Comparing Magnetic Resonance Imaging and Prostate-Specific Membrane Antigen-Positron Emission Tomography for Prediction of Extraprostatic Extension of Prostate Cancer and Surgical Guidance: A Prospective Nonrandomized Clinical Trial.

PURPOSE: Survivors of surgically managed prostate cancer may experience urinary incontinence and erectile dysfunction. Our aim was to determine if 68Ga-prostate-specific membrane antigen-11 positron emission tomography CT (PSMA-PET) in addition to multiparametric (mp) MRI scans improved surgical decision-making for nonnerve-sparing or nerve-sparing approach. MATERIALS AND METHODS: We prospectively enrolled 50 patients at risk for extraprostatic extension (EPE) who were scheduled for prostatectomy. After mpMRI and PSMA-PET images were read for EPE prediction, surgeons prospectively answered questionnaires based on mpMRI and PSMA-PET scans on the decision for nerve-sparing or nonnerve-sparing approach. Final whole-mount pathology was the reference standard. Sensitivity, specificity, positive predictive value, negative predictive value, and receiver operating characteristic curves were calculated and McNemar's test was used to compare imaging modalities. RESULTS: The median age and PSA were 61.5 years and 7.0 ng/dL. The sensitivity for EPE along the posterior neurovascular bundle was higher for PSMA-PET than mpMRI (86% vs 57%, P = .03). For MRI, the specificity, positive predictive value, negative predictive value, and area under the curve for the receiver operating characteristic curves were 77%, 40%, 87%, and 0.67, and for PSMA-PET were 73%, 46%, 95%, and 0.80. PSMA-PET and mpMRI reads differed on 27 nerve bundles, with PSMA-PET being correct in 20 cases and MRI being correct in 7 cases. Surgeons predicted correct nerve-sparing approach 74% of the time with PSMA-PET scan in addition to mpMRI compared to 65% with mpMRI alone (P = .01). CONCLUSIONS: PSMA-PET scan was more sensitive than mpMRI for EPE along the neurovascular bundles and improved surgical decisions for nerve-sparing approach. Further study of PSMA-PET for surgical guidance is warranted in the unfavorable intermediate-risk or worse populations. CLINICALTRIALS.GOV IDENTIFIER: NCT04936334.

Assessing extra-prostatic extension for surgical guidance in prostate cancer: Comparing two PSMA-PET tracers with the standard-of-care.

BACKGROUND: Incontinence and impotence occur following radical prostatectomy due to injury to nerves and sphincter muscle. Preserving nerves and muscle adjacent to prostate cancer risks positive surgical margins. Advanced imaging with MRI has improved cancer localization but limitations exist. OBJECTIVE: To measure the accuracy for assessing extra-prostatic extension at nerve bundles for 2 PSMA-PET tracers and to compare the PET accuracy to standard-of-care predictors including MRI and biopsy results. MATERIALS AND METHODS: We studied men with PSMA-targeted PET imaging, performed prior to prostatectomy in men largely with intermediate to high-risk prostate cancer, and retrospectively evaluated for assessment of extra-prostatic extension with whole-mount analysis as reference standard. Two different PSMA-PET tracers were included: 68Ga-PSMA-11 and 68Ga-P16-093. Blinded reviews of the PET and MRI scans were performed to assess extra-prostatic extension (EPE). Sensitivity and specificity for extra-prostatic extension were compared using McNemar's Chi2. RESULTS: Pre-operative PSMA-PET imaging was available for 71 patients with either 68Ga-P16-093 (n = 25) or 68Ga-PSMA-11 (n = 46). There were 24 (34%) with pT3a (EPE) and 16 (23%) with pT3b (SVI). EPE Sensitivity (87% vs. 92%), Specificity (77% vs. 76%), and ROC area (0.82 vs. 0.84) were similar between P16-093 and PSMA-11, respectively (P = 0.87). MRI (available in only 45) found high specificity (83%) but low sensitivity (60%) for EPE when using a published grading system. MRI sensitivity was significantly lower than the PSMA-PET (60% vs. 90%, P = 0.02), but similar to PET when using a >5 mm capsular contact (76% vs. 90%, P = 0.38). A treatment change to "nerve sparing" was recommended in 21 of 71 (30%) patients based on PSMA-PET imaging. CONCLUSIONS: Presurgical PSMA-PET appeared useful as a tool for surgical planning, changing treatment plans in men with ≥4+3 or multi-core 3+4 prostate cancer resulting in preservation of nerve-bundles.

Inter- and intra-observer variability of computed tomography-based parenchymal- and ductal diameters in chronic pancreatitis: a multi-observer international study.

PURPOSE: The need for incorporation of quantitative imaging biomarkers of pancreatic parenchymal and ductal structures has been highlighted in recent proposals for new scoring systems in chronic pancreatitis (CP). To quantify inter- and intra-observer variability in CT-based measurements of ductal- and gland diameters in CP patients. MATERIALS AND METHODS: Prospectively acquired pancreatic CT examinations from 50 CP patients were reviewed by 12 radiologists and four pancreatologists from 10 institutions. Assessment entailed measuring maximum diameter in the axial plane of four structures: (1) pancreatic head (PDhead), (2) pancreatic body (PDbody), (3) main pancreatic duct in the pancreatic head (MPDhead), and (4) body (MPDbody). Agreement was assessed by the 95% limits of agreement with the mean (LOAM), representing how much a single measurement for a specific subject may plausibly deviate from the mean of all measurements on the specific subject. Bland-Altman limits of agreement (LoA) were generated for intra-observer pairs. RESULTS: The 16 observers completed 6400 caliper placements comprising a first and second measurement session. The widest inter-observer LOAM was seen with PDhead (± 9.1 mm), followed by PDbody (± 5.1 mm), MPDhead (± 3.2 mm), and MPDbody (± 2.6 mm), whereas the mean intra-observer LoA width was ± 7.3, ± 5.1, ± 3.7, and ± 2.4 mm, respectively. CONCLUSION: Substantial intra- and inter-observer variability was observed in pancreatic two-point measurements. This was especially pronounced for parenchymal and duct diameters of the pancreatic head. These findings challenge the implementation of two-point measurements as the foundation for quantitative imaging scoring systems in CP.

When Benign Behaves Badly: Atypical Hemangiomas on Contrast-Enhanced Ultrasonography.

ABSTRACT: Hemangioma is the most common benign liver tumor and is frequently encountered as an incidental finding on imaging. The classic enhancement pattern of hemangioma is diagnostic on contrast-enhanced ultrasound (CEUS), and it follows the same pattern of enhancement on computed tomography and magnetic resonance imaging. However, there is a subset of hemangiomas that demonstrate atypical enhancement patterns on CEUS. The ability to recognize the different enhancement patterns and discern when additional imaging or biopsy may be necessary is essential to accurately interpret an atypical hemangioma on CEUS. This article reviews various enhancement patterns of hemangioma on CEUS to avoid pitfalls in characterization of focal liver lesions on CEUS.

Magnetic resonance imaging-derived fat fraction predicts risk of malignancy in intraductal papillary mucinous neoplasm.

PURPOSE: Assess the relationship between MRI-derived pancreatic fat fraction and risk of malignancy in intraductal papillary mucinous neoplasm (IPMN). METHODS: MRIs of patients with IPMN who underwent pancreaticoduodenectomy were analyzed. IPMN with low-grade dysplasia (n = 29) were categorized as low-risk while IPMN at high risk of malignancy consisted of those with high-grade dysplasia/invasive carcinoma (n = 33). Pancreatic fat-fraction (FFmean) was measured using the 2-point Dixon-method. Images were evaluated for the high-risk stigmata and worrisome features according to the revised 2017 Fukuoka consensus criteria. Data on serum CA19-9, Diabetes Mellitus (DM) status, body mass index (BMI), and histological chronic pancreatitis were obtained. RESULTS: A significant difference in FFmean was found between the high-risk IPMN (11.45%) and low-risk IPMN (9.95%) groups (p = 0.027). Serum CA19-9 level (p = 0.021), presence of cyst wall enhancement (p = 0.029), and solid mass (p = 0.008) were significantly associated with high-risk IPMN. There was a significant correlation between FFmean and mural nodule size (r = 0.36, p Ë‚ 0.01), type 2 DM (r = 0.34, p Ë‚ 0.01), age (r = 0.31, p Ë‚ 0.05), serum CA 19-9 (r = 0.30, p Ë‚ 0.05), cyst diameter (r = 0.30, p Ë‚ 0.05), and main pancreatic duct diameter (r = 0.26, p Ë‚ 0.05). Regression analysis revealed FFmean (OR 1.103, p = 0.035) as an independent predictive variable of high-risk IPMN. CONCLUSION: FFmean is significantly associated with high-risk IPMN and an independent predictor of IPMN malignant risk. FFmean may have clinical utility as a biomarker to complement the current IPMN treatment algorithm and improve clinical decision making regarding the need for surgical resection or surveillance.

Secretin-Enhanced MRCP: How and Why-AJR Expert Panel Narrative Review.

Secretin-enhanced MRCP (S-MRCP) has advantages over standard MRCP for imaging of the pancreaticobiliary tree. Through the use of secretin to induce fluid production from the pancreas and leveraging of fluid-sensitive MRCP sequences, S-MRCP facilitates visualization of ductal anatomy, and the findings provide insight into pancreatic function, allowing radiologists to provide additional insight into a range of pancreatic conditions. This narrative review provides detailed information on the practical implementation of S-MRCP, including patient preparation, logistics of secretin administration, and dynamic secretin-enhanced MRCP acquisition. Also discussed are radiologists' interpretation and reporting of S-MRCP examinations, including assessments of dynamic compliance of the main pancreatic duct and of duodenal fluid volume. Established indications for S-MRCP include pancreas divisum, anomalous pancreaticobiliary junction, Santorinicele, Wirsungocele, chronic pancreatitis, main pancreatic duct stenosis, and assessment of complex postoperative anatomy. Equivocal or controversial indications are also described along with an approach to such indications. These indications include acute and recurrent acute pancreatitis, pancreatic exocrine function, sphincter of Oddi dysfunction, and pancreatic neoplasms.

Quantitative assessment of disease severity of primary sclerosing cholangitis with T1 mapping and extracellular volume imaging.

PURPOSE: Assess the relationship between liver T1 relaxation time and extracellular volume (ECV) fraction and the disease severity of primary sclerosing cholangitis (PSC). METHODS: This retrospective study included 93 patients with PSC and 66 healthy patients in the control group. T1 relaxation times were measured in the right and left lobe, as well as in the area of stricture. T1PSC and ECVPSC were calculated by averaging T1 and ECV of both lobes and stricture site. T1 and ECV were compared between the two groups and according to PSC phenotypes and severity based on Mayo Risk Score (MRS). We also examined the relationship between T1 and ECV with non-invasive measures of fibrosis such as Fibrosis-4 index (FIB-4) and liver stiffness measurement (LSM) by transient elastography. RESULTS: Mean liver T1 (774 ± 111 ms, p < 0.001) and liver ECV (0.40 ± 0.14, p < 0.05) were significantly higher with both large-duct and small-duct-type PSC which may lack classic imaging findings on MRCP compared to the control group (p < 0.001). T1PSC and ECVPSC showed weak-moderate correlation with LSM, FIB-4, and MRS (p < 0.05). Cut-off values of liver T1 to detect patients in low-risk and high-risk MRS groups were 677 ms (AUC: 0.68, sensitivity: 76%, specificity: 53%, p = 0.03) and 743 ms (AUC: 0.83, sensitivity: 79%, specificity: 76%, p < 0.001), respectively. CONCLUSION: T1 relaxation time and ECV fraction can be used for quantitative assessment of disease severity in patients with PSC.

Is Cambridge scoring in chronic pancreatitis the same using ERCP and MRCP?: A need for revision of standards.

PURPOSE: Grading of chronic pancreatitis (CP) is a clinical and radiologic challenge. Retrograde cholangiopancreatography (ERCP) and magnetic resonance cholangiopancreatography (MRCP) use a version of the Cambridge criteria for ductal evaluation and CP staging, but interchangeability between the modalities lacks validation. This work compares ERCP and MRCP Cambridge scores and evaluates diagnostic performance of MRCP in a large cohort of patients with CP. METHODS: A large radiology database was searched for CP patients who underwent MRCP between 2003 and 2013. Next, patients who also had an ERCP within 90 days of their MRCP were selected. These were categorized into mild, moderate, and severe CP using the standardized Cambridge classification for ERCP. Radiologists blinded to ERCP findings then rated MRCP with modified Cambridge scores. RESULTS: The cohort comprised 325 patients (mean age 51 years; 56% female). By ERCP Cambridge classification, 122 had mild CP, 109 moderate CP, and 94 severe CP. MRCP and ERCP showed total agreement of Cambridge score in only 43% of cases. With ERCP as reference, the sensitivity and specificity of MRCP in detecting Cambridge scores 4 + 5 (main-duct predominant) were 75.9% and 64.3%, and for Cambridge score 3 (side-branch predominant) it was 60.0% and 76.9%, respectively. CONCLUSIONS: There is a lack of strong concordance between ERCP- and MRCP-based grading of CP using the Cambridge criteria. MRCP had moderate to good performance in diagnosing side-branch predominant versus main-duct predominant CP. This suggests an inherent challenge in comparing literature and calls for a revision of the standards.

Wirsungocele: evaluation by MRCP and clinical significance.

PURPOSE: Wirsungocele is a rare cystic dilatation of the main pancreatic duct seen at the terminal portion of the duct of Wirsung. The purpose of our study is to evaluate the diagnostic value of MRCP in detection of Wirsungocele and the association between the MRCP-determined size of Wirsungocele and the MRCP-clinical findings of pancreatitis. METHODS: Thirty-four patients with reported 'Wirsungocele' were analyzed in the study. Two radiologists reviewed MRCP/S-MRCP images for the presence and diameter of Wirsungocele (WD), main pancreatic duct dilatation (MPDD), side branch ectasia (SBE), acinarization, and duodenal filling grade. Electronic medical record review included symptoms (abdominal pain), signs (recurrent acute/chronic pancreatitis), and select laboratory testing (serum amylase and lipase). Inter-reader agreement values were calculated by ICC. Pearson correlation analysis was performed to evaluate the association of WD with radiological and clinical findings. The comparison of WD on MRCP versus S-MRCP was calculated by Wilcoxon test. Mann-Whitney U test was used for two independent variable comparisons. RESULTS: The sensitivity of MRCP for the detection of Wirsungocele calculated using the S-MRCP and ERCP as the reference method was 76.9% and 100%, respectively. There was a significant difference in the diameter of Wirsungocele measured by MRCP vs S-MRCP (p < 0.001). There was good inter-reader agreement for the detection of Wirsungocele on MRCP and measurement of WD on MRCP and S-MRCP (ICC: 0.79, 0.89, and 0.80, respectively, p < 0.001). There was a significant difference in WD between the patients with and without MPDD (p < 0.05). There was a significant positive correlation between WD and MPDD (r = 0.66, p < 0.05). WD was significantly associated with recurrent acute pancreatitis (p < 0.05). CONCLUSION: MRCP is a highly sensitive and non-invasive imaging tool for detection of Wirsungocele. Greater Wirsungocele diameter is associated with MPDD and recurrent acute pancreatitis.

Contrast-Enhanced Ultrasound Versus Doppler Ultrasound for Detection of Early Vascular Complications of Pancreas Grafts.

OBJECTIVE. The purpose of this study is to compare conventional duplex ultrasound and contrast-enhanced ultrasound (CEUS) for identifying vascular abnormalities in pancreas allografts in the immediate posttransplant setting. Identification of pancreas allografts at risk of failure may impact patient care because early intervention for vascular insufficiency can lead to graft salvage. MATERIALS AND METHODS. Two radiologists who were blinded to patient outcomes performed a retrospective analysis of the postoperative Doppler ultrasound and CEUS images of 34 pancreas grafts from transplants performed between 2017 and 2019. A total of 28 patients who did not require surgical reexploration were considered the control group. Six patients had surgically proven arterial or venous abnormalities on surgical reexploration. Each radiologist scored grafts as having normal or abnormal vascularity on the basis of image sets obtained using Doppler ultrasound only and CEUS only. Comparisons of both the diagnostic performance of each modality and interobserver agreement were performed. RESULTS. Both readers showed that CEUS had increased sensitivity for detecting vascular abnormalities (83.3% for both readers) compared with Doppler ultrasound (66.7% and 50.0%). For both readers, the specificity of CEUS was similar to that of Doppler imaging (81.6% and 78.9% for reader 1 and reader 2 versus 76.3% and 84.2% for reader 1 and reader 2). For both readers, the negative predictive value of CEUS was higher than that of Doppler ultrasound (96.9% and 96.8% for reader 1 and reader 2 versus 93.5% and 91.4% for reader 1 and reader 2). Interobserver agreement was higher for CEUS than for Doppler ultrasound (κ = 0.54 vs κ = 0.28). CONCLUSION. CEUS may provide radiologists and surgeons with a means of timely and effective evaluation of pancreas graft perfusion after surgery, and it may help identify grafts that could benefit from surgical salvage.

Impact of age on the diagnostic performance of pancreatic ductal diameters in detecting chronic pancreatitis.

PURPOSE: In the diagnosis of chronic pancreatitis (CP), definition of main pancreatic duct (MPD) dilation is challenging due to lack of commonly accepted normal values. This study assessed the diagnostic performance of MPD diameters to detect CP including the impact of age. METHODS: 274 patients with ERCP-verified CP and 262 healthy controls were included. All had magnetic resonance cholangiopancreatography (MRCP) with measurement of MPD diameters in the pancreatic head, body, and tail. CP disease stage was defined as patients with and without functional (exocrine and/or endocrine) impairment. Diagnostic performance of MPD diameter and corresponding cut-offs values to diagnose CP were determined, including an age-stratified analysis. RESULTS: In healthy controls, an effect of age on MPD diameters was seen for the pancreatic head (P < 0.001), body (P = 0.006), and tail (P = 0.03). Patients with CP had increased MPD diameter compared to controls (all segments P < 0.001). Increased pancreatic head MPD diameter was seen in patients with functional pancreatic impairment compared to patients without (P = 0.03). The diagnostic performance of MPD diameter to detect CP was high (all segments ROC-AUC > 0.92). The optimal pancreatic MPD diameter cut-off values for diagnosing CP were: < 40 years: 2.0(head) and 1.8(body) mm; 40-60 years: 2.4(head) and 2.1(body) mm; > 60 years: 2.7(head) and 2.1(body) mm. CONCLUSION: Age is an important factor when evaluating the diameter of the pancreatic ductal system. Our findings challenge the existing reported thresholds for defining an abnormal duct diameter and point at age-stratified assessments as an integrated part of future imaging-based diagnostic and grading systems for CP.

Contrast-enhanced ultrasound of the transplant pancreas in the post-operative setting.

BACKGROUND/OBJECTIVES: Vascular thrombosis is the most common cause of early graft loss after transplantation. Routine grayscale and Doppler ultrasound frequently fail to adequately visualize vascular compromise. Contrast-enhanced ultrasound is a novel approach to identifying these complications. METHODS: This was a prospective study of 22 consecutive patients who received pancreas transplant at our institution between 2017 and 2018. All allografts were implanted with systemic venous and enteric exocrine drainage. Perfusion was assessed in the immediate post-operative period using grayscale, Doppler, and contrast-enhanced ultrasound. Imaging findings were compared between those who required surgical re-intervention and those who did not in order to evaluate for differences in perfusion. RESULTS: Of the 22 transplants, 15 did not require surgical re-intervention and were considered normal. These allografts demonstrated prompt and uniform enhancement, with washout usually by 90 seconds. All patients who had abnormal CEUS underwent re-exploration. Perfusion was acceptable or restored in all cases. Two patients ultimately required allograft pancreatectomy. Two patients had normal glands, and the remaining 3 grafts were salvaged following intervention. CONCLUSIONS: Contrast-enhanced ultrasound provides rapid evaluation of allograft perfusion following pancreas transplantation. The differences in perfusion provide a novel way of evaluating for complications in the immediate post-transplant period.

Differentiating IgG4-related sclerosing cholangiopathy from cholangiocarcinoma using CT and MRI: experience from a tertiary referring center.

PURPOSE: To compare the cross-sectional imaging findings of immunoglobulin G4-related sclerosing cholangiopathy (IgG4-SC) and cholangiocarcinoma (CCA). METHODS: Retrospective search of radiology and pathology databases identified 24 patients with IgG4-SC and over 500 patients with CCA from January 2009 to December 2016. Patients with no pre-treatment imaging studies available on PACS, non-contrasted imaging only, presence of mass lesions, metastatic disease or biliary stents were excluded. 17 patients with IgG4-SC and a selected group of 20 (age and gender matched) patients with CCA were obtained. Images were blinded and independently reviewed by two radiologists. Differences in proportions and means between groups were analyzed using Fishers and Mann-Whitney tests, respectively. RESULTS: Both readers identified a statistically significant difference in the presence of abrupt common bile duct narrowing between IgG4-SC and CCA (6.7% vs. 68.4%, p < 0.001; 33.3% vs. 75%, p = 0.019). No difference was seen in biliary wall thickening, wall enhancement, extrahepatic exclusive location of disease, or pancreatic duct dilation. Inter-observer variability was κ = 0.52. Total bilirubin and CA 19-9 were unable to differentiate between IgG4-SC and CCA. Serum IgG4 was positive in two of six IgG4-SC patients who were tested. CONCLUSION: IgG4-SC and CCA share many clinical and imaging findings on CT and MRI. Abrupt bile duct cut sign strongly favors CCA. In the absence of this finding, IgG4-SC should be considered in the differential diagnosis in all cases of suspected extrahepatic CCA.

Distribution and correlation of pancreatic gland size and duct diameters on MRCP in patients without evidence of pancreatic disease.

PURPOSE: To use MRCP to investigate age-related changes and gender differences of the pancreas and to correlate pancreatic gland size and duct diameter. METHODS: In this institutional review, board-approved, HIPAA-compliant study, 280 patients (age 20-88 years) without a history of pancreatic or liver disease who had undergone MRI/MRCP from 2004 to 2015 were identified. The anteroposterior size and main duct diameter of the pancreatic head, body, and tail were measured. The pancreatic gland and duct sizes were compared between genders, and among seven age subgroups (20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89). RESULTS: The pancreatic head and body were significantly larger in males than females (head, p < 0.01; body, p = 0.03), while the tail and the duct diameters of the pancreatic head, body, and tail showed no gender difference. As the age of male participants increased, there was an associated increase in size of the pancreatic gland initially (largest at age 50-59 (body) and 60-69 (head)), followed by subsequent decline in size thereafter. Additionally, the pancreatic duct diameter was found to increase gradually. In females, the size of the pancreatic gland decreased, while the diameter of the pancreatic duct increased with age. Moderate positive correlation for gland size and strong positive correlation for duct diameter among different pancreatic regions were found. Weak negative correlation was found between gland size and duct diameter. CONCLUSIONS: There are gender differences in the gland size of the pancreatic head and body. The pancreatic gland size increases until the sixth decade in males, with a more continuous decrease in gland size with age in females. Both males and females demonstrate a marked decrease in gland size after the eighth decade. The duct diameter increases with age in both males and females.

Detection of exocrine dysfunction by MRI in patients with early chronic pancreatitis.

PURPOSE: To determine if T1-weighted MR signal of the pancreas can be used to detect early CP. METHODS: A retrospective analysis was performed on 51 suspected CP patients, who had both secretin-enhanced magnetic resonance cholangiopancreatography (S-MRCP) and an intraductal secretin stimulation test (IDST). There were 29 patients in normal and 22 patients in the low bicarbonate group. Bicarbonate level, total pancreatic juice volume, and excretory flow rate were recorded during IDST. Signal intensity ratio of pancreas (SIR), fat signal fraction, pancreatograms findings, and grade of duodenal filling were recorded on S-MRCP by two blinded radiologists. RESULTS: There was a significant difference in the signal intensity ratio of the pancreas to spleen (SIRp/s) between the normal and low bicarbonate groups (p < 0.0001). A significant positive correlation was found between pancreatic fluid bicarbonate level and SIRp/s (p < 0.0001). SIRp/s of 1.2 yielded sensitivity of 77% and specificity of 83% for detection of pancreatic exocrine dysfunction (AUC: 0.89). CONCLUSION: T1-weighted MR signal of the pancreas has a high sensitivity and specificity for the detection of parenchymal abnormalities related to exocrine dysfunction and can therefore be helpful in evaluation of suspected early CP.

Curricula for Teaching MRI Safety, and MRI and CT Contrast Safety to Residents: How Effective Are Live Lectures and Online Modules?

PURPOSE: The advent of the diagnostic radiology core examination and the new ACGME "milestone" evaluation system for radiology residents places new emphasis on topics in MRI and CT safety, and MRI and CT contrast agents. We evaluated whether either lecture-based teaching or online modules would improve baseline resident knowledge in these areas, and assessed which intervention was more effective. METHODS: Before didactic intervention, 2 cohorts were created from 57 radiology residents, with equal numbers and a matched level of training. The residents were tested on their baseline knowledge of MRI, MRI contrast safety, and CT contrast safety, using a multiple-choice examination. One group attended a live, 1-hour lecture on the preceding topics. The other engaged in 3 short online educational modules. After 6 weeks, the residents were again tested with the same questions to assess for improvement in their understanding. RESULTS: Both the module and lecture cohorts demonstrated a statistically significant increase in questions answered correctly on CT contrast safety (13.1%, P < .001, and 19.1%, P < .001, respectively), and on MRI and MRI contrast safety (12.9%, P < .001, and 14.4%, P < .001). The preintervention and postintervention scores, and degree of improvement postintervention, were similar for the module versus lecture groups, without a statistically significant difference (P = .70). Resident confidence improved in both groups, for both modalities. CONCLUSIONS: Focused didactic intervention improves resident knowledge of MRI and CT safety, and MRI and CT contrast agents. Live lectures and online modules can be equally effective, allowing residency programs flexibility.