Single shot echo planar imaging (ssEPI) vs single shot turbo spin echo (ssTSE) DWI of the orbit in patients with ocular melanoma

Objectives:Diffusion weighted imaging (DWI) has become important for orbital imaging. However, the echoplanar imaging (EPI) DWI has inherent obstacles due to susceptibility to magnetic field inhomogeneities. We conducted a comparative study assessing the image quality of orbits in a patient cohort with uveal melanoma (UM). We hypothesized that single shot turbo spin echo (ssTSE) DWI would have better image quality in terms of less distortion and artifacts and yield better tissue evaluation compared to ssEPI-DWI.Methods:ssEPI-DWI and ssTSE-DWI of orbits were obtained from 50 patients with uveal melanoma who were prospectively enrolled in the study. Distortion ratio (DR), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), diffusion signal properties, and apparent diffusion coefficient (ADC) values were collected and compared between ssEPI-DWI and ssTSE-DWI. Two reviewers evaluated and compared the geometric distortion, susceptibility and ghosting artifacts, resolution, demarcation of ocular mass, and overall quality.Results:A higher DR was found in ssEPI-DWI compared to ssTSE-DWI (p < 0.001). SNR and CNR were lower for the temporal lobe cortex (p ≤ 0.004), but higher for melanoma in ssEPI-DWI than ssTSE-DWI (p ≤ 0.037). Geometric distortion and artifacts were more common in ssEPI-DWI (p < 0.001). Resolution (p ≤ 0.013) and overall quality (p < 0.001) were better in ssTSE-DWI. Ocular masses were demarcated better on ssEPI-DWI (p ≤ 0.002). Significant negative correlations between T1 and T2 signal intensities (r = −0.369, p ≤ 0.008) and positive correlations between T2 and both DWI signal intensities (r = 0.686 and p < 0.001 for ssEPI-DWI, r = 0.747 and p < 0.001 for ssTSE-DWI) were revealed.Conclusion:With less geometric distortion and susceptibility artifacts, better resolution, and overall quality, ssTSE-DWI can serve as an alternative to ssEPI-DWI for orbital DWI.Advances in knowledge:ssTSE-DWI can be a better alternative of diffusion imaging of orbits with less susceptibility artifact and geometric distortion compared to ssEPI-DWI.

Magnetic resonance imaging (MRI) is the imaging choice for evaluating orbital masses. Conventional MRI is commonly used in determining the location, extension of these mass and invasion to adjacent structures, and diffusion weighted imaging (DWI) has an additional role in delineating the lesion and its tissue characteristics. ^1–6 DWI is an imaging technique based on the motion of water molecules, showing restriction in highly cellular tumors due to the decrease in extracellular water molecules. ⁷ Single-shot echo-planar imaging (ssEPI) DWI is the widely used technique in radiology practice owing to its high speed. Unfortunately, it is highly susceptible to magnetic field inhomogeneities, therefore results in geometric distortions especially at tissue-air interfaces. ^8,9 Single-shot turbo spin echo (ssTSE) DWI, on the other hand, is another technique which is less sensitive to magnetic inhomogeneities, therefore susceptibility artifacts. ⁹ Several studies concerning head and neck showed ssTSE-DWI had better image quality compared to ssEPI-DWI. ^10–12 Orbits neighboring the paranasal sinuses are more prone to susceptibility artifacts and geometric distortion in DWI. In addition to geometric distortion and susceptibility artifacts, globe movement contributes to the difficulty of DWI when an intraocular lesion is encountered.So far, the studies concerning ssTSE-DWI of orbits showed that the apparent diffusion coefficients (ADC) derived from ssTSE-DWI had better performance in discrimination between orbital inflammation and lymphoma compared to ADCs from multi shot EPI-DWI.. ¹³ Another study demonstrated that ssTSE-DWI could discriminate viable and nonviable parts of retinoblastoma. ¹⁴ We aimed to conduct a comparative study assessing the image quality of orbits in a patient cohort with uveal melanoma to ensure homogeneity among participants. Uveal melanoma (UM) is the most common primary intraocular tumor in adults. It arises from melanocytes residing in the stroma. About 90% of uveal melanomas arise in the choroid, 7% in the ciliary body, and 3% in the iris. ¹⁵ A previous study suggested that ssEPI-DWI is useful to differentiate the UM and benign retinal detachment. ¹⁶ We hypothesized that ssTSE-DWI would have better image quality in terms of less distortion and artifacts and yield better tissue evaluation compared to ssEPI-DWI. Our secondary aim was to reveal the DWI properties of UM and its relationship with its conventional MRI signal properties.     

The clinical utility of reduced-distortion readout-segmented echo-planar imaging in the head and neck region: initial experience

Objectives

To evaluate whether readout-segmented echo-planar imaging (RS-EPI) diffusion weighted image (DWI) can diminish image distortion in the head and neck area, compared with single-shot (SS)-EPI DWI.

Methods

We conducted phantom and patient studies using 3 T magnetic resonance imaging (MRI) with a 16-channel coil. For the phantom study, we evaluated distortion and signal homogeneity in gel phantoms. For the patient study, 29 consecutive patients with clinically suspicious parotid lesions were prospectively enrolled. RS-EPI and SS-EPI DWI were evaluated by two independent readers for identification of organ/lesion and distortion, using semiquantitative scales and quantitative scores. Apparent diffusion coefficient (ADC) values and contrast-noise ratios of parotid tumours (if present; n?=?15) were also compared.

Results

The phantom experiments showed that RS-EPI provided less distorted and more homogeneous ADC maps than SS-EPI. In the patient study, RS-EPI was found to provide significantly less distortion in almost all organs/lesions (p?Conclusions The distortion in DWI was significantly reduced with RS-EPI in both phantom and patient studies. The RS-EPI technique provided more homogenous images than SS-EPI, and can potentially offer higher image quality in the head and neck area.

Key Points

? The distortion in DWI is significantly reduced with RS-EPI compared with SS-EPI. ? Structures in the head and neck were identified more clearly using RS-EPI. ? No significant difference in ADC values was found between the techniques.     

Clinical metric for differentiating intracranial hemangiopericytomas from meningiomas using diffusion weighted MRI

PurposeIntracranial Hemangiopericytomas (IHP) are dural based tumors that frequently recur/metastasize. Unfortunately, their imaging appearance overlaps significantly with more benign meningiomas. We evaluated the use of diffusion weighted imaging (DWI) to differentiate IHP from meningioma.MethodsWe compared MRI of IHP tumors (WHO Grades II/III) (n = 20) to meningioma (n = 48, WHO Grade I/II).FindingsADC values differed between IHP (1.05 × 10–3 mm2/s) and meningiomas (0.89 × 10–3 mm2/s) (p = 0.05). Normalized ADC ratios (nADC), differed between IHP and meningiomas (1.30 vs 1.07, p = 0.03).ConclusionImportantly, a nADC cutoff of >1.3 was specific (96%) but not sensitive (35%) for identifying IHP.     

Influence of windowing and metal artefact reduction algorithms on the volumetric dimensions of five different high-density materials: a cone-beam CT study

Objective:To assess the influence of windowing and metal artefact reduction (MAR) algorithms on the volumetric dimensions of high-density materials using two CBCT systems.Methods:Four cylinders of amalgam, cobalt-chromium, gutta-percha, titanium and zirconium, were manufactured and their physical volumes (PV) were measured. A polymethyl methacrylate phantom containing the cylinders was submitted to CBCT acquisitions with Picasso Trio and OP300 units with their MAR enabled and disabled. The tomographic volume (TV) of all the cylinders was obtained by semi-automatic segmentation using two windowing adjustments: W1—large window width and upper window level; W2—narrow window width and low window level. Volumetric distortion was expressed as the difference between TV and PV. Statistics comprised intraclass correlation coefficient (ICC) and analysis of variance (ANOVA) for repeated measures with Tukey post hoc test (α = 5%).Results:The ICC values ​​indicated excellent reproducibility of TV. Gutta-percha and titanium resulted in the smallest volumetric distortion. Using W1 provided less volumetric distortion for almost all experimental conditions (p < 0.05). Activating MAR algorithm of Picasso Trio underestimated gutta-percha and titanium TV (p < 0.05) and was inefficient in significantly reducing the volumetric distortion of the other materials (p > 0.05). Disabling MAR algorithm of OP300 resulted in smaller volumetric distortion for almost all experimental conditions (p < 0.05).Conclusions:The TV of gutta-percha and titanium were closer to the PV. In general, the MAR algorithms of both systems were inefficient in significantly reducing the volumetric distortion of high-density materials. We encourage the use of large window width and upper window level to evaluate high-density materials.     

Adaptive Iterative Dose Reduction Algorithm in CT: Effect on Image Quality Compared with Filtered Back Projection in Body Phantoms of Different Sizes

Objective

To evaluate the impact of the adaptive iterative dose reduction (AIDR) three-dimensional (3D) algorithm in CT on noise reduction and the image quality compared to the filtered back projection (FBP) algorithm and to compare the effectiveness of AIDR 3D on noise reduction according to the body habitus using phantoms with different sizes.

Materials and Methods

Three different-sized phantoms with diameters of 24 cm, 30 cm, and 40 cm were built up using the American College of Radiology CT accreditation phantom and layers of pork belly fat. Each phantom was scanned eight times using different mAs. Images were reconstructed using the FBP and three different strengths of the AIDR 3D. The image noise, the contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) of the phantom were assessed. Two radiologists assessed the image quality of the 4 image sets in consensus. The effectiveness of AIDR 3D on noise reduction compared with FBP were also compared according to the phantom sizes.

Results

Adaptive iterative dose reduction 3D significantly reduced the image noise compared with FBP and enhanced the SNR and CNR (p < 0.05) with improved image quality (p < 0.05). When a stronger reconstruction algorithm was used, greater increase of SNR and CNR as well as noise reduction was achieved (p < 0.05). The noise reduction effect of AIDR 3D was significantly greater in the 40-cm phantom than in the 24-cm or 30-cm phantoms (p < 0.05).

Conclusion

The AIDR 3D algorithm is effective to reduce the image noise as well as to improve the image-quality parameters compared by FBP algorithm, and its effectiveness may increase as the phantom size increases.     

Impact of total variation regularized expectation maximization reconstruction on the image quality of 68Ga-PSMA PET: a phantom and patient study

Objectives:To investigate the impact of total variation regularized expectation maximization (TVREM) reconstruction on the image quality of ⁶⁸Ga-PSMA-11 PET/CT using phantom and patient data.Methods:Images of a phantom with small hot sphere inserts and 20 prostate cancer patients were acquired with a digital PET/CT using list-mode and reconstructed with ordered subset expectation maximization (OSEM) and TVREM with seven penalisation factors between 0.01 and 0.42 for 2 and 3 minutes-per-bed (m/b) acquisition. The contrast recovery (CR) and background variability (BV) of the phantom, image noise of the liver, and SUV_max of the lesions were measured. Qualitative image quality was scored by two radiologists using a 5-point scale (1-poor, 5-excellent).Results:The performance of CR, BV, and image noise, and the gain of SUV_max was higher for TVREM 2 m/b groups with the penalization of 0.07 to 0.28 compared to OSEM 3 m/b group (all p < 0.05). The image noise of OSEM 3 m/b group was equivalent to TVREM 2 and 3 m/b groups with a penalization of 0.14 and 0.07, while lesions’ SUV_max increased 15 and 20%. The highest qualitative score was attained at the penalization of 0.21 (3.30 ± 0.66) for TVREM 2 m/b groups and the penalization 0.14 (3.80 ± 0.41) for 3 m/b group that equal to or greater than OSEM 3 m/b group (2.90 ± 0.45, p = 0.2 and p < 0.001).Conclusions:TVREM improves lesion contrast and reduces image noise, which allows shorter acquisition with preserved image quality for PSMA PET/CT.Advances in knowledge:TVREM reconstruction with optimized penalization factors can generate higher quality PSMA-PET images for prostate cancer diagnosis.     

Comparison of Genetic Profiles and Prognosis of High-Grade Gliomas Using Quantitative and Qualitative MRI Features: A Focus on G3 Gliomas

ObjectiveTo evaluate the association of MRI features with the major genomic profiles and prognosis of World Health Organization grade III (G3) gliomas compared with those of glioblastomas (GBMs).Materials and MethodsWe enrolled 76 G3 glioma and 155 GBM patients with pathologically confirmed disease who had pretreatment brain MRI and major genetic information of tumors. Qualitative and quantitative imaging features, including volumetrics and histogram parameters, such as normalized cerebral blood volume (nCBV), cerebral blood flow (nCBF), and apparent diffusion coefficient (nADC) were evaluated. The G3 gliomas were divided into three groups for the analysis: with this isocitrate dehydrogenase (IDH)-mutation, IDH mutation and a chromosome arm 1p/19q-codeleted (IDHmut1p/19qdel), IDH mutation, 1p/19q-nondeleted (IDHmut1p/19qnondel), and IDH wildtype (IDHwt). A prediction model for the genetic profiles of G3 gliomas was developed and validated on a separate cohort. Both the quantitative and qualitative imaging parameters and progression-free survival (PFS) of G3 gliomas were compared and survival analysis was performed. Moreover, the imaging parameters and PFS between IDHwt G3 gliomas and GBMs were compared.ResultsIDHmut G3 gliomas showed a larger volume (p = 0.017), lower nCBF (p = 0.048), and higher nADC (p = 0.007) than IDHwt. Between the IDHmut tumors, IDHmut1p/19qdel G3 gliomas had higher nCBV (p = 0.024) and lower nADC (p = 0.002) than IDHmut1p/19qnondel G3 gliomas. Moreover, IDHmut1p/19qdel tumors had the best prognosis and IDHwt tumors had the worst prognosis among G3 gliomas (p < 0.001). PFS was significantly associated with the 95th percentile values of nCBV and nCBF in G3 gliomas. There was no significant difference in neither PFS nor imaging features between IDHwt G3 gliomas and IDHwt GBMs.ConclusionWe found significant differences in MRI features, including volumetrics, CBV, and ADC, in G3 gliomas, according to IDH mutation and 1p/19q codeletion status, which can be utilized for the prediction of genomic profiles and the prognosis of G3 glioma patients. The MRI signatures and prognosis of IDHwt G3 gliomas tend to follow those of IDHwt GBMs.     

Readout-Segmented Echo-Planar Imaging in Diffusion-Weighted MR Imaging in Breast Cancer: Comparison with Single-Shot Echo-Planar Imaging in Image Quality

Objective

The purpose of this study was to compare the image quality of standard single-shot echo-planar imaging (ss-EPI) and that of readout-segmented EPI (rs-EPI) in patients with breast cancer.

Materials and Methods

Seventy-one patients with 74 breast cancers underwent both ss-EPI and rs-EPI. For qualitative comparison of image quality, three readers independently assessed the two sets of diffusion-weighted (DW) images. To evaluate geometric distortion, a comparison was made between lesion lengths derived from contrast enhanced MR (CE-MR) images and those obtained from the corresponding DW images. For assessment of image parameters, signal-to-noise ratio (SNR), lesion contrast, and contrast-to-noise ratio (CNR) were calculated.

Results

The rs-EPI was superior to ss-EPI in most criteria regarding the qualitative image quality. Anatomical structure distinction, delineation of the lesion, ghosting artifact, and overall image quality were significantly better in rs-EPI. Regarding the geometric distortion, lesion length on ss-EPI was significantly different from that of CE-MR, whereas there were no significant differences between CE-MR and rs-EPI. The rs-EPI was superior to ss-EPI in SNR and CNR.

Conclusion

Readout-segmented EPI is superior to ss-EPI in the aspect of image quality in DW MR imaging of the breast.     

Effect of treatment planning system parameters on beam modulation complexity for treatment plans with single-layer multi-leaf collimator and dual-layer stacked multi-leaf collimator

Objective:High levels of beam modulation complexity (MC) and monitor units (MU) can compromise the plan deliverability of intensity-modulated radiotherapy treatments. Our study evaluates the effect of three treatment planning system (TPS) parameters on MC and MU using different multi-leaf collimator (MLC) architectures.Methods:192 volumetric modulated arc therapy plans were calculated using one virtual prostate phantom considering three main settings: (1) three TPS-parameters (Convergence; Aperture Shape Controller, ASC; and Dose Calculation Resolution, DCR) selected from Eclipse v15.6, (2) four levels of dose-sparing priority for organs at risk (OAR), and (3) two treatment units with same nominal conformity resolution and different MLC architectures (Halcyon-v2 dual-layer MLC, DL-MLC & TrueBeam single-layer MLC, SL-MLC). We use seven complexity metrics to evaluate the MC, including two new metrics for DL-MLC, assessed by their correlation with γ passing rate (GPR) analysis.Results:DL-MLC plans demonstrated lower dose-sparing values than SL-MLC plans (p<0.05). TPS-parameters did not change significantly the complexity metrics for either MLC architectures. However, for SL-MLC, significant variations of MU, target volume dose-homogeneity, and dose spillage were associated with ASC and DCR (p<0.05). MU were found to be correlated (highly or moderately) with all complexity metrics (p<0.05) for both MLC plans. Additionally, our new complexity metrics presented a moderate correlation with GPR (r<0.65). An important correlation was demonstrated between MC (plan deliverability) and dose-sparing priority level for DL-MLC.Conclusions:TPS-parameters selected do not change MC for DL-MLC architecture, but they might have a potential use to control the MU, PTV homogeneity or dose spillage for SL-MLC. Our new DL-MLC complexity metrics presented important information to be considered in future pre-treatment quality assurance programs. Finally, the prominent dependence between plan deliverability and priority applied to OAR dose sparing for DL-MLC needs to be analyzed and considered as an additional predictor of GPRs in further studies.Advances in knowledge:Dose-sparing priority might influence in modulation complexity of DL-MLC.     

Diffusion tensor imaging in renal artery stenosis: a preliminary report

Objective:To investigate the diffusion properties in the kidneys affected by renal artery stenosis (RAS) using diffusion tensor imaging (DTI).Methods:In this prospective study, 35 patients with RAS and 15 patients without renal abnormalities were enrolled and examined using DTI. Cortical and medullary regions of interest (ROIs) were located to obtain the corresponding values of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA). The cortical and medullary ADC and FA were compared in the kidney affected by variable degrees of stenosis (RAS 50–75% and >75%) vs controls, using the one-way ANOVA and Student’s t-test. The Spearman correlation test was used to correlate the mean ADC and FA values in the cortex and medulla with the estimate glomerular filtration rate (eGFR).Results:For the controls, the ADC value was significantly (p = 0.03) higher in the cortex than in the medulla; the FA value was significantly (p = 0.001) higher in the medulla than in the cortex. Compared with the controls, a significant reduction in the cortical ADC was present with a RAS of 50–75% and >75% (p = 0.001 and 0.041, respectively); a significant reduction in the medullary FA was verified only for RAS >75% (p = 0.023). The Spearman correlation test did not show a statistically significant correlation between the cortical and medullary ADC and FA, and the eGFR.Conclusion:The alterations of the diffusional parameters caused by RAS can be detected by DTI and could be useful in the diagnostic evaluation of these patients.Advances in knowledge:1. Magnetic resonance DTI could provide useful information about renal involvement in RAS.2. Magnetic resonance DTI allows non-invasive repeatable evaluation of the renal parenchyma, without contrast media.     

Multiparametric MRI with diffusion-weighted imaging in predicting response to chemotherapy in cases of osteosarcoma and Ewing’s sarcoma

Objective:To evaluate the multiparametric MRI in predicting chemotherapy response in pathologically proven cases of osteosarcoma and Ewing’s sarcoma. Correlation between the tumor size changes and internal breakdown using RECIST 1.1, modified RECIST, quantitative apparent diffusion coefficient (ADC) and tumor volume as well as dynamic contrast-enhanced MRI (DCE-MRI).Methods:The study included 104 patients pathologically proved osteosarcoma (53) and Ewing`s sarcoma (51) underwent MRI examinations; before and after chemotherapy. All patients were assessed using the RECIST 1.1 criteria, m-RECIST, quantitative ADC, and tumor volume evaluation. 21 patients underwent DCE-MRI curve type with quantitative parameters. Correlation between the different evaluations was carried out. Results were correlated with the post-operative pathology in 42 patients who underwent surgery and for statistical evaluation, Those patients were classified into responders (≥90% necrosis) and non-responders (<90% necrosis).Results:The initial mean ADC of 104 patients of osteosarcoma and Ewing’s sarcoma (0.90 ± 0.29) and (0.71 ± 0.16) respectively, differed significantly from that after treatment (1.62 ± 0.46) and (1.6 ± 0.39) respectively with (p<0.001).ADC variations (ADC%) in the non-progressive group were higher than those of the progressive group (128.3 ± 63.49 vs 36.34 ± 78.7) % with (p<0.001).ADC values and ADC variations were inversely correlated with morphologic changes, regardless of the effectiveness of chemotherapy expressed as changes in tumor size based on (RECIST 1.1, RECIST, and 3D volume). Linear regression analysis revealed a Pearson correlation coefficient of r=-0.427, -0.498 and -0.408, respectively with (p<0.001).An increase in the ADC value was not always associated with a reduction in tumor volume. The disease control rate (defined as the percentage of CR+PR+SD patients) was 89.4% and 93.9% according to RECIST 1.1 and m-RECIST respectively.42 out of the 104 patients had postsurgical histological evaluation as regards the chemotherapeutic response divided into two groups. ADC values showed a statistically significant difference between Group A and Group B being more evident with minimum ADC% (p<0.001).Conclusion:Quantitative diffusion-weighted imaging with ADC mapping and ADC % after chemotherapy allows a detailed analysis of the treatment response in osteosarcoma and Ewing’s sarcoma. The therapeutic response can be underestimated using RECIST 1.1, so the modified RECIST should be also considered.Advances in knowledge:Quantitative ADC especially ADC% provided an accurate non-invasive tool in the assessment of post-therapeutic cases of osteosarcoma and Ewing''s sarcoma     

Feasibility of Three-Dimensional Balanced Steady-State Free Precession Cine Magnetic Resonance Imaging Combined with an Image Denoising Technique to Evaluate Cardiac Function in Children with Repaired Tetralogy of Fallot

ObjectiveTo investigate the feasibility of cine three-dimensional (3D) balanced steady-state free precession (b-SSFP) imaging combined with a non-local means (NLM) algorithm for image denoising in evaluating cardiac function in children with repaired tetralogy of Fallot (rTOF).Materials and MethodsThirty-five patients with rTOF (mean age, 12 years; range, 7–18 years) were enrolled to undergo cardiac cine image acquisition, including two-dimensional (2D) b-SSFP, 3D b-SSFP, and 3D b-SSFP combined with NLM. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) of the two ventricles were measured and indexed by body surface index. Acquisition time and image quality were recorded and compared among the three imaging sequences.Results3D b-SSFP with denoising vs. 2D b-SSFP had high correlation coefficients for EDV, ESV, SV, and EF of the left (0.959–0.991; p < 0.001) as well as right (0.755–0.965; p < 0.001) ventricular metrics. The image acquisition time ± standard deviation (SD) was 25.1 ± 2.4 seconds for 3D b-SSFP compared with 277.6 ± 0.7 seconds for 2D b-SSFP, indicating a significantly shorter time with the 3D than the 2D sequence (p < 0.001). Image quality score was better with 3D b-SSFP combined with denoising than with 3D b-SSFP (mean ± SD, 3.8 ± 0.6 vs. 3.5 ± 0.6; p = 0.005). Signal-to-noise ratios for blood and myocardium as well as contrast between blood and myocardium were higher for 3D b-SSFP combined with denoising than for 3D b-SSFP (p < 0.05 for all but septal myocardium).ConclusionThe 3D b-SSFP sequence can significantly reduce acquisition time compared to the 2D b-SSFP sequence for cine imaging in the evaluation of ventricular function in children with rTOF, and its quality can be further improved by combining it with an NLM denoising method.     

PET/MR in recurrent glioblastoma patients treated with regorafenib: [18F]FET and DWI-ADC for response assessment and survival prediction

Objective:The use of regorafenib in recurrent glioblastoma patients has been recently approved by the Italian Medicines Agency (AIFA) and added to the National Comprehensive Cancer Network (NCCN) 2020 guidelines as a preferred regimen. Given its complex effects at the molecular level, the most appropriate imaging tools to assess early response to treatment is still a matter of debate. Diffusion-weighted imaging and O-(2-¹⁸F-fluoroethyl)-L-tyrosine positron emission tomography ([¹⁸F]FET PET) are promising methodologies providing additional information to the currently used RANO criteria. The aim of this study was to evaluate the variations in diffusion-weighted imaging/apparent diffusion coefficient (ADC) and [¹⁸F]FET PET-derived parameters in patients who underwent PET/MR at both baseline and after starting regorafenib.Methods:We retrospectively reviewed 16 consecutive GBM patients who underwent [¹⁸F]FET PET/MR before and after two cycles of regorafenib. Patients were sorted into stable (SD) or progressive disease (PD) categories in accordance with RANO criteria. We were also able to analyze four SD patients who underwent a third PET/MR after another four cycles of regorafenib. [¹⁸F]FET uptake greater than 1.6 times the mean background activity was used to define an area to be superimposed on an ADC map at baseline and after treatment. Several metrics were then derived and compared. Log-rank test was applied for overall survival analysis.Results:Percentage difference in FET volumes correlates with the corresponding percentage difference in ADC (R = 0.54). Patients with a twofold increase in FET after regorafenib showed a significantly higher increase in ADC pathological volume than the remaining subjects (p = 0.0023). Kaplan–Meier analysis, performed to compare the performance in overall survival prediction, revealed that the percentage variations of FET- and ADC-derived metrics performed at least as well as RANO criteria (p = 0.02, p = 0.024 and p = 0.04 respectively) and in some cases even better. TBR Max and TBR mean are not able to accurately predict overall survival.ConclusionIn recurrent glioblastoma patients treated with regorafenib, [¹⁸F]FET and ADC metrics, are able to predict overall survival and being obtained from completely different measures as compared to RANO, could serve as semi-quantitative independent biomarkers of response to treatment.Advances in knowledgeSimultaneous evaluation of [¹⁸F]FET and ADC metrics using PET/MR allows an early and reliable identification of response to treatment and predict overall survival.     

Association between 18F-FDG metabolic activity and programmed death ligand-1 (PD-L1) expression using 22C3 immunohistochemistry assays in non-small cell lung cancer (NSCLC) resection specimens

Objective:This study sought to investigate the association between ¹⁸F-fludeoxyglucose (¹⁸F-FDG) uptake in positron emission tomography/CT (PET/CT) scans and different programmed death ligand-1 (PD-L1) expression conditions in non-small cell lung cancer (NSCLC).Methods:From October 2017 to December 2019, NSCLC was retrospectively identified in 419 consecutive patients who underwent ¹⁸F-FDG PET/CT scans and PD-L1 expression tests using the PD-L1 22C3 assay. The association between clinicopathological characteristics and PD-L1 expression was assessed.Results:The frequency of PD-L1-positive tumours was 38.2% (160/419) in NSCLC. In NSCLC, the multivariate analysis showed a high maximum standardised uptake value (SUVmax) (p < 0.0001) and an EGFR wild type genotype (p = 0.027) was significantly associated with PD-L1-positivity. In adenocarcinoma (ADC), the multivariate analysis showed that a high SUVmax (p < 0.0001) was significantly associated with PD-L1-positivity. In NSCLC and ADC, a Mann–Whitney U test showed significant differences between groups with PD-L1 high expression and PD-L1 low expression levels in terms of SUVmax (p = 0.011 and p = 0.013, respectively). The results of the receiver operating characteristic curve analysis showed that the area under the curve of the SUVmax was 0.767 (95% CI, 0.720–0.814; p < 0.0001) and 0.712 (95% CI, 0.651–0.774; p < 0.0001) in NSCLC and ADC, respectively.Conclusion:The study demonstrates that the SUVmax was significantly associated with PD-L1 expression in NSCLC and ADC. The SUVmax was significantly different between the PD-L1 high and low expression conditions, as quantified using a PD-L1 22C3 assay.Advances in knowledge:This study provides direct evidence that SUVmax as a metabolic biomarker may help select patients with NSCLC likely to benefit from pembrolizumab.     

Diffusion Tensor Imaging of the Lateral Pterygoid Muscle in Patients with Temporomandibular Joint Disorders and Healthy Volunteers

ObjectiveThis study aimed to explore the feasibility of functional evaluation of the lateral pterygoid muscle (LPM) using diffusion tensor imaging (DTI) in patients with temporomandibular joint disorders (TMDs).Materials and MethodsA total of 119 patients with TMD (23 male and 96 female; mean age ± standard deviation, 41 ± 15 years; 58 bilateral and 61 unilateral involvements for a total of 177 joints) and 20 healthy volunteers (9 male and 11 female; 40 ± 13 years; 40 joints) were included in this prospective study. Based on DTI of the jaw in the resting state, the diffusion parameters, apparent diffusion coefficient (ADC), fractional anisotropy (FA), λ1, λ2, and λ3 of the superior and inferior heads of the LPM (SHLPM and IHLPM) were measured. Patients with TMD with normal disc position (ND), anterior disc displacement with reduction (ADWR), and anterior disc displacement without reduction (ADWOR) were compared.ResultsPatients with TMD overall, and ADWR and ADWOR subgroups had significantly higher ADC, λ1, λ2, and λ3 in both the SHLPM and IHLPM than those in volunteers (p < 0.05 for all), whereas the ND subgroup only had significantly higher ADC and λ1 (p < 0.001). Meanwhile, significant differences in FA in the SHLPM and IHLPM were found between volunteers and ADWOR (p = 0.014 and p = 0.037, respectively). Among the three TMD subgroups, except for λ3 and FA in the ADWR subgroup, ADWR and ADWOR subgroups had significantly higher ADC, λ1, λ2, and λ3 and lower FA than those in the ND group (p < 0.050). There was no significant difference in diffusion variables between ADWR and ADWOR. In ADWOR, the osteoarthritis group had significantly higher λ3 and lower FA values in the IHLPM than those in the non-osteoarthritis group.ConclusionDTI successfully detected functional changes in the LPM in patients with TMD. The unsynchronized diffusivity changes in the LPM in different subgroups of TMD signified the possibility of using diffusion parameters as indicators to identify the severity of LPM hyperfunction at various stages of TMD.     

Low-dose whole-body CT using deep learning image reconstruction: image quality and lesion detection

Objectives:To evaluate image quality and lesion detection capabilities of low-dose (LD) portal venous phase whole-body computed tomography (CT) using deep learning image reconstruction (DLIR).Methods:The study cohort of 59 consecutive patients (mean age, 67.2 years) who underwent whole-body LD CT and a prior standard-dose (SD) CT reconstructed with hybrid iterative reconstruction (SD-IR) within one year for surveillance of malignancy were assessed. The LD CT images were reconstructed with hybrid iterative reconstruction of 40% (LD-IR) and DLIR (LD-DLIR). The radiologists independently evaluated image quality (5-point scale) and lesion detection. Attenuation values in Hounsfield units (HU) of the liver, pancreas, spleen, abdominal aorta, and portal vein; the background noise and signal-to-noise ratio (SNR) of the liver, pancreas, and spleen were calculated. Qualitative and quantitative parameters were compared between the SD-IR, LD-IR, and LD-DLIR images. The CT dose-index volumes (CTDI_vol) and dose-length product (DLP) were compared between SD and LD scans.Results:The image quality and lesion detection rate of the LD-DLIR was comparable to the SD-IR. The image quality was significantly better in SD-IR than in LD-IR (p < 0.017). The attenuation values of all anatomical structures were comparable between the SD-IR and LD-DLIR (p = 0.28–0.96). However, background noise was significantly lower in the LD-DLIR (p < 0.001) and resulted in improved SNRs (p < 0.001) compared to the SD-IR and LD-IR images. The mean CTDI_vol and DLP were significantly lower in the LD (2.9 mGy and 216.2 mGy•cm) than in the SD (13.5 mGy and 1011.6 mGy•cm) (p < 0.0001).Conclusion:LD CT images reconstructed with DLIR enable radiation dose reduction of >75% while maintaining image quality and lesion detection rate and superior SNR in comparison to SD-IR.Advances in knowledge:Deep learning image reconstruction algorithm enables around 80% reduction in radiation dose while maintaining the image quality and lesion detection compared to standard-dose whole-body CT.     

Intensity of Intraoperative Spinal Cord Hyperechogenicity as a Novel Potential Predictive Indicator of Neurological Recovery for Degenerative Cervical Myelopathy

ObjectiveTo analyze the correlations between intraoperative ultrasound and MRI metrics of the spinal cord in degenerative cervical myelopathy and identify novel potential predictive ultrasonic indicators of neurological recovery for degenerative cervical myelopathy.Materials and MethodsTwenty-two patients who underwent French-door laminoplasty for multilevel degenerative cervical myelopathy were followed up for 12 months. The Japanese Orthopedic Association (JOA) scores were assessed preoperatively and 12 months postoperatively. Maximum spinal cord compression and compression rates were measured and calculated using both intraoperative ultrasound imaging and preoperative T2-weight (T2W) MRI. Signal change rates of the spinal cord on preoperative T2W MRI and gray value ratios of dorsal and ventral spinal cord hyperechogenicity on intraoperative ultrasound imaging were measured and calculated. Correlations between intraoperative ultrasound metrics, MRI metrics, and the recovery rate JOA scores were analyzed using Spearman correlation analysis.ResultsThe postoperative JOA scores improved significantly, with a mean recovery rate of 65.0 ± 20.3% (p < 0.001). No significant correlations were found between the operative ultrasound metrics and MRI metrics. The gray value ratios of the spinal cord hyperechogenicity was negatively correlated with the recovery rate of JOA scores (ρ = −0.638, p = 0.001), while the ventral and dorsal gray value ratios of spinal cord hyperechogenicity were negatively correlated with the recovery rate of JOA-motor scores (ρ = −0.582, p = 0.004) and JOA-sensory scores (ρ = −0.452, p = 0.035), respectively. The dorsal gray value ratio was significantly higher than the ventral gray value ratio (p < 0.001), while the recovery rate of JOA-motor scores was better than that of JOA-sensory scores at 12 months post-surgery (p = 0.028).ConclusionFor degenerative cervical myelopathy, the correlations between intraoperative ultrasound and preoperative T2W MRI metrics were not significant. Gray value ratios of the spinal cord hyperechogenicity and dorsal and ventral spinal cord hyperechogenicity were significantly correlated with neurological recovery at 12 months postoperatively.     

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.     

Characterization of Brain Microstructural Abnormalities in High Myopia Patients: A Preliminary Diffusion Kurtosis Imaging Study

ObjectiveTo evaluate microstructural damage in high myopia (HM) patients using 3T diffusion kurtosis imaging (DKI).Materials and MethodsThis prospective study included 30 HM patients and 33 age- and sex-matched healthy controls (HCs) with DKI. Kurtosis parameters including kurtosis fractional anisotropy (FA), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) as well as diffusion metrics including FA, mean diffusivity, axial diffusivity (AD), and radial diffusivity derived from DKI were obtained. Group differences in these metrics were compared using tract-based spatial statistics. Partial correlation analysis was used to evaluate correlations between microstructural changes and disease duration.ResultsCompared to HCs, HM patients showed significantly reduced AK, RK, MK, and FA and significantly increased AD, predominately in the bilateral corticospinal tract, right inferior longitudinal fasciculus, superior longitudinal fasciculus, inferior fronto-occipital fasciculus, and left thalamus (all p < 0.05, threshold-free cluster enhancement corrected). In addition, DKI-derived kurtosis parameters (AK, RK, and MK) had negative correlations (r = −0.448 to −0.376, all p < 0.05) and diffusion parameter (AD) had positive correlations (r = 0.372 to 0.409, all p < 0.05) with disease duration.ConclusionHM patients showed microstructural alterations in the brain regions responsible for motor conduction and vision-related functions. DKI is useful for detecting white matter abnormalities in HM patients, which might be helpful for exploring and monitoring the pathogenesis of the disease.     

Repeatability and reproducibility of apparent diffusion coefficient and fat fraction measurement of focal myeloma lesions on whole body magnetic resonance imaging

Objective:To assess intra- and inter-reader variability of apparent diffusion coefficient (ADC) and fat fraction (FF) measurement in focal myeloma bone lesions and the influence of lesion size.Methods:22 myeloma patients with focal active disease on whole body MRI were included. Two readers outlined a small (5–10 mm) and large lesion (>10 mm) in each subject on derived ADC and FF maps; one reader performed this twice. Intra- and inter-reader agreement for small and large lesion groups were calculated for derived statistics from each map using within-subject standard deviation, coefficient of variation, interclass correlation coefficient measures, and visualized with Bland–Altman plots.Results:For mean ADC, intra- and inter-reader repeatability demonstrated equivalently low coefficient of variation (3.0–3.6%) and excellent interclass correlation coefficient (0.975–0.982) for both small and large lesions. For mean FF, intra- and inter-reader repeatability was significantly poorer for small lesions compared to large lesions (intra-reader within-subject standard variation estimate is 2.7 times higher for small lesions than large lesions (p = 0.0071), and for inter-reader variations is 3.8 times higher (p = 0.0070)).Conclusion:There is excellent intra- and inter-reader agreement for mean ADC estimates, even for lesions as small as 5 mm. For FF measurements, there is a significant increase in coefficient of variation for smaller lesions, suggesting lesions >10 mm should be selected for lesion FF measurement.Advances in knowledge:ADC measurements of focal myeloma have excellent intra- and inter-reader agreement. FF measurements are more susceptible to lesion size as intra- and inter-reader agreement is significantly impaired in lesions less than 10 mm.