Faculty Bibliography

OBJECTIVE: The apparent diffusion coefficient (ADC) values for benign central zone (CZ) of the prostate were compared with ADC values of benign peripheral zone (PZ), benign transition zone (TZ), and prostate cancer, using histopathologic findings from radical prostatectomy as the reference standard. MATERIALS AND METHODS: The study included 27 patients with prostate cancer (mean [+/- SD] age, 60.0 +/- 7.6 years) who had 3-T endorectal coil MRI of the prostate performed before undergoing prostatectomy with whole-mount histopathologic assessment. Mean ADC values were recorded from the ROI within the index tumor and within benign CZ, PZ, and TZ, with the use of histopathologic findings as the reference standard. ADC values of the groups were compared using paired t tests and ROC curve analysis. RESULTS: The ADC of benign CZ in the right (1138 +/- 123 x 10(-6) mm(2)/s) and left (1166 +/- 141 x 10(-6) mm(2)/s) lobes was not significantly different (p = 0.217). However, the ADC of benign CZ (1154 +/- 129 x 10(-6) mm(2)/s) was significantly lower (p < 0.001) than the ADCs of benign PZ (1579 +/- 197 x 10(-6) mm(2)/s) and benign TZ (1429 +/- 180 x 10(-6) mm(2)/s). Although the ADC of index tumors (1042 +/- 134 x 10(-6) mm(2)/s) was significantly lower (p = 0.002) than the ADC of benign CZ there was no significant difference (p = 0.225) between benign CZ and tumors with a Gleason score of 6 (1119 +/- 87 x 10(-6) mm(2)/s). In 22.2% of patients (6/27), including five patients who had tumors with a Gleason score greater than 6, the ADC was lower in benign CZ than in the index tumor. The AUC of ADC for the differentiation of benign CZ from index tumors was 72.4% (sensitivity, 70.4%; specificity, 51.9%), and the AUC of ADC for differentiation from tumors with a Gleason score greater than 6 was 76.7% (sensitivity, 75.0%; specificity, 65.0%). CONCLUSION: The ADC of benign CZ is lower than the ADC of other zones of the prostate and overlaps with the ADC of prostate cancer tissue, including high-grade tumors. Awareness of this potential diagnostic pitfall is important to avoid misinterpreting the normal CZ as suspicious for tumor.

This article presents our local experience in the implementation of a real-time web-based system for reporting and tracking quality issues relating to abdominal imaging examinations. This system allows radiologists to electronically submit examination quality issues during clinical readouts. The submitted information is e-mailed to a designate for the given modality for further follow-up; the designate may subsequently enter text describing their response or action taken, which is e-mailed back to the radiologist. Review of 558 entries over a 6-year period demonstrated documentation of a broad range of examination quality issues, including specific issues relating to protocol deviation, post-processing errors, positioning errors, artifacts, and IT concerns. The most common issues varied among US, CT, MRI, radiography, and fluoroscopy. In addition, the most common issues resulting in a patient recall for repeat imaging (generally related to protocol deviation in MRI and US) were identified. In addition to submitting quality problems, radiologists also commonly used the tool to provide recognition of a well-performed examination. An electronic log of actions taken in response to radiologists' submissions indicated that both positive and negative feedback were commonly communicated to the performing technologist. Information generated using the tool can be used to guide subsequent quality improvement initiatives within a practice, including continued protocol standardization as well as education of technologists in the optimization of abdominal imaging examinations.

AIM: To evaluate the performance of normalised apparent diffusion coefficient (ADC) values for prostate cancer assessment when performed by independent observers blinded to histopathology findings. MATERIALS AND METHODS: Fifty-eight patients undergoing 3 T phased-array coil magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm2) before prostatectomy were included. Two radiologists independently evaluated the images, unaware of the histopathology findings. Regions of interest (ROIs) were drawn within areas showing visually low ADC within the peripheral zone (PZ) and transition zone (TZ) bilaterally. ROIs were also placed within regions in both lobes not suspicious for tumour, allowing computation of normalised ADC (nADC) ratios between suspicious and non-suspicious regions. The diagnostic performance of ADC and nADC were compared. RESULTS: For PZ tumour detection, ADC achieved significantly higher area under the receiver operating characteristic curve (AUC; p=0.026) and specificity (p=0.021) than nADC for reader 1, and significantly higher AUC (p=0.025) than nADC for reader 2. For TZ tumour detection, nADC achieved significantly higher specificity (p=0.003) and accuracy (p=0.004) than ADC for reader 2. For PZ Gleason score >3+3 tumour detection, ADC achieved significantly higher AUC (p=0.003) and specificity (p=0.005) than nADC for reader 1, and significantly higher AUC (p=0.023) than nADC for reader 2. For TZ Gleason score >3+3 tumour detection, ADC achieved significantly higher specificity (p=0.019) than nADC for reader 1. CONCLUSION: In contrast to prior studies performing unblinded evaluations, ADC was observed to outperform nADC overall for two independent observers blinded to the histopathology findings. Therefore, although strategies to improve the utility of ADC measurements in prostate cancer assessment merit continued investigation, caution is warranted when applying normalisation to improve diagnostic performance in clinical practice.

Technologic advances enable performance of diffusion-weighted imaging (DWI) at ultrahigh b-values, where standard monoexponential model analysis may not apply. Rather, non-Gaussian water diffusion properties emerge, which in cellular tissues are, in part, influenced by the intracellular environment that is not well evaluated by conventional DWI. The novel technique, diffusion kurtosis imaging (DKI), enables characterization of non-Gaussian water diffusion behavior. More advanced mathematical curve fitting of the signal intensity decay curve using the DKI model provides an additional parameter Kapp that presumably reflects heterogeneity and irregularity of cellular microstructure, as well as the amount of interfaces within cellular tissues. Although largely applied for neural applications over the past decade, a small number of studies have recently explored DKI outside the brain. The most investigated organ is the prostate, with preliminary studies suggesting improved tumor detection and grading using DKI. Although still largely in the research phase, DKI is being explored in wider clinical settings. When assessing extracranial applications of DKI, careful attention to details with which body radiologists may currently be unfamiliar is important to ensure reliable results. Accordingly, a robust understanding of DKI is necessary for radiologists to better understand the meaning of DKI-derived metrics in the context of different tumors and how these metrics vary between tumor types and in response to treatment. In this review, we outline DKI principles, propose biostructural basis for observations, provide a comparison with standard monoexponential fitting and the apparent diffusion coefficient, report on extracranial clinical investigations to date, and recommend technical considerations for implementation in body imaging. J. Magn. Reson. Imaging 2015.

BACKGROUND: MRI-ultrasound fusion-targeted prostate biopsy (MRF-TB) may improve detection of prostate cancer (PCa) in men presenting for prostate biopsy. We report clinical outcomes of 12-core systematic biopsy (SB) and MRF-TB in men presenting for primary biopsy and further describe pathological characteristics of cancers detected by SB and not by MRF-TB. MATERIALS & METHODS: Clinical outcomes of 435 consecutive men who underwent pre-biopsy mpMRI followed by MRF-TB and SB at our institution between June 2012 and March 2015 were captured in an IRB-approved database Clinical characteristics, biopsy results and MRI suspicion scores (mSS) were queried from the database. RESULTS: Among 370 men (mean age 64+/-8.5 years; mean PSA 6.8, SEM 0.3 ng/mL) who met inclusion criteria, PCa was detected in 200 (54.1%) cases. Cancer detection rates for SB and MRF-TB were 47.3% and 43.5%, respectively (p = 0.104). MRF-TB detected more Gleason score >/=7 cancers than SB (114/128 (89.1%) vs 95/128 (74.2%), respectively, p = 0.008). Of 39 cancers detected by SB, but not by MRF-TB, 32/39 (82.1%) demonstrated Gleason 6 disease, and 24/39 (61.5%) and 32/39 (82.1%) were clinically insignificant by Epstein and UCSF CAPRA (score