Reduced Field-of-View Diffusion-Weighted Magnetic Resonance Imaging of the Pancreas: Comparison with Conventional Single-Shot Echo-Planar Imaging

ObjectiveTo investigate the image quality (IQ) and apparent diffusion coefficient (ADC) of reduced field-of-view (FOV) di-ffusion-weighted imaging (DWI) of pancreas in comparison with full FOV DWI.ResultsOn qualitative analysis, reduced FOV DWI showed better anatomic structure visualization (2.76 ± 0.79 at b = 0 s/mm² and 2.81 ± 0.64 at b = 400 s/mm²), lesion conspicuity (3.11 ± 0.99 at b = 0 s/mm² and 3.15 ± 0.79 at b = 400 s/mm²), IQ score (8.51 ± 2.05 at b = 0 s/mm² and 8.79 ± 1.60 at b = 400 s/mm²), and higher clinical utility (3.41 ± 0.64), as compared to full FOV DWI (anatomic structure, 2.18 ± 0.59 at b = 0 s/mm² and 2.56 ± 0.47 at b = 500 s/mm²; lesion conspicuity, 2.55 ± 1.07 at b = 0 s/mm² and 2.89 ± 0.86 at b = 500 s/mm²; IQ score, 7.13 ± 1.83 at b = 0 s/mm² and 8.17 ± 1.31 at b = 500 s/mm²; clinical utility, 3.14 ± 0.70) (p < 0.05). Artifacts were significantly improved on reduced FOV DWI (2.65 ± 0.68) at b = 0 s/mm² (full FOV DWI, 2.41 ± 0.63) (p < 0.001). On quantitative analysis, there were no significant differences between the 2 DWI sequences in ADCs of various pancreatic lesions and parenchyma (p > 0.05). ADCs of adenocarcinomas (1.061 × 10^-3 mm²/s ± 0.133 at reduced FOV and 1.079 × 10^-3 mm²/s ± 0.135 at full FOV) and neuroendocrine tumors (0.983 × 10^-3 mm²/s ± 0.152 at reduced FOV and 1.004 × 10^-3 mm²/s ± 0.153 at full FOV) were significantly lower than those of parenchyma (1.191 × 10^-3 mm²/s ± 0.125 at reduced FOV and 1.218 × 10^-3 mm²/s ± 0.103 at full FOV) (p < 0.05).ConclusionReduced FOV DWI of the pancreas provides better overall IQ including better anatomic detail, lesion conspicuity and subjective clinical utility.     

A study of using a deep learning image reconstruction to improve the image quality of extremely low-dose contrast-enhanced abdominal CT for patients with hepatic lesions

Objective:To investigate the feasibility of using deep learning image reconstruction (DLIR) to significantly reduce radiation dose and improve image quality in contrast-enhanced abdominal CT.Methods:This was a prospective study. 40 patients with hepatic lesions underwent abdominal CT using routine dose (120kV, noise index (NI) setting of 11 with automatic tube current modulation) in the arterial-phase (AP) and portal-phase (PP), and low dose (NI = 24) in the delayed-phase (DP). All images were reconstructed at 1.25 mm thickness using ASIR-V at 50% strength. In addition, images in DP were reconstructed using DLIR in high setting (DLIR-H). The CT value and standard deviation (SD) of hepatic parenchyma, spleen, paraspinal muscle and lesion were measured. The overall image quality includes subjective noise, sharpness, artifacts and diagnostic confidence were assessed by two radiologists blindly using a 5-point scale (1, unacceptable and 5, excellent). Dose between AP and DP was compared, and image quality among different reconstructions were compared using SPSS20.0.Results:Compared to AP, DP significantly reduced radiation dose by 76% (0.76 ± 0.09 mSv vs 3.18 ± 0.48 mSv), DLIR-H DP images had lower image noise (14.08 ± 2.89 HU vs 16.67 ± 3.74 HU, p < 0.001) but similar overall image quality score as the ASIR-V50% AP images (3.88 ± 0.34 vs 4.05 ± 0.44, p > 0.05). For the DP images, DLIR-H significantly reduced image noise in hepatic parenchyma, spleen, muscle and lesion to (14.77 ± 2.61 HU, 14.26 ± 2.67 HU, 14.08 ± 2.89 HU and 16.25 ± 4.42 HU) from (24.95 ± 4.32 HU, 25.42 ± 4.99 HU, 23.99 ± 5.26 HU and 27.01 ± 7.11) with ASIR-V50%, respectively (all p < 0.001) and improved image quality score (3.88 ± 0.34 vs 2.87 ± 0.53; p < 0.05).Conclusion:DLIR-H significantly reduces image noise and generates images with clinically acceptable quality and diagnostic confidence with 76% dose reduction.Advances in knowledge:(1) DLIR-H yielded a significantly lower image noise, higher CNR and higher overall image quality score and diagnostic confidence than the ASIR-V50% under low signal conditions. (2) Our study demonstrated that at 76% lower radiation dose, the DLIR-H DP images had similar overall image quality to the routine-dose ASIR-V50% AP images.     

Grading of small hepatocellular carcinomas (≤2 cm): correlation between histology,T2 and diffusion-weighted imaging

Objective:

To evaluate the capacity of diffusion-weighted imaging (DWI) to determine the histological grade of small-sized hepatocellular carcinomas (HCCs) in liver cirrhosis in comparison with T₂ weighted imaging.

Methods:

51 cirrhotic patients with 63 histologically proven HCCs ≤2 cm underwent abdominal MRI, including DWI (b-values 50, 400 and 800 s mm⁻²) and T₂ weighted sequences. HCCs were classified into well-differentiated HCCs (n = 37) and moderately differentiated HCCs (n = 26). Relative contrast ratios (RCRs) between the lesions and the surrounding liver were performed and compared between the two groups for T₂ weighted images, each b-value and apparent diffusion coefficients (ADCs). A receiver operating characteristic (ROC) analysis was performed to compare RCRs in T₂ and diffusion-weighted images.

Results:

We found significant differences in RCRs between well-differentiated vs moderately differentiated HCCs for b = 50, 400 and 800 s mm⁻² and T₂ weighted images (1.35 ± 0.36 vs 1.86 ± 0.62; 1.35 ± 0.38 vs 1.82 ± 0.60; 1.27 ± 0.30 vs 1.74 ± 0.53; 1.14 ± 0.18 vs 1.43 ± 0.28, respectively; p < 0.001), whereas no significant differences were observed in ADC and ADC RCR (1.05 ± 0.19 vs 0.99 ± 0.15 and 1.1 ± 0.22 vs 1.09 ± 0.23; p = 0.16 and p = 0.82, respectively). No significant difference was found in the areas under the ROC curve for RCRs of T₂ weighted images and every DWI b-value (p = 0.18).

Conclusion:

The RCR measurement performed in DWI 50, 400 and 800 b-values and T₂ demonstrated a significant difference between well-differentiated and moderately differentiated small-sized HCCs. Furthermore, no difference was shown by using either ADC or ADC RCR.

Advances in knowledge:

DWI with RCR measurement may be a valuable tool for non-invasively predicting the histological grade of small HCCs.Recent advances in liver imaging techniques and a better understanding of imaging findings have facilitated the detection of small nodules in cirrhotic livers. Nodular lesions ≤2 cm against a background of cirrhosis are diagnostically challenging in daily practice.¹ The early and accurate diagnosis of hepatocellular carcinomas (HCCs) is of great importance because the best treatment results are obtained in patients with small and non-invasive HCCs.^2,3 If small HCCs are not treated, they can grow aggressively and microscopic vascular invasion can occur before the 2-cm cut-off size for small HCCs.¹ Fukuda et al⁴ reported that moderately and poorly differentiated HCCs ≤2 cm have a greater tendency towards microvascular invasion, meaning that the malignant potential of small HCCs should also be taken into account when selecting a treatment. Therefore, the accurate distinction of well-differentiated HCCs from less well-differentiated HCCs is also considered an important issue in planning of the therapeutic strategy, even if the tumour is small.^5,6 Considering that histological confirmation of small suspicious hepatic nodules before treatment is often not possible owing to their location in the liver or the risks of track seeding, the role of a non-invasive pre-operative imaging technique for the discrimination of moderate to poorly differentiated HCCs from well-differentiated HCCs is important. Diffusion-weighted imaging (DWI) allows the characterization of microscopic proton displacement and has profoundly improved oncological imaging. Owing to the recent advances in MRI technology, DWI can be applied to liver imaging with improved image quality.⁷ Several clinical trials have demonstrated the benefit of DWI in the detection and characterization of focal liver lesions.^8–11 There have been attempts to correlate DWI findings with the histological grading of HCCs using signal intensity (SI) and apparent diffusion coefficient (ADC) values, but no consensus in the results was obtained.^12–18 To the best of our knowledge, the interplay between DWI and histopathological factors in a cohort of patients with exclusively small HCCs (<2 cm) has not been specifically investigated. The purpose of the present study was to investigate whether or not diffusion-weighted (DW) images and ADC could determine the histological grading of HCCs <2 cm in diameter.     

Diffusion-weighted MRI of ischemic stroke at 3T: Value of synthetic b-values

Objectives:Diffusion-weighted imaging (DWI) plays a crucial role in the diagnosis of ischemic stroke. We assessed the value of computed and acquired high b-value DWI in comparison with conventional b = 1000 s mm⁻² DWI for ischemic stroke at 3T.Methods:We included 36 patients with acute ischemic stroke who presented with diffusion abnormalities on DWI performed within 24 h of symptom onset. B-values of 0, 500, 1000 and 2000 s mm⁻² were acquired. Synthetic images with b-values of 1000, 1500, 2000 and 2500 s mm⁻² were computed. Two readers compared synthetic (syn) and acquired (acq) b = 2000 s mm⁻² images with acquired b = 1000 s mm⁻² images in terms of lesion detection rate, image quality, presence of uncertain hyperintensities and lesion conspicuity. Readers also selected their preferred b-value. Contrast ratio (CR) measurements were performed. Non-parametrical statistical tests and weighted Cohens’ κ tests were computed.Results:Syn1000 and syn1500 matched acq1000 images in terms of lesion detection rate, image quality and presence of uncertain hyperintensities but presented with significantly improved lesion conspicuity (p < 0.01) and were frequently selected as preferred b-values. Acq2000 images exhibited a similar lesion detection rate and improved lesion conspicuity (p < 0.01) but worse image quality (p < 0.01) than acq1000 images. Syn2000 and syn2500 images performed significantly worse (p < 0.01) than acq1000 images in most or all categories. CR significantly increased with increasing b-values.Conclusion:Synthetic images at b = 1000 and 1500 s mm⁻² and acquired DWI images at b = 2000 s mm⁻² may be of clinical value due to improved lesion conspicuity.Advances in knowledge:Synthetic b-values enable improved lesion conspicuity for DWI of ischemic stroke.     

Gender is a determinant of carotid artery stiffness independent of age and blood pressure

Objective:To identify the gender-specific differences in carotid artery structural and stiffening parameters by radiofrequency ultrasound (RFU) with an automatic arterial stiffness analyzing system.Methods:Seventy-two consecutive individuals (32 males and 40 females, age range from 36 to 62 years) with no history of significant cardiovascular diseases or carotid artery plaques were enrolled between September and December 2017. Quality intima-media thickness (QIMT) and quality arterial stiffness (QAS) parameters were automatically computed, including pulse wave velocity (PWV), vascular distension, compliance coefficient (CC), distensibility coefficient (DC), stiffness index α and β, augmentation pressure (AP), and augmentation index (AIx). Those parameters were compared between males and females. Multiple linear regression analysis was performed to assess the independent association between gender and RFU parameters.Results:The mean age had no difference between males and females (47.8 ± 3.3 vs 50.0 ± 8.5 years, p = 0.19). Females had higher systolic blood pressure (134.53 ± 9.65 vs 127.78 ± 6.12 mm Hg) and diastolic blood pressure (85.83 ± 3.94 vs 78.03 ± 5.22 mm Hg), greater carotid QIMT (598.73 ± 72.16 vs 550.84 ± 29.37 µm), advanced PWV (8.08 ± 1.60 vs 6.24 ± 0.70 m/s), higher stiffness index α (6.21 ± 1.94 vs 3.95 ± 0.78) and β (9.43 ± 3.17 vs 6.38 ± 0.78), higher AP (6.68 ± 2.24 vs 3.64 ± 1.22 mm Hg) and AIx (7.42 ± 2.08 vs 4.69 ± 1.26%), all p < 0.001. Multiple linear regression analysis demonstrated gender was independently associated with carotid structural and elastic parameters.Conclusion:Gender independently impacts carotid structure and function, with females more vulnerable to the progression of arterial aging. Awareness of the gender differences on the risk stratification of carotid artery disease will benefit reliable assessments and specific management recommendations in clinical practice.Advances in knowledge:(1) RFU provides an μm-unit quality IMT measurement and multiple quality arterial stiffness parameters. (2) Gender is an independent determinant in both the arterial structural and elastic aspects, with females of stiffer arteries in low CVD risk individuals.     

Differentiation of benign and malignant lesions of the tongue by using diffusion-weighted MRI at 3.0?T

Objectives:

Diffusion-weighted MRI (DWI) has been introduced in head and neck lesions and adds important information to the findings obtained through conventional MRI. The purpose of this study was to assess the role of DWI in differentiating benign and malignant lesions of the tongue at 3.0-T field strength imaging.

Methods:

78 patients with 78 lingual lesions underwent conventional MRI and DWI with b-values of 0 and 1000 s mm⁻² before therapy. The apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC values of the lingual lesions were calculated and compared between benign and malignant lesions of the tongue.

Results:

The mean ADC values of the malignant tumours, benign solid lesions and cystic lesions were (1.08 ± 0.16) × 10⁻³, (1.68 ± 0.33) × 10⁻³ and (2.21 ± 0.35) × 10⁻³ mm² s⁻¹, respectively. The mean ADC values of malignant tumours were significantly lower (p < 0.001) than those of benign solid lesions, and the mean ADC values of benign solid lesions were significantly lower (p < 0.001) than those of cystic lesions. Receiver operating characteristic analysis showed that when an ADC value <1.31 × 10⁻³ mm² s⁻¹ was used for predicting malignancy, the highest accuracy of 95.3%, sensitivity of 92.6% and specificity of 97.3% were obtained.

Conclusions:

ADC values of benign and malignant lesions are significantly different at 3.0-T imaging. DWI can be applied as a complementary tool in the differentiation of benign and malignant lesions of the tongue.     

Reducing contrast medium dose with low photon energy images in renal dual-energy spectral CT angiography and adaptive statistical iterative reconstruction (ASIR)

Objective:To evaluate the value of using low energy (keV) images in renal dual-energy spectral CT angiography (CTA) and adaptive statistical iterative reconstruction (ASIR) to reduce contrast medium dose.Methods:40 patients with renal CTA on a Discovery CT750HD were randomly divided into two groups: 20 cases (Group A) with 600 mgI kg⁻¹ and 20 cases (Group B) with 300 mgI kg⁻¹. The scan protocol for both groups was: dual-energy mode with mA selection for noise index of 10 HU, pitch 1.375:1, rotating speed 0.6 s/r. Images were reconstructed at 0.625 mm thickness with 40%ASIR, Group A used the conventional 70keV monochromatic images, and Group B used monochromatic images from 40 to 70 keV at 5 keV interval for analysis. The CT values and standard deviation (SD) values of the renal artery and erector spine in the plain and arterial phases were measured with the erector spine SD value representing image noise. The enhancement degree of the renal artery (ΔCT = CT(arterial) -CT(plain)), signal-to-noise ratio (SNR=CT_renal-artery/SD_renal-artery) and contrast-to-noise ratio (CNR=(CT_renal-artery-CT_{erector spine})/SD_{erector-spine}) were calculated. The single factor analysis of variance was used to analyze the difference of ΔCT, SNR and CNR among image groups with p < 0.05 being statistically significant. The subjective image scores of the groups were assessed blindly by two experienced physicians using a 5-point system and the score consistency was compared by the κ test.Results:Contrast medium dose in the 300 mgI kg⁻¹ group was reduced by 50% compared with the 600 mgI kg⁻¹ group, while radiation dose was similar between the two groups. The subjective scores were 4.00 ± 0.65, 4.50 ± 0.60 and 3.70 ± 0.80 for images at 70 keV (600 mgI kg⁻¹ group), 40 keV (300 mgI kg⁻¹ group) and 45 keV (300 mgI kg⁻¹ group), respectively with good consistency between the two reviewers (p > 0.05). The 40 keV images in the 300 mgI kg⁻¹ group had similar ΔCT (469.77 ± 86.95 HU vs 398.54 ± 73.68 HU) and CNR (15.52 ± 3.32 vs 18.78 ± 6.71) values as the 70 keV images in the 600 mgI kg⁻¹) group but higher SNR values (30.19 ± 4.41 vs 16.91 ± 11.12, p < 0,05)Conclusion:Contrast dose may be reduced by 50% while maintaining image quality by using lower energy images combined with ASIR in renal dual-energy CTA.Advances in knowledge:Combined with ASIR and energy spectrum, can reduce the amount of contrast dose in renal CTA.     

Investigating the Image Quality and Utility of Synthetic MRI in the Breast

PurposeSynthetic MRI reconstructs multiple sequences in a single acquisition. In the present study, we aimed to compare the image quality and utility of synthetic MRI with that of conventional MRI in the breast.MethodsWe retrospectively collected the imaging data of 37 women (mean age: 55.1 years; range: 20–78 years) who had undergone both synthetic and conventional MRI of T2-weighted, T1-weighted, and fat-suppressed (FS)-T2-weighted images. Two independent breast radiologists evaluated the overall image quality, anatomical sharpness, contrast between tissues, image homogeneity, and presence of artifacts of synthetic and conventional MRI on a 5-point scale (5 = very good to 1 = very poor). The interobserver agreement between the radiologists was evaluated using weighted kappa.ResultsFor synthetic MRI, the acquisition time was 3 min 28 s. On the 5-point scale evaluation of overall image quality, although the scores of synthetic FS-T2-weighted images (4.01 ± 0.56) were lower than that of conventional images (4.95 ± 0.23; P < 0.001), the scores of synthetic T1- and T2-weighted images (4.95 ± 0.23 and 4.97 ± 0.16) were comparable with those of conventional images (4.92 ± 0.27 and 4.97 ± 0.16; P = 0.484 and 1.000, respectively). The kappa coefficient of conventional MRI was fair (0.53; P < 0.001), and that of conventional MRI was fair (0.46; P < 0.001).ConclusionThe image quality of synthetic T1- and T2-weighted images was similar to that of conventional images and diagnostically acceptable, whereas the quality of synthetic T2-weighted FS images was inferior to conventional images. Although synthetic MRI images of the breast have the potential to provide efficient image diagnosis, further validation and improvement are required for clinical application.     

Optimising diffusion-weighted MR imaging for demonstrating pancreatic cancer: a comparison of respiratory-triggered, free-breathing and breath-hold techniques

Objectives

To compare respiratory-triggered, free-breathing, and breath-hold DWI techniques regarding (1) image quality, and (2) signal intensity (SI) and ADC measurements in pancreatic ductal adenocarcinoma (PDAC).

Methods

Fifteen patients with histopathologically proven PDAC underwent DWI prospectively at 1.5?T (b?=?0, 50, 300, 600 and 1,000?s/mm²) with the three techniques. Two radiologists, independently and blindly, assigned total image quality scores [sum of rating diffusion images (lesion detection, anatomy, presence of artefacts) and ADC maps (lesion characterisation, overall image quality)] per technique and ranked them. The lesion SI, signal-to-noise ratio, mean ADC and coefficient of variation (CV) were compared.

Results

Total image quality scores for respiratory-triggered, free-breathing and breath-hold techniques were 17.9, 16.5 and 17.1 respectively (respiratory-triggered was significantly higher than free-breathing but not breath-hold). The respiratory-triggered technique had a significantly higher ranking. Lesion SI on all b-values and signal-to-noise ratio on b300 and b600 were significantly higher for the respiratory-triggered technique. For respiratory-triggered, free-breathing and breath-hold techniques the mean ADCs were 1.201, 1.132 and 1.253?×?10^-3?mm²/s, and mean CVs were 8.9, 10.8 and 14.1?% respectively (respiratory-triggered and free-breathing techniques had a significantly lower mean CV than the breath-hold technique).

Conclusion

In both analyses, respiratory-triggered DWI showed superiority and seems the optimal DWI technique for demonstrating PDAC.

Key Points

? Diffusion-weighted magnetic resonance imaging is increasingly used to detect pancreatic cancer ? Images are acquired using various breathing techniques and multiple b-values ? Breathing techniques used: respiratory-triggering, free-breathing and breath-hold ? Respiratory-triggering seems the optimal breathing technique for demonstrating pancreatic cancer     

Reliability of respiratory-triggered two-dimensional cine k-adaptive-t-autocalibrating reconstruction for Cartesian sampling for the assessment of biventricular volume and function in patients with repaired tetralogy of Fallot

Objective:To compare left ventricular (LV) and right ventricular (RV) volume, function, and image quality of a respiratory-triggered two-dimensional (2D)-cine k-adaptive-t-autocalibrating reconstruction for Cartesian sampling (2D kat-ARC) with those of the standard reference, namely, breath-hold 2D balanced steady-state free precession (2D SSFP), in patients with repaired tetralogy of Fallot (TOF).Methods:30 patients (14 males, mean age 32.2 ± 13.9 years) underwent cardiac magnetic resonance, and 2D kat-ARC and 2D SSFP images were acquired on short-axis view. Biventricular end-diastolic volume (EDV) and end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), and LV mass (LVM) were analysed.Results:The 2D kat-ARC had significantly shorter scan time (35.2 ± 9.1 s vs 80.4 ± 16.7 s; p < 0.0001). Despite an analysis of image quality showed significant impairment using 2D kat-ARC compared to 2D SSFP cine (p < 0.0001), the two sequences demonstrated no significant difference in terms of biventricular EDV, LVESV, LVSV, LVEF, and LVM. However, the RVESV was overestimated for 2D kat-ARC compared with that for 2D SSFP (73.8 ± 43.2 ml vs 70.3 ± 44.5 ml, p = 0.0002) and the RVSV and RVEF were underestimated (RVSV = 46.2±20.5 ml vs 49.4 ± 20.4 ml, p = 0.0024; RVEF = 40.2±12.7% vs. 43.5±14.0%, p = 0.0002).Conclusion:Respiratory-triggered 2D kat-ARC cine is a reliable technique that could be used in the evaluation of LV volumes and function.Advances in knowledge:2D cine kat-ARC is a reliable technique for the assessment LV volume and function in patients with repaired TOF.     

Prostate magnetic resonance imaging at 3 Tesla: Is administration of hyoscine-N-butyl-bromide mandatory?

AIM: To evaluate the value of administration of hyoscine-N-butyl-bromide (HBB) for image quality magnetic resonance imaging (MRI) of the prostate. METHODS: Seventy patients were retrospectively included in the study. Thirty-five patients were examined with administration of 40 milligrams of HBB (Buscopan ; Boehringer, Ingelheim, Germany); 35 patients were examined without HBB. A multiparametric MRI protocol was performed on a 3.0 Tesla scanner without using an endorectal coil. The following criteria were evaluated independently by two experienced radiologists on a five-point Likert scale: anatomical details (delineation between peripheral and transitional zone of the prostate, visualisation of the capsule, depiction of the neurovascular bundles); visualisation of lymph nodes; motion related artefacts; and overall image quality.RESULTS: Comparison of anatomical details between the two cohorts showed no statistically significant difference (3.9 ± 0.7 vs 4.0 ± 0.9, P = 0.54, and 3.8 ± 0.7 vs 4.2 ± 0.6, P = 0.07) for both readers. There was no significant advantage regarding depiction of local and iliac lymph nodes (3.9 ± 0.6 vs 4.2 ± 0.6, P = 0.07, and 3.8 ± 0.9 vs 4.1 ± 0.8, P = 0.19). Motion arte- facts were rated as "none" to "few" in both groups and showed no statistical difference (2.3 ± 1.0 vs 1.9 ± 0.9, P = 0.19, and 2.3 ± 1.1 vs 1.9 ± 0.7, P = 0.22). Overall image quality was rated "good" in average for both cohorts without significant difference (4.0 ± 0.6 vs 4.0 ± 0.9, P = 0.78, and 3.8 ± 0.8 vs 4.2 ± 0.6, P = 0.09). CONCLUSION: The results demonstrated no significant effect of HBB administration on image quality. The study suggests that use of HBB is not mandatory for MRI of the prostate at 3.0 Tesla.     

Imaging diagnosis of basal ganglia germ cell tumors: subtype features subtype imaging features of GCTs

Objectives:To evaluate the subtype imaging features of basal ganglia germ cell tumors (GCTs).Methods:Clinical and imaging data of 33 basal ganglia GCTs were retrospectively analyzed, including 17 germinomas and 16 mixed germ cell tumors (MGCTs).Results:The cyst/mass ratio of germinomas (0.53 ± 0.32) was higher than that of MGCTs (0.28 ± 0.19, p = 0.030). CT density of the solid part of germinomas (41.47 ± 5.22 Hu) was significantly higher than that of MGCTs (33.64 ± 3.75 Hu, p < 0.001), while apparent diffusion coefficients (ADC, ×^10-3 mm²/s) value of the solid part was significantly lower in geminomas (0.86 ± 0.27 ×^10-3 mm²/s) than in MGCTs (1.42 ± 0.39 ×^10-3 mm²/s, p < 0.001). MGCTs were more common with intratumoral hemorrhage (68.75% vs 11.76%, p = 0.01), T1 hyperintense foci (68.75% vs 5.88%, p < 0.001) and calcification (64.29% vs 20.00%, p = 0.025) than germinomas. There was no significant difference in internal capsule involvement between the two subtypes (p = 0.303), but Wallerian degeneration was more common in germinomas than in MGCTs (70.59% vs 25.00%, p = 0.015).Conclusion:The subtypes of GCT have different imaging features. Tumoral cystic-solidity, heterogeneity, ADC value, CT density, and Wallerian degeneration are helpful to differentiate germinomas and MGCTs in basal ganglia.Advances in knowledge:The subtypes of GCT have different histological characteristics, leading to various imaging findings. The imaging features of GCT subtypes in basal ganglia may aid clinical diagnosis and treatment.     

Parotid gland tumors: comparison of conventional and diffusion-weighted MRI findings with histopathological results

Objectives:The aim of this study was to investigate the relationship between pathological classification of parotid gland tumors and conventional MRI – diffusion-weighted imaging findings and also contribute the possible effect of apparent diffusion coefficient (ADC) to diagnosis.Methods:60 patients with parotid masses diagnosed using histopathology and/or cytology were enrolled in this retrospective study. All patients were evaluated using a 1.5 T MRI. Demographic features, conventional MRI findings, and ADC values (mean, minimum, maximum, and relative) were recorded. MRI findings and ADC values were compared between benign–malignant groups and pleomorphic adenoma vs Warthin’s tumor groups.Results:60 tumors (48 benign, 12 malignant) were evaluated in a total of 60 patients (39 males, 21 females). The mean age was 59 (±14, 18–86) years old; the mean lesion size was 26 (±10, 11–61) mm. On the texture of conventional MRI, T2 dominantly hyperintense/with hypointensity signal was seen in 87% of pleomorphic adenomas and T2 dominantly hypointense/with hyperintesity signal was encountered in 64% of all Warthin’s tumors. Seven (28%) Warthin’s tumors were misdiagnosed as pleomorphic adenomas and two others (8%) as malignant tumors. The commonly used mean ADC value was 1.6 ± 0.6 × 10^–3 mm² s⁻¹ for benign tumors, 0.8 ± 0.3 × 10^–3 mm² s⁻¹ for malign tumors, 1 (0.9–1.8) × 10^–3 mm² s⁻¹ for Warthin’s tumors, and 1.9 ± 0.3 × 10^–3 mm² s⁻¹ for pleomorphic adenomas. There was a statistically significant difference in ADC values between benign-malignant tumors and pleomorphic adenomas-Warthin’s tumors.Conclusions:Warthin’s tumor may occasionally be misdiagnosed as pleomorphic adenoma and malignant tumor because of variable morphologic features. In addition to benign–malignant differentiation, the added ADC measurement may also be useful for differentiating Warthin’s tumors from pleomorphic adenomas.     

Region of interest demarcation for quantification of the apparent diffusion coefficient in breast lesions and its interobserver variability

PURPOSE

We aimed to compare two different methods of region of interest (ROI) demarcation and determine interobserver variability on apparent diffusion coefficient (ADC) in breast lesions.

METHODS

Thirty-two patients with 39 lesions were evaluated with a 3.0 Tesla scanner using a diffusion-weighted sequence with several b-values. Two observers independently performed the ADC measurements using: 1) a small fixed area of 10 mm² ROI within the area with highest restriction; 2) a large ROI so as to include the whole lesion. Differences were assessed using the Wilcoxon-rank test. Bland-Altman method and Spearman coefficient were applied for interobserver variability and correlation analysis.

RESULTS

ADC values measured using the two ROI demarcation methods were significantly different for both observers (P = 0.026; P = 0.033). There was no interobserver variability in ADC values using either method (large ROI, P = 0.21; small ROI, P = 0.64). ADC values of malignant lesions were significantly different between the two methods (P < 0.001). Variability in ADC was ≤0.008×10⁻³ mm²/s for both methods. When using the same method, ADC values were significantly correlated between the observers (small ROI: r=0.990, P < 0.001; large ROI: r=0.985, P < 0.001).

CONCLUSION

The choice of ROI demarcation method influences ADC measurements. Small ROIs show less overlap in ADC values and higher ADC reproducibility, suggesting that this method may improve lesion discrimination. Interobserver variability was low for both methods.Diffusion-weighted imaging (DWI) of the breast has been used to improve lesion diagnosis. However, due to lesion heterogeneity, differences between acquisition protocols, and lesion demarcation strategies, there is some overlap in apparent diffusion coefficient (ADC) values of different lesion types (1).Regarding lesion demarcation, different strategies can be found in the literature. Pereira et al. (2) suggest delimiting the whole lesion area, whereas others consider only its most solid part representing viable tumor (3, 4).A study focusing on the use of ADC minimum, average, and maximum to characterize breast lesions (5) has indirectly investigated the influence of region of interest (ROI) on ADC quantification, but has not specifically compared these two methods of demarcation. Here, we compare these two ROI demarcation methods and determine their interobserver variability in ADC quantification.     

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 role of the ADC value in the characterisation of renal carcinoma by diffusion-weighted MRI

The purpose of this study is to evaluate the role of diffusion-weighted imaging (DWI) in combination with T₁ and T₂ weighted MRI for the characterisation of renal carcinoma. The institutional review board approved the study protocols and waived informed consent from all of the patients. 47 patients (32 male and 15 female; age range, 21–85 years; median age, 65 years) who had suspected renal lesions on abdominal CT underwent MRI for further evaluation and characterisation of the lesions from April 2005 to August 2007 in our university hospital. A region of interest was drawn around the tumour area on apparent diffusion coefficient (ADC) maps. Final diagnosis was confirmed by histological examination of surgical specimens from all patients. The ADC value was significantly higher in renal cell carcinoma (RCC) than in transitional cell carcinoma (2.71±2.35 × 10⁻³ mm² s⁻¹ vs 1.61±0.80 × 10⁻³ mm² s⁻¹; p = 0.022). While analysing the histological subtypes of RCC, a significant difference in ADC values between clear cell carcinoma and non-clear cell carcinoma was found (1.59±0.55 × 10⁻³ mm² s⁻¹ vs 6.72±1.85 × 10⁻³ mm² s⁻¹; p = 0.0004). Similarly, ADC values of RCC revealed a significant difference between positive and negative metastatic lesions (1.06±0.38 × 10⁻³ mm² s⁻¹ vs 3.02±2.44 × 10⁻³ mm² s⁻¹; p = 0.0004), whereas intensity on T₁ and T₂ weighted imaging did not reach statistical significance. In conclusion, DWI has clinical value in the characterisation of renal carcinomas and could be applied in clinical practice for their management.Renal cell carcinoma (RCC) is the most common primary malignant tumour of the kidney; it accounts for 2–3% of all adult cancers and is the sixth cause of death by tumour throughout the world. More than 80% of renal cancers that arise in the renal parenchyma are RCC, whereas the majority of renal pelvis cancers are transitional cell carcinomas (TCCs) [1–3]. The three most common subtypes of RCC are (i) clear cell carcinoma, one of the most common types, accounting for 70–80% of cases; (ii) papillary renal cell carcinoma, accounting for about 10–15% of cases; and (iii) chromophobe renal carcinoma, which is the least common, accounting for 5% of all RCCs. The annual rate of RCC diagnosis is increasing as a result of incidental detection by cross-sectional abdominal imaging of patients with suspected abdominal disorders. Increased detection rates carry a favourable prognosis; however, mortality from RCC has not decreased [2–4].Diffusion-weighted imaging (DWI) is frequently used in cranial MRI studies and has shown potential for the characterisation of lesions such as acute cerebral infarctions, intracranial tumours, various infectious diseases and metabolic disorders [5–8]. The role of DWI is limited outside the central nervous system, owing to its inherent extreme sensitivity to motion, such as that related to respiration, peristalsis and artefacts, thus resulting in a high signal to noise ratio. With the development of advanced MR technology and the use of faster robust sequences, better quality has been obtained in abdominal imaging [9]. DWI with high b-values has been reported to have a high sensitivity for depicting malignant disease. Apparent diffusion coefficient (ADC) values of malignant hepatic, ovarian, breast, prostatic, colonic and uterine cervical tumours were lower than those of benign lesions or normal tissue [10–18].Previous studies have suggested that patients with chromophobe and papillary RCC have a better prognosis than patients with clear cell RCC [19]. Accurate characterisation of patients with renal masses is essential to ensure appropriate clinical management, staging and prognosis. The clinical utility of ADC values in kidney disease has been reported: a higher value of ADC was noted in simple renal cysts and renal pelvis of hydronephrotic kidney, whereas a lower value was noted in solid renal tumours and kidneys with chronic and acute renal failure [9, 20–22]. The role of the ADC value in characterising the histological subtypes of renal carcinoma is limited [3, 9]. Therefore, the present study aimed to evaluate the role of DWI in combination with T₁ and T₂ weighted MRI for the differential diagnosis and characterisation of renal carcinoma.     

Diffusion-weighted MRI in early assessment of tumour response to radiotherapy in high-risk prostate cancer

Objective:

The objective of this study was to assess the efficacy of diffusion-weighted MRI (DWI) in monitoring response to radiotherapy in high-risk prostate cancer (PC).

Methods:

This retrospective study included 78 patients with high-risk PC undergoing 3.0-T MRI (supplemented by DWI) before and after intensity-modulated radiotherapy (IMRT). Based on follow-up clinical examinations, patients were divided into two groups: the recurrence group (patients who suffered biochemical/clinical recurrence within 3 years, n = 13) and the non-recurrence group (patients who were recurrence free for over 3 years, n = 65). The apparent diffusion coefficient (ADC) values before and after IMRT were compared between these two groups. The receiver-operating characteristics (ROC) analysis was carried out to investigate the discriminatory capability for pre- and post-IMRT ADC values.

Results:

The overall ADC values were 1.04 ± 0.18 × 10⁻³ mm² s⁻¹ for PCs before IMRT and 1.45 ± 0.15 × 10⁻³ mm² s⁻¹ after IMRT (p < 0.001). A statistically significant difference in post-IMRT ADC values was noted between patients with and without recurrence (1.27 ± 0.14 × 10⁻³ mm² s⁻¹ vs 1.49 ± 0.12 × 10⁻³mm² s⁻¹; p < 0.001), although there was no statistical difference between them in pre-IMRT ADC values (1.00 ± 0.17 × 10⁻³ mm² s⁻¹ vs 1.05 ± 0.18 × 10⁻³ mm² s⁻¹; p = 0.31). The ROC curve analysis revealed that the post-IMRT ADC values could help identify patients suffering recurrences (area under the curve, 0.88; p < 0.001).

Conclusion:

Marked increase in ADC values was observed in PC after radiotherapy, especially in good responders. DWI is a valuable tool for monitoring the response to radiotherapy.

Advances in knowledge:

This study examined the relationship between ADC changes and tumour response to treatment of PC.Prostate cancer (PC) is the most common cancer in elderly males in Western Europe and North America.¹ Although China is considered to have low incidence, the trend appears to be on the rise. According to the 2002 database of the International Agency for Research on Cancer, the mortality-to-incidence rate ratio (MR/IR) of PC in China is 0.63, which was found to be higher than the average in Asia (MR/IR = 0.57) and much higher than that in North America (MR/IR = 0.13).^2,3 These data indicated that, in China, most PCs were at the advanced stage at the time of diagnosis, and patients had a short survival time thereafter. As such, it will be prudent to address this rising challenge by developing a method for an early detection of PC and for a reliable measure of tumour response to therapy, thereby improving the MR/IR of PC in China.Currently, clinical research in diffusion-weighted MRI (DWI) is undergoing rapid expansion to depict biological changes in humans, and it has been shown that early changes in apparent diffusion coefficient (ADC) values following anti-cancer treatment may hold promise to serve as an early surrogate for long-term response in various diseases such as metastatic liver tumours, breast cancers and bone sarcomas.^4–7 However, there are relatively few reports systematically examining the relationship between ADC changes and tumour response to treatment of PC.As such, the objective of the present study was to investigate the changes in ADC values after radiotherapy, in patients with high-risk PC who showed various degrees of response. It is hoped that this investigation can contribute to better evaluation of DWI in monitoring the response to radiotherapy in PC.     

Imaging Patterns of Bacillus Calmette–Guérin-Related Granulomatous Prostatitis Based on Multiparametric MRI

ObjectiveTo categorize multiparametric MRI features of Bacillus Calmette–Guérin (BCG)-related granulomatous prostatitis (GP) and discover potential manifestations for its differential diagnosis from prostate cancerMaterials and MethodsThe cases of BCG-related GP in 24 male (mean age ± standard deviation, 66.0 ± 9.4 years; range, 50–88 years) pathologically confirmed between January 2011 and April 2019 were retrospectively reviewed. All patients underwent intravesical BCG therapy followed by a MRI scan. Additional follow-up MRI scans, including diffusion-weighted imaging (DWI), were performed in 19 patients. The BCG-related GP cases were categorized into three: A, B, or C. The lesions with diffusion restriction and homogeneous enhancement were classified as type A. The lesions with diffusion restriction and a poorly enhancing component were classified as type B. A low signal intensity on high b-value DWI (b = 1000 s/mm²) was considered characteristic of type C. Two radiologists independently interpreted the MRI scans before making a consensus about the types.ResultsThe median lesion size was 22 mm with the interquartile range (IQR) of 18–26 mm as measured using the initial MRI scans. The lesion types were A, B, and C in 7, 15, and 2 patients, respectively. Cohen’s kappa value for the inter-reader agreement for the interpretation of the lesion types was 0.837. On the last follow-up MRI scans of 19 patients, the size decreased (median, 5.8 mm; IQR, 3.4–8.5 mm), and the type changed from A or B to C in 11 patients. The lesions resolved in four patients. In five patients who underwent prostatectomy, caseous necrosis on histopathology matched with the non-enhancing components of type B lesions and the entire type C lesions.ConclusionBCG-related GP demonstrated three imaging patterns on multiparametric MRI. Contrast-enhanced T1-weighted imaging and DWI may play a role in its differential diagnosis from prostate cancer.     

Diffusion-Weighted MRI of Malignant versus Benign Portal Vein Thrombosis

ObjectiveTo validate the diffusion-weighted MRI (DWI) for differentiation of benign from malignant portal vein thrombosis.ResultsThe mean ADC ± standard deviation of bland and malignant PVT were 1.00 ± 0.39 × 10^-3 mm²/sec and 0.92 ± 0.25 × 10^-3 mm²/sec, respectively; without significant difference (p = 0.799). The area under ROC curve for ADC was 0.520. An ADC value of > 1.35 × 10^-3 mm²/sec predicted bland PVT with a specificity of 94.6% (95% confidence interval [CI]: 84.9–98.9%) and a sensitivity of 22.2% (95% CI: 6.4–47.6%), respectively.ConclusionDue to the wide range and considerable overlap of the ADCs, DWI cannot differentiate the benign from malignant thrombi efficiently.     

Diffusion-Weighted Imaging with Sensitivity Encoding (SENSE) for Detecting Cranial Bone Marrow Metastases: Comparison with T1-Weighted Images

Objective

This study was designed to determine whether diffusion-weighted imaging (DWI) with sensitivity encoding (SENSE) could detect bone marrow involvement in patients with cranial bone marrow (CBM) metastases. DWI results obtained were compared with T1-weighted imaging (T1WI) findings.

Materials and Methods

DWI with sensitivity encoding (SENSE; b value = 1,000) was performed consecutively in 13 patients with CBM metastases diagnosed pathologically and radiologically. CBM lesions were dichotomized according to the involved site, i.e., skull base or calvarium. Two radiologists qualitatively evaluated the relative conspicuousness of CBM lesions and image qualities in B0 and in isotropic DWI and in T1WI. According to region of interest analysis of normal and pathologic marrow for these three sequences, absolute signal difference percentages (SD%) were calculated to quantitatively analyze lesion contrast.

Results

All 20 lesions in 13 patients with CBM metastases revealed abnormal DWI signals in areas corresponding to T1WI abnormalities. Both skull base and calvarial lesions provided better lesion conspicuousness than T1WI and B0 images. Although the image quality of DWI was less satisfactory than that of T1WI, relatively good image qualities were obtained. Quantitatively, B0 images (SD%, 82.1 ±7.9%) showed better lesion contrast than isotropic DWI (SD%, 71.4 ±13.7%) and T1WI (SD%, 65.7 ±9.3%) images.

Conclusion

For scan times of less than 30 seconds, DWI with SENSE was able to detect bone marrow involvement, and was superior to T1WI in terms of lesion conspicuity. DWI with SENSE may be helpful for the detection of cranial bone/bone marrow metastases when used in conjunction with conventional MR sequences.