Diffusion weighted cardiovascular magnetic resonance imaging for discriminating acute from non-acute deep venous Thrombus

Magnetic resonance (MR) evaluation of deep venous thrombosis of 338 discharged viral pneumonia patients

Background

Viral pneumonia (VP) often leads to the development of deep vein thrombosis (DVT) in hospitalized patients. The aim of the study was to investigate the incidence of DVT in discharged patients with VP, and whether new and old DVT differ in transverse relaxation time.

Methods

In this prospective cohort study in Wuhan, China, 338 consecutive discharged VP patients from February 2021 to March 2023 who underwent T2 weighted Sampling Perfection with Application Optimized Contrast Evolution (SPACE) were recruited to detect DVT. T2 mapping and T2* mapping were performed for the patients with DVT detected by magnetic resonance imaging (MRI). The minimum, maximum, mean of T2 time and T2* time of DVT were recorded as T2min, T2max, T2mean, T2*min, T2*max, and T2*mean, respectively. Clinical data and laboratory findings were compared between new and old DVT cases, which were defined based on the examination results before and after discharge. A Mann-Whitney test was used to compare transverse relaxation time parameters between new and old DVT.

Results

Twelve percent of VP patients (40/338) developed new DVT after discharge. Thirty-three out of 104 DVTs did not resolve after discharge. Compared with patients with new DVT, patients with old DVT were older (67 vs. 59 years, P=0.003); and had a higher proportion of bedridden time >72 hours (72.7% vs. 37.0%, P<0.001). Patients with old DVT had a lower lymphocyte count (0.67×109/L vs. 0.97×109/L, P=0.01), higher C-reactive protein (59 vs. 35 mg/L, P=0.019), and higher levels of D-dimer (6.7 vs. 0.9 µg/mL, P<0.001) than patients with new DVT. Patients with old DVT received more invasive mechanical ventilation (30.3% vs. 7.4%, P<0.001) and had a higher proportion of acute respiratory distress syndrome (75.8% vs. 51.9%, P<0.001), and a higher proportion of cardiac injury (39.4% vs. 14.8%, P=0.033) than patients with new DVT. T2min, T2max, T2mean, and T2*max of new DVT were significantly greater than old DVT (17.6±10.4 vs. 13.2±5.9 ms, 94.9±44.9 vs. 42.3±23.6 ms, 46.8±24.0 vs. 25.0±12.6 ms, 22.5±12.4 vs. 10.7±3.5 ms, P<0.05 for all). There was no significant difference in T2*min or T2*mean between new and old DVT (3.2±0.4 vs. 3.1±0.4 ms, 8.2±4.9 vs. 5.5±1.5 ms, P>0.05 for both).

Conclusions

T2 weighted SPACE magnetic resonance (MR) is valuable in the follow-up of thrombosis of discharged VP patients. T2 mapping distinguishes between new and old DVT.

[Translation into French and republication of: "Recurrent venous thromboembolism in anticoagulated cancer patients: diagnosis and treatment"]

Patients with cancer are at significantly increased risk of venous thromboembolism (VTE), due both to the impact of malignant disease itself and to the impact of certain anticancer drugs on haemostasis. This is true both for first episode venous thromboembolism and recurrence. The diagnosis and management of VTE recurrence in patients with cancer poses particular challenges, and these are reviewed in the present article, based on a systematic review of the relevant scientific literature published over the last decade. Furthermore, it is uncertain whether diagnostic algorithms for venous thromboembolism, validated principally in untreated non-cancer patients, are also valid in anticoagulated cancer patients: the available data suggests that clinical decision rules and D-dimer testing perform less well in this clinical setting. In patients with cancer, computed tomography pulmonary angiography and venous ultrasound appear to be the most reliable diagnostic tools for diagnosis of pulmonary embolism and deep vein thrombosis respectively. Options for treatment of venous thromboembolism include low molecular weight heparins (at a therapeutic dose or an increased dose), fondaparinux or oral direct factor Xa inhibitors. The choice of treatment should take into account the nature (pulmonary embolism or VTE) and severity of the recurrent event, the associated bleeding risk, the current anticoagulant treatment (type, dose, adherence and possible drug-drug interactions) and cancer progression.

Recurrent venous thromboembolism in anticoagulated cancer patients: Diagnosis and treatment

Patients with cancer are at significantly increased risk of venous thromboembolism (VTE), due both to the impact of malignant disease itself and to the impact of certain anticancer drugs on haemostasis. This is true both for first episode venous thromboembolism and recurrence. The diagnosis and management of VTE recurrence in patients with cancer poses particular challenges, and these are reviewed in the present article, based on a systematic review of the relevant scientific literature published over the last decade. Furthermore, it is uncertain whether diagnostic algorithms for venous thromboembolism, validated principally in untreated non-cancer patients, are also valid in anticoagulated cancer patients: the available data suggests that clinical decision rules and D-dimer testing perform less well in this clinical setting. In patients with cancer, computed tomography pulmonary angiography and venous ultrasound appear to be the most reliable diagnostic tools for diagnosis of pulmonary embolism and deep vein thrombosis respectively. Options for treatment of venous thromboembolism include low molecular weight heparins (at a therapeutic dose or an increased dose), fondaparinux or oral direct factor Xa inhibitors. The choice of treatment should take into account the nature (pulmonary embolism or VTE) and severity of the recurrent event, the associated bleeding risk, the current anticoagulant treatment (type, dose, adherence and possible drug-drug interactions) and cancer progression.

Intratumoral heterogeneity after targeted therapy in murine cancer models with differing degrees of malignancy

INTRODUCTION

Conventional morphologic and volumetric assessment of treatment response is not suitable for adequately assessing responses to targeted cancer therapy. The aim of this study was to evaluate changes in tumor composition after targeted therapy in murine models of breast cancer with differing degrees of malignancy via non-invasive magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Mice bearing highly malignant 4T1 tumors or low malignant 67NR tumors were treated with either a combination of two immune checkpoint inhibitors (ICI, anti-PD1 and anti-CTLA-4) or the multi-tyrosine kinase inhibitor sorafenib, following experiments with macrophage-depleting clodronate-loaded liposomes and vessel-stabilizing angiopoietin-1. Mice were imaged on a 9.4 T small animal MRI system with a multiparametric (mp) protocol, comprising T1 and T2 mapping and diffusion-weighted imaging. Tumors were analyzed ex vivo with histology.

RESULTS AND DISCUSSIONS

All treatments led to an increase in non-viable areas, but therapy-induced intratumoral changes differed between the two tumor models and the different targeted treatments. While ICI treatment led to intratumoral hemorrhage, sorafenib treatment mainly induced intratumoral necrosis. Treated 4T1 tumors showed increasing and extensive areas of necrosis, in comparison to 67NR tumors with only small, but also increasing, necrotic areas. After either of the applied treatments, intratumoral heterogeneity, was increased in both tumor models, and confirmed ex vivo by histology. Apparent diffusion coefficient with subsequent histogram analysis proved to be the most sensitive MRI sequence. In conclusion, mp MRI enables to assess dedicated therapy-related intratumoral changes and may serve as a biomarker for treatment response assessment.

Lipid and smooth muscle architectural pathology in the rabbit atherosclerotic vessel wall using Q-space cardiovascular magnetic resonance

BACKGROUND

Atherosclerosis is an arterial vessel wall disease characterized by slow, progressive lipid accumulation, smooth muscle disorganization, and inflammatory infiltration. Atherosclerosis often remains subclinical until extensive inflammatory injury promotes vulnerability of the atherosclerotic plaque to rupture with luminal thrombosis, which can cause the acute event of myocardial infarction or stroke. Current bioimaging techniques are unable to capture the pathognomonic distribution of cellular elements of the plaque and thus cannot accurately define its structural disorganization.

METHODS

We applied cardiovascular magnetic resonance spectroscopy (CMRS) and diffusion weighted CMR (DWI) with generalized Q-space imaging (GQI) analysis to architecturally define features of atheroma and correlated these to the microscopic distribution of vascular smooth muscle cells (SMC), immune cells, extracellular matrix (ECM) fibers, thrombus, and cholesteryl esters (CE). We compared rabbits with normal chow diet and cholesterol-fed rabbits with endothelial balloon injury, which accelerates atherosclerosis and produces advanced rupture-prone plaques, in a well-validated rabbit model of human atherosclerosis.

RESULTS

Our methods revealed new structural properties of advanced atherosclerosis incorporating SMC and lipid distributions. GQI with tractography portrayed the locations of these components across the atherosclerotic vessel wall and differentiated multi-level organization of normal, pro-inflammatory cellular phenotypes, or thrombus. Moreover, the locations of CE were differentiated from cellular constituents by their higher restrictive diffusion properties, which permitted chemical confirmation of CE by high field voxel-guided CMRS.

CONCLUSIONS

GQI with tractography is a new method for atherosclerosis imaging that defines a pathological architectural signature for the atheromatous plaque composed of distributed SMC, ECM, inflammatory cells, and thrombus and lipid. This provides a detailed transmural map of normal and inflamed vessel walls in the setting of atherosclerosis that has not been previously achieved using traditional CMR techniques. Although this is an ex-vivo study, detection of micro and mesoscale level vascular destabilization as enabled by GQI with tractography could increase the accuracy of diagnosis and assessment of treatment outcomes in individuals with atherosclerosis.

Diffusion-weighted MR is useful to assess peripheral nerve invasion of soft tissue tumor

To investigate the feasibility of readout-segmented diffusion-weighted (rsDW) magnetic resonance (MR) in assessing nerve invasion of soft tissue tumor. Forty-four patients with soft tissue mass in upper leg suspected of nerve invasion underwent rsDW MR. Nerve invasion by tumor was rated by 2 radiologists, respectively. Sensitivity and specificity of rsDW MR in identifying nerve invasion were calculated, with operation findings as reference of standard. Apparent diffusion coefficient and fraction of anisotropy of nerve were obtained using DW MR, and then were compared between invaded nerves and noninvasion cases. Inter-reader agreement in using rsDW MR to rate nerve invasion was excellent (kappa = 0.891 ± 0.043, P < 0.001). Sensitivity and specificity of rsDW MR in identifying nerve invasion were 89% and 88%, respectively. Apparent diffusion coefficient was significantly higher in invaded nerves versus normal nerves (1.45 ± 0.67 × 10-3 mm2/s vs 1.39 ± 0.46 × 10-3 mm2/s, P < 0.05). Fraction of anisotropy was significantly lower in invaded nerves versus normal nerves (0.22 ± 0.11 vs 0.37 ± 0.13, P < .05). Readout-segmented DW MR was feasible in assessing sciatic nerve invasion by soft tissue tumor in selected patients.

Diffusion-Weighted Imaging Prior to Percutaneous Sclerotherapy of Venous Malformations—Proof of Concept Study for Prediction of Clinical Outcome

Prediction of response to percutaneous sclerotherapy in patients with venous malformations (VM) is currently not possible with baseline clinical or imaging characteristics. This prospective single-center study aimed to predict treatment outcome of percutaneous sclerotherapy as measured by quality of life (QoL) by using radiomic analysis of diffusion-weighted (dw) magnetic resonance imaging (MRI) before and after first percutaneous sclerotherapy. In all patients (n = 16) pre-interventional (PRE-) and delta (DELTA-) radiomic features (RF) were extracted from dw-MRI before and after first percutaneous sclerotherapy with ethanol gel or polidocanol foam, while QoL was assessed using the Toronto Extremity Salvage Score (TESS) and the 36-Item Short Form Survey (SF-36) health questionnaire. For selecting features that allow differentiation of clinical response, a stepwise dimension reduction was performed. Logistic regression models were fitted and selected PRE-/DELTA-RF were tested for their predictive value. QoL improved significantly after percutaneous sclerotherapy. While no common baseline patient characteristics were able to predict response to percutaneous sclerotherapy, the radiomics signature of VMs (independent PRE/DELTA-RF) revealed high potential for the prediction of clinical response after percutaneous sclerotherapy. This proof-of-concept study provides first evidence on the potential predictive value of (delta) radiomic analysis from diffusion-weighted MRI for Quality-of-Life outcome after percutaneous sclerotherapy in patients with venous malformations.

High Signal Intensity on Diffusion-Weighted Images Reflects Acute Phase of Deep Vein Thrombus

The effects of antithrombotic therapy on deep vein thrombosis (DVT) can be affected by thrombus age, which cannot be reliably determined by noninvasive imaging modalities. We investigated whether magnetic resonance (MR) diffusion-weighted imaging (DWI) can localize and determine the age of venous thrombus in patients with DVT, animal models, and human blood in vitro. Signal intensity (SI) on DWI and the apparent diffusion coefficient (ADC) of thrombi were assessed in eight patients with DVT using a 1.5-T MR imaging (MRI) system. We assessed the organizing processes as venous thrombus developed in the rabbit jugular vein using a 3.0-T MRI system over time. We also assessed MRI signals of human blood in vitro using the 1.5-T MRI system. Venous thrombi were detected by DWI as areas of high or mixed high and iso SI in all patients. The ADCs were lower in the proximal, than in the distal portion of the thrombi. The thrombi of rabbit jugular veins histologically organized in a time-dependent manner, with high SI on DWI at 4 hours, mixed high and iso SI at 1 and 2 weeks, and iso SI at 3 weeks. The ADC correlated negatively with erythrocyte content, and positively with smooth muscle cells, macrophages, hemosiderin, and collagen content. MRI signals of human blood in vitro showed that ADCs were affected by erythrocyte content, but not by blood clotting. MR-DWI can detect venous thrombus, and high SI on DWI accompanied by a low ADC might reflect erythrocyte-rich, acute-phase thrombi.