MRI of the Prostate With and Without Endorectal Coil at 3 T: Correlation With Whole-Mount Histopathologic Gleason Score.

OBJECTIVE. The purpose of this article is to prospectively compare image quality and diagnostic accuracy of clinically significant prostate cancer with and without endorectal coil (ERC) at 3 T using a combination of T2-weighted and diffusion-weighted MRI. SUBJECTS AND METHODS. Twenty-three patients with biopsy-proven prostate cancer underwent MRI with and without ERC at the same visit. Patients subsequently underwent radical prostatectomy. Specimens were assessed by whole-mount histopathologic examination. Two radiologists reviewed MR images for image quality (5-point scale) and disease using Prostate Imaging Reporting and Data Systems version 2 (PI-RADSv2). Sensitivity, specificity, and area under the ROC curve (AUC) were calculated with and without ERC. Additionally, apparent diffusion coefficient (ADC) was correlated with Gleason score and ADC values of each lesion were compared with and without ERC. RESULTS. Image quality was comparable with and without ERC (3.8 vs 3.5). Twenty-nine cancer foci larger than 0.5 cm in diameter were found in 23 patients on histopathologic examination; 18 tumors had a Gleason score of 7 or greater. Two radiologists recorded AUC for tumors with a Gleason score of 7 or greater as 0.96 and 0.96 with ERC and 0.88 and 0.91 without ERC. All 13 tumors with a Gleason score of 3 + 4 were detected with ERC, but only 9 were detected without ERC. One of five tumors with Gleason scores less than 3 + 4 was missed with and without ERC. ADC significantly correlated with Gleason score. There was no significant difference in the ADC of a lesion on MRI with and without an ERC. CONCLUSION. MRI with and without ERC was equally accurate at showing prostate cancers with Gleason scores of 4 + 3 or greater. However, MRI with ERC was superior at showing cancer with a Gleason score of 3 + 4. There was no significant difference in ADC values between scores acquired with or without an ERC.

Comparison of image noise and image quality between full-dose abdominal computed tomography scans reconstructed with weighted filtered back projection and half-dose scans reconstructed with improved sinogram-affirmed iterative reconstruction (SAFIRE*).

PURPOSE: To retrospectively compare the image noise, signal-to-noise ratio (SNR), and subjective image quality between CT images acquired with a dual-source, split-dose imaging protocol reconstructed at full and half doses with weighted filtered back projection (wFBP) and an improved sinogram-affirmed iterative reconstruction algorithm (SAFIRE*). METHODS: Fifty-three consecutive patients underwent contrast-enhanced CT of the abdomen using a standardized dual-source, single energy CT protocol. Half-dose images were retrospectively generated using data from one detector only. Full-dose datasets were reconstructed with wFBP, while half-dose datasets were reconstructed with wFBP and SAFIRE* strengths 1-5. Region of interest analysis was performed to assess SNR and noise. Diagnostic acceptability, subjective noise, and spatial resolution were graded on a 10-point scale by two readers. Statistical analysis was carried out with repeated measures analysis of variance, Wilcoxon signed rank test, and Cohen's κ test. RESULTS: With the increasing strengths of SAFIRE*, a progressive reduction in noise and increase in SNR (p < 0.01) was observed. There was a statistically significant decrease in objective noise and increase in SNR in half-dose SAFIRE* strength 4 and 5 reconstructions compared to full-dose reconstructions using wFBP (p < 0.01). Qualitative analysis revealed a progressive increase in diagnostic acceptability, decrease in subjective noise and increase in spatial resolution for half-dose images reconstructed with the increasing strengths of SAFIRE* (p < 0.01). CONCLUSIONS: Half-dose CT images reconstructed with SAFIRE* at strength 4 and 5 have superior image quality compared to full-dose images reconstructed with wFBP. SAFIRE* potentially allows dose reductions in the order of 50% over wFBP.

Safety and efficiency of outpatient versus emergency department-based coronary CT angiography for evaluation of patients with potential ischemic chest pain.

BACKGROUND: While coronary CT angiography (coronary CTA) may be comparable to standard care in diagnosing acute coronary syndrome (ACS) in emergency department (ED) chest pain patients, it has traditionally been obtained prior to ED discharge and a strategy of delayed outpatient coronary CTA following an ED visit has not been evaluated. OBJECTIVE: To investigate the safety of discharging stable ED patients and obtaining outpatient CCTA. METHODS: At two urban Canadian EDs, patients up to 65 years with chest pain but no findings indicating presence of ACS were further evaluated depending upon time of presentation: (1) ED-based coronary CTA during normal working hours, (2) or outpatient coronary CTA within 72 hours at other times. All data were collected prospectively. The primary outcome was the proportion of patients who had an outpatient coronary CTA ordered and had a predefined major adverse cardiac event (MACE) between ED discharge and outpatient CT; secondary outcome was the ED length of stay in both groups. RESULTS: From July 1, 2012 to June 30, 2014, we enrolled 521 consecutive patients: 350 with outpatient CT and 171 with ED-based CT. Demographics and risk factors were similar in both cohorts. No outpatient CT patients had a MACE prior to coronary CTA. (0.0%, 95% CI 0 to 0.9%) The median length of stay for ED-based evaluation was 6.6 hours (interquartile range 5.4 to 8.3 hours) while the outpatient group had a median length of stay of 7.0 hours (IQR 6.0 to 9.8 hours, n.s.). CONCLUSIONS: In ED chest pain patients with a low risk of ACS, performing coronary CTA as an outpatient may be a safe strategy.

Pulmonary functional magnetic resonance imaging: asthma temporal-spatial maps.

RATIONALE AND OBJECTIVES: Hyperpolarized (3)He magnetic resonance imaging (MRI) previously revealed the temporal and spatial heterogeneity of ventilation defects in asthmatics, but these findings have not been used in treatment studies or to guide personalized therapy. Our objective was to exploit the temporal and spatial information inherent to (3)He MRI and develop image processing methods to generate pulmonary ventilation temporal-spatial maps that could be used to measure, optimize, and guide asthma therapy. MATERIALS AND METHODS: In this proof-of-concept study, seven asthmatics provided written informed consent to an approved protocol and underwent spirometry and (3)He MRI on three occasions, each 5 ± 2 days apart. A registration and segmentation pipeline was developed to generate three-dimensional, temporal-spatial, pulmonary function maps. Briefly, (3)He ventilation images were segmented to generate ventilation masks that were coregistered and voxels classified according to their temporal behavior. This enabled the regional mapping of temporally persistent and intermittent ventilation defects that were normalized to the (1)H MRI thoracic cavity volume to generate persistent ventilation defect percent (VDPP) and intermittent ventilation defect percent (VDPI). RESULTS: (3)He temporal-spatial pulmonary function maps identified temporally persistent and intermittent ventilation defects. VDP(I) was significantly greater in the posterior (P = .04) and inferior (P = .04) lung as compared to the anterior and superior lung. Persistent and intermittent ventilation defect percent were strongly correlated with forced expiratory volume in one second/forced vital capacity (VDP(P): r = -0.87, P = .01; VDP(I): r = -0.96, P = .0008). CONCLUSIONS: Temporal-spatial pulmonary maps generated from (3)He MRI can be used to quantify temporally persistent and intermittent ventilation defects as asthma intermediate end points and targets for therapy.

Hyperpolarized (3)He magnetic resonance imaging-derived pulmonary pressure-volume curves.

We aimed to evaluate the potential for the use of hyperpolarized helium-3 magnetic resonance imaging (MRI) apparent diffusion coefficient (ADC) surrogates of alveolar size, together with literature-based morphological parameters in a theoretical model of lung mechanics to simulate noninvasive transpulmonary pressure-volume curves. Fourteen ex-smokers with chronic obstructive pulmonary disease (COPD) (n = 8 stage II, n = 6 stage III/IV COPD) and five age-matched never-smokers, provided written, informed consent and were evaluated at baseline and 26 + or - 2 mo later (n = 15 subjects) using plethysmography, spirometry, and (3)He MRI at 3.0 T. Total lung capacity, residual volume, and literature-based morphological parameters were used with alveolar volumes derived from (3)He ADC to simulate noninvasive pressure-volume curves. The resultant anterior-posterior transpulmonary pressure gradient was significantly decreased for stage II COPD (P < 0.01) and stage III COPD subjects (P < 0.001) compared with healthy volunteers. Both COPD subgroups showed increased alveolar radius compared with healthy subjects (P < 0.01, stage II COPD; P < 0.001, stage III COPD). In addition, surface area and surface tension were significantly increased in stage III COPD compared with healthy volunteers (P < 0.01). These results suggest that (3)He MRI provides a potential noninvasive approach to evaluate lung mechanics regionally and further supports the use of ADC values as a regional noninvasive probe of pulmonary microstructure and compliance.

Simultaneous estimation of input functions: an empirical study.

In neuroreceptor mapping, methods for the estimation of distribution volume require determination of a metabolite-corrected arterial input function. In application, this may be accomplished by collecting arterial blood samples during scanning, adjusting these measurements according to a separate metabolite analysis, and then modeling the resulting concentration data. Although many groups do this routinely, it is invasive and requires considerable effort. Furthermore, both the plasma and the metabolite data are noisy, and thus estimation of kinetic parameters can be affected by this variability. One promising alternative to full-input function modeling is the simultaneous estimation (SIME) approach, in which kinetic parameters and common input function parameters are estimated using results obtained from several regions at once. We investigate the performance of this approach on data from four different radioligands, using various kinetic models, comparing the results with those obtained by estimation using full-input function modeling. Results indicate that SIME provides a promising alternative for all the radioligands considered.

Robust fitting of [11C]-WAY-100635 PET data.

Fitting of a positron emission tomography (PET) time-activity curve is typically accomplished according to the least squares (LS) criterion, which is optimal for data having Gaussian distributed errors, but not robust in the presence of outliers. Conversely, quantile regression (QR) provides robust estimates not heavily influenced by outliers, sacrificing a little efficiency relative to LS when no outliers are present. Given these considerations, we hypothesized that QR would improve parameter estimate accuracy as measured by reduced intersubject variance in distribution volume (V(T)) compared with LS in PET modeling. We compare V(T) values after applying QR with those using LS on 49 controls studied with [(11)C]-WAY-100635. QR decreases the standard deviation of the V(T) estimates (relative improvement range: 0.08% to 3.24%), while keeping the within-group average V(T) values almost unchanged. QR variance reduction results in fewer subjects required to maintain the same statistical power in group analysis without additional hardware and/or image registration to correct head motion.