TPSDicyc: Improved deformation invariant cross-domain medical image synthesis

Cycle-consistent generative adversarial network (CycleGAN) has been widely used for cross-domain medical image systhesis tasks particularly due to its ability to deal with unpaired data. However, most CycleGAN-based synthesis methods can not achieve good alignment between the synthesized images and data from the source domain, even with additional image alignment losses. This is because the CycleGAN generator network can encode the relative deformations and noises associated to different domains. This can be detrimental for the downstream applications that rely on the synthesized images, such as generating pseudo-CT for PET-MR attenuation correction. In this paper, we present a deformation invariant model based on the deformation-invariant CycleGAN (DicycleGAN) architecture and the spatial transformation network (STN) using thin-plate-spline (TPS). The proposed method can be trained with unpaired and unaligned data, and generate synthesised images aligned with the source data. Robustness to the presence of relative deformations between data from the source and target domain has been evaluated through experiments on multi-sequence brain MR data and multi-modality abdominal CT and MR data. Experiment results demonstrated that our method can achieve better alignment between the source and target data while maintaining superior image quality of signal compared to several state-of-the-art CycleGAN-based methods

SEGMA: an automatic SEGMentation Approach for human brain MRI using sliding window and random forests

Quantitative volumes from brain magnetic resonance imaging (MRI) acquired across the life course may be useful for investigating long term effects of risk and resilience factors for brain development and healthy aging, and for understanding early life determinants of adult brain structure. Therefore, there is an increasing need for automated segmentation tools that can be applied to images acquired at different life stages. We developed an automatic segmentation method for human brain MRI, where a sliding window approach and a multi-class random forest classifier were applied to high-dimensional feature vectors for accurate segmentation. The method performed well on brain MRI data acquired from 179 individuals, analyzed in three age groups: newborns (38–42 weeks gestational age), children and adolescents (4–17 years) and adults (35–71 years). As the method can learn from partially labeled datasets, it can be used to segment large-scale datasets efficiently. It could also be applied to different populations and imaging modalities across the life course

Human cardiac 31P magnetic resonance spectroscopy at 3T with a receive array: is single-loop or dual-loop RF transmission superior?

Human cardiac phosphorous MR spectroscopy (31P-MRS) provides direct insight into cardiac energetics by measuring concentrations of ATP, ADP, phosphocreatine (PCr) and other species. Yet at 3T, excitation flip angles in the inferior segments of the myocardium have been limited to be much less than the "Ernst angle" needed to maximise spectral SNR. This has made it impossible so far to acquire spectroscopic images that cover the whole heart, which in turn has limited 31P-MRS to the study of diffuse rather than focal disease. In this study, we test whether splitting the RF transmission between anterior and posterior coils improves spectral quality across the myocardium compared to transmission from the anterior side alone

Human cardiac 31P magnetic resonance spectroscopy at 3T with a receive array: is single-loop or dual-loop RF transmission superior?

Human cardiac phosphorous MR spectroscopy (31P-MRS) provides direct insight into cardiac energetics by measuring concentrations of ATP, ADP, phosphocreatine (PCr) and other species. Yet at 3T, excitation flip angles in the inferior segments of the myocardium have been limited to be much less than the "Ernst angle" needed to maximise spectral SNR. This has made it impossible so far to acquire spectroscopic images that cover the whole heart, which in turn has limited 31P-MRS to the study of diffuse rather than focal disease. In this study, we test whether splitting the RF transmission between anterior and posterior coils improves spectral quality across the myocardium compared to transmission from the anterior side alone

Diffusion-weighted imaging in uterine artery embolisation: do findings correlate with contrast enhancement and volume reduction?

Objectives The objective of this study was to determine the role of diffusion-weighted imaging (DWI) in uterine artery embolisation (UAE), and to assess the apparent diffusion coefficient (ADC) of the dominant fibroid and its relationship to contrast enhancement and fibroid volume reduction. Methods We carried out a retrospective study of 15 patients who underwent UAE. Calculations were performed at baseline and 6 months post-embolisation. Fibroid ADC (expressed in 10−3 mm2 s−1) was calculated using b=0 and b=1000 DWI values. Fibroid enhancement was compared with background myometrium by measuring signal-difference-to-noise ratio (SDNR). Fibroid volume was calculated using a prolate ellipse formula. Results There was a significant reduction (p<0.001) in fibroid ADC at 6 months (0.48; standard deviation, SD=0.26) as compared with baseline (1.01; SD=0.39). No significant change (p=0.07) was identified in 6-month myometrial ADC (1.09; SD=0.28) as compared with baseline (1.24; SD=0.20). Moderately strong and significant positive correlation was identified between baseline ADC and 6-month percentage volume reduction of the fibroid (correlation=0.66, p=0.007). No correlation was identified between SDNR and ADC at baseline or 6 months (r=0.01, p=0.97 and r=−0.13, p=0.64, respectively) or SDNR and percentage volume reduction at 6 months (correlation r=0.18, p=0.51). Conclusion Baseline ADC of dominant fibroids shows a moderately strong correlation with subsequent volume reduction at 6 months following UAE. No correlation was identified between ADC values and contrast enhancement on the baseline or 6-month scans. Further prospective evaluation is needed before DWI can be utilised in clinical practice. Advances in knowledge DWI imaging may provide additional information about UAE and possibly help to predict uterine volume reduction

Altered relative concentrations of high-energy phosphates in patients with uraemic cardiomyopathy measured by magnetic resonance spectroscopy

<p><b>Background:</b> Premature sudden cardiovascular death is the commonest cause of death in end-stage renal disease (ESRD) patients and is associated with uraemic cardiomyopathy [left ventricular hypertrophy (LVH), systolic dysfunction (LVSD) or LV dilation]. High-energy phosphates (HEP), quantified using phosphorus-31 magnetic resonance spectroscopy, are reduced in patients with diabetes, heart failure and uraemia. Phosphocreatine:β adenosine triphosphate (PCr:ATP) ratio is an index of metabolic activity. We compared resting HEPs in ESRD patients and hypertensive patients (with and without LVH) who had normal renal function (LVH-only or normal myocardia). We also assessed associations of HEP levels with abnormalities of uraemic cardiomyopathy.</p> <p><b>Methods:</b> Fifty-three ESRD and 30 hypertensive patients (18 with LVH, 12 with normal myocardia) underwent phosphorus magnetic resonance spectroscopy of their left ventricle. PCr:ATP ratios were calculated from 31P-MR spectra obtained from long-axis views of the left ventricle.</p> <p><b>Results:</b> There were no significant differences in age, LV mass, chamber sizes and ejection fraction between patient groups. PCr:ATP was significantly lower in ESRD patients compared to hypertensive patients, irrespective of the presence or absence of LVH (P = 0.01). In the ESRD group, PCr:ATP was significantly lower in patients with LVSD (P = 0.05) and LV dilation (P = 0.01). LVH was not associated with significant difference in PCr:ATP.</p> <p><b>Conclusions:</b> ESRD patients have lower HEP levels compared to hypertensive patients. Lower PCr:ATP ratio, indicating altered myocardial metabolic function in ESRD patients, is associated with features of uraemic cardiomyopathy.</p&gt