Daniel N. Costa

Body MRI using IDEAL

OBJECTIVE The intrinsic differences of water and fat protons in the MR environment allow selective interrogation of their contribution to the MR signal. Fat-suppression techniques and chemical shift imaging are routinely used in clinical body MRI. Iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) is a novel imaging technique for separating fat and water. CONCLUSION This article describes the basic principles of IDEAL MRI and illustrates the use of IDEAL imaging as an alternative to fat-suppression techniques and chemical shift imaging for body MRI.

MRI features of groove pancreatitis

OBJECTIVE The purpose of this article is to discuss and illustrate the most relevant and unique MRI features of groove pancreatitis. CONCLUSION Groove pancreatitis in an uncommon type of focal chronic pancreatitis. Its appearance may resemble pancreatic adenocarcinoma. Although distinction between these two entities remains challenging, knowledge of MRI findings is important in suggesting the correct diagnosis and programming therapeutic decisions.

MR Imaging–Transrectal US Fusion for Targeted Prostate Biopsies: Implications for Diagnosis and Clinical Management

Cancer of the prostate gland is a common but heterogeneous disease requiring individualized risk stratification for optimal clinical management. However, transrectal ultrasonography (US)-guided biopsy-the standard of care for diagnosis of prostate cancer-frequently fails to detect aggressive tumors or provide reliable parameters for pretreatment risk stratification. Multiparametric magnetic resonance (MR) imaging is the most accurate imaging technique for prostate cancer detection and local staging. Recently, different approaches have been developed to allow targeted biopsies of areas that are suspicious for cancer at MR imaging, including direct MR imaging guidance and MR imaging-transrectal US fusion, which can be achieved with cognitive fusion or software assistance. Regardless of the technique used, targeted prostate biopsies have the potential to increase detection of clinically relevant prostate cancer and provide more reliable risk stratification in patients with known cancer. The authors discuss the shortcomings of traditional diagnostic workup for prostate cancer, the rationale for targeted prostate biopsies, the different techniques available for targeting suspicious areas seen at MR imaging, and the clinical contexts in which targeted prostate biopsies might be useful. In addition, they discuss opportunities and challenges associated with MR imaging-transrectal US fusion biopsy, as well as questions that need to be addressed before formal incorporation of this technique into practice guidelines.

Prevalence of noncardiac findings on clinical cardiovascular MRI.

OBJECTIVE The purpose of our study was to determine the prevalence and significance of noncardiac findings on clinical cardiovascular MRI and to identify the cardiovascular MRI sequences that most frequently depict noncardiac findings. MATERIALS AND METHODS Images from 495 clinical cardiovascular MRI studies performed during 2006 were reviewed specifically for noncardiac findings by a cardiovascular imaging fellowship-trained radiologist without knowledge of the prior study interpretation. Noncardiac findings were classified as benign (e.g., gynecomastia), indeterminate (e.g., pleural effusion), or worrisome (e.g., lung nodule). The cardiovascular MRI sequences depicting the noncardiac finding were recorded. RESULTS On image review, 295 noncardiac findings were identified in 212 (43%) of 495 studies, including 148 benign, 133 indeterminate, and 14 worrisome noncardiac findings. Of these, 47% of indeterminate and 57% of worrisome noncardiac findings were not previously known. Cardiovascular MRI sequences that most frequently showed noncardiac findings included the single-shot fast steady-state free precession (SSFP) scout images (63% of all noncardiac findings) and axial T1-weighted fast spin-echo thoracic images (60% of all noncardiac findings), with 99% of management-changing noncardiac findings visualized on one of these two sequences. CONCLUSION Noncardiac findings on clinical cardiovascular MRI are common. Although only a small minority of studies contain management-changing noncardiac findings, the vast majority of management-changing noncardiac findings are seen on thoracic SSFP scout and axial T1-weighted thoracic fast spin-echo images.

Decision analysis model comparing cost of multiparametric magnetic resonance imaging vs. repeat biopsy for detection of prostate cancer in men with prior negative findings on biopsy

PURPOSE We compared cost of multiparametric magnetic resonance imaging (MP-MRI) vs. repeat biopsy in detection of prostate cancer (PCa) in men with prior negative findings on biopsy. METHODS A decision tree model compared the strategy of office-based transrectal ultrasound-guided biopsy (TRUS) for men with prior negative findings on biopsy with a strategy of initial MP-MRI with TRUS performed only in cases of abnormal results on imaging. Study end points were cost, number of biopsies, and cancers detected. Cost was based on Medicare reimbursement. Cost of sepsis and minor complications were incorporated into analysis. Sensitivity analyses were performed by varying model assumptions. RESULTS The baseline model with 24% PCa found that the overall cost for 100 men was

Assessment of Prospectively Assigned Likert Scores for Targeted Magnetic Resonance Imaging-Transrectal Ultrasound Fusion Biopsies in Patients with Suspected Prostate Cancer

90,400 and

Geometric Distortion in Diffusion-weighted MR Imaging of the Prostate—Contributing Factors and Strategies for Improvement

87,700 for TRUS and MP-MRI arms, respectively. The MP-MRI arm resulted in 73 fewer biopsies per 100 men but detected 4 fewer cancers (16 vs. 20.4) than the TRUS arm did. A lower risk of PCa resulted in lower costs for the MP-MRI arm and a small difference in detected cancers. At lower cancer rates, MP-MRI is superior to TRUS over a wide range of sensitivity and specificity of MRI. A lower sensitivity of MP-MRI decreases the cost of the MP-MRI, as fewer biopsies are performed, but this also reduces the number of cancers detected. CONCLUSIONS The use of MP-MRI to select patients for repeat biopsy reduced the number of biopsies needed by 73% but resulted in a few cancers being missed at lower cost when compared with the TRUS arm. Further studies are required to determine whether cancers missed represent clinically significant tumors.

Comparison of prostate cancer detection at 3-T MRI with and without an endorectal coil: A prospective, paired-patient study

PURPOSE We assess the performance of prospectively assigned magnetic resonance imaging based Likert scale scores for the detection of clinically significant prostate cancer, and analyze the pre-biopsy imaging variables associated with increased cancer detection using targeted magnetic resonance imaging-transrectal ultrasound fusion biopsy. MATERIALS AND METHODS In this retrospective review of prospectively generated data including men with abnormal multiparametric prostate magnetic resonance imaging (at least 1 Likert score 3 or greater lesion) who underwent subsequent targeted magnetic resonance imaging-transrectal ultrasound fusion biopsy, we determined the association between different imaging variables (Likert score, lesion size, lesion location, prostate volume, radiologist experience) and targeted biopsy positivity rate. We also compared the detection of clinically significant cancer according to Likert scale scores. Tumors with high volume (50% or more of any core) Gleason score 3+4 or any tumor with greater Gleason score were considered clinically significant. Each lesion served as the elementary unit for analysis. We used logistic regression for univariate and multivariate (stepwise selection) analysis to assess for an association between targeted biopsy positivity rate and each tested variable. The relationship between Likert scale and Gleason score was evaluated using the Spearman correlation coefficient. RESULTS A total of 161 men with 244 lesions met the study eligibility criteria. Targeted biopsies diagnosed cancer in 41% (66 of 161) of the men and 41% (99 of 244) of the lesions. The Likert score was the strongest predictor of targeted biopsy positivity (OR 3.7, p <0.0001). Other imaging findings associated with a higher targeted biopsy positivity rate included smaller prostate volume (OR 0.7, p <0.01), larger lesion size (OR 2.2, p <0.001) and anterior location (OR 2.0, p=0.01). On multiple logistic regression analysis Likert score, lesion size and prostate volume were significant predictors of targeted biopsy positivity. Higher Likert scores were also associated with increased detection of clinically significant tumors (p <0.0001). CONCLUSIONS The Likert scale score used to convey the degree of suspicion on multiparametric magnetic resonance imaging is the strongest predictor of targeted biopsy positivity and of the presence of clinically significant tumor.

Diagnosis of relevant prostate cancer using supplementary cores from magnetic resonance imaging-prompted areas following multiple failed biopsies

RATIONALE AND OBJECTIVES Image distortion on diffusion-weighted imaging (DWI) of the prostate in 3T endorectal magnetic resonance imaging (MRI) examinations is common. The aim of this study was to determine the degree of distortion on DWI using a state-of-the-art clinical protocol and to explore the main contributors to geometric distortion. MATERIALS AND METHODS Forty consecutive patients underwent 3T MRI of the prostate with an endorectal coil filled with air (n = 20) or barium sulfate (n = 20). Distortion was measured as the maximum displacement of the outer boundary of the prostate on DWI relative to T2-weighted imaging. The effects of phase-encoding direction, receiver bandwidth, and parallel imaging were then assessed in a prostate phantom on two MRI scanners from different manufacturers. RESULTS There was no statistical difference in the mean displacement of the prostate on DWI between the air cohort (1.8 ± 1.2 mm, range 0-4.2 mm) and barium cohort (1.8 ± 2.2 mm, range 0-9 mm). Displacement of the prostate was observed in the phase-encoding direction. Phantom experiments demonstrated a horizontal displacement of 6.0 mm in the phase-encoding direction, which decreased with the use of parallel imaging and higher bandwidth. Geometric distortion was similar for all b values and across manufacturers. CONCLUSIONS Geometric distortion on DWI of the prostate is common in the phase-encoding direction and does not improve with inflating the coil with barium sulfate. Strategies to reduce this artifact include the use of higher bandwidth and accelerated imaging. Correction of this phenomenon should improve localization of prostate cancer, particularly important for targeted prostate biopsies or focal therapies.

Diagnostic Accuracy of Multiparametric Magnetic Resonance Imaging to Identify Clear Cell Renal Cell Carcinoma in cT1a Renal Masses

OBJECTIVES To compare the sensitivity of 2 different non-endorectal coil strategies vs. endorectal coil (ERC) magnetic resonance imaging (MRI) for detection of prostate cancer (PCa). METHODS In this prospective, single-center, paired-patient, paired-reader study, 49 men with a clinical indication for MRI underwent non-ERC (phased-array coil only) T2-weighted imaging and diffusion-weighted imaging followed by the same sequences using both ERC and phased-array coils (ERC Protocol). Patients were randomized into 1 of 2 arms: standard non-ERC protocol and augmented non-ERC protocol. Lesions with Likert score≥3 were defined as suspicious for cancer. Radical prostatectomy specimen or combined systematic plus targeted biopsies served as the standard of reference. Cancers were stratified into risk groups according to the National Comprehensive Cancer Network guidelines. Generalized estimating equations with Bonferroni correction were used for comparisons. The level of reader confidence was inferred by the Likert scores assigned to index lesions. RESULTS The ERC protocol provided sensitivity (78%) superior to MRI without ERC for PCa detection, both with a standard (43%) (P<0.0001) or augmented (60%) (P<0.01) protocol. The ERC MRI missed less-intermediate or high-risk index lesions (4%) than standard non-ERC (42%) (P = 0.02) and augmented non-ERC MRI (25%), although the latter did not reach significance (P = 0.09). The ERC improved radiologist confidence for the detection of PCa (average Likert score = 4.2±1.4) compared to standard (2.3±2.3) and augmented (2.9±2.1) non-ERC (P = 0.001). CONCLUSIONS The use of combined ERC and pelvic phased-array coil for T2-weighted imaging and diffusion-weighted imaging provides superior sensitivity for the detection of PCa compared to an examination performed without the ERC.