A magnetic resonance-compatible experimental set-up for hyperthermia studies

This study presents the development and testing of an experimental set-up for simultaneous measurements of pH (intracellular by MR and extracellular by fibre-optic pH meter), tumour bio-energetics (by MR), and core/tumour temperatures (by thermocouples) in tumour-bearing mice. Potential sources of measurement errors when using these techniques concurrently in an MR set-up are discussed. Emphasis is placed on simple practical solutions to these problems.     

Magnetic resonance imaging contrast of iron oxide nanoparticles developed for hyperthermia is dominated by iron content

Purpose: Magnetic iron oxide nanoparticles (MNPs) are used as contrast agents for magnetic resonance imaging (MRI) and hyperthermia for cancer treatment. The relationship between MRI signal intensity and cellular iron concentration for many new formulations, particularly MNPs having magnetic properties designed for heating in hyperthermia, is lacking. In this study, we examine the correlation between MRI T₂ relaxation time and iron content in cancer cells loaded with various MNP formulations. Materials and methods: Human prostate carcinoma DU-145 cells were loaded with starch-coated bionised nanoferrite (BNF), iron oxide (Nanomag® D-SPIO), Feridex?, and dextran-coated Johns Hopkins University (JHU) particles at a target concentration of 50?pg Fe/cell using poly-D-lysine transfection reagent. T₂-weighted MRI of serial dilutions of these labelled cells was performed at 9.4?T and iron content quantification was performed using inductively coupled plasma mass spectrometry (ICP-MS). Clonogenic assay was used to characterise cytotoxicity. Results: No cytotoxicity was observed at twice the target intracellular iron concentration (～100?pg Fe/cell). ICP-MS revealed highest iron uptake efficiency with BNF and JHU particles, followed by Feridex and Nanomag-D-SPIO, respectively. Imaging data showed a linear correlation between increased intracellular iron concentration and decreased T₂ times, with no apparent correlation among MNP magnetic properties. Conclusions: This study demonstrates that for the range of nanoparticle concentrations internalised by cancer cells the signal intensity of T₂-weighted MRI correlates closely with absolute iron concentration associated with the cells. This correlation may benefit applications for cell-based cancer imaging and therapy including nanoparticle-mediated drug delivery and hyperthermia.     

Pictorial essay on MRI local staging of rectal carcinoma: An easy approach

Rectal cancer is common and accounts for more than one-third of colorectal tumors. It is associated with significant morbidity and mortality. Previously computed tomography scan is the key imaging modality in preoperative assessment to detect local invasion and distant metastasis. However, the advent of magnetic resonance imaging (MRI) has aided in local staging and prognosticates the outcome of rectal tumor. Here, the author briefly explains why rectal MRI has a comprehensive role and provides a simple and easy way in reporting an MRI rectal carcinoma, even for a non-radiologist.     

Online MRI guidance for healthy tissue sparing in patients with cervical cancer: An IMRT planning study

BACKGROUND AND PURPOSE: During cervical cancer treatment, target volumes change position and shape due to organ motion and tumour regression. An MRI-accelerator will provide information on these changes by online magnetic resonance imaging (MRI) guidance throughout each treatment fraction. The purpose of this intensity-modulated radiation therapy (IMRT) planning study is to assess the benefit of online MRI guidance in healthy tissue sparing. MATERIALS AND METHODS: Weekly MRI scans of 11 cervical cancer patients were used. We created four IMRT plans per patient, based on these weekly MRI scans, to simulate an online-IMRT approach. We applied a primary and nodal planning target volume (PTV) margin of 4mm. As reference, we created an IMRT plan based on the pre-treatment MRI scan (pre-IMRT) using a primary and nodal PTV margin of 15 and 10mm. The weekly defined bladder, rectum, bowel, and sigmoid contours were evaluated on the online-IMRT and pre-IMRT dose distributions at six dose levels (V10(Gy), V20(Gy), V30(Gy), V40(Gy), V42.8(Gy), and V45(Gy)). RESULTS: Online-IMRT compared to pre-IMRT significantly reduced the volume of healthy tissue irradiated to all dose levels, except V10(Gy). CONCLUSIONS: Online MRI guidance reduces healthy tissue involvement in patients with cervical cancer.     

Acute intracerebral haematomas: Assessment for possible underlying cause with MRI scanning

Forty-seven patients presenting with acute intracerebral haematomas between 1989 and 1992 were retrospectively examined to assess the role of Magnetic Resonance Imaging (MRI) in identifying any underlying lesion. None had any prior known intracerebral pathology. Magnetic resonance imaging scans were done on a 0.5 T unit. Ten patients with an average age of 35 years had angiographically occult vascular malformations (AOVM) found by MRI (one with biopsy confirmation). One of three cases of glioma, three of three cases with secondary tumour, one case of superior sagittal sinus thrombosis with haemorrhagic infarction, one of two cases of venous angioma and one case of arteriovenous malformation were detected by MRI. Progress computed tomography scans discovered two cases of glioma and angiography found a venous angioma and an arterial aneurysm, all undetected by MRI. It is concluded that MRI scanning is helpful in detecting underlying AOVM as a cause of intracerebral haemorrhage but its role in imaging haemorrhagic tumours remains unclear.     

CT和MRI确定鼻咽癌原发肿瘤靶区对比研究

目的探讨鼻咽癌放疗计划设计中CT和MRI确定肿瘤靶区(GTV)的价值比较。方法分析经病理证实的39例NPC患者的影像学资料,治疗前1周内均有CT和MRI资料。CT扫描采用GE Lightspeed型16排螺旋CT机,常规轴位平扫。MRI检查使用GE Signa 1.5Tesla超导磁共振成像系统,标准头部正交线圈,常规SE序列,扫描方向为横断面、矢状面和冠状面,10例增加FLAIR序列,扫描范围上至鞍上池,下至第2颈椎下缘水平。部分病例行Ultravist CT扫描或/ 和GD-DTPA MR扫描。统计方法为配对t检验。结果CT组和MRI组勾画的靶区中,肿瘤平均体积分别为32.49±19.91cm3,29.06±18.75cm3,二组对比具有极显著性差异(t= 5.268,P=0.000)。早期(T1 T2)和进展期(T3 T4)二组对比有极显著性差异(t=5.677,P=0.000;t=3.310,P=0.005)。在T1、T2、13期中二组对比差异明显(P值分别为0.005、0.001和0.004),而在T4期中二组对比无统计学意义(P=0.146)。结论MRI组勾画靶区较CT组精确。因此,建议在鼻咽癌肿瘤靶区勾画中应以MRI较为适合。     

An MRI radiomics nomogram improves the accuracy in identifying eligible candidates for fertility-preserving treatment in endometrioid adenocarcinoma

It is difficult to identify eligible candidates for fertility-preserving treatment (FPT) among endometrioid adenocarcinoma (EAC) and atypical hyperplasia (AH) patients. Therefore, new approaches for improving the accuracy of candidate selection are warranted. From December 2014 to January 2020, 236 EAC/AH patients (age <50 and premenopausal) were retrospectively reviewed and randomly divided into the primary group (n=158) and validation group 1 (n=78). From February 2020 to December 2021, 51 EAC/AH patients were prospectively enrolled and formed the validation group 2. From the primary group, 385 features were extracted using pyradiomics from multiparameter magnetic resonance imaging (MRI) (including T2-weighted imaging, diffusion-weighted imaging, apparent diffusion coefficient, and contrast enhancement sequences) and 13 radiomics features were selected using a least absolute shrinkage and selection operator. A clinical model based on clinical information (myometrial invasion on MRI and tumor grade in curettage) and a radiomics nomogram by integrating clinical information with the radiomics features was developed to identify eligible candidates of FPT. For identifying eligible candidates of FPT, the areas under the receiver operating characteristic curve (AUCs) were 0.63 (95% confidence interval [CI]: 0.53-0.73) in the primary group, and 0.62 (95% CI: 0.45-0.78) and 0.69 (95% CI: 0.53-0.86) in validation groups 1 and 2, respectively, for the clinical model; were 0.86 (95% CI: 0.80-0.93) in the primary group, and 0.82 (95% CI: 0.71-0.93) and 0.94 (95% CI: 0.87-1.0) in validation groups 1 and 2, respectively, for the radiomics nomogram. With the help of radiomics nomogram, the treatment decision determined from the clinical model was revised in 45 EAC/AH patients. The net reclassification index (NRI) was 0.80 and integrated discrimination improvement (IDI) was 0.17, indicating that the nomogram could improve the accuracy in identifying eligible EAC/AH candidates for FPT.     

An MRI comparative image evaluation under diagnostic and radiotherapy planning set-ups using a carbon fibre tabletop for pelvic radiotherapy

PurposeTo quantitatively and qualitatively evaluate and compare MR images acquired from the usual diagnostic set-up with images acquired in a radiotherapy set-up.Materials and methodsMR images of a phantom and 18 prostate cancer patients imaging using the usual diagnostic set-up with a curved tabletop (DX-set-up) and using a radiotherapy set-up (RT-set-up) with a flat tabletop, were analysed retrospectively. Quantitative assessments were made by measuring signal-to-noise ratio (SNR) and contrast to noise ratio (CNR). Non-parametric tests were used. Qualitative assessments were made independently by three radiologists. Inter-rater reliability was measured as the percentage of agreement and Gwet's AC2 test.ResultsThe use of the RT-set-up was linked to 19.3% SNR drop on the phantom image. Up to 24% SNR prostate drop was observed in patients’ images. Up to 34% CNR drop was observed in patients’ images. Although image quality of the RT-set-up was acceptable, all measured domains were worse than the corresponding DX-set-up. Additionally diagnostic images were linked to a better percentage of agreement among raters.ConclusionsSNR, CNR and image quality were significantly worse when using the RT-set-up than with the DX-set-up although Image quality in the RT-set-up was acceptable.