Can a single image processing algorithm work equally well across all phases of DCE-MRI?

Image segmentation and registration are said to be challenging when applied to dynamic contrast enhanced MRI sequences (DCE-MRI). The contrast agent causes rapid changes in intensity in the region of interest and elsewhere, which can lead to false positive predictions for segmentation tasks and confound the image registration similarity metric. While it is widely assumed that contrast changes increase the difficulty of these tasks, to our knowledge no work has quantified these effects. In this paper we examine the effect of training with different ratios of contrast enhanced (CE) data on two popular tasks: segmentation with nnU-Net and Mask R-CNN and registration using VoxelMorph and VTN. We experimented further by strategically using the available datasets through pretraining and fine tuning with different splits of data. We found that to create a generalisable model, pretraining with CE data and fine tuning with non-CE data gave the best result. This interesting find could be expanded to other deep learning based image processing tasks with DCE-MRI and provide significant improvements to the models performance

Feasibility of a multiparametric MRI protocol for imaging biomarkers associated with neoadjuvant radiotherapy for soft tissue sarcoma

OBJECTIVE: Soft tissue sarcoma (STS) is a rare malignancy with a 5 year overall survival rate of 55%. Neoadjuvant radiotherapy is commonly used in preparation for surgery, but methods to assess early response are lacking despite pathological response at surgery being predictive of overall survival, local recurrence and distant metastasis. Multiparametric MR imaging (mpMRI) is used to assess response in a variety of tumours but lacks a robust, standardised method. The overall aim of this study was to develop a feasible imaging protocol to identify imaging biomarkers for further investigation. METHODS: 15 patients with biopsy-confirmed STS suitable for pre-operative radiotherapy and radical surgery were imaged throughout treatment. The mpMRI protocol included anatomical, diffusion-weighted and dynamic contrast-enhanced imaging, giving estimates of apparent diffusion coefficient (ADC) and the area under the enhancement curve at 60 s (iAUC(60)). Histological analysis of resected tumours included detection of CD31, Ki67, hypoxia inducible factor and calculation of a hypoxia score. RESULTS: There was a significant reduction in T1 at visit 2 and in ADC at visit 3. Significant associations were found between hypoxia and pre-treatment iAUC(60), pre-treatment ADC and mid-treatment iAUC(60). There was also statistically significant association between mid-treatment ADC and Ki67. CONCLUSION: This work showed that mpMRI throughout treatment is feasible in patients with STS having neoadjuvant radiotherapy. The relationships between imaging parameters, tissue biomarkers and clinical outcomes warrant further investigation. ADVANCES IN KNOWLEDGE: mpMRI-based biomarkers have good correlation with STS tumour biology and are potentially of use for evaluation of radiotherapy response

A multimodality cross-validation study of cardiac perfusion using MR and CT.

Modern advances in magnetic resonance (MR) and computed tomography (CT) perfusion imaging techniques have developed methods for myocardial perfusion assessment. However, individual imaging techniques present limitations that are possible to be surpassed by a multimodality cross-validation of perfusion imaging and analysis. We calculated the absolute myocardial blood flow (MBF) in MR using a Fermi function and the transmural perfusion ratio (TPR) in CT perfusion data in a patient with coronary artery disease (CAD). Comparison of MBF and TPR results showed good correlation emphasizing a promising potential to continue our multimodality perfusion assessment in a cohort of patients with CAD

Preliminary study of proton magnetic resonance spectroscopy to assess bone marrow adiposity in the third metacarpus or metatarsus in Thoroughbred racehorses

Background: Magnetic resonance spectroscopy (MRS) has been used to investigate metabolic changes within human bone. It may be possible to use MRS to investigate bone metabolism and fracture risk in the distal third metacarpal/tarsal bone (MC/MTIII) in racehorses. Objectives: To determine the feasibility of using MRS as a quantitative imaging technique in equine bone by using the 1H spectra for the MC/MTIII to calculate fat content (FC). Study Design: Observational cross-sectional study Methods: Limbs from Thoroughbred racehorses were collected from horses that died or were subjected to euthanasia on racecourses. Each limb underwent magnetic resonance imaging (MRI) at 3T followed by single-voxel MRS at 3 regions of interest (ROI) within MC/MTIII (lateral condyle, medial condyle, proximal bone marrow (PBM)). Percentage FC was calculated at each ROI. Each limb underwent computed tomography (CT) and bone mineral density (BMD) was calculated for the same ROIs. All MR and CT images were graded for sclerosis. Histology slides were graded for sclerosis and proximal marrow space was calculated. Pearson or Spearman correlations were used to assess the relationship between BMD, FC and marrow space. Kruskall-Wallis tests were used to check for differences between sclerosis groups for BMD or FC. Results: Eighteen limbs from 10 horses were included. A negative correlation was identified for mean BMD and FC for the lateral condyle (correlation coefficient =-0.60, p=0.01) and PBM (correlation coefficient =-0.5, p=0.04). There was a significant difference between median BMD for different sclerosis grades in the condyles on both MRI and CT. A significant difference in FC was identified between sclerosis groups in the lateral condyle on MRI and CT . Main Limitations: Small sample size. Conclusions: 1H Proton MRS is feasible in the equine MC/MTIII. Further work is required to evaluate the use of this technique to predict fracture risk in racehorses

Manganese-enhanced Magnetic Resonance Imaging in Dilated Cardiomyopathy and Hypertrophic Cardiomyopathy.

Patients with dilated cardiomyopathy (n= 10) or hypertrophic cardiomyopathy (n= 17) underwent both gadoliniumand manganese contrast-enhanced magnetic resonance imaging and were compared with healthy volunteers(n= 20). Differential manganese uptake (Ki) was assessed using a two-compartment Patlak model. Compared withhealthy volunteers, reduction in T1 with manganese-enhanced magnetic resonance imaging was lower in patientswith dilated cardiomyopathy [mean reduction 257 ± 45 (21%) vs. 288 ± 34 (26%) ms,P< 0.001], with higher T1 at40 min (948 ± 57 vs. 834 ± 28 ms,P< 0.0001). In patients with hypertrophic cardiomyopathy, reductions in T1 wereless than healthy volunteers [mean reduction 251 ± 86 (18%) and 277 ± 34 (23%) vs. 288 ± 34 (26%) ms, with andwithout fibrosis respectively,P< 0.001]. Myocardial manganese uptake was modelled, rate of uptake was reducedin both dilated and hypertrophic cardiomyopathy in comparison with healthy volunteers (meanKi19 ± 4, 19 ± 3,and 23 ± 4 mL/100 g/min, respectively;P= 0.0068). In patients with dilated cardiomyopathy, manganese uptake ratecorrelated with left ventricular ejection fraction (r2= 0.61,P= 0.009). Rate of myocardial manganese uptake demon-strated stepwise reductions across healthy myocardium, hypertrophic cardiomyopathy without fibrosis and hyper-trophic cardiomyopathy with fibrosis providing absolute discrimination between the healthy myocardium andfibrosed myocardium (meanKi23 ± 4, 19 ± 3, and 13 ± 4 mL/100 g/min, respectively;P< 0.0001)