Purpose MRI is increasingly used in the diagnosis and therapy planning of uveal melanoma (UM). In this prospective cohort study, we assessed the radiological characteristics, in terms of anatomical and functional imaging, of UM after ruthenium-106 plaque brachytherapy or proton beam therapy (PBT) and compared them to conventional ultrasound. Methods Twenty-six UM patients were evaluated before and 3, 6 and 12 months after brachytherapy (n = 13) or PBT (n = 13). Tumour prominences were compared between ultrasound and MRI. On diffusion-weighted imaging, the apparent diffusion value (ADC), and on perfusion-weighted imaging (PWI), the time-intensity curves (TIC), relative peak intensity and outflow percentages were determined. Values were compared between treatments and with baseline. Results Pre-treatment prominences were comparable between MRI and ultrasound (mean absolute difference 0.51 mm, p = 0.46), but larger differences were observed post-treatment (e.g. 3 months: 0.9 mm (p = 0.02)). Pre-treatment PWI metrics were comparable between treatment groups. After treatment, brachytherapy patients showed favourable changes on PWI (e.g. 67% outflow reduction at 3 months, p < 0.01). After PBT, significant perfusion changes were observed at a later timepoint (e.g. 38% outflow reduction at 6 months, p = 0.01). No consistent ADC changes were observed after either treatment, e.g. a 0.11 × 10−3mm2/s increase 12 months after treatment (p = 0.15). Conclusion MR-based follow-up is valuable for PBT-treated patients as favourable perfusion changes, including a reduction in outflow, can be detected before a reduction in size is apparent on ultrasound. For brachytherapy, a follow-up MRI is of less value as already 3 months post-treatment a significant size reduction can be measured on ultrasound.
Conversely to most tumour types, magnetic resonance imaging (MRI) was rarely used for eye tumours. As recent technical advances have increased ocular MRI’s diagnostic value, various clinical applications have been proposed. This systematic review provides an overview of the current status of MRI in the clinical care of uveal melanoma (UM) patients, the most common eye tumour in adults. In total, 158 articles were included. Two- and three-dimensional anatomical scans and functional scans, which assess the tumour micro-biology, can be obtained in routine clinical setting. The radiological characteristics of the most common intra-ocular masses have been described extensively, enabling MRI to contribute to diagnoses. Additionally, MRI’s ability to non-invasively probe the tissue’s biological properties enables early detection of therapy response and potentially differentiates between high- and low-risk UM. MRI-based tumour dimensions are generally in agreement with conventional ultrasound (median absolute difference 0.5 mm), but MRI is considered more accurate in a subgroup of anteriorly located tumours. Although multiple studies propose that MRI’s 3D tumour visualisation can improve therapy planning, an evaluation of its clinical benefit is lacking. In conclusion, MRI is a complementary imaging modality for UM of which the clinical benefit has been shown by multiple studies.
Purpose: Comparison of Magnetic Resonance Imaging (MRI) with conventional ultrasound for the follow‐up in Uveal Melanoma (UM) patients treated with brachytherapy or proton beam therapy (PBT). Methods: 26 UM patients were scanned before, 3, 6 and 12 months after ruthenium brachytherapy (n = 13) or PBT (n = 13) at 3Tesla MRI. Tumour prominence measurements were compared between MRI and ultrasound. On Perfusion weighted MR‐imaging (PWI), the relative enhancement and outflow at 2 min after peak were assessed. Treatment response was defined as a reduction of ≥0.6 mm prominence and/or ≥5% perfusion outflow was achieved. Results: Pretreatment prominences were comparable on MR and ultrasound (mean absolute difference 0.49 ± 0.46 mm), larger differences were observed at 3 and 6 months post treatment (0.88 ± 0.86 mm and 0.74 ± 0.72 mm, respectively). At 12 months post treatment, the difference was reduced to 0.55 ± 0.33 mm. Pretreatment, 76% of the UM showed a washout perfusion curve. The pretreatment average enhancement and outflow were 98% (SD:49%) and 31% (SD: 25%) respectively. At 3 months post treatment tumours showed 41% less outflow on average with more favourable perfusion curves (e.g. 68% showed a persistent or plateau curve). At 6 and 12 months post treatment, tumours continued to show less outflow (respectively, −47% and −38%) and more favourable perfusion curves (respectively, 79% and 76% with either persistent or plateau curves). These, generally favourable, perfusion changes were also observed when no reduction in prominence was yet apparent, which is why treatment response was more frequently detected on MRI as opposed to ultrasound. For example, at 3 months post treatment >80% of patients were already detected on MRI versus 46% on ultrasound. Conclusions: MRI is beneficial for the follow‐up of UM patients, especially for PBT treated patients as these generally take longer before a reduction in prominence can be observed.
The aim of this study was to assess the inter-observer variation in gross target volume (GTV) delineation of uveal melanoma on MRI. Six observers delineated the GTV in ten different patients on T2-weighted and contrast-enhanced T1-weighted scans. The average interobserver variation appeared slightly higher on T1gd (0.41 mm) compared to T2 (0.35 mm), although the difference was not significant (p=0.12). We recommend to delineate based on the T1gd-weighted scans, as parts of the tumour might be missed on T2.
Purpose: Several efforts are being undertaken towards MRI‐based treatment planning for ocular proton therapy for uveal melanoma (UM). The inter‐observer variability of the gross target volume (GTV) on MRI is one of the important parameters to design safety margins for a reliable treatment. Therefore, this study assessed the inter‐observer variation in tumour delineation of UM on MRI. Methods: Six observers delineated the tumour in 10 different UM patients using the Big Brother contouring software. Patients were scanned at 3 T MRI with a surface coil and tumours were delineated separately on contrast enhanced 3DT1 (T1gd) and 3DT2‐weighted scans with a resolution of 0.8 mm isotropic for the acquisition voxels (1). Volume difference and overall local variation were analysed for each patient. Additionally the local variation was analysed for four interfaces: sclera, vitreous, retinal detachment, and tumour‐choroid interface. Results: The average tumour contour was significantly larger on T1gd (0.57 cm3) compared to T2 (0.51cm3, p = 0.01). A not significant higher interobserver variation was found on T1gd (0.4 1 mm) compared to T2 (0.35 mm). The largest variations were found at the tumour‐choroid interface, due to peritumoral enhancement (T1gd: 0.62 mm and T2: 0.5 2 mm). As a result, a larger part of this tumour‐choroid interface appeared to be included on T1gd based GTVs compared to T2, explaining the smaller volumes on T2. Conclusions: The interobserver variation of 0.4 mm on MRI are low with respect to the voxel size of 0.8 mm. We recommend to delineate based on the T1gd‐weighted scans, as choroidal tumour extensions might be missed. Reference 1. Ferreira, et al. MR imaging characteristics of uveal melanoma with histopathological validation. Neuroradiology. 2022; 64:171. doi: 10.1007/s00234‐021‐02825‐5.
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