Non-endorectal Coil Research Articles

Optimization of non-endorectal prostate MR image quality using PI-QUAL: A multidisciplinary team approach

PurposeTo evaluate the utility of the PI-QUAL score in assessing protocol changes aimed to improve image quality from a non-endorectal coil prostate MR imaging protocol during a 9-month quality improvement (QI) project and to quantify the inter-reader agreement of PI-QUAL scores between radiologists, technologists, and physicists. MethodsThis retrospective study audited 1,012 multiparametric prostate MRI examinations as part of a national QI project according to the PI-QUAL standard. PI-QUAL scores were used to inform MR protocol changes. Following the project, 4 radiologists, 2 technologists, and 1 medical physicist collectively audited an additional set of 150 examinations to identify statistical improvements in image quality using the two-tailed Wilcoxon rank sum test. The improvements due to individual protocol changes were assessed among subsets of the 1,012 examinations which compared examinations occurring before and after the isolated protocol change. Inter-reader variability was assessed using the percent majority agreement and the average standard deviation of PI-QUAL scores between evaluators. ResultsDuring this QI project, PI-QUAL scores improved from 3.67 ± 0.75 to 4.16 ± 0.59 (p < 0.01) after implementing a series of protocol changes. Among a subset of 451 cases, we found that adopting R/L rather than A/P phase encoding reduced distortion in diffusion-weighted imaging (DW) from 21.6% (41/190 A/P phase encoded cases) to 11.5% (30/261 R/L phase encoded cases) (p < 0.01). Similarly, in the same 451 cases, adopting R/L phase encoding in T2WI reduced breathing motion artifacts from 34.6% (94/272 A/P phase encoding cases) to 12.8% (23/179 R/L phase encoding cases) (p < 0.01). DWI wraparound artifact was mitigated by employing a full-pelvis shim and enabling the abdomen shim option. The occurrence of low signal-to-noise ratio was reduced from 19.4% (19/98 cases without a weight-based threshold) to 6.3% (10/160) by instituting a weight-based threshold for using an endorectal coil (p < 0.01). The percent majority agreement was similar between radiologists, technologists and physicists, and all evaluators combined (72%, 77%, and 67%, respectively). ConclusionsPI-QUAL can evaluate image quality changes resulting from protocol optimizations at both the exam- and series-levels. With training, radiologists, technologists, and physicists can perform PI-QUAL scoring with similar performance. Broadening the scope of the quality improvement team can result in meaningful and lasting change.

Prostate MRI: Is Endorectal Coil Necessary?-A Review.

To assess the necessity of endorectal coil use in 3 Tesla (T) prostate magnetic resonance imaging (MRI), a literature review comparing the image quality and diagnostic performance with an endorectal coil (ERC) and a without endorectal coil (NERC), with a phased array coil or a wearable perineal coil (WPC), was performed. A PubMed search of 3T prostate MRI using an endorectal coil for studies published until 31 July 2021 was performed. A total of 14 studies comparing 3T prostate MRI with and without endorectal coil use were identified. The quality scores and diagnostic performances were recorded for each study. In total, five studies compared image quality; five studies compared quality and performance; and four studies compared performance of detection, size of detected lesions, accuracy of cancer localization, and aggressiveness/staging. The use of an endorectal coil improved image quality with a higher overall signal to noise ratio, posterior and peripheral zone signal to noise ratio, high b-value attenuation diffusion coefficient (ADC) signal to noise ratio, and contrast to noise ratio. Endorectal coil use improved subjective image quality for anatomic detail on T2 weighted images (T2WI) and diffusion weighted images (DWI). Endorectal coil use had less motion artifact on DWI than non-endorectal coil use, but produced a higher occurrence of other artifacts on DWI. Endorectal coils had higher sensitivity, specificity, and positive predictive value (PPV) in the detection of overall and index lesions, as well as smaller and less aggressive lesions, missing fewer and smaller lesions than non-endorectal coils. Endorectal coils had higher sensitivity than non-endorectal coils in localizing and staging lesions. Endorectal coils improved quantitative and qualitative image quality and diagnostic performance in the detection of smaller and less aggressive cancers in 3T prostate MRI.

Head-to-head comparison of prostate MRI using an endorectal coil versus a non-endorectal coil: meta-analysis of diagnostic performance in staging T3 prostate cancer

To compare the diagnostic performance of prostate magnetic resonance imaging (MRI) with an endorectal coil (ERC) to performance without an ERC using either body-array (BAC) or pelvic phased-array coil (PAC) in staging T3 prostate cancer. An electronic search of the PUBMED and EMBASE databases was performed until 10 October 2018 to identify studies performing a head-to-head comparison of prostate MRI using a 1.5 or 3 T magnet with an ERC and with a BAC/PAC for staging T3 prostate cancer. Pooled sensitivity and specificity of all studies were plotted in a hierarchical summary receiver operating characteristic plot. The diagnostic performance of the two techniques in staging T3 disease was evaluated using bivariate random-effects meta-analysis. Eight studies comparing head-to-head prostate MRI with an ERC and with a BAC/PAC were identified of which six studies compared the diagnostic performance. The pooled sensitivity and specificity of MRI with an ERC for detecting T3a, T3b and T3a+b was 53% and 95%; 52% and 92%; 72% and 65% respectively. For MRI with a BAC/PAC these were 34%, and 95%; 45% and 94%; 70% and 66%. There was no statistical difference between an ERC and a BAC/PAC in terms of sensitivity (p=0.41) and specificity (p=0.63) for T3a. The area under the receiver operating characteristic (AUROC) curve for T3a, T3b and T3a+b was 0.830, 0.901, 0.741 for an ERC and 0.790, 0.645, 0.711 for BAC, respectively. There is no significant difference in the diagnostic performance of MRI of prostate with an ERC and with a BAC/PAC in staging T3 prostate cancer.

Apparent Diffusion Coefficient (ADC) Ratio Versus Conventional ADC for Detecting Clinically Significant Prostate Cancer With 3-T MRI.

OBJECTIVE. The purpose of this study is to evaluate the performance of the apparent diffusion coefficient ratio (ADCratio; the ADC of the suspected prostate cancer [PCa] focus on MRI divided by the ADC in a noncancerous reference area) with that of conventional ADC for detection of high-grade PCa (Gleason score [GS] ≥ 3 + 4) versus low-grade PCa (GS = 3 + 3) with whole-mount (WM) histopathologic analysis used as a reference. MATERIALS AND METHODS. The cohort of this retrospective study included 218 men with 240 unilateral PCa lesions assessed by both 3-T multiparametric MRI and whole-mount histopathologic analysis. ROIs were placed on individual lesions verified by WM histopathologic analysis, to calculate the mean ADC (ADCtumor_mean) and lowest ADC within each lesion (ADCtumor_min), and within non-tumor-containing regions of the same tumor zone but on the contralateral side (ADCbenign), to calculate the background ADC. The ADCratio_mean (the ADCtumor_mean divided by the ADCbenign) was calculated. The performance of individual ADCtumor and ADCratio_mean values in discriminating PCa with a GS of 3 + 3 from PCa with a GS of 3 + 4 or greater was assessed using the AUC value. RESULTS. The ADCratio_mean had a higher AUC value for discriminating PCa lesions with a GS of 3 + 3 from those with a GS of 3 + 4 or greater (the AUC value increased from 0.70 using the ADCtumor_mean and 0.67 using the ADCtumor_min [the minimum ADC of the PCa lesion] to 0.80 for the ADCratio_mean and 0.72 for the ADCratio_min [the ADCtumor_min divided by the ADCbenign]; p = 0.043). When stratified by PCa zonal location, the ADCratio_mean had significantly more robust accuracy in the transition zone (the AUC value increased from 0.63 for ADCtumor_mean to 0.87 for ADCratio_mean; p = 0.019) compared with the peripheral zone (the AUC value increased from 0.74 for ADCtumor_mean to 0.78 for ADCratio_mean; p = 0.44). When analyzed on the basis of endorectal coil use, the ADCratio_mean performed nonsignificantly better in both the endorectal coil and non-endorectal coil subcohorts, although it performed better in the former. CONCLUSION. As an intrapatient-normalized diagnostic tool, the ADC ratio provided the best AUC value for discrimination of low-grade from high-grade PCa on 3-T MRI.

Integration and Diagnostic Accuracy of 3T Nonendorectal coil Prostate Magnetic Resonance Imaging in the Context of Active Surveillance

To evaluate the integration of 3T nonendorectal coil multiparametric prostate magnetic resonance imaging (mpMRI) at 2 high-volume practices that routinely use mpMRI in the setting of active surveillance. This was an institutional review board-approved, Health Insurance Portability and Accountability Act-compliant, and dual-institution retrospective cohort study. Subjects undergoing 3T mpMRI without endorectal coil at either study institution over a 13-month period (August 1, 2015-August 31, 2016) were selected based on predefined criteria: clinical T1/T2 Gleason 6 prostate cancer, prostate-specific antigen <15 ng/mL, ≥40 years old, mpMRI within 2 years of prostate biopsy, and Prostate Imaging Reporting and Data System (PI-RADS) v2 score assigned. Subjects surveilled for Gleason ≥3 + 4 prostate cancer were excluded. The primary outcome was detection of Gleason ≥3 + 4 prostate cancer on magnetic resonance-ultrasound fusion biopsy, standard biopsy, or prostatectomy within 6 months following mpMRI. Positive predictive values (PPVs) were calculated. A total of 286 subjects (N = 193 from institution 1, N = 93 from institution 2) met the criteria. Most (87% [90 of 104]) with maximum PI-RADS v2 scores of 1-2 did not receive immediate biopsy or treatment and remained on active surveillance. Incidence and PPVs for PI-RADS v2 scores of ≥3 were the following: PI-RADS 3 (n = 57 [20%], PPV 21% [6 of 29]), PI-RADS 4 (n = 96 [34%], PPV 51% [39 of 77]), and PI-RADS 5 (n = 29 [13%], PPV 71% [20 of 28]). No Gleason ≥4 + 3 prostate cancer was identified for PI-RADS v2 scores of 1-3 (0 of 43 with histology). Following mpMRI and subsequent biopsy, 21% (61 of 286) of subjects were removed from active surveillance and underwent definitive therapy. The 3T nonendorectal coil mpMRI has been integrated into the care of patients on active surveillance and effectively stratifies risk of Gleason ≥3 + 4 prostate cancer in this population.

Tumour-Targeted Treatment Intensification for Prostate Cancer Using Magnetic Resonance Imaging Guidance

IntroductionLocal control in prostate cancer may be improved with targeted dose escalation to regions with high tumour burden. Multiparametric magnetic resonance imaging (mpMRI) combined with MRI-guided biopsies may aid in defining tumour-dense regions before radiation therapy. Deformable registration techniques may be used to map these tumour regions onto the radiotherapy planning MRI. Radiation therapy delivery techniques such as volumetric modulated arc therapy and high-dose-rate brachytherapy may allow for highly conformal dose escalation, and when coupled with image-guided radiation delivery (ie, cone beam computed technology and fiducial markers), may allow high-precision dose-escalated treatment. MethodsEligible prostate cancer patients were enrolled on a prospective trial of tumour dose escalation. Two strategies were investigated: (1) an integrated boost to external beam radiation for a total tumour dose of 95 Gy in 38 fractions or (2) a focal high-dose-rate boost of 10 Gy before 76 Gy in 38 fractions external beam radiation. Patients underwent MRI-guided biopsy with fiducial marker placement before therapy. mpMRI was acquired and used in conjunction with a non-endorectal coil T2 MRI and computed technology simulation images to define the gross tumour volume via a deformable registration approach for intraprostatic tumour dose escalation. ResultsA case example for each dose escalation strategy illustrates the tumour-targeted approach using MRI guidance. ConclusionsCombining mpMRI sequences with a deformable registration approach may aid in more accurate and reproducible definition of tumour-dense regions. This novel process coupled with daily image guidance may allow high-precision dose-escalated tumour-targeted radiotherapy for prostate cancer.

Atlas registration and ensemble deep convolutional neural network-based prostate segmentation using magnetic resonance imaging

Automatic segmentation of prostate in magnetic resonance (MR) images has been more and more applied to the diagnosis of prostate disease and various clinical applications. However, due to the inhomogeneous and varying anatomical appearance around prostate boundary, the segmentation of prostate MR images faces great challenges. Since deep learning shows superior performance in computer vision, we propose a coarse-to-fine segmentation strategy by using deep neural networks to tackle the segmentation problem of the endorectal coil prostate images and non-endorectal coil prostate images separately. First, we present a registration-based coarse segmentation to the pre-processed prostate MR images to get the potential boundary region. Second, we train deep neural networks as pixel-based classifier to predict whether the pixel in the potential boundary region is prostate pixel or not. To improve the discriminability of the algorithm, we further introduce ensemble learning for fine segmentation. Finally, a boundary refinement is used to eliminate the outlier and smooth the boundary. The proposed method has been extensively evaluated on the PROMIS12 challenge dataset and PROSTATEx17 challenge dataset. Experimental results show superior segmentation performance (0.910 ± 0.036 in dice ratio, 1.583 ± 0.441 in average boundary distance and 4.579 ± 1.791 in Hausdorff distance), which demonstrates the effectiveness of the proposed algorithm.

Biparametric versus Multiparametric MRI with Non-endorectal Coil at 3T in the Detection and Localization of Prostate Cancer.

To assess the sensitivity of biparametric magnetic resonance imaging (bpMRI) with non-endorectal coil in the detection and localization of index (dominant) and non-index lesions in patients suspected of having prostate cancer. We carried-out a retrospective analysis of multiparametric MRI (mpMRI) of 41 patients who underwent radical prostatectomy. Results of MRI for detection and localization of index and non-index lesions were correlated with those of histology. No statistically significant difference in size was seen between tumor lesion at histology and index lesion at MRI. In 41 patients, a total of 131 tumors were identified at histology, while bpMRI (T2-weighted and diffusion-weighted MRI) approach detected 181 lesions. bpMRI gave 27.6% false-positives and 3.3% false-negatives. Sensitivity in lesion detection by bpMRI increased with lesion size assuming high values for lesions ≥10 mm. For bpMRI and mpMRI, the sensitivity for detecting index lesions was the same and equal: 100% in the peripheral zone 97.6% and 94.7% in the entire prostate and transitional zone, respectively. bpMRI can be used alternatively to mpMRI to detect and localize index prostate cancer.

Performance Comparison of 1.5-T Endorectal Coil MRI with 3.0-T Nonendorectal Coil MRI in Patients with Prostate Cancer

To compare prostate morphology, image quality, and diagnostic performance of 1.5-T endorectal coil magnetic resonance (MR) imaging (MRI) and 3.0-T nonendorectal coil MRI in patients with prostate cancer. MR images obtained of 83 patients with prostate cancer using 1.5-T MRI systems with an endorectal coil were compared to images collected from 83 patients with a 3.0-T MRI system. Prostate diameters were measured, and image quality was evaluated by one American Board of Radiology (ABR)-certified radiologist (reader 1) and one ABR-certified diagnostic medical physicist (reader 2). The likelihood of the presence of peripheral zone cancer in each sextant and local extent was rated and compared to histopathologic findings. Prostate anterior-posterior diameter measured by both readers was significantly shorter with 1.5-T endorectal MRI than with 3.0-T MRI. The overall image quality score difference was significant only for reader 1. Both readers found that the two MRI systems provided a similar diagnostic accuracy in cancer localization, extraprostatic extension, and seminal vesicle involvement. Nonendorectal coil 3.0-T MRI provides prostate images that are natural in shape and that have comparable image quality to those obtained at 1.5 T with an endorectal coil, but not superior diagnostic performance. These findings suggest an opportunity exists for improving technical aspects of the 3.0-T prostate MRI.

Comparison of endorectal coil and nonendorectal coil T2W and diffusion-weighted MRI at 3 Tesla for localizing prostate cancer: Correlation with whole-mount histopathology

To compare utility of T2-weighted (T2W) MRI and diffusion-weighted MRI (DWI-MRI) obtained with and without an endorectal coil at 3 Tesla (T) for localizing prostate cancer.This Institutional Review Board-approved study included 20 patients (median prostate-specific antigen, 8.4 ng/mL). Patients underwent consecutive prostate MRIs at 3T, first with a surface coil alone, then with combination of surface, endorectal coils (dual coil) followed by robotic assisted radical prostatectomy. Lesions were mapped at time of acquisition on dual-coil T2W, DWI-MRI. To avoid bias, 6 months later nonendorectal coil T2W, DWI-MRI were mapped. Both MRI evaluations were performed by two readers blinded to pathology with differences resolved by consensus. A lesion-based correlation with whole-mount histopathology was performed.At histopathology 51 cancer foci were present ranging in size from 2 to 60 mm. The sensitivity of the endorectal dual-coil, nonendorectal coil MRIs were 0.76, 0.45, respectively. PPVs for endorectal dual-coil, nonendorectal coil MRI were 0.80, 0.64, respectively. Mean size of detected lesions with nonendorectal coil MRI were larger than those detected by dual-coil MRI (22 mm versus 17.4 mm).Dual-coil prostate MRI detected more cancer foci than nonendorectal coil MRI. While nonendorectal coil MRI is an attractive alternative, physicians performing prostate MRI should be aware of its limitations.