Diffusion-weighted imaging of the head and neck: comparison between integrated slice-specific dynamic shimming and simultaneous multi-slice readout-segmented echo-planar sequences.

Readout-segmented echo-planar imaging (rs-EPI) with simultaneous multislice (SMS) technology has been successfully applied to tumor research in many organs, but no feasibility study in rectal cancer has been reported, and the optimal acceleration of SMS with rs-EPI in rectal cancer has not been well determined yet. To investigate the feasibility of SMS rs-EPI of rectal cancer with different acceleration factors (AFs) and its influence on image quality, acquisition time and apparent diffusion coefficients (ADCs) in comparison to conventional sequences. All patients underwent rs-EPI and SMS rs-EPI with AFs of 2 and 3 (2 × SMS rs-EPI and 3 × SMS rs-EPI, respectively) using a 3T scanner. Acquisition times of the three rs-EPI sequences were measured. Image qualitative parameters (5-point Likert scale), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), geometric distortion, and apparent diffusion coefficient (ADC) values of the three sequences were compared. A total of eighty-three patients were enrolled in our study. rs-EPI and 2 × SMS rs-EPI offered equivalently high overall image quality with a scan time reduction to nearly half (rs-EPI: 137 s, 2 × SM rs-EPI: 60 s). 3 × SMS rs-EPI showed significantly poorer image quality (p < 0.05). ADC values were significantly lower in 3 × SMS rs-EPI compared to rs-EPI in rectal tumors and normal tissue (tumor tissue: rs-EPI 1.19 ± 0.21 × 10-3 mm2/s, 3 × SMS rs-EPI 1.10 ± 0.26 × 10-3 mm2/s, p < 0.001; normal tissue: rs-EPI 1.68 ± 0.13 × 10-3 mm2/s, 3 × SMS rs-EPI 1.54 ± 0.20 × 10-3 mm2/s, p < 0.001). SMS rs-EPI using an AF of 2 is feasible for rectal MRI resulting in substantial reductions in acquisition time while maintaining diagnostic image quality and similar ADC values to those of rs-EPI when the slice distance and number of shots are the same among three rs-EPI sequences.

Effectiveness of simultaneous multislice accelerated readout-segmented echo planar imaging for the assessment of rectal cancer

Phase-sensitive inversion recovery (PSIR) is a powerful cardiac MRI method to assess myocardial viability, which can eliminate the background phase and preserve the sign of the desired magnetization during inversion recovery. To shorten the acquisition time of myocardial viability imaging by introducing both simultaneous multislice (SMS) and parallel imaging (PI) into PSIR without additional acquisitions for calibration data. Prospective study. A high-resolution phantom and three vials with doped solutions matching typical postcontrast T1 and T2 values of scar, healthy myocardium, and blood; 18 patients (six with known myocardial infarction) were included in this study. 3T/segmented fast spoiled gradient echo pulse sequence. Phantom and in vivo experiments were performed to compare the performance of conventional PSIR, SMS accelerated PSIR (SMS-PSIR, 2× acceleration), and SMS as well as PI accelerated PSIR (SMS + PI-PSIR, 4× acceleration). In phantom experiments, the error maps, local signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated. In in vivo experiments, the image quality and artifact level of each study were qualitatively graded (by three radiologists). G-factor maps were calculated. The infarct size presented as a percentage of the left ventricle was measured (full-width half-maximum). Acquisition time of each study was recorded. One-way analysis of variance, Kruskal-Wallis test. In phantom experiments, SNR and CNR were well preserved for SMS-PSIR, while they dropped for SMS + PI-PSIR, as expected. In 15 subjects, the overall image quality scores were not significantly different among conventional PSIR (3.70 ± 1.06), SMS-PSIR (3.78 ± 0.99), and SMS + PI-PSIR (3.47 ± 0.94; P = 0.20). The artifact level scores were also comparable among conventional PSIR (3.67 ± 1.04), SMS-PSIR (3.77 ± 1.03), and SMS + PI-PSIR (3.45 ± 1.00; P = 0.22). SMS-PSIR achieved negligible g-factor noise amplification (1.04 ± 0.03) and SMS + PI-PSIR showed higher g-factors (2.83 ± 0.48). The infarct size was consistent among conventional PSIR (22.51 ± 25.05%) and SMS-PSIR (22.98 ± 26.19%), as well as SMS + PI-PSIR (22.93 ± 25.68%; P = 0.98). The acquisition time of two short-axis slices for SMS-PSIR (17.6 ± 1.7 sec, 16 heartbeats) and SMS + PI-PSIR (9.8 ± 1.9 sec, 8 heartbeats) was 30% and 17% of that for conventional PSIR (56.2 ± 8.5 sec, 32 heartbeats), respectively. SMS can be implemented in PSIR without additional reference scan. The image quality is comparable with conventional PSIR, while the acquisition time is much shorter. The proposed method is also compatible with PI to further reduce the scan time. 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1964-1972.

Diffusion-weighted imaging (DWI) using single-shot echo-planar imaging (ss-EPI) is prone to artifacts, geometric distortion, and T2* blurring. Readout-segmented echo-planar imaging (rs-EPI) may improve image quality in the DWI of cervical cancer (CC). This study aimed to compare the image quality between rs-EPI and ss-EPI DWI in CC and to evaluate whether the apparent diffusion coefficient (ADC) values of ss-EPI (ssADC) and rs-EPI (rsADC) can differentiate the status of lymphovascular space invasion (LVSI) and lymph node metastasis (LNM). This prospective study included 69 patients with CC who underwent ss-EPI and rs-EPI DWI before surgery. Qualitative reader scores, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and ADC values derived from ss-EPI and rs-EPI were compared. The differences in ADC values were analyzed in patients who were (a) LNM-positive (LNM+, n = 17) and LNM-negative (LNM-, n = 52); (b) LVSI-positive (LVSI+, n = 33) and LVSI-negative (LVSI-, n = 36). The rs-EPIs of CC had higher subjective image quality scores and a lower SNR than ss-EPI (all P < 0.001); no significant differences existed between rs-EPI and ss-EPI for either CNR or ADC (CNR, P = 0.313; ADC, P = 0.949; P > 0.05 for all). The rsADC and ssADC of the LNM+ group were substantially lower than those of the LNM- group (rsADC, P = 0.000; ssADC, P = 0.000; P < 0.001 for all); the areas under the receiver operating characteristic curve were 0.855 and 0.851, respectively. However, there were no differences in ADC values between the LVSI+ and LVSI- groups (rsADC, P = 0.271; ssADC, P = 0.200; P > 0.05 for all). Over a similar scan time, rs-EPI improves the qualitative image quality of DWI significantly more than ss-EPI and has good diagnostic accuracy for LNM status in CC. However, neither could predict the LVSI status. Readout-segmented EPI improves the qualitative image quality of DWI and has good diagnostic accuracy for LNM status in CC, compared with conventional ss-EPI. It is more inclined to qualitative analysis of CC foci and provides a better scheme when choosing the DWI sequence scanning strategy for CC.

Objective To compare ADC values obtained from readout-segmented echo-planar imaging (RS-EPI) and single-shot echo-planar imaging (SS-EPI) techniques of prostate cancer and to investigate the correlation between RS-EPI ADC values and Gleason scores. Methods A retrospective analysis of RS-EPI and SS-EPI DWI were performed in 23 patients with pathologically confirmed prostate cancer. Routine MRI, RS-EPI DWI and SS-EPI DWI were obtained prior to ultrasound guided systemic biopsy in all cases. According to the location of lesion from biopsy report, a ROI was drawn on ADC map obtained from RS-EPI DWI and SS-EPI DWI, respectively, at cancerous foci with low T2WI and high DWI signal intensity. Foci were classified into well differentiated group (Gleason score≤6) and poorly and moderately differentiated group (Gleason score≥7). ADC values between RS-EPI and SS-EPI were compared by using t test. The relationship between ADC values and Gleason scores was assessed using Spearman test. The sensitivity and specificity of RS-EPI ADC value for differential diagnosis of two groups and the best cutoff were evaluated from ROC. Results Twenty nine well differentiated foci and 126 poorly and moderately differentiated foci were identified. The mean RS-EPI ADC value and the mean SS-EPI ADC value of well differentiated group and poorly and moderately differentiated group were (1.136 ± 0.136) × 10-3mm2/s, (1.125±0.198)×10-3mm2/s; (0.891±0.161)×10-3mm2/s, (0.875 ±0.184)×10-3mm2/s, respectively. Neither well differentiated group nor poorly and moderately differentiated group had a significant difference between the mean ADC value of two techniques (t values were 0.359 and 1.727, P values were 0.722 and 0.087, respectively). Either mean RS-EPI ADC value or mean SS-EPI ADC value between two groups had a significant difference (t values were 7.572 and 6.499, P<0.01, respectively). There was an inverse relationship between ADC values obtained from RS-EPI and SS-EPI and Gleason scores (r values were -0.638 and -0.565, P<0.01, respectively). When the cutoff value was 1.041×10-3mm2/s, the sensitivity and specificity of RS-EPI ADC value to differentiate two groups were 85.7% (108/126), 86.2% (25/29), respectively, and the area under ROC curve was 0.882. Conclusions There were no significant difference between ADC values obtained from RS-EPI and SS-EPI. ADC values of both techniques had positive correlation with Gleason scores. RS-EPI ADC values may have potential to allow noninvasive assessment of prostate cancer aggressiveness, which could help in the stratification of patients for appropriate therapy. Key words: Prostate neoplasms; Magnetic resonance imaging; Pathology

Diffusion tensor imaging (DTI) of the brain provides essential information on the white matter integrity and structural connectivity. However, it suffers from a low signal-to-noise ratio (SNR) and requires a long scan time to achieve high spatial and/or diffusion resolution and wide brain coverage. With recent advances in parallel and simultaneous multislice (multiband) imaging, the SNR efficiency has been improved by reducing the repetition time (TR ). However, due to the limited number of RF coil channels available on preclinical MRI scanners, simultaneous multislice acquisition has not been practical. In this study, we demonstrate the ability of multiband DTI to acquire high-resolution data of the mouse brain with 84 slices covering the whole brain in 0.2 mm isotropic resolution without a coil array at 9.4 T. Hadamard-encoding four-band pulses were used to acquire four slices simultaneously, with the reduction in the TR maximizing the SNR efficiency. To overcome shot-to-shot phase variations, Hadamard decoding with a self-calibrated phase was developed. Compared with single-band DTI acquired with the same scan time, the multiband DTI leads to significantly increased SNR by 40% in the white matter. This SNR gain resulted in reduced variations in fractional anisotropy, mean diffusivity, and eigenvector orientation. Furthermore, the cerebrospinal fluid signal was attenuated, leading to reduced free-water contamination. Without the need for a high-density coil array or parallel imaging, this technique enables highly efficient preclinical DTI that will facilitate connectome studies.

Deep learning image reconstruction improves 40keV virtual monoenergetic image quality in rectal cancer.

This study quantitatively compared image quality and radiation dose between fixed scanning conditions and automatic exposure control (AEC)-applied conditions in ankle CT. The experiments were conducted using a Siemens SOMATOM X.ceed CT scanner and an RSD ankle phantom. The study was conducted with a total of four groups (A-D). Group A applied CARE kV and CARE Dose4D. Groups B and C applied only CARE Dose4D, with varying tube voltages (kVp). Group D was set to the fixed scanning condition. Dose was evaluated using CT dose index volume (CTDIvol), dose length product (DLP), and size-specific dose estimate (SSDE). Image quality was compared by setting region of interset (ROI) using Image J and FIJI programs to measure signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), peak signal-to-noise ratio (PSNR), and structural similarity index measure (SSIM). SNR and CNR were highest in Group A and lowest in Group D. The results showed that SNR and CNR were highest in Group A and lowest in Group D,(p&lt;0.001) and PSNR exhibited a similar trend. SSIM values were greater than 0.999 in all groups, indicating high structural similarity. Radiation dose was lowest in Group D, followed by Group A. The results showed that the AEC-applied condition in ankle CT maintained a radiation dose comparable to that of the fixed scanning condition while demonstrating relatively favorable quantitative image quality metrics. However, as this study was limited to a phantom-based experiment and quantitative image quality evaluation, further patient-based studies are required to confirm its clinical applicability. These findings suggest that AEC may serve as an alternative scanning strategy for balancing radiation dose and image quality in ankle CT.

Objective To assess image quality and optimal keV levels of spectral CT virtual monochromatic series in atypical vertebral osteoblastic metastases of lung cancer. Methods Patients with pathologically proven lung cancer who had undergone spectral CT (Discovery CT750 HD, GE) of the chest or abdomen more than twice were analyzed retrospectively. Vertebral osteoblastic metastases were confirmed by follow-up CT examinations, biopsy ,emission CT, PET/CT. The bone lesions were missed due to atypicalappearance or presented with suspicious density at the first exmaination were chosen. A total of twenty two patients with 72 lesions were enrolled. Conventional polychromatic images (140 kVp) and monochromatic images were generated (40 to 140 keV at an interval of 10 keV). The signal to noise ratio(SNR) and contrast to noise ratio (CNR) of the lesions were measured and calculated at all the 12 series images by two radiologists. The two radiologists scored the different series of images independently. Paired sample t test was used to compare SNR and CNR among 40 to 140 keV and 140 kVp images. The inter-observer agreement between the two radiologists was evaluated using Kappa statistics and the difference of different images intrarobserver was compared using Wilcoxon signed rank test. Results The SNR of 140 kVp was 48.03±20.17, and those of 50, 60 70 keV images were 58.52±22.92, 64.07±24.88, 59.54±22.04. SNR of 50, 60, 70 keV images was higher than that of 140 kVp (t values were 13.366,16.278, 18.889,P<0.01), 60 keV images had the highest SNR. The CNR of 140 kVp was 7.64±4.52 and those of 50, 60, 70 and 80 keV images were 7.95±4.99, 8.12±5.08, 8.16±5.05, 7.89±4.81. CNR of 50, 60, 70 and 80 keV images were higher than that of 140 kVp image (t values were 3.519, 5.050, 6.231, 4.413, P<0.01), 60 keV and 70 keV images had the higher CNR than 50 keV and 80 keV. Good interobserver agreement was found for the evaluation of image quality (Kappa =0.864,P<0.05).Moreover, the scores of both the two observes for 60 keV images were higher than 140 kVp images and higher than other monochromatic images. Conclusion Atypical vertebral osteoblastic metastases of lung cancer are more conspicuous in virtual monochromatic images as compared wtih 140 kVp polychromatic images and the optimal energy level was 60 keV, repectively. Key words: Lung neoplasms; Bone neoplasms; Neoplasm metastasis; Tomography, X-ray computed

Objectives:In the present study, we introduced a practical approach to quantify organ-specific radiation doses and investigated whether low-dose head circumference (HC)-based protocols for non-enhanced head computed tomography (CT) could reduce organs-specific radiation dose in pediatric patients while maintaining high image quality.Methods:A total of 83 pediatric patients were prospectively recruited. Without limits to the HC, 15 patients were selected as a convention group (CON group) and underwent non-enhanced head CT scan with standard-dose protocols (tube current-time products of 250mAs). Low-dose group (LD group), including remaining 68 pediatrics were divided into 3 subgroups based on the HC: 54.1-57.0 cm for LD200mAs group (HC-based protocols of 200mAs), 51.1-54.0 cm for LD150mAs group (HC-based protocols of 150mAs), 48.1-51.0 cm for LD100mAs group (HC-based protocols of 100mAs). Subjective and objective image quality was evaluated and measured by 2 experienced radiologists. Radimetrics was used to calculate organs-specific radiation dose, including the brain, eye lenses, and salivary glands.Results:In CON250mAs group, radiation doses in the brain and salivary glands were conversely correlated with HC, and pediatric patients with smaller HC received higher organs-specific radiation dose. Reducing tube current-time product from 250 to 100mAs could significantly reduce the organ-specific radiation dose. The subjective image quality score ≥ 3.0 is acceptable for diagnosis purposes. The signal to noise ratio (SNR) and the contrast to noise ratio (CNR) of bilateral thalamus and centrum semiovale in 3 LD subgroups were not statistically different compared with the CON group.Conclusion:Our research indicated that low-dose HC-based protocols of non-enhanced head CT scan can evidently reduce the organ-specific radiation doses, while maintaining high image quality. HC can serve as a vital tool to guide personalized low-dose head CT scan for pediatric patients.

To evaluate the effects of arm positioning and reconstruction algorithms on radiation dose and image quality of abdominal CT. Abdominal CT scans were performed using a customized body phantom at 100 kVp with automatic tube current modulation based on noise indices (NI) of 9, 11, and 13 across seven arm positions: arms up (AU), arms down (AD), arms down with one or two-layered air cushions (ADAC, ADAC2), arms on the belly (AB), and arms on the belly with one or two-layered air cushions (ABAC, ABAC2). Images were reconstructed using filtered back projection (FBP), iterative reconstruction, and deep learning-based reconstruction (DLIR). Radiation dose was recorded. Quantitative image quality metrics included image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), sharpness, and structural similarity. Qualitative assessment of sharpness, noise, artifacts, and overall image quality was performed using fixed-dose AU-FBP images as the reference standard. Compared with the AU position, radiation dose increased by up to 83% in non-AU configurations, with similar trends across all NI settings. In contrast, air cushion use caused only minor, configuration-dependent dose changes. Qualitatively, non-AU FBP images showed marked degradation, whereas DLIR enabled selected non-AU configurations to approach near-reference diagnostic quality. Air cushion-related benefits were modest overall but more apparent in AB than AD configurations. Arm positioning is the primary determinant of radiation dose and image quality in abdominal CT. When arm elevation is not feasible, DLIR effectively mitigates image quality degradation, while air cushions provide limited, configuration-dependent benefits. When arms cannot be raised during abdominal CT, avoiding arms-on-belly and using air cushions may help maintain image quality without substantially increasing radiation dose, while deep learning image reconstruction further enhances diagnostic performance under restricted positioning conditions. Arm positioning is a major determinant of radiation dose and image quality in abdominal CT. Arms-on-belly positioning produces poorer image quality despite increased radiation dose. DLIR improves image quality across arm positions but does not eliminate positioning-related degradation.

Elimination of motion and pulsation artifacts using BLADE sequences in knee MR imaging

Whole-tumor apparent diffusion coefficient (ADC) analyses of breast lesions based on simultaneous multi-slice readout-segmented echo-planar diffusion-weighted imaging

To evaluated the impact of a deep learning (DL)-based image reconstruction on multi-arterial-phase magnetic resonance imaging (MA-MRI) for small hypervascular hepatic masses in patients who underwent gadoxetic acid-enhanced liver MRI. We retrospectively enrolled 55 adult patients (aged ≥ 18years) with small hepatic hypervascular mass (≤ 3cm) between December 2022 and February 2023. All patients underwent MA-MRI, subsequently reconstructed with a DL-based application. Qualitative assessment with Linkert scale including motion artifact (MA), liver edge (LE), hepatic vessel clarity (HVC) and image quality (IQ) was performed. Quantitative image analysis including signal to noise ratio (SNR), contrast to noise ratio (CNR) and noise was performed. On both arterial phases (APs), all qualitative parameters were significantly improved after DL-based image reconstruction. (LE on 1st AP, 1.22 vs 1.61; LE on 2nd AP, 1.21 vs 1.65; HVC on 1st AP, 1.24 vs 1.39; HVC on 2nd AP, 1.24 vs 1.44; IQ on 1st AP, 1.17 vs 1.45; IQ on 2nd AP, 1.17 vs 1.47, all p values < 0.05). The SNR, CNR and noise were significantly improved after DL-based image reconstruction. (SNR on AP1, 279.08 vs 176.14; SNR on AP2, 334.34 vs 199.24; CNR on AP1, 106.09 vs 64.14; CNR on AP2, 129.66 vs 73.73; noise on AP1, 1.51 vs 2.33; noise on AP2, 1.45 vs 2.28, all p values < 0.05). Gadoxetic acid-enhanced MA-MRI with DL-based image reconstruction improved the qualitative and quantitative parameters. Despite the short acquisition time, high-quality MA-MRI is now achievable.

We retrospectively examined image quality (IQ) of thin-slice virtual monochromatic imaging (VMI) of half-iodine-load, abdominopelvic, contrast-enhanced CT (CECT) by dual-energy CT (DECT) with deep learning image reconstruction (DLIR). In 28 oncology patients with moderate-to-severe renal impairment undergoing half-iodine-load (300 mgI/kg) CECT by DECT during the nephrographic phase, we reconstructed VMI at 40-70 keV with a slice thickness of 0.625 mm using filtered back-projection (FBP), hybrid iterative reconstruction (HIR), and DLIR; measured contrast-noise ratio (CNR) of the liver, spleen, aorta, portal vein, and prostate/uterus; and determined the optimal keV to achieve the maximal CNR. At the optimal keV, two independent radiologists compared each organ's CNR and subjective IQ scores among FBP, HIR, and DLIR to subjectively grade image noise, contrast, sharpness, delineation of small structures, and overall IQ. CNR of each organ increased continuously from 70 to 40 keV using FBP, HIR, and DLIR. At 40 keV, CNR of the prostate/uterus was significantly higher with DLIR than with FBP; however, CNR was similar between FBP and HIR and between HIR and DLIR. The CNR of all other organs increased significantly from FBP to HIR to DLIR (P < 0.05). All IQ scores significantly improved from FBP to HIR to DLIR (P < 0.05) and were acceptable in all patients with DLIR only. The combination of 40 keV and DLIR offers the maximal CNR and a subjectively acceptable IQ for thin-slice VMI of half-iodine-load CECT.