Faculty Bibliography

OBJECTIVE: This study evaluates use of an abbreviated magnetic resonance imaging protocol with T2-weighted imaging in detecting biopsy-proven unifocal breast cancer. MATERIALS AND METHODS: This is an institutional review board approved retrospective study of patients with biopsy-proven unifocal breast cancer (88% invasive; 12% in situ) undergoing magnetic resonance imaging. In three separate sessions, three breast imagers evaluated (1) T1-weighted non-contrast, post-contrast and post-contrast subtracted images, (2) T1-weighted images with clinical history and prior imaging, and (3) T1-weighted images and T2-weighted images with clinical history and prior imaging. Protocols were compared for cancer detection, reading time and lesion conspicuity. An independent breast radiologist retrospectively analyzed initial enhancement ratio of cancers and retrospectively reviewed lesion morphology and final pathology. RESULTS: All 107 cancers were identified at first protocol by at least one reader; five cancers were missed by either one or two readers. One cancer was missed by one reader at protocols two and three. Mean percentage detection for protocol one was 97.8%; protocol two, 99.4%, protocol three, 99.4%. T2-weighted images did not alter cancer detection but increased lesion conspicuity for 2/3 readers. 3/5 missed lesions were low grade cancers. Initial enhancement ratio was positively associated with increasing tumor grade (p=0.031) and pathology (p=0.002). Reader interpretation time decreased and lesion conspicuity increased as initial enhancement ratio increased. CONCLUSION: Abbreviated magnetic resonance imaging has high rate of detection for known breast cancer and short interpretation time. T2 weighted imaging increased lesion conspicuity without altering detection rate. Initial enhancement ratio correlated with invasive disease and tumor grade.

PURPOSE: To assess outcomes of lung nodules missed on simultaneous positron emission tomography and magnetic resonance imaging (PET/MRI) compared to the reference standard PET and computed tomography (PET/CT) in patients with primary malignancy. MATERIALS AND METHODS: In all, 208 patients with primary malignancy undergoing clinically indicated (18 F) fluorodeoxyglucose (FDG) PET/CT followed by PET/MRI were independently reviewed by two readers. Upon review of the thoracic station on PET/MRI and PET/CT, 89 non-FDG avid small lung nodules in 43 patients were detected (by reader 1) only on the CT component of the PET/CT but were not identified on PET/MRI. Overall, 84 of these 89 nodules were examined on follow-up imaging with PET/CT or chest CT. The remaining five nodules had no follow-up imaging but had remote imaging available for comparison. RESULTS: Among the 84 nodules with follow-up, three nodules (3%) in one patient progressed, 10 (12%) nodules partially/completely resolved, whereas 71 nodules (85%) remained stable. The five nodules without follow-up were all stable since prior imaging of over 21 months. CONCLUSION: The vast majority (97%) of small non-FDG avid lung nodules missed on PET/MRI either resolved or remained stable on follow-up, suggestive of benignity. PET/MRI remains a viable alternative imaging modality in oncology patients, despite its low sensitivity in detecting small lung nodules. J. Magn. Reson. Imaging 2015.

OBJECTIVE: The objective of our study was to assess the role of recently introduced hybrid PET/MRI in the evaluation of lymphoma patients using PET/CT as a reference standard. SUBJECTS AND METHODS: In this prospective study 28 consecutive lymphoma patients (18 men, 10 women; mean age, 53.6 years) undergoing clinically indicated PET/ CT were subsequently imaged with PET/MRI using residual FDG activity from the PET/ CT study. Blinded readers evaluated PET/CT (reference standard), PET/MRI, and diffusion-weighted imaging (DWI) studies separately; for each study, they assessed nodal and extranodal involvement. Each FDG-avid nodal station was marked and compared on DWI, PET/MRI, and PET/CT. Modified Ann Arbor staging was performed and compared between PET/MRI and PET/CT. The maximum standardized uptake value (SUVmax) on PET/MRI for FDG-avid nodal lesions was compared with the SUVmax on PET/CT. The apparent diffusion coefficient (ADC) for FDG-avid nodal lesions was compared to SUVmax on PET/MRI. RESULTS: Fifty-one FDG-avid nodal groups were identified on PET/CT in 13 patients. PET/MRI identified 51 of these nodal groups with a sensitivity of 100%. DWI identified 32 nodal groups for a sensitivity of 62.7%. PET/MRI staging and PET/CT staging were concordant in 96.4% of patients. For the one patient with discordant staging results, disease was correctly upstaged to stage IV on the basis of the PET/MRI finding of bone marrow involvement, which was missed on PET/CT. DWI staging was concordant with PET/CT staging in 64.3% of the patients. The increased staging accuracy of PET/MRI relative to DWI was significant (p = 0.004). SUVmax measured on PET/MRI and PET/CT showed excellent statistically significant correlation (r = 0.98, p < 0.001). There was a poor negative correlation between ADC and SUVmax (r = -0.036, p = 0.847). CONCLUSION: PET/MRI can be used to assess disease burden in lymphoma with sensitivity similar to PET/CT and can be a viable alternative for lymphoma staging and follow-up.

OBJECTIVE. The purpose of this article is to evaluate factors associated with the likelihood that abdominopelvic MRI examinations performed for characterization of lesions identified on other imaging modalities will provide information that adds value to patient management. MATERIALS AND METHODS. One thousand one hundred thirty-two lesions in 863 patients undergoing MRI for further characterization after detection by an alternative imaging modality were identified. Reports of the MRI examinations and of previous studies were reviewed to classify cases in terms of patient-, examination-, and lesion-related factors. MRI reports were also classified in terms of measures reflecting inclusion of content with the potential to add value to patient management. Data were analyzed using logistic regression for correlated data. RESULTS. MRI provided a definitive diagnosis in 79.2% (897/1132), upgraded the severity of the favored diagnosis in 5.3% (60/1132), downgraded the severity of the favored diagnosis in 34.5% (390/1132), and showed an absence of the suspected lesion in 12.1% (137/1132) of cases. Provision of a definitive diagnosis (most common in liver, kidney, gallbladder, bowel, myometrium, and adrenal gland) was significantly associated with the organ containing the lesion (p < 0.001). A change in severity of the favored diagnosis (most common after CT or PET/CT) and the absence of the suspected lesion (most common after PET/CT) were significantly associated with the prior imaging modality (p