Three-dimensional MRI-based treatment planning approach for non-invasive ocular proton therapy.

PURPOSE: To develop a high-resolution three-dimensional (3D) magnetic resonance imaging (MRI)-based treatment planning approach for uveal melanomas (UM) in proton therapy. MATERIALS/METHODS: For eight patients with UM, a segmentation of the gross tumor volume (GTV) and organs-at-risk (OARs) was performed on T1- and T2-weighted 7 Tesla MRI image data to reconstruct the patient MR-eye. An extended contour was defined with a 2.5-mm isotropic margin derived from the GTV. A broad beam algorithm, which we have called πDose, was implemented to calculate relative proton absorbed doses to the ipsilateral OARs. Clinically favorable gazing angles of the treated eye were assessed by calculating a global weighted-sum objective function, which set penalties for OARs and extreme gazing angles. An optimizer, which we have named OPT'im-Eye-Tool, was developed to tune the parameters of the functions for sparing critical-OARs. RESULTS: In total, 441 gazing angles were simulated for every patient. Target coverage including margins was achieved in all the cases (V95%  > 95%). Over the whole gazing angles solutions space, maximum dose (Dmax ) to the optic nerve and the macula, and mean doses (Dmean ) to the lens, the ciliary body and the sclera were calculated. A forward optimization was applied by OPT'im-Eye-Tool in three different prioritizations: iso-weighted, optic nerve prioritized, and macula prioritized. In each, the function values were depicted in a selection tool to select the optimal gazing angle(s). For example, patient 4 had a T2 equatorial tumor. The optimization applied for the straight gazing angle resulted in objective function values of 0.46 (iso-weighted situation), 0.90 (optic nerve prioritization) and 0.08 (macula prioritization) demonstrating the impact of that angle in different clinical approaches. CONCLUSIONS: The feasibility and suitability of a 3D MRI-based treatment planning approach have been successfully tested on a cohort of eight patients diagnosed with UM. Moreover, a gaze-angle trade-off dose optimization with respect to OARs sparing has been developed. Further validation of the whole treatment process is the next step in the goal to achieve both a non-invasive and a personalized proton therapy treatment.

Reaction on "Ocular ultrasound versus MRI in the detection of extrascleral extension in a patient with choroidal melanoma".

BACKGROUND: In the recently published article entitled "Ocular ultrasound versus MRI in the detection of extrascleral extension in a patient with choroidal melanoma" Jacobsen et al. describe a case in which a hyper-intense extra-ocular lesion on MRI was erroneously diagnosed as an extrascleral extension of the tumor. Based upon this the authors conclude "the superiority of ocular ultrasound in the diagnostic management of extra scleral extension in choroidal melanoma". In our view, there are numerous flaws in the investigation that cast doubt on this message. MAIN: First of all, this is quite a bold statement when only one patient has been evaluated. Secondly, the manuscript only presents a post-contrast T1-weighted image, whereas multiple MRI-sequences need to be included to determine if a hyperintense region is an extrascleral invasion. Moreover, no modern MRI-techniques such Dynamic Contrast Enhanced (DCE) or Diffusion Weighted Imaging (DWI) have been included in the evaluation of this patient, making it hard to use this single case to compare the efficacy of MRI and Ultrasound. The presented data do, however, give clear clues that the hyperintense lesion is likely to be inflammatory. CONCLUSION: Although the study falls short in providing a comprehensive comparison between current MRI techniques and ultrasound, it does show that the evaluation of ocular MR-images should be made in a multi-disciplinary setting involving both ophthalmologist and radiologists, since the field of ocular MRI is continuously progressing.

CT and MR imaging of orbital inflammation.

PURPOSE: Orbital inflammation can be idiopathic or in the context of a specific disease and it can involve different anatomical orbital structures. On imaging, inflammatory disease is frequently mistaken for infection and malignant tumors, and its underlying cause is often not determined. Through this article we aim to improve orbital inflammation diagnosis and underlying inflammatory diseases recognition. METHODS: The imaging protocols and characteristics of orbital inflammation were reviewed. RESULTS: A decision tree for the evaluation of these patients is provided. First, a combination of clinical and radiological clues is used to recognize inflammation, in particular to differentiate it both from orbital infection and tumor. Subsequently, different radiological patterns are recognized, often allowing the differentiation of the several orbital inflammatory diseases. CONCLUSION: The use of adequate imaging protocols and subsequent evaluation allow the recognition of an orbital lesion as inflammatory and the diagnosis of the underlying inflammatory disease. All in all, a proper treatment can be established, and at times, a biopsy can be avoided.

A multi-purpose open-source triggering platform for magnetic resonance.

Many MR scans need to be synchronised with external events such as the cardiac or respiratory cycles. For common physiological functions commercial trigger equipment exists, but for more experimental inputs these are not available. This paper describes the design of a multi-purpose open-source trigger platform for MR systems. The heart of the system is an open-source Arduino Due microcontroller. This microcontroller samples an analogue input and digitally processes these data to determine the trigger. The output of the microcontroller is programmed to mimic a physiological signal which is fed into the electrocardiogram (ECG) or pulse oximeter port of MR scanner. The microcontroller is connected to a Bluetooth dongle that allows wireless monitoring and control outside the scanner room. This device can be programmed to generate a trigger based on various types of input. As one example, this paper describes how it can be used as an acoustic cardiac triggering unit. For this, a plastic stethoscope is connected to a microphone which is used as an input for the system. This test setup was used to acquire retrospectively-triggered cardiac scans in ten volunteers. Analysis showed that this platform produces a reliable trigger (>99% triggers are correct) with a small average 8 ms variation between the exact trigger points.

High-resolution MRI of uveal melanoma using a microcoil phased array at 7 T.

High-field MRI is a promising technique for the characterisation of ocular tumours, both in vivo and after enucleation. For in vivo imaging at 7 T, a dedicated three-element microcoil array was constructed as a high-sensitivity receive-only device. Using a dedicated blink/fixation protocol, high-resolution in vivo images could be acquired within 3 min in volunteers and patients with no requirement for post-acquisition image registration. Quantitative measures of axial length, aqueous depth and lens thickness in a healthy volunteer were found to agree well with standard ocular biometric techniques. In a patient with uveal melanoma, in vivo MRI gave excellent tumour/aqueous body contrast. Ex vivo imaging of the enucleated eye showed significant heterogeneity within the tumour.