Automated MR Image Prescription of the Liver Using Deep Learning: Development, Evaluation, and Prospective Implementation.

BACKGROUND: There is an unmet need for fully automated image prescription of the liver to enable efficient, reproducible MRI. PURPOSE: To develop and evaluate artificial intelligence (AI)-based liver image prescription. STUDY TYPE: Prospective. POPULATION: A total of 570 female/469 male patients (age: 56 ± 17 years) with 72%/8%/20% assigned randomly for training/validation/testing; two female/four male healthy volunteers (age: 31 ± 6 years). FIELD STRENGTH/SEQUENCE: 1.5 T, 3.0 T; spin echo, gradient echo, bSSFP. ASSESSMENT: A total of 1039 three-plane localizer acquisitions (26,929 slices) from consecutive clinical liver MRI examinations were retrieved retrospectively and annotated by six radiologists. The localizer images and manual annotations were used to train an object-detection convolutional neural network (YOLOv3) to detect multiple object classes (liver, torso, and arms) across localizer image orientations and to output corresponding 2D bounding boxes. Whole-liver image prescription in standard orientations was obtained based on these bounding boxes. 2D detection performance was evaluated on test datasets by calculating intersection over union (IoU) between manual and automated labeling. 3D prescription accuracy was calculated by measuring the boundary mismatch in each dimension and percentage of manual volume covered by AI prescription. The automated prescription was implemented on a 3 T MR system and evaluated prospectively on healthy volunteers. STATISTICAL TESTS: Paired t-tests (threshold = 0.05) were conducted to evaluate significance of performance difference between trained networks. RESULTS: In 208 testing datasets, the proposed method with full network had excellent agreement with manual annotations, with median IoU > 0.91 (interquartile range < 0.09) across all seven classes. The automated 3D prescription was accurate, with shifts <2.3 cm in superior/inferior dimension for 3D axial prescription for 99.5% of test datasets, comparable to radiologists' interreader reproducibility. The full network had significantly superior performance than the tiny network for 3D axial prescription in patients. Automated prescription performed well across single-shot fast spin-echo, gradient-echo, and balanced steady-state free-precession sequences in the prospective study. DATA CONCLUSION: AI-based automated liver image prescription demonstrated promising performance across the patients, pathologies, and field strengths studied. EVIDENCE LEVEL: 4. TECHNICAL EFFICACY: Stage 1.

Evaluation of Guideline Adherence and Subsequent Follow-Up Outcomes for Incidental Thyroid Nodules Detected in Hybrid Academic-Community Practice.

OBJECTIVE: Incidental thyroid nodules (ITNs) are common, and variability regarding follow-up and recommendation practices exist. The study purpose was to determine adherence to the American College of Radiology (ACR) ITN criteria and analyze recommendation outcomes. METHODS: ITNs listed in the impression section on computed tomography, magnetic resonance imaging, and positron emission tomography studies over a 6-month period were included. Report recommendations were compared with ACR white paper criteria for adherence (concordant recommendation) or nonadherence (discordant recommendation). Reader characteristics, further ITN workup, and pathology were recorded. A P value less than 0.05 was used for significance. RESULTS: Three hundred fifty patients (mean age, 64.6 years) were included with a median ITN size of 18-mm. Most nodules (289/350) were reported on computed tomography and were identified for follow-up due to size (235/350). Only 39 of 350 reports (11.1%) did not follow ACR recommendations. Patient age was significantly related to recommendation adherence ( P < 0.05) as opposed to radiologist practice type (ie, community-based or academic) which was not. Nonadherence most often involved recommending ultrasound follow-up for nonactionable small ITNs. The rate of fine-needle aspiration biopsy from concordant ITNs was significantly higher than discordant ITNs ( P < 0.05). Six patients, all with concordant recommendations, had malignant final pathology results. CONCLUSION: Recommendation adherence to the ACR ITN criteria was high, approaching 90%. Nonadherence was mostly due to recommending thyroid ultrasound when not indicated and was correlated with a younger patient age. The rate of fine-needle aspiration biopsy stemming from nonindicated ultrasounds was significantly lower and did not result in the diagnosis of any malignancies.

Water-Soluble Contrast Challenge for Suspected Small-Bowel Obstruction: Technical Success Rate, Accuracy, and Clinical Outcomes.

Among 109 iohexol-based water-soluble contrast (WSC) challenges performed for suspected small-bowel obstruction, 105 were technically adequate. Among technically adequate studies, colonic contrast (i.e., successful challenge) was seen on 66 abdominal radiographs obtained 8 hours after WSC challenge and 86 abdominal radiographs obtained 24 hours after WSC challenge. Fourteen patients underwent operative management, and 91 underwent nonoperative management (NOM). Successful challenge had a sensitivity of 91.2%, specificity of 78.5%, PPV of 96.5%, NPV of 57.8%, and odds ratio of 38.0 (95% CI, 8.7-165.2) for NOM. Three of 86 patients with successful challenge underwent operative management.

Removing rician bias in diffusional kurtosis of the prostate using real-data reconstruction.

PURPOSE: To compare prostate diffusional kurtosis imaging (DKI) metrics generated using phase-corrected real data with those generated using magnitude data with and without noise compensation (NC). METHODS: Diffusion-weighted images were acquired at 3T in 16 prostate cancer patients, measuring 6 b-values (0-1500 s/mm2 ), each acquired with 6 signal averages along 3 diffusion directions, with noise-only images acquired to allow NC. In addition to conventional magnitude averaging, phase-corrected real data were averaged in an attempt to reduce rician noise-bias, with a range of phase-correction low-pass filter (LPF) sizes (8-128 pixels) tested. Each method was also tested using simulations. Pixelwise maps of apparent diffusion (D) and apparent kurtosis (K) were calculated for magnitude data with and without NC and phase-corrected real data. Average values were compared in tumor, normal transition zone (NTZ), and normal peripheral zone (NPZ). RESULTS: Simulations indicated LPF size can strongly affect K metrics, where 64-pixel LPFs produced accurate metrics. Relative to metrics estimated from magnitude data without NC, median NC K were lower (P < 0.0001) by 6/11/8% in tumor/NPZ/NTZ, 64-LPF real-data K were lower (P < 0.0001) by 4/10/7%, respectively. CONCLUSION: Compared with magnitude data with NC, phase-corrected real data can produce similar K, although the choice of phase-correction LPF should be chosen carefully.

Diagnostic evaluation of magnetization transfer and diffusion kurtosis imaging for prostate cancer detection in a re-biopsy population.

OBJECTIVE: To evaluate diffusion kurtosis imaging (DKI) and magnetisation transfer imaging (MTI) compared to standard MRI for prostate cancer assessment in a re-biopsy population. METHODS: Thirty-patients were imaged at 3 T including DKI (Kapp and Dapp) with b-values 150/450/800/1150/1500 s/mm2 and MTI performed with and without MT saturation. Patients underwent transperineal biopsy based on prospectively defined MRI targets. Receiver-operating characteristic (ROC) analyses assessed the parameters and Wilcoxon-signed ranked test assessed relationships between metrics. RESULTS: Twenty patients had ≥ 1 core positive for cancer in a total of 26 MRI targets (Gleason 3+3 in 8, 3+4 in 12, ≥ 4+3 in 6): 13 peripheral (PZ) and 13 transition zone (TZ). The apparent diffusion coefficient (ADC) and Dapp were significantly lower and the Kapp and MT ratio (MTR) significantly higher in tumour versus benign tissue (all p ≤ 0.005); ROC values 0.767-1.000. Normal TZ had: lower ADC and Dapp and higher Kapp and MTR compared to normal PZ. MTR showed a moderate correlation to Kapp (r = 0.570) and Dapp (r = -0.537) in normal tissue but a poor correlation in tumours. No parameter separated low-grade (Gleason 3+3) from high-grade (≥ 3+4) disease for either PZ (p = 0.414-0.825) or TZ (p = 0.148-0.825). CONCLUSION: ADC, Dapp, Kapp and MTR all distinguished benign tissue from tumour, but none reliably differentiated low- from high-grade disease. KEY POINTS: • MTR was significantly higher in PZ and TZ tumours versus normal tissue • K app was significantly lower and D app higher for PZ and TZ tumours • There was no incremental value for DKI/MTI over mono-exponential ADC parameters • No parameter could consistently differentiate low-grade (Gleason 3+3) from high-grade (≥ 3+4) disease • Divergent MTR/DKI values in TZ tumours suggests they offer different functional information.

Opportunistic Screening for Hereditary Hemochromatosis With Unenhanced CT: Determination of an Optimal Liver Attenuation Threshold.

OBJECTIVE: The purpose of this study was to assess whether a specific liver attenuation threshold for unenhanced CT allows both sensitive opportunistic detection of unsuspected hereditary hemochromatosis and low overall screening test-positive rates. MATERIALS AND METHODS: We used a standard ROI placement method on unenhanced CT studies of 3357 consecutive adults (mean age, 57.0 years) with no symptoms of liver disease who underwent colorectal screening. Hepatic attenuation (in HU) was measured to assess test-positive rates at various liver attenuation thresholds. To assess sensitivity, unenhanced hepatic CT attenuation was also measured in 12 patients with hereditary hemochromatosis (mean age, 48.3 years), who were homozygous for the HFE C282Y mutation. All scans were obtained at 120 kV. Serum ferritin levels were recorded for the hereditary hemochromatosis cohort. RESULTS: Mean liver attenuation ± SD among screened adults was 59.4 ± 12.7 HU, compared with 78.7 ± 13.1 HU (range, 59-105 HU) in the hereditary hemochromatosis cohort (p < 0.001). Screening test-positive rates were 30.6% (n = 1028) at 65 HU, 8.2% (n = 275) at 70 HU, 1.2% (n = 39) at 75 HU, and 0.2% (n = 7) at 80 HU. Corresponding sensitivities for hereditary hemochromatosis at these thresholds were 83.3% (10/12) at 65, 70, and 75 HU; and 50.0% (6/12) at 80 HU. Serum ferritin levels were elevated in all patients with hereditary hemochromatosis (mean, 1678 ng/mL; range, 477-3991 ng/mL). CONCLUSION: An unenhanced CT liver attenuation threshold of 75 HU was sensitive (83.3%) for hereditary hemochromatosis while maintaining an acceptably low screening test-positive rate (1.2%). An unexplained liver attenuation of 75 HU or more on unenhanced CT should trigger appropriate laboratory investigation for iron overload; early intervention with phlebotomy can limit or prevent organ damage in patients with hemochromatosis.

Ratio of Tumor to Normal Prostate Tissue Apparent Diffusion Coefficient as a Method for Quantifying DWI of the Prostate.

OBJECTIVE: The purpose of this study was to investigate the ability of the apparent diffusion coefficient (ADC) ratio of tumor to normal prostate tissue to overcome inherent variability based on choice of b values, with whole-mount histopathologic analysis as the reference standard for tumor identification. MATERIALS AND METHODS: Thirty-nine patients with prostate cancer underwent 3-T MRI, including DWI with b values of 0, 150, 750, and 1000 s/mm(2). ADC maps were derived from four b value combinations. Histologically derived ROIs were defined for prostate tumor and benign prostate tissue to generate a ratio. The concordance correlation coefficient was used to evaluate agreement and reproducibility at different b values. Bland-Altman plots were used to evaluate the pattern of relative measurement difference between b value combinations. The relationship between ADC values and Gleason score was tested by Spearman rank correlation. RESULTS: ADC values varied depending on the b value combination selected. The concordance correlation coefficient was higher for ADC ratios (0.883; 95% CI, 0.816-0.927) compared with absolute ADC values for normal tissue (0.873; 95% CI, 0.799-0.921) and tumor (0.792; 95% CI, 0.688-0.864). The ADC ratio concordance correlation coefficient for transition zone tumors was considerably higher than that for the peripheral zone in all cases. Bland-Altman analysis showed higher variation for ADC maps incorporating a b value of zero for both ratio and absolute values. There was a stronger inverse relationship to Gleason score for ADC ratios (rho, -0.354 to -0.456) compared with absolute ADC values (rho, -0.117 to -0.379). CONCLUSION: The use of a simple ratio of prostate tumor ADC to normal tissue ADC improved the concordance between different b value combinations and could provide a more robust means of assessing restricted diffusion in the prostate.

Prostate cancer: performance characteristics of combined T2W and DW-MRI scoring in the setting of template transperineal re-biopsy using MR-TRUS fusion.

OBJECTIVES: To measure the performance characteristics of combined T2-weighted (T2W) and diffusion-weighted (DW) magnetic resonance imaging (MRI) suspicion scoring prior to MR-transrectal ultrasound (TRUS) fusion template transperineal (TTP) re-biopsy. METHODS: Thirty-nine patients referred for prostate re-biopsy, with prior MRI examinations, were retrospectively included. The MR images, including T2W and DW-MRI, had been independently evaluated prospectively by two radiologists using a structured scoring system. An MR-TRUS fusion TTP re-biopsy was used for MR target and non-targeted biopsy cores. Targeting performance and correlation with disease status were evaluated on a per-patient and per-region basis. RESULTS: The cancer yield was 41% (16/39 patients). MR targeting accurately detected the disease in 12/16 (75%) cancerous patients and missed the disease in 4/16 (25%) patients, all with Gleason 3 + 3 disease. There was a significant relationship (P < 0.01) between MR suspicion score and the significance of cancer. Reader 1 had significantly higher sensitivity in the transition zone (TZ; 0.84) compared with the peripheral zone (PZ; 0.32) (P = 0.04). Inter-reader agreement was moderate for the PZ and substantial for the TZ. CONCLUSIONS: MRI targeting is beneficial in the setting of TTP MR-TRUS fusion re-biopsy and MR suspicion score relates to prostate cancer clinical significance. A T2W and DW-MRI structured scoring system results in good inter-reader agreement in this setting. KEY POINTS: • Pre-biopsy MRI aids the detection of high significance cancer during prostate re-biopsy. • MRI suspicion level correlates with the clinical significance of prostate cancer detected. • T2W and DW-MRI structured scoring of pre-biopsy MRI permits good inter-reader agreement.

Preoperative 3-T diffusion-weighted MRI for the qualitative and quantitative assessment of extracapsular extension in patients with intermediate- or high-risk prostate cancer.

OBJECTIVE: The purpose of this study was to prospectively evaluate the value of diffusion-weighted MRI (DWI) for the assessment of extracapsular extension (ECE) in patients with prostate cancer. SUBJECTS AND METHODS: Between November 2010 and April 2012, 40 patients with intermediate- to high-risk prostate cancer were prospectively recruited. MR images were obtained at 3 T with a phased-array coil. Two independent readers scored the T2-weighted images alone and then in combination with DW images. ROIs were drawn on the apparent diffusion coefficient (ADC) maps, and histogram-derived values were calculated. Whole-mount histopathologic examination was the standard of reference. Reader performance was analyzed, and differences in patient characteristics and histogram-based ADC values, according to ECE status, were evaluated. RESULTS: ECE was present in 23 of 40 (58%) patients and 23 of 43 (53%) tumors. The sensitivity for side-specific ECE detection significantly increased, from 0.22 to 0.44 for reader 1 and 0.33 to 0.82 for reader 2 (both p < 0.05) without a significant change in specificity for either reader with the addition of DWI and ADC mapping. The positive and negative predictive values for both readers also increased. The ADC parameters of median and 10th and 25th centiles showed a statistically significant difference between tumors with and those without ECE (p < 0.05). CONCLUSION: The addition of DWI and ADC mapping to T2-weighted MRI improved the accuracy of preoperative detection of ECE. Median and 10th and 25th centile ADC values were significantly associated with the presence of ECE and may be useful in the pretreatment assessment of patients with prostate cancer.

Definitions of terms, processes and a minimum dataset for transperineal prostate biopsies: a standardization approach of the Ginsburg Study Group for Enhanced Prostate Diagnostics.

OBJECTIVES: To define terms and processes and agree on a minimum dataset in relation to transperineal prostate biopsy procedures and enhanced prostate diagnostics. To identify the need for further evaluation and establish a collaborative research practice. PATIENTS AND METHODS: A 19-member multidisciplinary panel rated 66 items for their appropriateness and their definition to be incorporated into the international databank using the Research and Development/University of California Los Angeles Appropriateness Method. The item list was developed from interviews conducted with healthcare professionals from urology, radiology, pathology and engineering. RESULTS: The panel agreed on 56 items that were appropriate to be incorporated into a prospective database. In total, 10 items were uncertain and were omitted. These items were within the categories: definitions (n = 2), imaging (n = 1), surgical protocols (n = 2) and histology (n = 5). CONCLUSIONS: The components of a minimum dataset for transperineal prostate biopsy have been defined. This provides an opportunity for multicentre collaborative data analysis and technique development. The findings of the present study will facilitate prospective studies into the application and outcome of transperineal prostate biopsies.

Appendiceal length as an independent risk factor for acute appendicitis.

OBJECTIVES: To determine if appendiceal lengths differ between adults with acute appendicitis and asymptomatic controls. METHODS: In vivo appendiceal length at computed tomography (CT) in 321 adults with surgically proven appendicitis was compared with that in 321 consecutive asymptomatic adult controls. CT length was derived using curved multiplanar reformats along the long axis. Gross pathological length provided external validation for appendectomy cases. RESULTS: Appendiceal length at CT correlated well with appendicitis specimens (mean length, 6.8 cm vs 6.6 cm; 79 % within 1.5 cm). For asymptomatic controls, mean CT appendiceal length was 7.9 cm, longer in men (8.4 ± 3.8 vs 7.4 ± 3.1 cm; P = 0.02), matching closely historical normative post-mortem data. The mean and standard deviation of appendiceal length at CT were significantly greater among negative controls than in the positive appendicitis group (7.9 ± 3.5 vs 6.8 ± 1.9 cm; P = 0.03). Of appendicitis cases, 90 % (288/321) fell within the range 4.0-10.0 cm, compared with 59 % (189/321) of negative controls (P < 0.001). Among controls, a fivefold increase in appendixes >10 cm and a twofold increase in appendixes <4 cm were observed. Half (9/18) of long appendicitis cases showed tip appendicitis at CT. CONCLUSIONS: "Intermediate" appendiceal lengths (4-10 cm) are more frequently complicated by acute appendicitis, whereas both "long" (>10 cm) and "short" (<4 cm) lengths are more frequently observed in unaffected adults.

Assessment of 18F-DCFPyL PSMA PET/CT and PET/MR quantitative parameters for reference standard organs: Inter-reader, inter-modality, and inter-patient variability.

Prostate specific membrane antigen (PSMA)-based radiotracers have shown promise for prostate cancer assessment. Evaluation of quantitative variability and establishment of reference standards are important for optimal clinical and research utility. This work evaluates the variability of PSMA-based [18F]DCFPyL (PyL) PET quantitative reference standards. Consecutive eligible patients with biochemically recurrent prostate cancer were recruited for study participation from August 2016-October 2017. After PyL tracer injection, whole body PET/CT (wbPET/CT) was obtained with subsequent whole body PET/MR (wbPET/MR). Two readers independently created regions of interest (ROIs) including a 40% standardized uptake value (SUV) threshold ROI of the whole right parotid gland and separate spherical ROIs in the superior, mid, and inferior gland. Additional liver (right lobe) and blood pool spherical ROIs were defined. Bland-Altman analysis, including limits of agreement (LOA), as well as interquartile range (IQR) and coefficient of variance (CoV) was used. Twelve patients with prostate cancer were recruited (mean age, 61.8 yrs; range 54-72 years). One patient did not have wbPET/MR and was excluded. There was minimal inter-reader SUVmean variability (bias±LOA) for blood pool (-0.13±0.42; 0.01±0.41), liver (-0.55±0.82; -0.22±1.3), or whole parotid gland (-0.05±0.31; 0.08±0.24) for wbPET/CT and wbPET/MR, respectively. Greater inter-reader variability for the 1-cm parotid gland ROIs was present, for both wbPET/CT and wbPET/MR. Comparing wbPET/CT to the subsequently acquired wbPET/MR, blood pool had a slight decrease in SUVmean. The liver as well as parotid gland showed a slight increase in activity although the absolute bias only ranged from 0.45-1.28. The magnitude of inter-subject variability was higher for the parotid gland regardless of modality or reader. In conclusion, liver, blood pool, and whole parotid gland quantitation show promise as reliable reference normal organs for clinical/research PET applications. Variability with 1-cm parotid ROIs may limit its use.

Alternative diagnoses to suspected appendicitis at CT.

PURPOSE: To assess alternative diagnoses in adults undergoing computed tomography (CT) for suspected acute appendicitis in routine clinical practice. MATERIALS AND METHODS: This retrospective study was HIPAA compliant and institutional review board approved; informed consent was waived. A total of 1571 consecutive adults were referred from emergency department or urgent care settings for evaluation of suspected acute appendicitis at a single academic medical center from January 2006 to December 2009. Diagnoses given by board-certified radiologists at nonfocused abdominopelvic CT and ultimate clinical diagnoses by a combination of clinical, surgical, pathologic, and other radiologic findings were analyzed. Comparisons were made by using the Fisher exact test and Mann-Whitney test, where appropriate, with a two-tailed P value of less than .05 used as the criterion for statistical significance. RESULTS: A specific diagnosis at CT examination was made in 867 of 1571 (55.2%) patients. Acute appendicitis was favored in 371 of 1571 (23.6%) patients. An alternative diagnosis other than appendicitis was suggested in 496 of 1571 (31.6%) patients. Among patients with an alternative CT diagnosis, 204 of 496 (41.1%) were hospitalized and 109 of 496 (22.0%) underwent surgical or image-guided intervention for diagnoses other than appendicitis, compared with rates of 14.1% and 4.4%, respectively, among patients in whom a specific diagnosis was not made at CT (P < .0001). The most common broad categories of disease included nonappendiceal gastrointestinal conditions (46.0%), gynecologic conditions (21.6%), genitourinary conditions (16.9%), and hepatopancreaticobiliary conditions (7.7%). CONCLUSION: In adult patients clinically suspected of having acute appendicitis, abdominopelvic CT frequently identifies an alternative cause for symptoms, which often requires hospitalization and surgery for treatment.

Diagnostic performance of multidetector computed tomography for suspected acute appendicitis.

BACKGROUND: Use of preoperative computed tomography for suspected acute appendicitis has dramatically increased since the introduction of multidetector CT (MDCT) scanners. OBJECTIVE: To evaluate the diagnostic performance of MDCT for suspected acute appendicitis in adults. DESIGN: Analysis of MDCT findings and clinical outcomes of consecutive adults referred for MDCT for suspected appendicitis from January 2000 to December 2009. SETTING: Single academic medical center in the United States. PATIENTS: 2871 adults. MEASUREMENTS: Interpretation of nonfocused abdominopelvic MDCT scans by radiologists who were aware of the study indication. Posttest assessment of diagnostic performance of MDCT for acute appendicitis, according to the reference standard of final combined clinical, surgical, and pathology findings. RESULTS: 675 of 2871 patients (23.5%) had confirmed acute appendicitis. The sensitivity, specificity, and negative and positive predictive values of MDCT were 98.5% (95% CI, 97.3% to 99.2%) (665 of 675 patients), 98.0% (CI, 97.4% to 98.6%) (2153 of 2196 patients), 99.5% (CI, 99.2% to 99.8%) (2153 of 2163 patients), and 93.9% (CI, 91.9% to 95.5%) (665 of 708 patients), respectively. Positive and negative likelihood ratios were 51.3 (CI, 38.1 to 69.0) and 0.015 (CI, 0.008 to 0.028), respectively. The overall rate of negative findings at appendectomy was 7.5% (CI, 5.8% to 9.7%) (54 of 716 patients), but would have decreased to 4.1% (28 of 690 patients) had surgery been avoided in 26 cases with true-negative findings on MDCT. The overall perforation rate was 17.8% (120 of 675 patients) but progressively decreased from 28.9% in 2000 to 11.5% in 2009. Multidetector computed tomography provided or suggested an alternative diagnosis in 893 of 2122 patients (42.1%) without appendicitis or appendectomy. LIMITATION: Possible referral bias, because some patients whose appendicitis was difficult to diagnose on clinical grounds may not have been referred for MDCT for evaluation of suspected appendicitis. CONCLUSION: Multidetector computed tomography is a useful test for routine evaluation of suspected appendicitis in adults. PRIMARY FUNDING SOURCE: None.

MDCT for suspected appendicitis in the elderly: diagnostic performance and patient outcome.

Elderly adults are at increased risk for complications related to both delayed diagnosis of appendicitis and to unnecessary appendectomy. We assessed the diagnostic performance of computed tomography (CT) in a consecutive elderly cohort with clinically suspected appendicitis. CT findings and clinical outcomes were analyzed for 262 consecutive adult patients age 65 and older (mean 75.6 ± 7.5 years; range 65-94; M/F 111:151) referred for clinically suspected appendicitis at a single medical center between January 2000 and December 2009. The overall prevalence of proven acute appendicitis in this elderly cohort with clinically suspected appendicitis was 16.8% (44/262). CT sensitivity, specificity, PPV, and NPV for acute appendicitis were 100% (44/44), 99.1% (216/218), 95.7% (44/46), and 100.0% (216/216), respectively. The negative appendectomy rate was 2.3% (1/43). The perforation rate was 40.9% (18/44). There were no false-negative and two false-positive CT interpretations. All patients with appendicitis suspected on CT were hospitalized (44/44), with an average stay of 5.7 ± 3.2 days, and 93.5% (43/46) underwent appendectomy. Overall surgical complication rate was 34.9% (15/43). Compared with younger adults over the same period, elderly patients had higher rates of perforation and surgical complications, and longer hospital stays (p < 0.003). CT is highly accurate for the evaluation of clinically suspected appendicitis in elderly patients. Prompt diagnosis is important given the higher rates perforation and surgical complications relative to younger adults.

Evaluating suspected small bowel obstruction with the water-soluble contrast challenge.

With optimized technique, the water-soluble contrast challenge is effective at triaging patients for operative vs non-operative management of suspected small bowel obstruction. Standardized study structure and interpretation guidelines aid in clinical efficacy and ease of use. Many tips and tricks exist regarding technique and interpretation, and their understanding may assist the interpreting radiologist. In the future, a CT-based water-soluble contrast challenge, utilizing oral contrast given as part of the initial CT examination, might allow for a more streamlined algorithm and provide more rapid results.

Ultrasound-guided biopsy of challenging abdominopelvic targets.

Percutaneous ultrasound-guided biopsies have become the standard of practice for tissue diagnosis in the abdomen and pelvis for many sites including liver, kidney, abdominal wall, and peripheral nodal stations. Additional targets may appear difficult or impossible to safely biopsy by ultrasound due to interposed bowel loops/vasculature, deep positioning, association with the bowel, or concern for poor visibility; however, by optimizing technique, it is often possible to safely and efficiently use real-time ultrasound guidance for sampling targets that normally would be considered only appropriate for CT guided or surgical/endoscopic biopsy.

Reduced field-of-view and multi-shot DWI acquisition techniques: Prospective evaluation of image quality and distortion reduction in prostate cancer imaging.

OBJECTIVES: To prospectively compare image quality and apparent diffusion coefficient (ADC) quantification for reduced field-of-view (rFOV)- and multi-shot echo-planar imaging (msEPI)-based diffusion weighted imaging (DWI), using single-shot echo-planar-imaging (ssEPI) DWI as the reference. METHODS: Under IRB approval and after informed consent, msEPI, rFOV, and ssEPI DWI acquisitions were prospectively added to clinical prostate MRI exams at 3.0 T. Image distortion was quantitatively evaluated by root-mean-squared displacement (dr.m.s.). Histogram-based quantitative ADC parameters were compared in a sub-set of patients for proven sites of prostate cancer and matched non-cancerous prostate. Three radiologists also independently evaluated the DWI sequences for subjective image quality and distortion/artifact on a 5-point Likert scale. RESULTS: Twenty-five patients were included (15 with proven sites of cancer). Average dr.m.s. demonstrated a small but statistically significant reduction in distortion for both rFOV and msEPI relative to ssEPI. Quantitative ADC parameters for prostate tumors demonstrated no significant difference across the 3 DWI acquisitions and each acquisition demonstrated a statistically significant decrease in mean ADC for tumor compared to normal prostate. Qualitative reader assessment demonstrated favorable image quality for rFOV and msEPI, more notable for msEPI. CONCLUSIONS: rFOV and msEPI DWI techniques achieved reduction in image distortion, improvement in image quality, and maintained reproducible ADC quantification compared to the standard ssEPI.

Colorectal polyps: stand-alone performance of computer-aided detection in a large asymptomatic screening population.

PURPOSE: To evaluate stand-alone performance of computer-aided detection (CAD) for colorectal polyps of 6 mm or larger at computed tomographic (CT) colonography in a large asymptomatic screening cohort. MATERIALS AND METHODS: In this retrospective, institutional review board-approved, HIPAA-compliant study, a CAD software system was applied to screening CT colonography in 1638 women and 1408 men (mean age, 56.9 years) evaluated at a single medical center between March 2006 and December 2008. All participants underwent cathartic preparation with stool tagging; electronic cleansing was not used. The reference standard consisted of interpretation by experienced radiologists in all cases. This interpretation was further refined for the subset of cases with positive findings by using subsequent colonoscopic or CT colonographic confirmation, as well as retrospective expert localization of polyps with CT colonography. This test set was not involved in training the CAD system. The Fisher exact test was used to evaluate significance; 95% confidence intervals (CIs) were obtained by using the exact method. RESULTS: Per-patient CAD sensitivities were 93.8% (350 of 373; 95% CI: 90.9%, 96.1%) and 96.5% (137 of 142; 95% CI: 92.0%, 98.8%) at 6- and 10-mm threshold sizes, respectively. Per-polyp CAD sensitivities for all polyps, regardless of histologic features, were 90.1% (547 of 607; 95% CI: 88.0%, 92.8%) and 96.0% (168 of 175; 95% CI: 91.9%, 98.4%) at 6- and 10-mm threshold sizes, respectively; CAD sensitivities for advanced neoplasia and cancer were 97.0% (128 of 132; 95% CI: 92.4%, 99.2%) and 100% (13 of 13; 95% CI: 79.4%, 100%), respectively. The mean and median false-positive rates were 4.7 and 3 per series, respectively (9.4 and 6 per patient). Among 373 patients with a positive finding at CT colonography, CAD marked an additional 15 polyps of 6 mm or larger, including four large polyps, that were missed at the prospective three-dimensional reading by an expert but were found at subsequent colonoscopy. CONCLUSION: Stand-alone CAD demonstrated excellent performance for polyp detection in a large screening population, with high sensitivity and an acceptable number of false-positive results.