Serial changes in tumour measurements and apparent diffusion coefficients in prostate cancer patients on active surveillance with and without histopathological progression

Objective:To analyse serial changes in MRI-derived tumour measurements and apparent diffusion coefficient (ADC) values in prostate cancer (PCa) patients on active surveillance (AS) with and without histopathological disease progression.Methods:This study included AS patients with biopsy-proven PCa with a minimum of two consecutive MR examinations and at least one repeat targeted biopsy. Tumour volumes, largest axial two-dimensional (2D) surface areas, and maximum diameters were measured on T ₂ weighted images (T ₂WI). ADC values were derived from the whole lesions, 2D areas, and small-volume regions of interest (ROIs) where tumours were most conspicuous. Areas under the ROC curve (AUCs) were calculated for combinations of T ₂WI and ADC parameters with optimal specificity and sensitivity.Results:60 patients (30 progressors and 30 non-progressors) were included. In progressors, T ₂WI-derived tumour volume, 2D surface area, and maximum tumour diameter had a median increase of +99.5%,+55.3%, and +21.7% compared to +29.2%,+8.1%, and +6.9% in non-progressors (p < 0.005 for all). Follow-up whole-volume and small-volume ROIs ADC values were significantly reduced in progressors (−11.7% and −9.5%) compared to non-progressors (−6.1% and −1.6%) (p < 0.05 for both). The combined AUC of a relative increase in maximum tumour diameter by 20% and reduction in small-volume ADC by 10% was 0.67.Conclusion:AS patients show significant differences in tumour measurements and ADC values between those with and without histopathological disease progression.Advances in knowledge:This paper proposes specific clinical cut-offs for T ₂WI-derived maximum tumour diameter (+20%) and small-volume ADC (−10%) to predict histopathological PCa progression on AS and supplement subjective serial MRI assessment.     

MRI-based radiomics as response predictor to radiochemotherapy for metastatic cervical lymph node in nasopharyngeal carcinoma

Objective:To establish and substantiate MRI-based radiomic models to predict the treatment response of metastatic cervical lymph node to radiochemotherapy in patients with nasopharyngeal carcinoma (NPC).Methods:A total of 145 consecutive patients with NPC were enrolled including 102 in primary cohort and 43 in validation cohort. Metastatic lymph nodes were diagnosed according to radiologic criteria and treatment response was evaluated according to the Response Evaluation Criteria in Solid Tumors. A total of 2704 radiomic features were extracted from contrast-enhanced T ₁ weighted imaging (CE- T ₁WI) and T ₂ weighted imaging (T ₂WI) for each patient, and were selected to construct radiomic signatures for CE-T ₁WI, T ₂WI, and combined CE-T ₁WI and T ₂WI, respectively. The area under curve (AUC) of receiver operating characteristic, sensitivity, specificity, and accuracy were used to estimate the performance of these radiomic models in predicting treatment response of metastatic lymph node.Results:No significant difference of AUC was found among radiomic signatures of CE-T ₁WI, T ₂WI, and combined CE-T ₁WI and T ₂WI in the primary and validation cohorts (all p > 0.05). For combined CE-T ₁WI and T ₂WI data set, 12 features were selected to develop the radiomic signature. The AUC, sensitivity, specificity, and accuracy were 0.927 (0.878–0.975), 0.911 (0.804–0.970), 0.826 (0.686–0.922), and 0.872 (0.792–0.930) in primary cohort, and were 0.772 (0.624–0.920), 0.792 (0.578–0.929), 0.790 (0.544–0.939), and 0.791 (0.640–0.900) in validation cohort.Conclusion:MRI-based radiomic models were developed to predict the treatment response of metastatic cervical lymph nodes to radiochemotherapy in patients with NPC, which might facilitate individualized therapy for metastatic lymph nodes before treatment.Advances in knowledge:Predicting the response in patients with NPC before treatment may allow more individualizing therapeutic strategy and avoid unnecessary side-effects and costs. Radiomic features extracted from metastatic cervical lymph nodes showed promising application for predicting the treatment response in NPC.     

Usefulness of two-point Dixon T2-weighted imaging in thyroid-associated ophthalmopathy: comparison with conventional fat saturation imaging in fat suppression quality and staging performance

Objective:To compare the two-point Dixon T ₂ weighted imaging (T ₂WI) with conventional fat-sat T ₂WI in fat suppression (FS) quality and staging performance for patients with TAO.Methods:We enrolled 37 thyroid-associated ophthalmopathy (TAO) patients and 15 healthy controls who underwent both coronal two-point Dixon and fat-sat T ₂WI. Qualitative (overall imaging quality, FS uniformity) and quantitative [signal intensity ratio of extraocular muscle (EOM-SIR)] parameters were assessed between the two-point Dixon T ₂WI and fat-sat T ₂WI. Additionally, water fraction of intraorbital fat (IF-WF) was measured on Dixon image. Dixon-EOM-SIR, Fat-sat-EOM-SIR and Dixon-IF-WF values were compared between active and inactive TAO groups, and the diagnostic efficiency for the active phase were evaluated.Results:Two-point Dixon T ₂WI showed significantly higher overall image quality score, FS uniformity score as well as EOM-SIR value than fat-sat T ₂WI in both TAO and control groups (all p < 0.05). Active TAOs had significantly higher Dixon-EOM-SIR (p < 0.001), Fat-sat-EOM-SIR (p < 0.001) and Dixon-IF-WF (p = 0.001) than inactive TAOs. ROC curves analyses indicated that Dixon-EOM-SIR ≥3.32 alone demonstrated the highest staging sensitivity (75.0%). When integrating Dixon-EOM-SIR ≥3.32 and Dixon-IF-WF ≥0.09, improved staging efficiency and specificity could be achieved (area under the curve, 0.872; specificity, 97.1%).Conclusion:Compared with conventional fat-sat technique, two-point Dixon T ₂WI offers better image quality, as well as improved staging sensitivity and specificity for TAO. Dixon T ₂WI is suggested to be used to evaluate the patients with TAO in clinical practice.Advances in knowledge:Two-point Dixon T ₂WI offers better image quality than fat-sat T ₂WI. Dixon-EOM-SIR alone demonstrated the highest staging sensitivity. Combining with Dixon-IF-WF showed improved staging efficiency and specificity. Dixon T ₂WI is suggested to be used to evaluate TAO patients in clinical practice.     

Assessment of bone marrow oedema-like lesions using MRI in patellofemoral knee osteoarthritis: comparison of different MRI pulse sequences

Objective:To compare bone marrow oedema-like lesion (BML) volume in subjects with symptomatic patellofemoral (PF) knee osteoarthritis (OA) using four different MRI sequences and to determine reliability of BML volume assessment using these sequences and their correlation with pain.Methods:76 males and females (mean age 55.8 years) with symptomatic patellofemoral knee OA had 1.5 T MRI scans. PD fat suppressed (FS), STIR, contrast-enhanced (CE) T₁W FS, and 3D T₁W fast field echo (FFE) sequences were obtained. All sequences were assessed by one reader, including repeat assessment of 15 knees using manual segmentation and the measurements were compared. We used random-effects panel linear regression to look for differences in the log-transformed BML volume (due to positive skew in the BML volume distribution) between sequences and to determine associations between BML volumes and knee pain.Results:58 subjects had PF BMLs present on at least one sequence. Median BML volume measured using T₁W FFE sequence was significantly smaller (224.7 mm³, interquartile range [IQR] 82.50–607.95) than the other three sequences. BML volume was greatest on the CE sequence (1129.8 mm³, IQR 467.28–3166.02). Compared to CE sequence, BML volumes were slightly lower when assessed using PDFS (proportional difference = 0.79; 95% confidence interval [CI] 0.62, 1.01) and STIR sequences (proportional difference = 0.85; 95% CI 0.67, 1.08). There were strong correlations between BML volume on PDFS, STIR, and CE T₁W FS sequences (ρs = 0.98). Correlations were lower between these three sequences and T₁W FFE (ρs = 0.80–0.81). Intraclass correlation coefficients were excellent for proton density fat-suppressed, short-tau inversion recovery, and CE T₁W FS sequences (0.991–0.995), while the ICC for T₁W FFE was good at 0.88. We found no significant association between BML volumes assessed using any of the sequences and knee pain.Conclusion:T₁W FFE sequences were less reliable and measured considerably smaller BML volume compared to other sequences. BML volume was larger when assessed using the contrast enhanced T₁W FS though not statistically significantly different from BMLs when assessed using PDFS and STIR sequences.Advances in knowledge:This is the first study to assess BMLs by four different MRI pulse sequences on the same data set, including different fluid sensitive sequences and gradient echo type sequence.     

Synthetic MRI with T2-based Water Suppression to Reduce Hyperintense Artifacts due to CSF–Partial Volume Effects in the Brain

Purpose:Our purpose was to assess our proposed new synthetic MRI (synMRI) technique, combined with T₂-based water suppression (T₂wsup), to reduce cerebral spinal fluid (CSF)–partial volume effects (PVEs). These PVEs are problematic in the T₂-weighted fluid-attenuation inversion recovery (FLAIR) images obtained by conventional synMRI techniques.Methods:Our T₂wsup was achieved by subtracting additionally acquired long TE spin echo (SE) images of water signals dominant from the originally acquired images after T₂ decay correction and a masking on the long TE image using the water volume (V_w) map to preserve tissue SNR, followed by quantitative mapping and then calculation of the synthetic images. A simulation study based on a two-compartment model including tissue and water in a voxel and a volunteer MR study were performed to assess our proposed method. Parameters of long TE and a threshold value in the masking were assessed and optimized experimentally. Quantitative parameter maps of standard and with T₂wsup were generated, then wsup-synthetic FLAIR and SE images were calculated using those suitable combinations and compared.Results:Our simulation clarified that the CSF–PVE artifacts in the standard synthetic FLAIR increase T₂ as the water volume increases in a voxel, and the volunteer MR brain study demonstrated that the hyperintense artifacts on synthetic images were reduced to < 10% of V_w in those with the standard synMRI while keeping the tissue SNR by selecting optimal masking parameters on additional long TE images of TE = 300 ms. In addition, the wsup-synthetic SE provided better gray-white matter contrasts compared with the wsup-synthetic FLAIR while keeping CSF suppression.Conclusion:Our proposed T₂wsup-synMRI technique makes it easy to reduce the CSF–PVE artifacts problematic in the synthetic FLAIR images using the current synMRI technique by adding long TE images and simple processing. Although further optimizations in data acquisition and processing techniques are required before actual clinical use, we expect our technique to become clinically useful.     

A New Method for Aortic Valve Planimetry with High-Resolution 3-Dimensional MRI and Its Comparison with Conventional Cine MRI and Echocardiography for Assessing the Severity of Aortic Valvular Stenosis

ObjectiveWe aimed to compare the aortic valve area (AVA) calculated using fast high-resolution three-dimensional (3D) magnetic resonance (MR) image acquisition with that of the conventional two-dimensional (2D) cine MR technique.Materials and MethodsWe included 139 consecutive patients (mean age ± standard deviation [SD], 68.5 ± 9.4 years) with aortic valvular stenosis (AS) and 21 asymptomatic controls (52.3 ± 14.2 years). High-resolution T2-prepared 3D steady-state free precession (SSFP) images (2.0 mm slice thickness, 10 contiguous slices) for 3D planimetry (3DP) were acquired with a single breath hold during mid-systole. 2D SSFP cine MR images (6.0 mm slice thickness) for 2D planimetry (2DP) were also obtained at three aortic valve levels. The calculations for the effective AVA based on the MR images were compared with the transthoracic echocardiographic (TTE) measurements using the continuity equation.ResultsThe mean AVA ± SD derived by 3DP, 2DP, and TTE in the AS group were 0.81 ± 0.26 cm², 0.82 ± 0.34 cm², and 0.80 ± 0.26 cm², respectively (p = 0.366). The intra-observer agreement was higher for 3DP than 2DP in one observer: intraclass correlation coefficient (ICC) of 0.95 (95% confidence interval [CI], 0.94–0.97) and 0.87 (95% CI, 0.82–0.91), respectively, for observer 1 and 0.97 (95% CI, 0.96–0.98) and 0.98 (95% CI, 0.97–0.99), respectively, for observer 2. Inter-observer agreement was similar between 3DP and 2DP, with the ICC of 0.92 (95% CI, 0.89–0.94) and 0.91 (95% CI, 0.88–0.93), respectively. 3DP-derived AVA showed a slightly higher agreement with AVA measured by TTE than the 2DP-derived AVA, with the ICC of 0.87 (95% CI, 0.82–0.91) vs. 0.85 (95% CI, 0.79–0.89).ConclusionHigh-resolution 3D MR image acquisition, with single-breath-hold SSFP sequences, gave AVA measurement with low observer variability that correlated highly with those obtained by TTE.     

Predicting the pathological grade of breast phyllodes tumors: a nomogram based on clinical and magnetic resonance imaging features

Objective:To explore the potential factors related to the pathological grade of breast phyllodes tumors (PTs) and to establish a nomogram to improve their differentiation ability.Methods:Patients with PTs diagnosed by post-operative pathology who underwent pretreatment magnetic resonance imaging (MRI) from January 2015 to June 2020 were retrospectively reviewed. Traditional clinical features and MRI features evaluated according to the fifth BI-RADS were analyzed by statistical methods and introduced to a stepwise multivariate logistic regression analysis to develop a prediction model. Then, a nomogram was developed to graphically predict the probability of non-benign (borderline/malignant) PTs.Results:Finally, 61 benign, 73 borderline and 48 malignant PTs were identified in 182 patients. Family history of tumor, diameter, lobulation, cystic component, signal on fat saturated T₂ weighted imaging (FS T₂WI), BI-RADS category and time–signal intensity curve (TIC) patterns were found to be significantly different between benign and non-benign PTs. The nomogram was finally developed based on five risk factors: family history of tumor, lobulation, cystic component, signal on FS T₂WI and internal enhancement. The AUC of the nomogram was 0.795 (95% CI: 0.639, 0.835).Conclusion:Family history of tumor, lobulation, cystic components, signals on FS T₂WI and internal enhancement are independent predictors of non-benign PTs. The prediction nomogram developed based on these features can be used as a supplemental tool to pre-operatively differentiate PTs grades.Advances in knowledge:More sample size and characteristics were used to explore the factors related to the pathological grade of PTs and establish a predictive nomogram for the first time.     

Comparison of lumbar degenerative disc disease using conventional fast spin echo T2W MRI and T2 fast spin echo dixon sequences

Objectives:To compare the grading of lumbar degenerative disc disease (DDD), Modic end-plate changes (MEPC) and identification of high intensity zones (HIZ) on a combination of sagittal T₁weighted turbo spin echo (T₁W TSE), T₂weighted fast spin echo (T₂W FSE) and short tau inversion recovery (STIR) sequences (routine protocol) with a single sagittal T₂W FSE Dixon MRI sequence which provides in-phase, opposed-phase, water only and fat only images in a single acquisition (Dixon protocol).Methods:50 patients underwent lumbar spine MRI using the routine protocol with the addition of a T₂W FSE Dixon sequence. DDD grade, MEPC and HIZ for each disc level were assessed on the routine and Dixon protocols. Each protocol was reviewed independently by three readers (consultant musculoskeletal radiologists with 26-, 8- and 4 years’ experience), allowing assessment of inter-reader agreement and inter protocol agreement for each assessed variable.Results:The study included 17 males and 33 females (mean age 51 years; range 8–82 years). Inter-reader agreement for DDD grade on the routine protocol was 0.57 and for the Dixon protocol was 0.63 (p = 0.08). Inter-reader agreement for MEPC on the routine protocol was 0.45 and for the Dixon protocol was 0.53 (p = 0.02), and inter-reader agreement for identification of the HIZ on the routine protocol was 0.52 and for the Dixon protocol was 0.46 (p = 0.27). Intersequence agreement for DDD grade ranged from 0.61 to 0.97, for MEPC 0.46–0.62 and for HIZ 0.39–0.5.Conclusion:A single sagittal T₂W FSE Dixon MRI sequence could potentially replace the routine three sagittal sequence protocol for assessment of lumbar DDD, MEPC and HIZ resulting in ~60% time saving.Advances in knowledge:Grading of lumbar DDD, presence of Modic changes and high intensity zones were compared on sagittal T₁W TSE, T₂W FSE and STIR sequences with a T₂W FSE Dixon sequence, with fair-to-good correlation suggesting that three conventional sequences could be replaced by a single Dixon sequence.     

Analysis of left ventricular function,left ventricular outflow tract and aortic valve area using computed tomography: Influence of reconstruction parameters on measurement accuracy

Objectives:Computed tomography (CT) allows reproducible assessment of left ventricular (LV) function, left ventricular outflow tract area (LVOT_area) and aortic valve area (AVA). We evaluated the influence of image reconstruction parameters on these measurements.Methods:We analyzed 45 contrast-enhanced, retrospectively ECG-gated CT datasets acquired on a third-generation dual source system. A standard filtered-back-projection data set (20 cardiac phases (5% steps, 0–95%), 0.6-mm-slice thickness, 512 × 512 matrix) and eight reconstructions with modified slice thickness (1–8 mm), number of cardiac phases (5, 10), matrix size (256×256) and an iterative reconstruction (IR) algorithm were obtained. LV parameters (ejection fraction (EF), stroke volume (SV), end-diastolic (EDV), end-systolic volumes (ESV)), LVOT_area and AVA were assessed.Results:Differences in LV parameters, LVOT_area and AVA, were only minimal between standard reconstructions and those with modified matrix size, IR algorithm and ≤2 mm slice thickness, while reconstructions with 8-mm slice thickness significantly overestimated SV (p < 0.001) and EDV (p = 0.016). AVA planimetry in reconstructions with ≥5 mm slice thickness was not feasible in 56% of patients. A decrease in the number of reconstructed phases (10 or 5) underestimated EF, SV, EDV, LVOT_area and AVA and overestimated ESV.Conclusions:Modifications of reconstruction parameters (except a slice thickness ≤2 mm) have only a marginal effect on LV, LVOT_area and AVA assessment. However, a reduced number of reconstructions per cardiac cycle may significantly influence measurements.Advances in knowledge:Substantial modifications in number of reconstructions per cardiac cycle significantly affect the assessment of LV function, LVOT_area and AVA also in modern CT scanners.     

Histologic Distribution and Characteristics on MR Imaging of Ultrasmall Superparamagnetic Iron Oxide in Ethyl-nitrosourea-induced Endogenous Rat Glioma

Purpose:(1) To evaluate the enhancement patterns of an ultrasmall superparamagnetic iron oxide contrast agent (USPIO-CA) compared with those of a gadolinium-based contrast agent (Gd-BCA). (2) To compare the histologic distribution of USPIO-related iron particles (USPIO-IPs) with the USPIO-enhancement area in the early vascular and in the cellular imaging phase (E- and L-phase, respectively) after intravenous CA administration.Methods:We performed USPIO-enhanced MRI of N-ethyl-N-nitrosourea (ENU)-induced endogenous rat glioma, including spin-echo (SE) T₁-weighted images (T₁WIs) and gradient-recalled-echo (GRE) T₂-weighted images (T₂WIs), before and at 3–6 h after USPIO-CA administration for E-phase images. For L-phase images, MRI was performed at 16–19 and 62–69 h after administration. Two observers determined the USPIO-enhancement area on E-phase images and Gd-enhancement areas. We compared the USPIO-enhancement size (USPIO-ES) and Gd-ES on SE T₁WIs, and the hypo-intense USPIO-ES on GRE T₂WIs and Gd-ES using the Wilcoxon signed-rank test. In addition, two raters visually evaluated the correspondence between the histologic distribution of USPIO-IPs and the USPIO-enhancement area on corresponding GRE T₂WIs at each phase using a 3-rating scale.Results:Significantly smaller hyper-intense, hypo-intense and combined hyper-/hypo-intense areas were observed on USPIO-enhanced SE T₁WIs compared with Gd-enhanced images (all P < 0.001). The hypo-intense USPIO-ES on GRE T₂WIs was significantly smaller than the Gd-ES (P = 0.001). The distribution of USPIO-IPs on histopathological specimen and USPIO-enhancement on GRE T₂WIs exhibited poor agreement in 5 of 9 tumors with enhancement from rats sacrificed early. The distribution of microglia containing USPIO-IPs corresponded with the pattern of USPIO-enhancement in the 2 tumors with late enhancement.Conclusion:The enhancement pattern and size of USPIO-CA in a rat glioma model were statistically different from those of Gd-BCA. Our histological data suggests that USPIO-enhanced MRI offers vascular bed imaging in E-phase and might depict the intra-tumoral distribution of immune effector cells in L-phase.     

Does PSA level affect the choice of prostate puncture methods among MRI-ultrasound fusion targeted biopsy,transrectal ultrasound systematic biopsy or the combination of both?

Objectives:To explore whether prostate-specific antigen (PSA) affects the choice of prostate puncture methods by comparing MRI-ultrasound fusion targeted biopsy (MRI-TBx) with transrectal ultrasound systematic biopsy (TRUS-SBx) in the detection of prostate cancer (PCa), clinically significant prostate cancer (csPCa) and non-clinically significant prostate cancer (nsPCa) in different PSA groups (<10.0,10.0–20.0 and>20.0 ng ml⁻¹).Methods:A total of 190 patients with 215 lesions who underwent both MRI-TBx and TRUS-SBx were included in this retrospective study. PSA was measured pre-operatively and stratified to three levels. The detection rates of PCa, csPCa and nsPCa through different methods (MRI-TBx, TRUS-SBx, or MRI-TBx +TRUS SBx) were compared with stratification by PSA.Results:Among the 190 patients, the histopathological results revealed PCa in 126 cases, including 119 csPCa. In PSA <10.0 ng ml⁻¹ group, although the detection rates of PCa and csPCa by MRI-TBx were higher than those of TRUS-SBx, no significant differences were observed (p = 0.741; p = 0.400). In PSA 10.0–20.0 ng ml⁻¹ group, difference between the detection rate of csPCa with TRUS-SBx and the combined method was statistically significant (p = 0.044). As for PSA >20.0 ng ml⁻¹, MRI-TBx had a higher csPCa rate than TRUS-SBx with no statistical significance noted (p = 0.600).Conclusion:MRI-TBx combined with TRUS-SBx could be suitable as a standard detection approach for csPCa in patients with PSA 10.0–20.0 ng ml⁻¹. As for PSA >20.0 and <10.0 ng ml⁻¹, both MRI-TBx and TRUS-SBx might provide effective solutions for tumor detection.Advances in knowledge:This study gives an account of choosing appropriate prostate puncture methods through PSA level.     

Performance of Prediction Models for Diagnosing Severe Aortic Stenosis Based on Aortic Valve Calcium on Cardiac Computed Tomography: Incorporation of Radiomics and Machine Learning

ObjectiveWe aimed to develop a prediction model for diagnosing severe aortic stenosis (AS) using computed tomography (CT) radiomics features of aortic valve calcium (AVC) and machine learning (ML) algorithms.Materials and MethodsWe retrospectively enrolled 408 patients who underwent cardiac CT between March 2010 and August 2017 and had echocardiographic examinations (240 patients with severe AS on echocardiography [the severe AS group] and 168 patients without severe AS [the non-severe AS group]). Data were divided into a training set (312 patients) and a validation set (96 patients). Using non-contrast-enhanced cardiac CT scans, AVC was segmented, and 128 radiomics features for AVC were extracted. After feature selection was performed with three ML algorithms (least absolute shrinkage and selection operator [LASSO], random forests [RFs], and eXtreme Gradient Boosting [XGBoost]), model classifiers for diagnosing severe AS on echocardiography were developed in combination with three different model classifier methods (logistic regression, RF, and XGBoost). The performance (c-index) of each radiomics prediction model was compared with predictions based on AVC volume and score.ResultsThe radiomics scores derived from LASSO were significantly different between the severe AS and non-severe AS groups in the validation set (median, 1.563 vs. 0.197, respectively, p < 0.001). A radiomics prediction model based on feature selection by LASSO + model classifier by XGBoost showed the highest c-index of 0.921 (95% confidence interval [CI], 0.869–0.973) in the validation set. Compared to prediction models based on AVC volume and score (c-indexes of 0.894 [95% CI, 0.815–0.948] and 0.899 [95% CI, 0.820–0.951], respectively), eight and three of the nine radiomics prediction models showed higher discrimination abilities for severe AS. However, the differences were not statistically significant (p > 0.05 for all).ConclusionModels based on the radiomics features of AVC and ML algorithms may perform well for diagnosing severe AS, but the added value compared to AVC volume and score should be investigated further.     

Symmetry based prostate cancer detection

Objective:

To retrospectively assess the value of left and right half symmetry analysis in prostate T₂ weighted images (T2WI) for improving prostate cancer (PCa) screening.

Methods:

T2WI and other data of a total of 66 males were collected; the control group and cancer group had 33 patients each. Thresholding geometric active contours algorithm was used for prostate region segmentation, and the measure of local reflectional symmetry algorithm was applied to extract the longitudinal symmetry axes. After that, cross-correlation coefficients (CCs) of the left and right halves of each prostate were obtained.

Results:

Data analysis showed that the mean and variance of the value of the left and right half CCs of prostate T2WI in the cancer group and control group were 0.73 ± 0.05 and 0.82 ± 0.06, respectively. The area under the receiver operating characteristic curve was 0.87, and the specificity and the sensitivity were 91% and 70%, respectively. The p < 0.001 indicated that the value of CCs of the prostates between the two groups was significantly different.

Conclusion:

The symmetry in T2WI is a potential useful index for PCa screening and has a potential value for PCa detection and localizations of tumours for biopsy.

Advances in knowledge:

Texture bilateral symmetry of prostate T2WI is employed to screen the suspected prostate tumour.Prostate cancer (PCa) is the second most common cancer among males worldwide¹ and the most common cancer among Western males.^2,3 With rapid increase, especially, in old people, the number of total sufferers is expected to increase so that by 2020, it is only exceeded by lung cancer.^4–7 PCa was the sixth most frequently diagnosed cancer among males during 2008 in the Asia–Pacific region, behind cancers of the lung, stomach, liver, colorectum and oesophagus. This pattern was mainly driven by Eastern Asia, and in particular China, which represents about 62% of the region''s male population.⁸ More than that, PCa is now becoming an emerging health priority in East Asia. Because East Asia remains the world''s most populous region, the number of individuals with PCa will increase substantially in the coming decades.⁹Currently, PCa screening relies on digital rectal examinations (DREs) and serum prostate specific antigen (PSA) levels. But PCa diagnosis is based on histological tissue analysis, which is most often obtained via needle biopsy, guided by transrectal ultrasound (TRUS). However, it has been reported that its accuracy is only 20–25% in patients with PSA levels between 4 and 10 g ml⁻¹ owing to the inevitable inaccurate positioning during TRUS, and often leads to the failure to detect cancer.^10,11 Additionally, repetitive biopsies will not only increase the suffering of patients but also lead to increased rate of complications. For these reasons, image modalities and suspicious lesion identification via computer-aided diagnosis (CAD) methods are expected to provide more accurate detection and localization of prostate tumours. MRI is commonly employed in some areas to assist in the diagnosis of PCa and provide locations of suspicious tumours before biopsy, and accurate CAD methods are urgently needed.^11–18In recent years, many efforts have been made to evaluate MR-based suspected prostate lesions. Firstly, Dickinson et al¹⁹ developed a standardized reporting scheme that may be widely adopted and validated to ensure comparability of research outputs and optimal clinical practice. Secondly, dynamic contrast-enhanced MRI (DCE-MRI) has been extensively used for the diagnosis of PCa. DCE-MRI is an important imaging technique because it can detect angiogenesis and vasculogenesis of tumours. Jackson et al¹² calculated the accuracy of DCE-MRI for cancer detection by a pixel-by-pixel correlation of quantitative DCE-MRI parameter maps and pathology, and the results showed a significant difference between the benign peripheral zone and tumour for the parameters K^trans, v_e and k_ep. Based on DCE-MRI, Puech et al¹⁵ provided a standardized cancer suspicion score for suspicious foci based on the median wash-in and wash-out values of peripheral zone cancer, peripheral zone benign, transitional zone cancer and transitional zone benign to provide useful data for an unbiased and reproducible assessment of hypervascularized prostatic areas in routine practice.T₂ weighted images (T2WI) play a crucial role in clinical practice, by distinguishing between normal and abnormal foci in prostate zonal anatomy and periprostatic structures.²⁰ With fast spin-echo techniques, T2WI was adopted by Sommer et al²¹ to detect some early stages of PCa, such as pelvic lymph nodes or pelvic bone metastases,^22–24 and it is already routinely used in prostate lesion identification.Some recent studies have provided clinical assessments utilizing the prostate T2WI features. Madabhushi et al¹⁰ firstly presented a CAD system for detecting PCa from high-resolution MRI studies, which used three-dimensional (3D) texture operators to capture a wider range of variation in appearance, size, orientation and anisotropy of the cancer. Lv et al¹⁶ offer a robust MR-based indicator to distinguish prostate tumours from normal tissue with a fractal analysis to extract the features of the prostate texture and intensity distribution on T2WI as indices in the differential diagnosis of PCa. Local texture patterns in T2WI were considered in previous computer-aided approaches for automatic prostate lesion detection, but the morphological characteristics, such as symmetry, which is easily observed in prostate T2WI, were ignored. Bilateral symmetry appears commonly in nature, including many organs in our bodies such as the brain, bones, skin and prostate. As for a developing lesion, asymmetry gradually appears with symmetry breaking down in tissue because of differentiation of perfusion, blood supply and metabolism beyond normal tissues.²⁵ Radiologists have reported that symmetry in prostate MRI can be important to detect PCa.²⁶ Litjens et al²⁷ also investigated a fully automated computer-aided detection system for the diagnosis of PCa that includes feature of symmetry, local contrast and shape. In this study, texture bilateral symmetry of prostate T2WI is employed to screen the suspected prostate tumour, which is a potential useful index to help identify and localize the lesions or tumours in patients who undergo PCa screening.     

Susceptibility-Weighted Imaging of the Pediatric Brain after Repeat Doses of Gadolinium-Based Contrast Agent

BACKGROUND AND PURPOSE:Gadolinium complexes have paramagnetic properties; thus, we aimed to determine the susceptibility changes in the globus pallidus and dentate nucleus following administration of linear or macrocyclic gadolinium-based contrast agents in children.MATERIALS AND METHODS:Thirty-three patients with linear gadolinium-based contrast agent gadopentetate dimeglumine administration, 33 age- and sex-matched patients with macrocyclic gadolinium-based contrast agent gadobutrol administration, and 33 age- and sex-matched control subjects without gadolinium exposure were enrolled in this retrospective study. The signal intensity on SWI and T1WI was determined in the dentate nucleus, middle cerebellar peduncle, globus pallidus, and pulvinar of the thalamus in an ROI-based analysis to calculate dentate nucleus–to–middle cerebellar peduncle and globus pallidus–to–thalamus ratios. A repeated measures ANOVA was performed to compare SWI_minimum, SWI_mean, and T1WI signal intensity ratios between gadolinium-based contrast agent groups and control subjects. Pearson correlation analysis was performed to determine any correlation between signal intensity ratios and variables.RESULTS:Dentate nucleus–to–middle cerebellar peduncle and globus pallidus–to–thalamus ratios for both SWI_mean and SWI_minimum were lower for the linear gadolinium-based contrast agent group compared with macrocyclic gadolinium-based contrast agent and control groups (P < .05). No significant difference of the SWI_mean and SWI_minimum ratios were noted between the macrocyclic gadolinium-based contrast agent group and the control group (P > .05). Both dentate nucleus–to–middle cerebellar peduncle and globus pallidus–to–thalamus ratios on T1WI in the linear gadolinium-based contrast agent group were higher than in the control group and the macrocyclic gadolinium-based contrast agent group (P < .05). A negative correlation was identified between SWI_mean and SWI_minimum ratios and the number of linear gadolinium-based contrast agent administrations (dentate nucleus–to–middle cerebellar peduncle ratio: SWI_mean, r = –0.43, P = .005; SWI_minimum, r = –0.38, P = .011; globus pallidus–to–thalamus ratio: SWI_mean, r = –0.39, P = .009; SWI_minimum, r = –0.33, P = .017).CONCLUSIONS:SWI analysis of the pediatric brain demonstrated a statistically significant decrease in SWI_minimum and SWI_mean values for the dentate nucleus and globus pallidus after administration of linear gadolinium-based contrast agents but not macrocyclic gadolinium-based contrast agents.

Gadolinium-based contrast agents (GBCAs) are essential components of clinical diagnosis and treatment decision-making for millions of patients worldwide.¹ Recent studies have shown gadolinium deposition in multiple organs,² including the brain, after repeat administration of GBCAs.³ Intracranial gadolinium deposition in the brain has been associated with increased signal intensity (SI) on T1WI,⁴ most notably in the globus pallidus (GP) and cerebellar dentate nucleus (DN).⁵ Substantial evidence has been provided by histopathologic analysis indicating that the reported T1WI SI increase in the DN and GP corresponds to gadolinium deposition.⁶SI changes in the brain parenchyma on unenhanced T1-weighted MR imaging have been identified in association with various histopathologic processes.⁷ Particularly, hyperintensity within the DN on T1WI due to shortening of the T1 relaxation time is believed to occur secondary to several factors, including ferric iron accumulation, ferritin accumulation associated with lipid peroxidation, and the presence of paramagnetic free radicals as well as paramagnetic compounds like metal ions such as iron and manganese.^8,9 Any of these histopathologic mechanisms could play a role in the T1WI SI observed in the DN and GP of patients with gadolinium retention. Recently, numerous studies have focused on the association between increased SI on unenhanced T1WI and exposure to intravenously administered GBCAs.¹⁰SWI is a high-resolution 3D gradient-echo sequence that incorporates phase and magnitude data to identify variations in magnetic susceptibility between adjacent tissues with a sensitivity greater than conventional gradient-echo sequences.¹¹ Its higher sensitivity in the detection of paramagnetic and diamagnetic compounds such as iron particles, blood-breakdown products, and calcifications provides clinically relevant information in the assessment of various conditions, including neurodegeneration, cerebral neoplasm, vascular malformation, and intracranial hemorrhage.¹² Because gadolinium has a paramagnetic effect, SWI can be used for noninvasive visualization of gadolinium retention within the DN and GP that may not be apparent by T1WI.¹³In this study, we hypothesized that sequential use of GBCAs would increase the magnetic susceptibility within the DN and GP as seen on SWI. Thus, we analyzed the susceptibility values in the DN and GP of children who had consecutive applications of the linear GBCA gadopentetate dimeglumine or the macrocyclic GBCA gadobutrol compared with control subjects who had no history of GBCA administration.     

The quantitative diagnostic capability of routine MR imaging and diffusion-weighted imaging in osteoporosis patients

ObjectivesTo determine the quantitative diagnostic capability of magnetic resonance imaging (MRI), compared to dual-energy X-ray absorptiometry (DEXA), for osteoporosis.Materials and MethodsEight male volunteers and eight patients underwent both DEXA and MRI. Results were obtained from each subject's L2 to L4, for a total of 48 lumbar vertebrae. Based on their bone mineral density (BMD) acquired from DEXA, the vertebrae were classified as follows: normal (n= 28), osteopenic (n= 0), and osteoporotic (n= 20). All MR examinations were performed on a 1.5-T scanner to obtain T₁-weighted imaging (T1WI), fat-suppression T₂-weighted imaging (FS-T2WI), and diffusion-weighted imaging (DWI). These quantitative MR parameters were determined: T1WI and FS-T2WI signal-to-noise ratios and DWI apparent diffusion coefficient values. To determine the diagnostic capability of MRI as an osteoporosis indicator, MR parameters were assessed statistically.ResultsAll MR parameters significantly correlated with BMD (T1WI: r=?0.64, FS-T2WI: r=?0.36, DWI: r=?0.29), with significant differences among normal and osteoporotic vertebrae (P< .05). By receiver operating characteristic analysis, the area under the curve of T1WI was significantly higher than others (P< .05). When adapted as feasible threshold values, sensitivity, specificity, and accuracy of T1WI were 95.0% (19/20), 92.9% (26/28), and 93.8% (45/48), respectively.ConclusionRoutine MRI, in particular T1WI, had a potential for the assessment of osteoporosis.     

Development and Validation of a Model Using Radiomics Features from an Apparent Diffusion Coefficient Map to Diagnose Local Tumor Recurrence in Patients Treated for Head and Neck Squamous Cell Carcinoma

ObjectiveTo develop and validate a model using radiomics features from apparent diffusion coefficient (ADC) map to diagnose local tumor recurrence in head and neck squamous cell carcinoma (HNSCC).Materials and MethodsThis retrospective study included 285 patients (mean age ± standard deviation, 62 ± 12 years; 220 male, 77.2%), including 215 for training (n = 161) and internal validation (n = 54) and 70 others for external validation, with newly developed contrast-enhancing lesions at the primary cancer site on the surveillance MRI following definitive treatment of HNSCC between January 2014 and October 2019. Of the 215 and 70 patients, 127 and 34, respectively, had local tumor recurrence. Radiomics models using radiomics scores were created separately for T2-weighted imaging (T2WI), contrast-enhanced T1-weighted imaging (CE-T1WI), and ADC maps using non-zero coefficients from the least absolute shrinkage and selection operator in the training set. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic performance of each radiomics score and known clinical parameter (age, sex, and clinical stage) in the internal and external validation sets.ResultsFive radiomics features from T2WI, six from CE-T1WI, and nine from ADC maps were selected and used to develop the respective radiomics models. The area under ROC curve (AUROC) of ADC radiomics score was 0.76 (95% confidence interval [CI], 0.62–0.89) and 0.77 (95% CI, 0.65–0.88) in the internal and external validation sets, respectively. These were significantly higher than the AUROC values of T2WI (0.53 [95% CI, 0.40–0.67], p = 0.006), CE-T1WI (0.53 [95% CI, 0.40–0.67], p = 0.012), and clinical parameters (0.53 [95% CI, 0.39–0.67], p = 0.021) in the external validation set.ConclusionThe radiomics model using ADC maps exhibited higher diagnostic performance than those of the radiomics models using T2WI or CE-T1WI and clinical parameters in the diagnosis of local tumor recurrence in HNSCC following definitive treatment.     

Computed diffusion-weighted MRI for prostate cancer detection: the influence of the combinations of b-values

Objective:

To evaluate the influence of the combinations of b-values on computed diffusion-weighted images (cDWIs) for prostate cancer (PCa) detection at b = 2000 s mm⁻².

Methods:

Diffusion-weighted imaging (DWIs) for 31 patients with PCa (65.2 ± 7.1 years) were obtained pre-operatively at different b-values (0, 100, 500, 1000 and 2000 s mm⁻²) on a 3-T MRI. cDWIs at b = 2000 were generated by using six b-value combinations: 0–100 s mm⁻² (cDWI_0–100); 0–500 s mm⁻² (cDWI_0–500); 100–500 s mm⁻² (cDWI_100–500); 0–1000 s mm⁻² (cDWI_0–1000); 100–1000 s mm⁻² (cDWI_100–1000); and 500–1000 s mm⁻² (cDWI_500–1000). These cDWIs and measured DWIs with b = 2000 s mm⁻² (mDWI₂₀₀₀) were evaluated in this setting. To assess image quality for each DWI, contrast ratios (CRs) of cancerous and non-cancerous lesions were evaluated. To compare the detectability of PCa for each DWI, receiver operating characteristic analysis was used.

Results:

CRs of all cDWIs were significantly higher than those of mDWI₂₀₀₀ (p < 0.05). Areas under the curve of cDWI_0–100 (0.62) and cDWI_0–500 (0.65) were significantly smaller (p < 0.05) than those of others (cDWI_100–500, 0.72; cDWI_0–1000, 0.73; cDWI_100–1000, 0.71; cDWI_500–1000, 0.74; mDWI₂₀₀₀, 0.72).

Conclusion:

The combinations of b-values influenced image quality and diagnostic ability of cDWIs for PCa detection. The combinations of b ≥ 100 and b ≥ 500 s mm⁻², as well as b = 0 and b = 1000 s mm⁻², were optimal in this study.

Advances in knowledge:

For generating the useful cDWI for PCa detection, radiologists should take care of the combination of b-values when including low b-values.Diffusion-weighted imaging (DWI) and MRI are now being widely used in body cancer imaging for detection, characterization and assessment of treatment response.^1–3 Prostate cancer (PCa) detection is sometimes difficult because of the high background signal of parenchyma due to the presence of hypertrophy, bleeding and inflammation.Therefore, for better cancer detection with DWI, the focus should be on contrast in signal intensity (SI) between cancer and normal parenchyma.^4,5 It has recently been reported that DWI obtained with ultrahigh b-values provide good contrast between cancerous and background tissue for better PCa detection.^6–8 Furthermore, two studies in particular have demonstrated the advantage of DWI obtained with a b-value of 2000 s mm⁻² rather than with 1000 s mm⁻² for PCa diagnosis using either 1.5- or 3.0-T MR systems.^8,9 These studies found that the background tissue signal on DWI obtained with 2000 s mm⁻² is more suppressed and the contrast between signals of cancerous and non-cancerous lesions thus more enhanced than on DWI obtained with 1000 s mm⁻². Although images obtained with b-values >1000 s mm⁻² are clinically preferable, they are more difficult to obtain in practice because of certain disadvantages such as poor signal-to-noise ratio (SNR) and potential eddy current distortions resulting from the large diffusion-sensitizing gradients used.Computed DWI (cDWI) is a recently introduced computational technique that can produce any b-value images from DWI acquired with at least two different b-values.^10–12 Blackledge et al have proved that the cDWI technique allows higher b-value images to be obtained with a good SNR because it can suppress background noise while maintaining the original lesion signal. Furthermore, cDWI generated at b = 2000 s mm⁻² from DWI obtained with b = 0 and 1000 s mm⁻² reportedly attained a better contrast ratio (CR) between cancerous and non-cancerous lesions than did an actual DWI measured with b = 2000 s mm⁻² and showed a detection ability for PCa comparable to that of an actual DWI measured with b = 2000 s mm⁻².¹³ However, it remains unclear which combination of b-values is optimal for generating cDWI with a high b-value such as 2000 s mm⁻² for detection of PCa in routine clinical practice. The aim of our study was therefore to evaluate the influence of the combinations of b-values on cDWI at b = 2000 s mm⁻² for PCa detection and to determine the optimal combination on a 3-T MR system.     

Utility of minimum intensity projection images based on three-dimensional CUBE T1 weighted imaging for evaluating middle cerebral artery stenosis

Objective:This study investigated the diagnostic performance of MinIP images based on three-dimensional variable-flip-angle turbo spin echo T₁ weighted imaging (3D CUBE T₁WI) from high-resolution vessel wall magnetic resonance imaging for detecting middle cerebral artery (MCA) stenosis.Methods:A total of 63 consecutive patients were included in this study. MinIP images were reconstructed using 3D CUBE T₁WI as the source images. The degree and length of MCA stenosis were measured on MinIP images and were compared with digital subtraction angiography (DSA) as the reference standard.Results:The intra- and interobserver agreement for both the rate and length of MCA stenosis were excellent for the MinIP images. There was also excellent agreement in the degree of MCA stenosis calculated using MinIP images and DSA. MinIP images had a high sensitivity, specificity for diagnosing MCA stenosis. There was a good correlation between the two methods for measuring the rate and length of MCA stenosis.Conclusion:MinIP images based on 3D CUBE T₁WI are highly consistent with DSA for evaluating the degree and length of MCA stenosis.Advances in knowledge:MinIP images can be produced as a derivative from vessel wall imaging and implemented as an adjunct to vessel wall imaging without extra acquisition time.     

Assessing the reliability of MRI-CBCT image registration to visualize temporomandibular joints

Objectives:

To evaluate image quality of two methods of registering MRI and CBCT images of the temporomandibular joint (TMJ), particularly regarding TMJ articular disc–condyle relationship and osseous abnormality.

Methods:

MR and CBCT images for 10 patients (20 TMJs) were obtained and co-registered using two methods (non-guided and marker guided) using Mirada XD software (Mirada Medical Ltd, Oxford, UK). Three radiologists independently and blindly evaluated three types of images (MRI, CBCT and registered MRI-CBCT) at two times (T₁ and T₂) on two criteria: (1) quality of MRI-CBCT registrations (excellent, fair or poor) and (2) TMJ disc–condylar position and articular osseous abnormalities (osteophytes, erosions and subcortical cyst, surface flattening, sclerosis).

Results:

75% of the non-guided registered images showed excellent quality, and 95% of the marker-guided registered images showed poor quality. Significant difference was found between the non-guided and marker-guided registration (χ² = 108.5; p < 0.01). The interexaminer variability of the disc position in MRI [intraclass correlation coefficient (ICC) = 0.50 at T₁, 0.56 at T₂] was lower than that in MRI-CBCT registered images [ICC = 0.80 (0.52–0.92) at T₁, 0.84 (0.62–0.93) at T₂]. Erosions and subcortical cysts were noticed less frequently in the MRI-CBCT images than in CBCT images.

Conclusions:

Non-guided registration proved superior to marker-guided registration. Although MRI-CBCT fused images were slightly more limited than CBCT alone to detect osseous abnormalities, use of the fused images improved the consistency among examiners in detecting disc position in relation to the condyle.     

Carotid Plaque Characterization Using 3D T1-Weighted MR Imaging with Histopathologic Validation: A Comparison with 2D Technique

BACKGROUND AND PURPOSE:3D FSE T1WI has recently been used for carotid plaque imaging, given the potential advantages in contrast and spatial resolutions. However, its diagnostic performance remains unclear. Hence, we compared the ability of this technique to readily assess plaque characteristics with that of conventional images and validated the results with histologic classification.MATERIALS AND METHODS:We prospectively examined 34 patients with carotid stenosis who underwent carotid endarterectomy by using 1.5T scanners and obtained 3D-FSE T1WI and 2D spin-echo T1WI scans. After generating reformatted images obtained from the 3D-FSE T1-weighted images, we calculated the contrast ratios for the plaques and the adjacent muscles and compared these findings with the pathologic classifications.RESULTS:Carotid plaques were histologically classified as types VII, VIII, IV–V, or VI. With 3D-FSE T1WI, the range of contrast ratios for each classification was the following: 0.94–0.97 (median, 0.95), 0.95–1.29 (median, 1.10), 1.33–1.54 (median, 1.42), and 1.53–2.12 (median, 1.80), respectively. With 2D imaging, the range of contrast ratios for each classification was the following: 0.79–1.02 (median, 0.90), 0.88–1.19 (median, 1.01), 1.17–1.46 (median, 1.23), and 1.55–2.51 (median, 2.07), respectively. Results were significantly different among the 4 groups (P < .001). Sensitivity and specificity for discriminating vulnerable plaques (IV–VI) from stable plaques (VII, VIII) were both 100% for the 3D technique and 100% and 91%, respectively, for the 2D technique.CONCLUSIONS:3D-FSE T1WI accurately characterizes intraplaque components of the carotid artery, with excellent sensitivity and specificity compared with those of 2D-T1WI.

Cervical carotid stenosis is an important cause of cerebral infarction and transient ischemic attack. Carotid endarterectomy or carotid artery stent placement is performed to prevent future stroke events but may also cause embolic complications during the surgery, especially if the plaque contains substantial vulnerable components such as intraplaque hemorrhage or lipid.^1,2 Therefore, establishing a method for characterizing intraplaque components is an important prerequisite for predicting perisurgical complications.Several modalities have been used for plaque characterization, including ultrasonography and MR imaging. Although ultrasonography is widely used, the interpretation is typically subjective and may be impossible in the presence of extensive calcification or a high-positioned carotid bifurcation. Although gray-scale median and integrated backscatter have been introduced as quantitative metrics, previous reports suggest that they are unsuitable for evaluating intraplaque components.^3,4 MR plaque imaging is another popular method for assessing plaque characteristics. Although various imaging techniques have been used, a 2D spin-echo (SE) T1WI technique with appropriate scanning parameters has been reported to accurately quantify intraplaque components, compared with other conventional techniques.^5–8 Recently, a 3D T1WI FSE technique has been adopted for this purpose because it can minimize partial volume effects and motion artifacts, as well as enhance black-blood effects, while maintaining T1WI contrast. However, whether the 3D-FSE technique can more accurately discriminate among intraplaque components than the more conventional techniques, such as 2D-SE T1WI, remains unknown. Hence, in the present study, we investigated whether the diagnostic accuracy of 3D-FSE T1WI, in terms of carotid plaque characterization, is comparable with that of 2D-SE T1WI, by using pathologic specimens excised from carotid endarterectomy as our validation standards.