison With Gold Standard Histology STROKE Hoffmann, A., Bredno, J., Wendland, M. F., Derugin, N., Hom, J., Schuster, T., Su, H., Ohara, P. T., Young, W. L., Wintermark, M. 2011; 42 (7): 2054-2060


    We sought to validate the blood-brain barrier permeability measurements extracted from perfusion-weighted MRI through a relatively simple and frequently applied model, the Patlak model, by comparison with gold standard histology in a rat model of ischemic stroke.Eleven spontaneously hypertensive rats and 11 Wistar rats with unilateral 2-hour filament occlusion of the right middle cerebral artery underwent imaging during occlusion at 4 hours and 24 hours after reperfusion. Blood-brain barrier permeability was imaged by gradient echo imaging after the first pass of the contrast agent bolus and quantified by a Patlak analysis. Blood-brain barrier permeability was shown on histology by the extravasation of Evans blue on fluorescence microscopy sections matching location and orientation of MR images. Cresyl-violet staining was used to detect and characterize hemorrhage. Landmark-based elastic image registration allowed a region-by-region comparison of permeability imaging at 24 hours with Evans blue extravasation and hemorrhage as detected on histological slides obtained immediately after the 24-hour image set.Permeability values in the nonischemic tissue (marginal mean ± SE: 0.15 ± 0.019 mL/min 100 g) were significantly lower compared to all permeability values in regions of Evans blue extravasation or hemorrhage. Permeability values in regions of weak Evans blue extravasation (0.23 ± 0.016 mL/min 100 g) were significantly lower compared to permeability values of in regions of strong Evans blue extravasation (0.29 ± 0.020 mL/min 100 g) and macroscopic hemorrhage (0.35 ± 0.049 mL/min 100 g). Permeability values in regions of microscopic hemorrhage (0.26 ± 0.024 mL/min 100 g) only differed significantly from values in regions of nonischemic tissue (0.15 ± 0.019 mL/min 100 g).Areas of increased permeability measured in vivo by imaging coincide with blood-brain barrier disruption and hemorrhage observed on gold standard histology.

    View details for DOI 10.1161/STROKEAHA.110.597997

    View details for Web of Science ID 000292090900054

    View details for PubMedID 21636816

  • Stroke Imaging Research Road Map NEUROIMAGING CLINICS OF NORTH AMERICA Leiva-Salinas, C., Hom, J., Warach, S., Wintermark, M. 2011; 21 (2): 239-?


    Although acute stroke imaging has made significant progress in the last few years, several improvements and validation steps are needed to make stroke-imaging techniques fully operational and appropriate in daily clinical practice. This review outlines the needs in the stroke-imaging field and describes a consortium that was founded to provide them.

    View details for DOI 10.1016/j.nic.2011.01.009

    View details for Web of Science ID 000292007900005

    View details for PubMedID 21640297

  • Blood-Brain Barrier Permeability Assessed by Perfusion CT Predicts Symptomatic Hemorrhagic Transformation and Malignant Edema in Acute Ischemic Stroke AMERICAN JOURNAL OF NEURORADIOLOGY Hom, J., Dankbaar, J. W., Soares, B. P., Schneider, T., Cheng, S., Bredno, J., LAU, B. C., Smith, W., Dillon, W. P., Wintermark, M. 2011; 32 (1): 41-48


    SHT and ME are feared complications in patients with acute ischemic stroke. They occur >10 times more frequently in tPA-treated versus placebo-treated patients. Our goal was to evaluate the sensitivity and specificity of admission BBBP measurements derived from PCT in predicting the development of SHT and ME in patients with acute ischemic stroke.We retrospectively analyzed a dataset consisting of 32 consecutive patients with acute ischemic stroke with appropriate admission and follow-up imaging. We calculated admission BBBP by using delayed-acquisition PCT data and the Patlak model. Collateral flow was assessed on the admission CTA, while recanalization and reperfusion were assessed on the follow-up CTA and PCT, respectively. SHT and ME were defined according to ECASS III criteria. Clinical data were obtained from chart review. In our univariate and forward selection-based multivariate analysis for predictors of SHT and ME, we incorporated both clinical and imaging variables, including age, admission NIHSS score, admission blood glucose level, admission blood pressure, time from symptom onset to scanning, treatment type, admission PCT-defined infarct volume, admission BBBP, collateral flow, recanalization, and reperfusion. Optimal sensitivity and specificity for SHT and ME prediction were calculated by using ROC analysis.In our sample of 32 patients, 3 developed SHT and 3 developed ME. Of the 3 patients with SHT, 2 received IV tPA, while 1 received IA tPA and treatment with the Merci device; of the 3 patients with ME, 2 received IV tPA, while 1 received IA tPA and treatment with the Merci device. Admission BBBP measurements above the threshold were 100% sensitive and 79% specific in predicting SHT and ME. Furthermore, all patients with SHT and ME--and only those with SHT and ME--had admission BBBP measurements above the threshold, were older than 65 years of age, and received tPA. Admission BBBP, age, and tPA were the independent predictors of SHT and ME in our forward selection-based multivariate analysis. Of these 3 variables, only BBBP measurements and age were known before making the decision of administering tPA and thus are clinically meaningful.Admission BBBP, a pretreatment measurement, was 100% sensitive and 79% specific in predicting SHT and ME.

    View details for DOI 10.3174/ajnr.A2244

    View details for Web of Science ID 000287016200008

    View details for PubMedID 20947643

  • Reperfusion Is a More Accurate Predictor of Follow-Up Infarct Volume Than Recanalization A Proof of Concept Using CT in Acute Ischemic Stroke Patients STROKE Soares, B. P., Tong, E., Hom, J., Cheng, S., Bredno, J., Boussel, L., Smith, W. S., Wintermark, M. 2010; 41 (1): E34-E40


    The purpose of this study was to compare recanalization and reperfusion in terms of their predictive value for imaging outcomes (follow-up infarct volume, infarct growth, salvaged penumbra) and clinical outcome in acute ischemic stroke patients. Material andTwenty-two patients admitted within 6 hours of stroke onset were retrospectively included in this study. These patients underwent a first stroke CT protocol including CT-angiography (CTA) and perfusion-CT (PCT) on admission, and similar imaging after treatment, typically around 24 hours, to assess recanalization and reperfusion. Recanalization was assessed by comparing arterial patency on admission and posttreatment CTAs; reperfusion, by comparing the volumes of CBV, CBF, and MTT abnormality on admission and posttreatment PCTs. Collateral flow was graded on the admission CTA. Follow-up infarct volume was measured on the discharge noncontrast CT. The groups of patients with reperfusion, no reperfusion, recanalization, and no recanalization were compared in terms of imaging and clinical outcomes.Reperfusion (using an MTT reperfusion index >75%) was a more accurate predictor of follow-up infarct volume than recanalization. Collateral flow and recanalization were not accurate predictors of follow-up infarct volume. An interaction term was found between reperfusion and the volume of the admission penumbra >50 mL.Our study provides evidence that reperfusion is a more accurate predictor of follow-up infarct volume in acute ischemic stroke patients than recanalization. We recommend an MTT reperfusion index >75% to assess therapy efficacy in future acute ischemic stroke trials that use perfusion-CT.

    View details for DOI 10.1161/STROKEAHA.109.568766

    View details for Web of Science ID 000273093400042

    View details for PubMedID 19910542

  • Age- and anatomy-related values of blood-brain barrier permeability measured by perfusion-CT in non-stroke patients JOURNAL OF NEURORADIOLOGY Dankbaar, J. W., Hom, J., Schneider, T., Cheng, S., LAU, B. C., van der Schaaf, I., Virmani, S., Pohlman, S., Wintermark, M. 2009; 36 (4): 219-227


    The goal of this study was to determine blood-brain barrier permeability (BBBP) values extracted from perfusion-CT (PCT) using the Patlak model and possible variations related to age, gender, race, vascular risk factors and their treatment and anatomy in non-stroke patients.We retrospectively identified 96 non-stroke patients who underwent a PCT study using a prolonged acquisition time up to 3 minutes. Patients' charts were reviewed for demographic data, vascular risk factors and their treatment. The Patlak model was applied to calculate BBBP values in regions of interest drawn within the basal ganglia and the gray and white matter of the different cerebral lobes. Differences in BBBP values were analyzed using a multivariate analysis considering clinical variables and anatomy.Mean absolute BBBP values were 1.2 ml 100 g(-1) min(-1) and relative BBBP/CBF values were 3.5%. Statistical differences between gray and white matter were not clinically relevant. BBBP values were influenced by age, history of diabetes and/or hypertension and aspirin intake.This study reports ranges of BBBP values in non-stroke patients calculated from delayed phase PCT data using the Patlak model. These ranges will be useful to detect abnormal BBBP values when assessing patients with cerebral infarction for the risk of hemorrhagic transformation.

    View details for DOI 10.1016/j.neurad.2009.01.001

    View details for Web of Science ID 000271524500005

    View details for PubMedID 19251320

  • Optimal Duration of Acquisition for Dynamic Perfusion CT Assessment of Blood-Brain Barrier Permeability Using the Patlak Model AMERICAN JOURNAL OF NEURORADIOLOGY Hom, J., Dankbaar, J. W., Schneider, T., Cheng, S., Bredno, J., Wintermark, M. 2009; 30 (7): 1366-1370


    A previous study demonstrated the need to use delayed acquisition rather than first-pass data for accurate blood-brain barrier permeability surface product (BBBP) calculation from perfusion CT (PCT) according to the Patlak model, but the optimal duration of the delayed acquisition has not been established. Our goal was to determine the optimal duration of the delayed PCT acquisition to obtain accurate BBBP measurements while minimizing potential motion artifacts and radiation dose.We retrospectively identified 23 consecutive patients with acute ischemic anterior circulation stroke who underwent a PCT study with delayed acquisition. The Patlak model was applied for the full delayed acquisition (90-240 seconds) and also for truncated analysis windows (90-210, 90-180, 90-150, 90-120 seconds). Linear regression of Patlak plots was performed separately for the full and truncated analysis windows, and the slope of these regression lines was used to indicate BBBP. The full and truncated analysis windows were compared in terms of the resulting BBBP values and the quality of the Patlak fitting.BBBP values in the infarct and penumbra were similar for the full 90- to 240-second acquisition (95% confidence intervals for the infarct and penumbra: 1.62-2.47 and 1.75-2.41 mL x100 g(-1) x min(-1), respectively) and the 90- to 210-second analysis window (1.82-2.76 and 2.01-2.74 mL x 100 g(-1) x min(-1), respectively). BBBP values increased significantly with shorter acquisitions. The quality of the Patlak fit was excellent for the full 90- to 240-second and 90- to 210-second acquisitions, but it degraded with shorter acquisitions.The duration for the delayed PCT acquisition should be at least 210 seconds, because acquisitions shorter than 210 seconds lead to significantly overestimated BBBP values.

    View details for DOI 10.3174/ajnr.A1592

    View details for Web of Science ID 000269169600020

    View details for PubMedID 19369610

  • Dynamic Perfusion CT Assessment of the Blood-Brain Barrier Permeability: First Pass versus Delayed Acquisition AMERICAN JOURNAL OF NEURORADIOLOGY Dankbaar, J. W., Hom, J., Schneider, T., Cheng, S., LAU, B. C., van der Schaaf, I., Virmani, S., Pohlman, S., Dillon, W. P., Wintermark, M. 2008; 29 (9): 1671-1676


    The Patlak model has been applied to first-pass perfusion CT (PCT) data to extract information on blood-brain barrier permeability (BBBP) to predict hemorrhagic transformation in patients with acute stroke. However, the Patlak model was originally described for the delayed steady-state phase of contrast circulation. The goal of this study was to assess whether the first pass or the delayed phase of a contrast bolus injection better respects the assumptions of the Patlak model for the assessment of BBBP in patients with acute stroke by using PCT.We retrospectively identified 125 consecutive patients (29 with acute hemispheric stroke and 96 without) who underwent a PCT study by using a prolonged acquisition time up to 3 minutes. The Patlak model was applied to calculate BBBP in ischemic and nonischemic brain tissue. Linear regression of the Patlak plot was performed separately for the first pass and for the delayed phase of the contrast bolus injection. Patlak linear regression models for the first pass and the delayed phase were compared in terms of their respective square root mean squared errors (square root MSE) and correlation coefficients (R) by using generalized estimating equations with robust variance estimation.BBBP values calculated from the first pass were significantly higher than those from the delayed phase, both in nonischemic brain tissue (2.81 mL x 100 g(-1) x min(-1) for the first pass versus 1.05 mL x 100 g(-1) x min(-1) for the delayed phase, P < .001) and in ischemic tissue (7.63 mL x 100 g(-1) x min(-1) for the first pass versus 1.31 mL x 100 g(-1) x min(-1) for the delayed phase, P < .001). Compared with regression models from the first pass, Patlak regression models obtained from the delayed data were of better quality, showing significantly lower square root MSE and higher R.Only the delayed phase of PCT acquisition respects the assumptions of linearity of the Patlak model in patients with and without stroke.

    View details for DOI 10.3174/ajnr.A1203

    View details for Web of Science ID 000260023800015

    View details for PubMedID 18635616

  • Accuracy and Anatomical Coverage of Perfusion CT Assessment of the Blood-Brain Barrier Permeability: One Bolus versus Two Boluses CEREBROVASCULAR DISEASES Dankbaar, J. W., Hom, J., Schneider, T., Cheng, S., Lau, B. C., van der Schaaf, I., Virmani, S., Pohlman, S., Dillon, W. P., Wintermark, M. 2008; 26 (6): 600-605


    To assess whether blood-brain barrier permeability (BBBP) values, extracted with the Patlak model from the second perfusion CT (PCT) contrast bolus, are significantly lower than the values extracted from the first bolus in the same patient.125 consecutive patients (29 with acute hemispheric stroke and 96 without stroke) who underwent a PCT study using a prolonged acquisition time up to 3 min were retrospectively identified. The Patlak model was applied to calculate the rate of contrast leakage out of the vascular compartment. Patlak plots were created from the arterial and parenchymal time enhancement curves obtained in multiple regions of interest drawn in ischemic brain tissue and in nonischemic brain tissue. The slope of a regression line fit to the Patlak plot was used as an indicator of BBBP. Square roots of the mean squared errors and correlation coefficients were used to describe the quality of the linear regression model. This was performed separately for the first and the second PCT bolus. Results from the first and the second bolus were compared in terms of BBBP values and the quality of the linear model fitted to the Patlak plot, using generalized estimating equations with robust variance estimation.BBBP values from the second bolus were not lower than BBBP values from the first bolus in either nonischemic brain tissue [estimated mean with 95% confidence interval: 1.42 (1.10-1.82) ml x 100 g(-1) x min(-1) for the first bolus versus 1.64 (1.31-2.05) ml x 100 g(-1) x min(-1) for the second bolus, p = 1.00] or in ischemic tissue [1.04 (0.97-1.12) ml x 100 g(-1) x min(-1) for the first bolus versus 1.19 (1.11-1.28) ml x 100 g(-1)min(-1) for the second bolus, p = 0.79]. Compared to regression models from the first bolus, the Patlak regression models obtained from the second bolus were of similar or slightly better quality. This was true both in nonischemic and ischemic brain tissue.The contrast material from the first bolus of contrast for PCT does not negatively influence measurements of BBBP values from the second bolus. The second bolus can thus be used to increase anatomical coverage of BBBP assessment using PCT.

    View details for DOI 10.1159/000165113

    View details for Web of Science ID 000261132400005

    View details for PubMedID 18946215

  • Quantitative Assessment of the Impact of the Service-Learning Course “Mental Health and the Veteran Population: Case Study and Practicum” on Undergraduate Students. Stanford Undergraduate Research Journal Hom J., Bahl M. 2006; 5: 24-30
  • Service-Learning Courses at Stanford: How to Make a Good Thing Even Better. Public Service Education at Stanford: The Haas Center's First Twenty Years Hom, J. Stanford University Press. 2005