Reduced Field of View APT Imaging of Rectum (RAPTOR) at 3T MRI Scanner / 生物化学与生物物理进展

ObjectiveThe chemical exchange saturation transfer (CEST) technique has become a valuable tool in diagnosing metabolic changes associated with cerebral and systemic diseases, leveraging the calculation of compounds with exchangeable protons in proximity to water molecules. Specifically, the amide proton transfer (APT) CEST technique has shown promise in diagnosing cerebral strokes and tumors by comparing altered endogenous proteins or peptides with normal tissues. Reduced field of view (rFOV) imaging technology has been widely used in the diagnosis of small organ lesions in the body. In this study, we aim to apply the rFOV imaging to identify CEST signals in the rectum, investigating the potential utility of rFOV technique in clinical diagnosis of rectal diseases and providing metabolic insights for chemoradiotherapy. MethodsMRI images of eleven healthy volunteers were acquired using transverse Full_FOV and rFOV CEST imaging on a 3T scanner. The resolution was set at 2.5×2.5×6 mm³ and 1.5×1.5×6 mm³ for Full_FOV or the rFOV method. Saturation powers of 0.7 μT and 2 μT were applied. For the 2 μT saturation, MTRasym at ±3.5 ppm was employed, while for 0.7 μT saturation, Lorentzian difference was used for CEST quantification of the contrast maps and curves. ResultsThe rFOV method has the advantage of halving the scan time while maintaining the same contrast as the Full_FOV method. When compared to Full_FOV methods, rFOV methods exhibited nearly identical Z_spec and very similar MTRasym curves. Additionally, rFOV with a 1.5 mm×1.5 mm in-plane resolution could be achieved in approximately 3 min. rFOV method displayed better structural details for the entire rectum, including CEST contrast maps and quantitative curves. ConclusionCEST MRI proves valuable in diagnosing rectal diseases, and employing the rFOV technique could provide higher spatial and temporal resolution. CEST MRI should be the preferred choice for offering improved diagnostic capabilities with its potential for rectal disease diagnosis.

Value of Reduced Field-of-view DWI in Quantitative Assessment of Axial Spondyloarthritis / 中山大学学报(医学科学版)

ObjectiveTo investigate the value of reduced field-of-view DWI （r-FOV DWI） in quantitative assessment of axial spondyloarthritis. MethodsA total of 112 patients with chronic back pain or suspected axial spondyloarthritis receiving full field-of-view DWI （f-FOV DWI） and reduced field-of-view DWI （r-FOV DWI） from December 2019 to December 2021 were enrolled. Next， subjective image quality assessment （anatomical detail， artifacts， distortion， overall image quality） and objective image quality assessment including （signal to noise ratio and contrast to noise ratio） were conducted by two experienced radiologists. In addition， the Apparent Diffusion Coefficient （ADC） values of three groups （active group， inactive group， and control group） on the two DWI sequences were measured by the two radiologists， respectively. Finally， the consistency of measurement between the two researchers was evaluated and the differences in ADC values was compared. Results102 patients were included and were divided into three groups， including the active group （n=32）， inactive group （n=29）， and control group （n=41） according to ASAS diagnostic criteria. All subjective and objective image quality metrics were rated in favor of r-FOV DWI images compared with f-FOV DWI images ［overall image quality： DWI 4（3~4） vs. 3（3~3） and SNR： 6.58（5.05~10.38） vs. 4.46（2.37~10.04）， CNR： 2.04（-1.14~8.29） vs. 0.97（-8.19~7.12）；P＜0.05］. Inter-rater consistency of the two researchers were 0.60~0.74. According to the AUC curve， group inactive vs. control showed r-FOV DWI was better than f-FOV DWI. In other groups （lesion vs. control， active vs. inactive）， there were no differences between both sequences（P＜0.05）. ConclusionThe subjective image quality score and signal to noise ratio of r-FOV DWI were higher than those of f-FOV DWI， which could be used for quantitative assessment of axial spondyloarthritis.

Functional Evaluation of Transplanted Kidneys with Reduced Field-of-View Diffusion-Weighted Imaging at 3T

OBJECTIVE: To determine the feasibility of reduced field-of-view diffusion-weighted imaging (rFOV DWI) with multi-b values to detect functional variability in transplanted kidneys. MATERIALS AND METHODS: Using a 3T MRI scanner, multi-b rFOV DWI of transplanted kidney or native kidney was performed in 40 renal transplantation recipients and 18 healthy volunteers. The patients were stratified, according to an estimated glomerular filtration rate (eGFR): Group 1, eGFR ≥ 60 mL/min/1.73 m2; Group 2, eGFR ≥ 30 mL/min/1.73 m2 and < 60 mL/min/1.73 m2; Group 3, eGFR < 30 mL/min/1.73 m2. Total apparent diffusion coefficient (ADCT), perfusion-free ADC (ADCD) and perfusion fraction (FP) of kidneys were calculated and compared among the four groups. Correlations between the imaging results and eGFR were assessed. RESULTS: All volunteers had eGFR ≥ 60 mL/min/1.73 m2, while 16, 16, and 8 patients were included in Groups 1, 2, and 3, respectively. In the renal cortex, ADCT was higher in Group 1 ([1.65 ± 0.13] × 10−3 mm2/s) than Group 3 ([1.44 ± 0.11] × 10−3 mm2/s) (p < 0.05), and the inter-group differences of FP values were significant (all p < 0.05) (0.330 ± 0.024, 0.309 ± 0.019, 0.278 ± 0.033, and 0.250 ± 0.028 for control group, Groups 1, 2, and 3, respectively). Renal cortical ADCT, ADCD, FP, and renal medullary ADCT and FP correlated positively with eGFR (r = 0.596, 0.403, 0.711, 0.341, and 0.323, respectively; all p < 0.05). When using 0.278 as the cutoff value, renal cortical FP had a sensitivity of 97.1% and a specificity of 66.7% for predicting decreased renal function. CONCLUSION: Multi-b rFOV DWI presents transplanted kidneys with high resolution, which is a promising functional tool for non-invasively monitoring function of transplanted kidneys.

Reduced field-of-view diffusion weighted imaging in diagnosis of prostate cancer / 医学研究生学报

Objective With the improvement of technology and strategy , reduced field-of-view diffusion weighted imaging ( rFOV DWI) has provided more robust imaging .This article was intended to compare the clinical utility between rFOV DWI and con-ventional DWI in the diagnosis of prostate cancer . Methods Retrospective analysis was made on 58 prostate cancer patients under-going verification of biopsy or surgery after 3.0 T MRI rFOV DWI and regular DWI examinations in Nanjing General Hospital of Nan-jing Military Command from August 2014 to September 2015 , among whom prostate cancer and benign prostatic hyperplasia were 31 cases and 27 cases respectively .Independent grading was made by 2 radiol-ogists who were unaware of any clinical data and sequences in the as-pects of distortion on DW images , lesion conspicuity on DWI ( b=1000 ) and ADC images according to a 4-point Likert scale .rFOV and conventional DWI sequences were acquired using b =400,1000,0s/mm2.The IVIM double exponential model software was applied to generate ACD value, slow dispersive coefficient(D value) and parameterized image of volume fraction of fast dispersion (f value).Se-quence analysis was made in suspected peripheral tumor regions of prostate cancer patients and and healthy peripheral zones of patients with benign prostatic hyperplasia respectively to get ACD , D and f values .The ratio values rADC , rD and rf were attained compared with obturator internus .ROC analysis was made on the efficacy of different parameters of two sequences in prostate cancer . Results Image qualities of rFOV DWI were rated superior to conventional DWI (P<0.001,Wilcoxon Signed-Rank Test).Compared with con-ventional DWI, ADC value (0.728 ±0.094 vs 0.789 ±0.116, P<0.05)and D value(0.622 ±0.077 vs 0.651 ±0.099, P<0.05)of peripheral tumor regions in rFOV DWI were lower and the difference was statistically significant , whereas no significant difference was found in f value(P=0.932).No difference was found in area under ROC curve of f value between rFOV DWI and traditional DWI (0.853 vs 0.767, P=0.283). Conclusion The rFOV DWI sequence yielded can efficiently improve image quality , which is of important value to the clinical diagnosis of prostate cancer .

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

OBJECTIVE: To 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. MATERIALS AND METHODS: In this retrospective study, 2 readers independently performed qualitative analysis of full FOV DWI (FOV, 38 × 38 cm; b-value, 0 and 500 s/mm²) and reduced FOV DWI (FOV, 28 × 8.5 cm; b-value, 0 and 400 s/mm²). Both procedures were conducted with a two-dimensional spatially selective radiofrequency excitation pulse, in 102 patients with benign or malignant pancreatic diseases (mean size, 27.5 ± 14.4 mm). The study parameters included 1) anatomic structure visualization, 2) lesion conspicuity, 3) artifacts, 4) IQ score, and 5) subjective clinical utility for confirming or excluding initially considered differential diagnosis on conventional imaging. Another reader performed quantitative ADC measurements of focal pancreatic lesions and parenchyma. Wilcoxon signed-rank test was used to compare qualitative scores and ADCs between DWI sequences. Mann Whitney U-test was used to compare ADCs between the lesions and parenchyma. RESULTS: On 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). 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). CONCLUSION: Reduced FOV DWI of the pancreas provides better overall IQ including better anatomic detail, lesion conspicuity and subjective clinical utility.