Luke Yoon, MD, is a Clinical Associate Professor and Associate Chair of Faculty Well-being and Development in the Department of Radiology at Stanford University School of Medicine. Dr. Yoon is a radiologist specializing in body imaging and musculoskeletal imaging. A graduate of Yale College and Yale School of Medicine, Dr. Yoon completed his post-graduate training at Harvard affiliated hospitals: internal medicine internship at Brigham and Women’s Hospital, and radiology residency and fellowship at Massachusetts General Hospital. Prior to joining Stanford Radiology, Dr. Yoon worked as an attending radiologist at Brigham and Women’s Hospital, Singleton Associates, and Baylor College of Medicine. His clinical interests include physician well-being, cystic renal mass imaging, and liver mass classification.

Clinical Focus

  • Body Imaging
  • Musculoskeletal Imaging
  • Physician Well-being

Academic Appointments

  • Clinical Associate Professor, Radiology

Administrative Appointments

  • Associate Chair of Faculty Well-being and Development, Department of Radiology, Stanford School of Medicine (2023 - Present)
  • Director of Faculty Well-being, Department of Radiology, Stanford School of Medicine (2021 - 2023)
  • Associate Professor, Baylor College of Medicine (2017 - 2019)
  • Clinical Assistant Professor, Baylor College of Medicine (2009 - 2017)
  • Adjunct Assistant Professor, MD Anderson Cancer Center (2009 - 2019)
  • Instructor, Harvard Medical School (2008 - 2008)

Professional Education

  • Board Certification: American Board of Radiology, Diagnostic Radiology (2007)
  • Fellowship: Massachusetts General Hospital Body Imaging Fellowship (2007) MA
  • Residency: Massachusetts General Hospital Radiology Residency (2007) MA
  • Internship: Brigham and Women's Hospital Internal Medicine Residency (2003) MA
  • Medical Education: Yale School Of Medicine (2002) CT
  • Undergraduate Education, Yale University (1997)

All Publications

  • Top down and bottom up: A review of strategies for wellness programs in academic radiology. Clinical imaging Yoon, L., Desser, T., Jokerst, C., Snyder, E., Kennedy, T., Korngold, E., Azour, L. 2024; 109: 110131


    Formal physician-wellness programs have come into vogue in professional organizations in recent years. Wellness programs in academic centers vary from institution to institution but foundational to all is their aim to reduce burnout and increase professional fulfillment. As radiologists in charge of wellness program implementation in different academic institutions, we describe existing academic radiology wellness programs with two detailed examples. Physician well-being programs need to be both leadership-driven (i.e., "top down") and receptive to feedback ("bottom up").

    View details for DOI 10.1016/j.clinimag.2024.110131

    View details for PubMedID 38490079

  • World Health Organization (WHO) 2022 Classification Update: Radiologic and Pathologic Features of Papillary Renal Cell Carcinomas. Academic radiology Shen, L., Yoon, L., Mullane, P. C., Liang, T., Tse, J. R. 2024


    To describe imaging and pathology features of newly defined papillary renal cell carcinoma (pRCC) based on the WHO 2022 update.This retrospective study included 87 patients with 93 pathologically proven papillary renal cell carcinomas who underwent pre-treatment renal mass protocol CT or MRI. Baseline and post-treatment follow-up imaging was evaluated by two radiologists systematically based on established lexicon.At pathology, 63 (68%) were grade 1-2, 29 (31%) were grade 3-4, and 1 (%) was unreported. At surgical pathology, 84 (90%) were localized (≤pT2b), 5 (5%) were pT3a, and none were ≥pT3b; 4 (4%) had unknown pT stage (core biopsies). 33 (35%) had necrosis and 39 (41%) had hemorrhage. None had sarcomatoid or rhabdoid differentiation. At imaging, 73 (83%) were solid and 16 (17%) were cystic. Of 16 cystic masses, four were Bosniak class IIF (three were heterogeneously T1 hyperintense) and 12 were class IV. All were well-circumscribed. 92 (99%) were hypovascular. Median follow-up for 74 patients was 30 months (IQR 12-56). One untreated patient had non-regional nodal metastasis at presentation, and one patient had metastasis to lymph nodes and bones after surgery, but the patient had unresected renal masses elsewhere without pathology. Otherwise, no recurrence or metastases were detected.Most pRCCs present as a hypovascular, circumscribed, solid renal mass. A few pRCCs present as the newly defined Bosniak class IIF subtype. Our results can form the basis of a non-invasive, likelihood score to identify this relatively indolent pathology in the era of virtual biopsy and active surveillance.

    View details for DOI 10.1016/j.acra.2024.01.034

    View details for PubMedID 38365492

  • Risk of malignancy in T1-hyperintense Bosniak version 2019 class II and IIF cystic renal masses. Abdominal radiology (New York) Shen, L., Tse, J. R., Lemieux, S., Yoon, L., Mullane, P. C., Liang, T., Davenport, M. S., Pedrosa, I., Silverman, S. G. 2023


    Bosniak classification version 2019 includes cystic masses in class II and IIF based partly on their hyperintense appearance at T1-weighted MRI. The prevalence of malignancy in non-enhancing heterogeneously T1-hyperintense masses is unknown, nor whether the pattern of T1 hyperintensity affects malignancy likelihood.To determine the malignancy proportion among six patterns of T1 hyperintensity within non-enhancing cystic renal masses.This retrospective, single-institution study included 72 Bosniak class II and IIF, non-enhancing, T1-hyperintense cystic renal masses. Diagnosis was confirmed by histopathology or by follow-up imaging demonstrating 5-year size and morphologic stability, decreased in size by ≥ 30%, resolution, or Bosniak down-classification. Six patterns of T1 hyperintensity were pre-defined: homogeneous (pattern A), fluid-fluid level (pattern B), peripherally markedly T1-hyperintense (pattern C), containing a T1-hyperintense non-enhancing nodule (pattern D), peripherally T1-hypointense (pattern E), and heterogeneously T1-hyperintense without a distinct pattern (pattern F). Three readers independently assigned each mass to a pattern. Individual and mean malignancy proportion were determined. Mann-Whitney test and Fischer's exact test compared the likelihood of malignancy between patterns. Inter-reader agreement was analyzed with Gwet's agreement coefficient (AC).Among 72 masses, the mean number of masses assigned was 11 (15%) to pattern A, 21 (29%) to pattern B, 6 (8%) to pattern C, 7 (10%) to pattern D, 5 (7%) to pattern E, and 22 (31%) to pattern F. Five of 72 masses (7%) were malignant; none was assigned pattern A, B, or D. Mean malignancy proportion was 5% (0/9, 1/6, and 0/4) for pattern C, 13% (0/4, 1/3, and 1/7) for pattern E, and 18% (5/20, 3/21, and 4/25) for pattern F. Malignant masses were more likely assigned to pattern E or F (p = 0.003-0.039). Inter-reader agreement was substantial (Gwet's AC: 0.68).Bosniak version 2019 class IIF masses that are non-enhancing and heterogeneously T1-hyperintense with a fluid-fluid level are likely benign. Those that are non-enhancing and heterogeneously T1-hyperintense without a distinct pattern have a malignancy proportion up to 25% (5/20).

    View details for DOI 10.1007/s00261-023-03955-5

    View details for PubMedID 37202641

    View details for PubMedCentralID 2550668

  • Growth Kinetics of Pancreatic Neuroendocrine Neoplasms by Histopathologic Grade. Pancreas Cao, J. J., Shen, L., Visser, B. C., Yoon, L., Kamaya, A., Tse, J. R. 2023; 52 (2): e135-e143


    The aims of the study are to describe the growth kinetics of pathologically proven, treatment-naive pancreatic neuroendocrine neoplasms (panNENs) at imaging surveillance and to determine their association with histopathologic grade and Ki-67.This study included 100 panNENs from 95 patients who received pancreas protocol computed tomography or magnetic resonance imaging from January 2005 to July 2022. All masses were treatment-naive, had histopathologic correlation, and were imaged with at least 2 computed tomography or magnetic resonance imaging at least 90 days apart. Growth kinetics was assessed using linear and specific growth rate, stratified by grade and Ki-67. Masses were also assessed qualitatively to determine other possible imaging predictors of grade.There were 76 grade 1 masses, 17 grade 2 masses, and 7 grade 3 masses. Median (interquartile range) linear growth rates were 0.06 cm/y (0-0.20), 0.40 cm/y (0.22-1.06), and 2.70 cm/y (0.41-3.89) for grade 1, 2, and 3 masses, respectively (P < 0.001). Linear growth rate correlated with Ki-67 with r2 of 0.623 (P < 0.001). At multivariate analyses, linear growth rate was the only imaging feature significantly associated with grade (P = 0.009).Growth kinetics correlate with Ki-67 and grade. Grade 1 panNENs grow slowly versus grade 2-3 panNENs.

    View details for DOI 10.1097/MPA.0000000000002221

    View details for PubMedID 37523605

  • Diagnostic performance of hypoechoic perinephric fat as a predictor of prediabetes and diabetes. Abdominal radiology (New York) Shen, L., Tse, J. R., Negrete, L. M., Shon, A., Yoon, L., Liang, T., Kamaya, A. 2022


    To evaluate prevalence and predictive value of hypoechoic perinephric fat (HPF) in patients with prediabetes and diabetes compared to non-diabetics.Of 240 patients with renal ultrasound and hemoglobin A1c (HbA1c) measurements, 114 patients had either prediabetes (HbA1c 5.7-6.4%) or diabetes (HbA1c ≥ 6.5%), and 126 patients did not. Two radiologists (blinded to diagnosis) reviewed images and discrepancies were resolved by a third. Inter-reader agreement was compared using free-marginal kappa and intraclass correlation coefficient. Fisher's exact test, Mann-Whitney test, multivariable logistic regression, and Spearman's rank correlation test with two-tailed p < 0.05 were used to determine statistical significance.HPF was exclusively identified in prediabetic and diabetic patients with a prevalence of 23% (vs 0%; p < 0.001). Identification of HPF had almost perfect inter-reader agreement (k = 0.94) and was statistically significant (p = 0.034) while controlling for body mass index (BMI) and estimated glomerular filtration rate in multivariable analysis. HPF had extremely high specificity and positive predictive value (100% for both) in patients with prediabetes and diabetes although it was not a sensitive finding (23% sensitivity). In patients with prediabetes and diabetes, those with HPF were statistically significantly more likely to have chronic kidney disease (CKD) (p = 0.003). There was no statistically significant difference in BMI, stages of CKD, and types of diabetes.Hypoechoic perirenal fat has almost perfect inter-reader agreement and is highly specific for and predictive of prediabetes and diabetes. Its presence may also help identify those with chronic kidney disease among prediabetic and diabetic patients.

    View details for DOI 10.1007/s00261-022-03763-3

    View details for PubMedID 36480029

  • Outcomes of Bosniak Classification Version 2019 Class IIF Cystic Renal Masses at Imaging Surveillance. AJR. American journal of roentgenology Shen, L., Yoon, L., Chung, B. I., Kamaya, A., Tse, J. R. 2022


    Background: Bosniak classification system version 2019 (v2019) recommends that class IIF masses undergo follow-up imaging at 6 months, 12 months, and then annually for 5 years. The frequency and timing of upgrade on follow-up imaging are incompletely understood. Purpose: To describe the temporal evolution of Bosniak v2019 class IIF cystic renal masses, with attention to outcomes at 6-month follow-up, time to class upgrade, and malignant histologic diagnoses. Methods: This retrospective study included 219 patients (91 women, 128 men; median age, 72 years) with 246 localized class IIF masses from January 2005 to June 2022. Patients underwent both a baseline and at least one follow-up renal-mass protocol contrast-enhanced CT or MRI. Two radiologists evaluated masses at all follow-up time points to categorize masses as downgraded (class I or II), stable (localized class IIF), or upgraded (class III or IV, solid, or ≥T3a, N1, or M1 disease); a third radiologist resolved discrepancies. Incidence rate of upgrade was determined. Histopathologic outcomes were assessed for resected masses. Results: Median follow-up was 28.4 months (IQR, 13.7-59.4 months). At 6-month follow-up, 5 (2%) masses were downgraded, 241 (98%) were stable, and none were upgraded. Based on final follow-up, 14 (6%) masses were downgraded, 223 (91%) were stable, and 9 (4%) were upgraded. All upgrade events entailed a class increase to III (n=7) or IV (n=2); no mass became solid or developed T3, N1, or M1 disease. Among the nine upgraded masses, median time to upgrade was 53.5 months (IQR, 23.2-63.7 months). Incidence rate of upgrade was 3.006 per 100,000 person-days (95% CI, 1.466-5.516). Ten masses were resected; histopathology was benign in six, and malignant in four. Of the four malignant masses, one was upgraded to class III after 15 months of preoperative follow-up imaging, and three remained class IIF on preoperative follow-up imaging. No resected malignant mass developed postoperative recurrence. Conclusion: Bosniak v2019 class IIF masses are unlikely to represent aggressive malignancy; only 4% were upgraded over time, and never on initial 6-month follow-up. Clinical Impact: The currently recommended initial 6-month follow-up imaging examination for class IIF masses is of questionable clinical utility.

    View details for DOI 10.2214/AJR.22.28599

    View details for PubMedID 36416398

  • Positive predictive value of LI-RADS US-3 observations: multivariable analysis of clinical and imaging features. Abdominal radiology (New York) Tse, J. R., Shen, L., Tiyarattanachai, T., Bird, K. N., Liang, T., Yoon, L., Kamaya, A. 2022


    PURPOSE: To determine how clinical and imaging features affect the positive predictive values (PPV) of US-3 observations.METHODS: In this retrospective study, 10,546 adult patients who were high risk for hepatocellular carcinoma (HCC) from 2017 to 2021 underwent ultrasound screening/surveillance. Of these, 225 adult patients (100 women, 125 men) with an US-3 observation underwent diagnostic characterization with multiphasic CT (93; 41%), MRI (130; 58%), or contrast-enhanced ultrasound (2; 1%). US-3 observations included focal observations≥10mm in 216 patients and new venous thrombi in 9 patients. PPV with 95% confidence intervals were calculated using diagnostic characterization as the reference standard. Multivariable analysis of clinical and imaging features was performed to determine the strongest associations with cancer.RESULTS: Overall PPV for an US-3 observationwas 33% (27-39%) for at least intermediate probability of cancer (≥LR-3) and 15% (10-20%) for at least probable cancer (≥LR-4). At multivariable analysis, cirrhosis had the strongest effect size for at least probable cancer (p<0.001; odds ratio OR 20.4), followed by observation size (p<0.001; OR 2.65) and age (p=0.004; OR 1.05). Alpha-fetoprotein, visualization score, and observation echogenicity were not statistically significant associations. Modality (MRI versus CT) did not affect PPV. Due to the large effect of cirrhosis, PPV was then stratified by the presence (n=116; 52%) or absence (n=109; 48%) of cirrhosis. For at least probable cancer (≥LR-4), PPV increased from 4% (0-7%; non-cirrhotic) to 26% (18-34%; p<0.001; cirrhosis).CONCLUSION: Cirrhosis most strongly affects PPV of US-3 observations for at least probable cancer at diagnostic characterization among high-risk patients, increasing to 1 in 4 among cirrhotic patients from 1 in 25 among non-cirrhotic patients.

    View details for DOI 10.1007/s00261-022-03681-4

    View details for PubMedID 36253490

  • Predictive value and prevalence of refractive edge shadow in diagnosis of ovarian dermoids. Abdominal radiology (New York) Shen, L., Tse, J. R., Negrete, L. M., Lo, E., Yoon, L., Kamaya, A. 2022


    To evaluate the diagnostic performance of refractive edge shadow in evaluation of ovarian dermoids compared to other benign adnexal masses.Ultrasound images of 139 patients with 154 dermoids, endometriomas, and hemorrhagic cysts were retrospectively reviewed by 3 radiologists blinded to final diagnosis. Ultrasound and clinical features were compared to pathology or follow-up ultrasound results as reference standard. Inter-reader agreements with free-marginal kappa and diagnostic performance were evaluated. The former was compared using Fisher's exact test or Mann-Whitney test with p < 0.05 to determine statistical significance.The study sample consisted of 154 lesions: 50 dermoids, 50 endometriomas, and 54 hemorrhagic cysts. Refractive edge shadow, homogeneous echogenic appearance, tip of the iceberg sign, mural echogenic nodule, echogenic shadowing focus, and dot-dash sign all were statistically significant across all readers for the diagnosis of dermoid. Prevalence of each feature in dermoids compared to other entities were as follows: refractive edge shadow (70% vs 8%; p < 0.001), homogeneously echogenic appearance (34% vs 2%; p < 0.001), tip of the iceberg sign (16% vs 1%; p < 0.001), mural echogenic nodule (38% vs 2%; p < 0.001), echogenic shadowing focus (13% vs 1%; p < 0.001), and dot-dash sign (44% vs 1%; p < 0.001). Refractive edge shadow had the highest sensitivity, negative predictive value, and accuracy among all ultrasound features associated with dermoids (70%, 86%, and 85%, respectively).Refractive edge shadow is a promising ultrasound feature for diagnosis of dermoids, with the highest diagnostic accuracy and prevalence compared to other previously described features associated with dermoids.

    View details for DOI 10.1007/s00261-022-03666-3

    View details for PubMedID 36098759

  • Clinical and ultrasound features of dermoid-associated adnexal torsion. Abdominal radiology (New York) Shen, L., Tse, J. R., Negrete, L. M., Flory, M. N., Yoon, L., Kamaya, A. 2022


    To determine the clinical and ultrasound features of dermoid-associated adnexal torsion.Forty-four patients with at least one dermoid and ultrasound ≤ 30 days of surgery were retrospectively reviewed by three radiologists. Ultrasound and clinical findings were compared to intra-operative findings using Fisher's exact test or Mann-Whitney test with p < 0.05 to determine statistical significance.Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.Correct. No edit RESULTS: Twenty patients had torsion, while 24 patients did not. Patients with dermoid-associated torsion were more likely to present to emergency department (ED) (100% vs 13%; p < 0.001) and have acute unilateral pelvic pain (100% vs 42%; p < 0.001). On ultrasound, patients with torsion had larger dermoids (median largest dimension 9.0 cm (IQR 7.7-11.1) vs 6.0 cm (IQR 4.4-7.5); p < 0.001), displaced dermoid anterior or superior to the uterus (59% vs 21%; p = 0.016), and ipsilateral adnexal fluid (41% vs 4%; p = 0.003). Displaced dermoid and ipsilateral adnexal fluid had substantial (kappa = 0.72) and moderate inter-rater agreement (kappa = 0.49), respectively. The combination of ED presentation and each statistically significant ultrasound feature (dermoid size ≥ 5.0 cm, displaced dermoid, and ipsilateral adnexal fluid) yielded high specificity and positive predictive value (ranging from 93-100% to 92-100%, respectively). The combination of ED presentation and dermoid size ≥ 5.0 cm yielded the highest sensitivity, negative predicative value, and accuracy (100%, 100%, and 96%, respectively).Please check and confirm whether the edit made to the article title is in order.Looks great. No edits. Thank you!Although the diagnosis of adnexal torsion in the presence of an ovarian dermoid is traditionally challenging, the combination of ED presentation and ultrasound features increase diagnostic confidence of dermoid-associated adnexal torsion.

    View details for DOI 10.1007/s00261-022-03601-6

    View details for PubMedID 35809127

  • Nyquist sampling theorem and Bosniak classification, version 2019: effect of thin axial sections on categorization and agreement. European radiology Tse, J. R., Shen, L., Shen, J., Yoon, L., Kamaya, A. 2022


    To determine if CT axial images reconstructed at current standard of care (SOC; 2.5-3 mm) or thin (≤ 1 mm) sections affect categorization and inter-rater agreement of cystic renal masses assessed with Bosniak classification, version 2019.In this retrospective single-center study, 3 abdominal radiologists reviewed 131 consecutive cystic renal masses from 100 patients performed with CT renal mass protocol from 2015 to 2021. Images were reviewed in two sessions: first with SOC and then the addition of thin sections. Individual and overall categorizations are reported, latter of which is based on majority opinion with 3-way discrepancies resolved by a fourth reader. Major categorization changes were defined as differences between classes I-II, IIF, or III-IV.Thin sections led to a statistically significant major category change with class II for all readers individually (p = 0.004-0.041; McNemar test), upgrading 10-17% of class II masses, most commonly to class IIF followed by III. Modal reason for upgrades was due to identification of additional septa followed by larger measurement of enhancing features. Masses categorized as class I, III, or IV on SOC sections were unaffected, as were identification of protrusions. Inter-rater agreements using weighted Cohen's kappa were 0.679 for SOC and 0.691 for thin sections (both substantial).Thin axial sections upgraded up to one in six class II masses to IIF or III through identification of additional septa or larger feature. Other classes, including III-IV, were unaffected. Inter-rater agreements were substantial regardless of section thickness.• Thin axial sections (≤ 1 mm) compared to standard of care sections (2.5-3 mm) led to identification of additional septa but did not affect identification of protrusions. • Thin axial sections (≤ 1 mm) compared to standard of care sections (2.5-3 mm) can upgrade a small proportion of cystic renal masses from class II to IIF or III when applying Bosniak classification, version 2019. • Inter-rater agreements were substantial regardless of section thickness.

    View details for DOI 10.1007/s00330-022-08876-3

    View details for PubMedID 35705828

  • Outcomes of LI-RADS US-2 Subthreshold Observations Detected on Surveillance Ultrasound. AJR. American journal of roentgenology Tse, J. R., Shen, L., Bird, K. N., Yoon, L., Kamaya, A. 2022


    Background: Ultrasound LI-RADS version 2017 recommends that patients with US-2 subthreshold observations undergo repeat surveillance ultrasound in 3-6 months and return to routine surveillance if the observation shows no growth for 2 years. However, outcomes of US-2 observations are unknown. Objective: To determine imaging outcomes of US-2 observations detected on surveillance ultrasound examinations. Methods: This retrospective study included 175 patients (median age, 59 years; 70 women, 105 men) at high risk for hepatocellular carcinoma (HCC) with US-2 observations (i.e., subcentimeter observations) on surveillance ultrasound. Observations were classified on ≥2-year follow-up ultrasound as showing no correlate, stable (if remaining subcentimeter), or progressed (if measuring ≥10 mm, meeting US-3 criteria). Observations were classified on follow-up multiphasic CT or MR (stratified as <2-year vs ≥2-year follow-up) as showing no correlate or, if showing a correlate, using CT/MRI LI-RADS version 2018. Results: A total of 111 patients had ≥2-year follow-up ultrasound and 106 had follow-up CT or MRI (79 before 2 years, 27 after 2 years). Based on final follow-up examinations, 173/175 observations were stable on ≥2-year follow-up ultrasound (n=68); showed no correlate on follow-up ultrasound, CT, or MRI (n=88); or were classified as LR-1 or LR-2 on CT or MRI (n=17). The remaining 2/175 observations were LR-3 on CT or MRI. No observations progressed to US-3 on follow-up ultrasound or were classified as ≥LR-4 on CT or MRI. A correlate was observed in 25 of the 106 follow-up CT or MRI examinations, (LR-1 or LR-2 in 23; LR-3 in 2). Eight patients developed HCC at a median of 2.0 years after initial US-2 observation detection; all HCCs were in separate locations from the baseline observations and were preceded by a surveillance ultrasound that could not re-identify the baseline observation. In three patients who underwent liver transplant, the explant showed no dysplastic nodule or HCC. Conclusion: US-2 subthreshold observations are unlikely to progress or become HCC and commonly have no correlate on follow-up imaging. Clinical Impact: Because of the low progression rate of US-2 subthreshold observations, it is unclear if an extended period of intensive surveillance, as recommended by multiple professional societies, is warranted.

    View details for DOI 10.2214/AJR.22.27812

    View details for PubMedID 35703411

  • Growth Kinetics and Progression Rate of Bosniak Classification, Version 2019 III and IV Cystic Renal Masses on Imaging Surveillance. AJR. American journal of roentgenology Tse, J. R., Shen, L., Shen, J., Yoon, L., Chung, B. I., Kamaya, A. 2022


    Background: Active surveillance is increasingly used as first-line management for localized renal masses. Triggers for intervention primarily reflect growth kinetics, which are poorly investigated for cystic masses defined by Bosniak classification version 2019 (v2019). Objective: To determine growth kinetics and incidence rates of progression of class III and IV cystic renal masses, as defined by Bosniak classification v2019. Methods: This retrospective study included 105 patients (68 men, 37 women; median age, 67 years) with 112 Bosniak v2019 class III or IV cystic renal masses on baseline renal-mass protocol CT or MRI examinations from January 2005 to September 2021. Mass dimensions were measured. Progression was defined as any of: linear growth rate (LGR) ≥5 mm per year (representing clinical guideline threshold for intervention), volume doubling time <1 year, T category increase, or N1 or M1 disease. Class III and IV masses were compared. Time-to-progression was estimated using Kaplan-Meier curve analysis. Results: At baseline, 58 masses were class III and 54 were class IV. Median follow-up was 406 days. Median LGR was for class III masses 0.0 mm per year [interquartile range (IQR) -1.3 to 1.8] and for class IV masses 2.3 mm per year (IQR 0.0¬¬-5.7) (p<.001). LGR exceeded 5 mm per year in 4 (7%) class 3 masses and 15 (28%) class IV masses (p=.005). Two patients, both with class IV masses, developed distant metastases. Incidence rate of progression was for class III masses 11.0 (95% CI 4.5-22.8) and for class IV masses 73.6 (95% CI 47.8-108.7) per 100,000 person-days of follow-up. Median time-to-progression was undefined for class III mases given small number of progression events and 710 days for class IV masses. Hazard ratio of progression for class IV relative to class III masses was 5.1 (95% CI 2.5-10.8) (p<.001). Conclusion: During active surveillance of cystic masses evaluated using Bosniak classification v2019, class IV masses grew faster and were more likely to progress than class III masses. Clinical Impact: In comparison with current active surveillance guidelines that treat class III and IV masses similarly, future iterations may incorporate relatively more intensive surveillance for class IV masses.

    View details for DOI 10.2214/AJR.22.27400

    View details for PubMedID 35293234

  • Effect of sarcopenia on survival and spinal cord deficit outcomes after thoracoabdominal aortic aneurysm repair in patients 60 years of age and older. The Journal of thoracic and cardiovascular surgery Chatterjee, S., Shi, A., Yoon, L., Green, S. Y., Zhang, Q., Amarasekara, H. S., Orozco-Sevilla, V., Preventza, O., LeMaire, S. A., Coselli, J. S. 2021


    Sarcopenia (core muscle loss) has been used as a surrogate marker of frailty. We investigated whether sarcopenia would adversely affect survival after thoracoabdominal aortic aneurysm repair.We retrospectively reviewed prospectively collected data from patients aged 60 years or older who underwent thoracoabdominal aortic aneurysm repairs from 2006 to 2016. Imaging was reviewed by 2 radiologists blinded to clinical outcomes. The total psoas index was derived from total psoas muscle cross-sectional area (cm2) at the mid-L4 level, normalized for height (m2). Patients were divided by sex-specific total psoas index values into sarcopenia (lower third) and nonsarcopenia (upper two-thirds) groups. Multivariable modeling identified operative mortality and spinal cord injury predictors. Unadjusted and adjusted survival curves were analyzed.Of 392 patients identified, those with sarcopenia (n = 131) were older than nonsarcopenic patients (n = 261) (70.0 years vs 68.0 years; P = .02) and more frequently presented with aortic rupture or required urgent/emergency operations. Operative mortality was comparable (sarcopenia 13.7% vs nonsarcopenia 10.0%; P = .3); sarcopenia was not associated with operative mortality in the multivariable model (odds ratio, 1.40; 95% confidence interval, 0.73-2.77; P = .3). Sarcopenic patients experienced more frequent delayed (13.0% vs 4.6%; P = .005) and persistent (10.7% vs 3.4%; P = .008) paraplegia. Sarcopenia independently predicted delayed paraplegia (odds ratio, 3.17; 95% confidence interval, 1.42-7.08; P = .005) and persistent paraplegia (odds ratio, 3.29; 95% confidence interval, 1.33-8.13; P = .01) in the multivariable model. Adjusted for preoperative/operative covariates, midterm survival was similar for sarcopenic and nonsarcopenic patients (P = .3).Sarcopenia did not influence early mortality or midterm survival after thoracoabdominal aortic aneurysm repair but was associated with greater risk for delayed and persistent paraplegia.

    View details for DOI 10.1016/j.jtcvs.2021.05.037

    View details for PubMedID 34147254

  • Prevalence of Malignancy and Histopathologic Association of Bosniak Classification, Version 2019 Class III and IV Cystic Renal Masses. The Journal of urology Tse, J. R., Shen, L., Shen, J., Yoon, L., Kamaya, A. 2020: 101097JU0000000000001438


    PURPOSE: Bosniak Classification, version 2019 (v2019) describes two types of class III and IV masses each: 1) thick, wall/septa ≥4 mm (III-WS), 2) obtuse protrusion ≤3 mm (III-OP), 3) obtuse protrusion ≥4 mm (IV-OP), and 4) acute protrusion of any size (IV-AP). The purposes were to determine the prevalence of malignancy and histopathologic features of class III and IV masses and subclasses.MATERIALS AND METHODS: In this IRB-approved and HIPAA-compliant study, three fellowship-trained abdominal radiologists (R1-3) reviewed cystic renal masses that had tissue pathology and pre-operative renal mass protocol CT or MRI. Classes based on v2019 and prior classification systems were retrospectively re-assigned and associated with malignancy, aggressive histologic features (necrosis or high Fuhrman grade), and radiologic progression following resection.RESULTS: The final sample included 79 masses (59 malignant, 20 benign) from 74 patients. Based on v2019, prevalence of malignancy ranged from 56-61% (mean 60%) for class III and 83-83% (mean 83%) for class IV (p=0.036, 0.013, 0.036 for R1-3). Prevalence of malignancy within subclasses were: III-WS (47-53%); III-OP (71-85%); IV-OP (75-87%); IV-AP (87-95%; p=0.029, 0.001, 0.005). All readers were more likely to classify malignancies with aggressive histologic features as class IV (88-100%) rather than class III (0-12%; p=0.012, <0.001, 0.002), corresponding to a negative predictive value of 96-100%. Following treatment (mean follow-up length 1210 days), one patient developed metastases.CONCLUSIONS: Bosniak Classification, version 2019 can help risk stratification of class III-IV masses by identifying those likely to be malignant and have aggressive histologic features.

    View details for DOI 10.1097/JU.0000000000001438

    View details for PubMedID 33085925

  • Bosniak Classification Version 2019 of Cystic Renal Masses Assessed With MRI. AJR. American journal of roentgenology Tse, J. R., Shen, J. n., Yoon, L. n., Kamaya, A. n. 2020: 1–7


    OBJECTIVE. The purpose of this study was to determine how use of Bosniak classification version 2019 affects categorization and overall accuracy of MRI evaluation of cystic renal masses with tissue pathologic analysis as the reference standard. MATERIALS AND METHODS. MR images of 50 consecutively registered patients with tissue pathologic results from 2005 to 2019 were retrospectively reviewed by two abdominal radiologists. Each radiologist independently assigned a category based on the original and Bosniak classification version 2019 systems. Interreader agreements (kappa statistic) for both were calculated, and consensus reading was performed. Tissue pathologic analysis was used as the reference standard to determine whether a lesion was benign or renal cell carcinoma. RESULTS. Fifty-nine cystic renal masses were characterized as 38 renal cell carcinomas and 21 benign lesions on the basis of the results of tissue pathologic analysis. By consensus, according to the original Bosniak criteria, the renal masses were classified into three category I, five category II, four category IIF, 25 category III, and 22 category IV lesions. By consensus, according to the version 2019 criteria, the renal masses were classified into three category I, two category II, 12 category IIF, 18 category III, and 24 category IV lesions. Overall sensitivity and specificity for identifying renal cell carcinoma were 95% and 81%, respectively, with the original classification system and 100% and 86%, respectively, with version 2019. Weighted interreader agreement was moderate for both the original system (κ = 0.57) and version 2019 (κ = 0.55). CONCLUSION. Use of Bosniak classification version 2019 system improves sensitivity and specificity for malignancy among cystic renal masses characterized with MRI. Most lesions that changed categories were reclassified as Bosniak category IIF.

    View details for DOI 10.2214/AJR.19.22740

    View details for PubMedID 32515608

  • Bosniak Classification of Cystic Renal Masses Version 2019: Comparison of Categorization using CT and MRI. AJR. American journal of roentgenology Tse, J. R., Shen, J. n., Shen, L. n., Yoon, L. n., Kamaya, A. n. 2020


    Please see the Author Video associated with this article. Background: Bosniak Classification, version 2019 recently proposed refinements for cystic renal mass characterization and now formally incorporates MRI, which may improve concordance with CT. Purpose: To compare concordance of CT and MRI in evaluation of cystic renal masses using Bosniak Classification, version 2019. Materials and Methods: In this IRB-approved and HIPAA compliant study, three abdominal radiologists (R1-R3) retrospectively reviewed 68 consecutive cystic renal masses from 45 patients assessed with both CT and MR renal mass protocols within a year between 2005-2019. CT and MRI were reviewed independently and in separate sessions, using both the original and version 2019 Bosniak Classification systems. Results: Using Bosniak Classification, version 2019, cystic renal masses were classified into 12 category I, 19 category II, 13 category IIF, 4 category III, and 20 category IV by CT and 8 category I, 15 category II, 23 category IIF, 9 category III, and 13 category IV by MRI. Among individual features, MRI depicted more septa (p<0.001, p=0.046, p=0.005 for R1-R3; McNemar's test) for all radiologists, though both CT and MRI showed a similar number of protrusions (p=0.823, 1.0, 0.302) and maximal septa/wall thickness (p=1.0, 1.0, 0.145). Of discordant cases with version 2019, MRI led to the higher category in 12 masses. Reason for upgrade was most commonly due to protrusions identified only on MRI (n=4), increased number of septa (n=3), and a new category of heterogeneously T1-hyperintense (n=3). Neither modality was more likely to lead to a category change for both version 2019 (p=0.502; McNemar's test) and the original Bosniak classification system (p=0.823). Overall inter-rater agreement was substantial for both CT (κ=0.745) and MRI (κ=0.655) using version 2019 and was slightly higher than that of the original system (CT κ=0.707; MRI κ=0.623). Conclusion: CT and MRI were concordant in the majority of cases using Bosniak Classification, version 2019 and category changes by modality were not statistically significant. Inter-rater agreements were substantial for both CT and MRI. Clinical Impact: Bosniak Classification, version 2019 applied to cystic renal masses has substantial inter-rater agreement and does not lead to systematic category upgrades with either CT or MRI.

    View details for DOI 10.2214/AJR.20.23656

    View details for PubMedID 32755181

  • Disseminated coccidioidomycosis with multifocal musculoskeletal disease involvement. Radiology case reports McConnell, M. F., Shi, A., Lasco, T. M., Yoon, L. 2017; 12 (1): 141-145


    We report a rare case of disseminated coccidioidomycosis with multifocal musculoskeletal involvement. The patient presented to the emergency department with left shoulder pain and swelling. Magnetic resonance imaging of the left shoulder revealed enhancing soft tissue masses, bony lesions, and fluid collections in and around the glenohumeral joint with involvement of the proximal humerus, glenoid, and rotator cuff musculature. Multiple additional areas of involvement were subsequently discovered. Fungal cultures confirmed coccidioidomycosis infection at all surgical sites with superimposed polymicrobial bacterial infection in the left shoulder.

    View details for DOI 10.1016/j.radcr.2016.11.017

    View details for PubMedID 28228898

    View details for PubMedCentralID PMC5310389

  • Another dimension in magnetic resonance cholangiopancreatography: comparison of 2- and 3-dimensional magnetic resonance cholangiopancreatography for the evaluation of intraductal papillary mucinous neoplasm of the pancreas. Journal of computer assisted tomography Yoon, L. S., Catalano, O. A., Fritz, S., Ferrone, C. R., Hahn, P. F., Sahani, D. V. 2009; 33 (3): 363-8


    The purpose of this study was to compare 2-dimensional (2D) and 3D magnetic resonance cholangiopancreatography (MRCP) for image quality and diagnostic performance in the evaluation of pathologically verified intraductal papillary mucinous neoplasm (IPMN) of the pancreas.In this institutional review board-approved retrospective review, 21 patients (14 women and 7 men; mean age, 69 years; range, 43-93 years) who underwent 2D and 3D MRCPs on a 1.5-T system for pathologically confirmed IPMN were studied. Two-dimensional MRCP protocol included multiplanar thin- and thick-slab single-shot fast spin-echo imaging, coronal single-shot fast spin-echo, and transverse T2-weighted fast spin-echo imaging. Three-dimensional MRCP was performed using a fast-recovery fast spin-echo sequence with single-volume acquisition and maximum intensity projection reconstructions. Using a 5-point scale, 2 readers independently evaluated MRCPs for (1) image quality, (2) visualization of the pancreatic duct (PD), and (3) visualization of the cystic lesions. Intraductal papillary mucinous neoplasm's morphological features (septa, mural nodules, and duct communication) were also graded similarly to predict benignity or malignancy. Surgical and pathological data served as reference standard. A pancreatic surgeon reviewed the 21 MRCPs to determine the usefulness of 3D MRCP compared with that of 2D MRCP for surgical planning.Of the 21 IPMNs, 11 were side-branch IPMNs and 10 were main-duct-lesions IPMNs with side-branch involvement. A statistically significant improvement in image quality and visualization of the PD and cystic lesion was demonstrated with 3D MRCP in comparison with that demonstrated with 2D MRCP (P < or = 0.002). The morphological details of IPMN were also identified, with higher confidence with 3D MRCP in comparison with that using 2D MRCP. Two-dimensional and 3D MRCPs performed similarly for predicting benign and malignant lesions, with sensitivity ranging from 50.0% to 66.7% and specificity ranging from 86.7% to 93.3%. The pancreatic surgeon preferred 3D to 2D MRCP for surgical evaluation and planning in 14 of 21 cases.Compared with 2D MRCP, 3D MRCP provides better image quality, offers superior evaluation of the PD and morphological details of IPMN, and is preferred for surgical planning.

    View details for DOI 10.1097/RCT.0b013e3181852193

    View details for PubMedID 19478628

  • Evaluation of radial-sequence imaging in detecting acetabular labral tears at hip MR arthrography. Skeletal radiology Yoon, L. S., Palmer, W. E., Kassarjian, A. 2007; 36 (11): 1029-33


    In recent years, radial imaging has been advocated for improved visualization of the acetabular labrum in magnetic resonance arthrography of the hip. The purpose of this study was to investigate whether radial imaging demonstrates labral tears not visible on standard imaging planes.Fifty-four consecutive magnetic resonance (MR) arthrograms of the hip that included radial imaging over 2 years were retrospectively analyzed by two radiologists. Standard imaging planes and radial imaging were reviewed for identification of labral tears in four specific areas of the labrum: anterosuperior, posterosuperior, anteroinferior, and posteroinferior. The standard imaging sequences include fat-saturated spin-echo T1-weighted images in the coronal and oblique axial planes, non-fat-saturated T1-weighted images in the coronal and sagittal planes, and T2-weighted sequence in the axial plane. Radial imaging was performed as previously described using fat-saturated T1-weighted sequences.Using standard imaging planes, 50 anterosuperior, 31 posterosuperior, 10 anteroinferior, and 9 posteroinferior labral tears were detected in 54 MR arthrograms of the hip. Using radial sequences alone, 44 anterosuperior, 25 posterosuperior, 9 anteroinferior, and 5 posteroinferior labral tears were detected. In all four areas of the labrum, the radial imaging did not show any labral tear not seen on standard imaging planes.In MR arthrography of the hip, radial imaging did not reveal any additional labral tears. Standard imaging planes sufficiently demonstrate all acetabular labral tears.

    View details for DOI 10.1007/s00256-007-0363-x

    View details for PubMedID 17712555

  • Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology Kassarjian, A., Yoon, L. S., Belzile, E., Connolly, S. A., Millis, M. B., Palmer, W. E. 2005; 236 (2): 588-92


    To retrospectively analyze magnetic resonance (MR) arthrographic findings in patients with clinical cam-type femoroacetabular impingement.This study was approved by the institutional review board, and informed consent was waived. Study was compliant with the Health Insurance Portability and Accountability Act. Forty-two MR arthrograms obtained in 40 patients with clinical femoroacetabular impingement were analyzed retrospectively by two radiologists. Quantitative analysis by using alpha angle measurement was performed to assess anterosuperior femoral head-neck morphology. Presence of labral tears, articular cartilage lesions, paralabral cysts, os acetabuli, and synovial herniation pits was recorded. Presence of the typical triad of anterosuperior labral tear, anterosuperior cartilage lesion, and abnormal alpha angle was recorded. Surgical comparison was available for 11 patients.At imaging, in 40 patients (22 male, 18 female) with a mean age of 36.5 years, 39 of 42 hips (93%) had an abnormal alpha angle, with a mean angle of 69.7 degrees ; 40 of 42 (95%) had an anterosuperior cartilage abnormality; and 42 of 42 (100%) had an anterosuperior labral tear. Thirty-seven of 42 hips (88%) had the triad. Six had paralabral cysts, 17 had an os acetabuli, and two had synovial herniation pits. Surgical comparison for 11 hips led to confirmation of all labral and cartilage abnormalities seen at imaging.MR arthrography demonstrated a triad of abnormal head-neck morphology, anterosuperior cartilage abnormality, and anterosuperior labral abnormality in 37 of 42 patients with cam-type femoroacetabular impingement.

    View details for DOI 10.1148/radiol.2362041987

    View details for PubMedID 15972331

  • Evaluation of an emergency radiology quality assurance program at a level I trauma center: abdominal and pelvic CT studies. Radiology Yoon, L. S., Haims, A. H., Brink, J. A., Rabinovici, R., Forman, H. P. 2002; 224 (1): 42-6


    To evaluate the use of a redundant system in improving quality of care in the trauma setting by examining a subset of our quality assurance program.Five hundred thirty-one consecutive abdominal and pelvic CT reports obtained in patients with trauma at a level I trauma center from August 22, 1999, to August 21, 2000, were retrospectively reviewed. Each case was initially interpreted by a board-certified or board-eligible radiologist during evaluation in the emergency department and was subsequently reviewed by a subspecialty abdominal imaging radiologist as part of a quality assurance program. Nineteen cases were excluded because available information was incomplete, resulting in 512 cases in the current study. Cases with discordant interpretations were followed up to discern care change.Of the 512 trauma cases, 153 (29.9%) showed discordant readings. Review of patient records demonstrated changes in patient care in 12 (7.8%) cases. Three (2.0%) cases were reviewed from the morbidity and mortality records of the Department of Trauma Surgery as a direct result of misinterpretations. Six (4%) cases involved additional diagnostic imaging for reevaluation; in four of these six cases the quality assurance reader's interpretation was confirmed, while in the other two, the initial interpretations were favored.Findings suggest that discordant radiologic interpretations most often do not result in a change in patient care and outcome. The quality assurance program did, however, identify and lead to changes in care in a number of cases by providing clinically important additional findings.

    View details for DOI 10.1148/radiol.2241011470

    View details for PubMedID 12091660

  • Isolation of temperature-sensitive mutations in the c-raf-1 catalytic domain and expression of conditionally active and dominant-defective forms of Raf-1 in cultured mammalian cells. Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research Lu, K. K., Bazarov, A. V., Yoon, L. S., Sedivy, J. M. 1998; 9 (5): 367-80


    The c-Raf-1 kinase is converted into an oncoprotein by functional inactivation of its NH2-terminal regulatory domain and into a dominant-interfering protein by mutations that eliminate catalytic activity. This report describes a systematic charged residue-to-alanine scanning mutagenesis of the ATP-binding subdomain of the c-raf-1 gene. Two temperature-sensitive mutations were found, which were then used to construct both conditionally active and conditionally dominant-defective alleles. Stable cell lines overexpressing both types of mutants were isolated, and their phenotypes were examined. Ectopic expression of Raf-1 activity in quiescent cells was not sufficient to elicit S-phase entry, but the Raf signal could be efficiently complemented by the progression factor insulin-like growth factor I. The results point to a function of Raf-1 in the platelet-derived growth factor and epidermal growth factor pathways, leading to the establishment of competence for cell cycle entry. Ectopic expression of the dominant-defective activity in quiescent cells efficiently blocked entry into S phase. Effects of the dominant-defective protein could be detected minutes after the shift to the restrictive conditions and resulted in the rapid down-regulation of the mitogen-activated protein kinase pathway. Taken together, the phenotypes of the conditionally active and conditionally dominant-defective mutants point to a critical function of Raf-1 at very early times during exit from G0 and entry into G1.

    View details for PubMedID 9607558

  • Inhibition of the Raf-1 kinase by cyclic AMP agonists causes apoptosis of v-abl-transformed cells. Molecular and cellular biology Weissinger, E. M., Eissner, G., Grammer, C., Fackler, S., Haefner, B., Yoon, L. S., Lu, K. S., Bazarov, A., Sedivy, J. M., Mischak, H., Kolch, W. 1997; 17 (6): 3229-41


    Here we investigate the role of the Raf-1 kinase in transformation by the v-abl oncogene. Raf-1 can activate a transforming signalling cascade comprising the consecutive activation of Mek and extracellular-signal-regulated kinases (Erks). In v-abl-transformed cells the endogenous Raf-1 protein was phosphorylated on tyrosine and displayed high constitutive kinase activity. The activities of the Erks were constitutively elevated in both v-raf- and v-abl-transformed cells. In both cell types the activities of Raf-1 and v-raf were almost completely suppressed after activation of the cyclic AMP-dependent kinase (protein kinase A [PKA]), whereas the v-abl kinase was not affected. Raf inhibition substantially diminished the activities of Erks in v-raf-transformed cells but not in v-abl-transformed cells, indicating that v-abl can activate Erks by a Raf-1-independent pathway. PKA activation induced apoptosis in v-abl-transformed cells while reverting v-raf transformation without severe cytopathic effects. Overexpression of Raf-1 in v-abl-transformed cells partially protected the cells from apoptosis induced by PKA activation. In contrast to PKA activators, a Mek inhibitor did not induce apoptosis. The diverse biological responses correlated with the status of c-myc gene expression. v-abl-transformed cells featured high constitutive levels of expression of c-myc, which were not reduced following PKA activation. Myc activation has been previously shown to be essential for transformation by oncogenic Abl proteins. Using estrogen-regulated c-myc and temperature-sensitive Raf-1 mutants, we found that Raf-1 activation could protect cells from c-myc-induced apoptosis. In conclusion, these results suggest (i) that Raf-1 participates in v-abl transformation via an Erk-independent pathway by providing a survival signal which complements c-myc in transformation, and (ii) that cAMP agonists might become useful for the treatment of malignancies where abl oncogenes are involved, such as chronic myeloid leukemias.

    View details for DOI 10.1128/mcb.17.6.3229

    View details for PubMedID 9154822

    View details for PubMedCentralID PMC232176