Luke Yoon, MD, is a clinical associate professor and Director of Faculty Well-being 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 interest includes physician well-being, cystic renal mass imaging and pain imaging with PET MRI.
- Body Imaging
- Musculoskeletal Imaging
- Diagnostic Radiology
- Physician Well-being
Clinical Associate Professor, Radiology
Director of Faculty Well-being, Department of Radiology, Stanford School of Medicine (2021 - Present)
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)
Medical Education: Yale School Of Medicine (2002) CT
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
Undergraduate Education, Yale University (1997)
Growth Kinetics and Progression Rate of Bosniak Classification, Version 2019 III and IV Cystic Renal Masses on Imaging Surveillance.
AJR. American journal of roentgenology
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
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
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
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
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
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
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.
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.
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.
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
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
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