Clinical evaluation of ultra-high-field MRI for three-dimensional visualisation of tumour size in uveal melanoma patients, with direct relevance to treatment planning

Anatomical and Micro-CT measurement analysis of ocular volume and intraocular volume in adult Bama Miniature pigs, New Zealand rabbits, and Sprague-Dawley rats

AIM

Utilizing a combination of micro-computed tomography (micro-CT) and anatomical techniques for the volumetric assessment of the eyeball and its constituents in Bama Miniature Pigs, New Zealand rabbits, and Sprague-Dawley(SD) rats.

METHOD

Six Bama Miniature pigs, New Zealand rabbits, and SD rats were enrolled in the study. Micro-CT and gross volumetric estimation of ocular volume were employed to acquire data on ocular volume, anterior chamber volume, lens volume, and vitreous cavity volume for each eye.

RESULTS

The eyeball volume of pigs ranges from approximately 5.36 ± 0.27 to 5.55 ± 0.28 ml, the lens volume from approximately 0.33 ± 0.02 to 0.37 ± 0.06 ml, the anterior chamber volume from approximately 0.19 ± 0.05 to 0.28 ± 0.04 ml, and the vitreous volume is approximately 3.20 ± 0.18 ml. For rabbits, the eye volume, lens volume, anterior chamber volume, and vitreous volume range from approximately 3.02 ± 0.24 to 3.04 ± 0.24 ml, 0.41 ± 0.02 to 0.44 ± 0.02 ml, 0.23 ± 0.04 to 0.26 ± 0.05 ml, and 1.54 ± 0.14 ml, respectively. In SD rats, the volumes are 0.14 ± 0.02 to 0.15 ± 0.01 ml for the eyeball, 0.03 ± 0.00 to 0.03 ± 0.00 ml for the lens, 0.01 ± 0.00 to 0.01 ± 0.01 ml for the anterior chamber, and 0.04 ± 0.01 ml for the vitreous volume.

CONCLUSION

The integration of micro-CT and gross volumetric estimation of ocular volume proves effective in determining the eyeball volume in Bama Miniature Pigs, New Zealand rabbits, and SD rats. Understanding the volume distinctions within the eyeballs and their components among these experimental animals can lay the groundwork for ophthalmology-related drug research.

PTCOG Ocular Statement: Expert Summary of Current Practices and Future Developments in Ocular Proton Therapy

Although rare cancers, ocular tumors are a threat to vision, quality of life, and potentially life expectancy of a patient. Ocular proton therapy (OPT) is a powerful tool for successfully treating this disease. The Particle Therapy Co-Operative Ocular Group) formulated an Evidence and Expert-Based Executive Summary of Current Practices and Future Developments in OPT: comparative dosimetric and clinical analysis with the different OPT systems is essential to set up planning guidelines, implement best practices, and establish benchmarks for eye preservation, vision, and quality of life measures. Contemporary prospective trials in select subsets of patients (eg, tumors near the optic disc and/or macula) may allow for dosimetric and clinical analysis between different radiation modalities and beamline systems to evaluate differences in radiation delivery and penumbra, and resultant tumor control, normal tissue complication rates, and overall clinical cost-effectiveness. To date, the combination of multimodal imaging (fundus photography, ultrasound, etc), ophthalmologist assessment, and clip surgery with radiation planning have been keys to successful treatment. Increased use of three-dimensional imaging (computed tomography/magnetic resonance imaging) is anticipated although its spatial resolution might be a limiting factor (eg, detection of flat diffuse tumor parts). Commercially produced ocular treatment-planning systems are under development and their future use is expected to expand across OPT centers. Future continuity of OPT will depend on the following: (1) maintaining and upgrading existing older dedicated low-energy facilities, (2) maintaining shared, degraded beamlines at large proton therapy centers, and (3) developing adapted gantry beams of sufficient quality to maintain the clinical benefits of sharp beam conformity. Option (1) potentially offers the sharpest beams, minimizing impact on healthy tissues, whereas (2) and (3) potentially offer the advantage of substantial long-term technical support and development as well as the introduction of new approaches. Significant patient throughputs and close cooperation between medical physics, ophthalmology, and radiation therapy, underpinned by mutual understanding, is crucial for a successful OPT service.

Geometrical accuracy of magnetic resonance imaging for ocular proton therapy planning

Background & purpose

Magnetic resonance imaging (MRI) is increasingly used in treatment preparation of ocular proton therapy, but its spatial accuracy might be limited by geometric distortions due to susceptibility artefacts. A correct geometry of the MR images is paramount since it defines where the dose will be delivered. In this study, we assessed the geometrical accuracy of ocular MRI.

Materials & methods

A dedicated ocular 3 T MRI protocol, with localized shimming and increased gradients, was compared to computed tomography (CT) and X-ray images in a phantom and in 15 uveal melanoma patients. The MRI protocol contained three-dimensional T2-weighted and T1-weighted sequences with an isotropic reconstruction resolution of 0.3-0.4 mm. Tantalum clips were identified by three observers and clip-clip distances were compared between T2-weighted and T1-weighted MRI, CT and X-ray images for the phantom and between MRI and X-ray images for the patients.

Results

Interobserver variability was below 0.35 mm for the phantom and 0.30(T1)/0.61(T2) mm in patients. Mean absolute differences between MRI and reference were below 0.27 ± 0.16 mm and 0.32 ± 0.23 mm for the phantom and in patients, respectively. In patients, clip-clip distances were slightly larger on MRI than on X-ray images (mean difference T1: 0.11 ± 0.38 mm, T2: 0.10 ± 0.44 mm). Differences did not increase at larger distances and did not correlate to interobserver variability.

Conclusions

A dedicated ocular MRI protocol can produce images of the eye with a geometrical accuracy below half the MRI acquisition voxel (<0.4 mm). Therefore, these images can be used for ocular proton therapy planning, both in the current model-based workflow and in proposed three-dimensional MR-based workflows.

Uveal melanoma: Current evidence on prognosis, treatment and potential developments

Uveal Melanoma (UM) is a rare disease, yet it is the most common primary intraocular malignancy in adult patients. Despite continuous advancements and research, the risk of metastasis remains high. It is possible to stratify patients according to their risk of metastases using a variety of known risk factors. Even though there is no gold standard for the prognostication of patients with uveal melanoma, it is becoming increasingly clear that combining histo-pathological, patient-related and molecular prognostic markers allows a more accurate prediction of the metastatic risk than by using one parameter. Primary UM in the eye are treated very effectively with eye-sparing radiation-based techniques or enucleation. However, it is not yet possible to prevent or treat metastases with the current therapeutic options. Nonetheless, the efforts to find new therapeutic targets continue and progress is being made, especially in the field of targeted therapy, as exemplified by the anti-gp100 bispecific molecule Tebentafusp. This review delves into the history of uveal melanoma, its incidence, presentation and diagnosis, the known prognostic factors and the treatment options, both for the primary tumour and for metastases. We show that different populations may have different risks for developing UM, and that each country should evaluate their own patients.

Impact of tumour volume and treatment delay on the outcome after linear accelerator-based fractionated stereotactic radiosurgery of uveal melanoma

BACKGROUND/AIMS

Primary radiation therapy is used to treat malignant uveal melanoma (UM). We report our single-centre experience with fractionated radiosurgery (fSRS) with a linear accelerator (LINAC) after specific adaptation for small target volumes with HybridArc.

METHODS

From October 2014 to January 2020, 101 patients referred to Dessau City Hospital with unilateral UM underwent fSRS with 50 Gy given in five fractions on five consecutive days. Primary endpoints were local tumour control, globe preservation, metastasis and death. Potential prognostic features were analysed. Kaplan-Meier analysis, Cox proportional hazards model and linear models were used for calculations.

RESULTS

The median baseline tumour diameter was 10.0 mm (range, 3.0-20.0 mm), median tumour thickness 5.0 mm (range, 0.9-15.5 mm) and median gross tumour volume (GTV) 0.4 cm³ (range, 0.2-2.6 cm³). After a median follow-up of 32.0 months (range, 2.5-76.0 months), 7 patients (6.9%) underwent enucleation: 4 (4.0%) due to local recurrence and 3 (3.0%) due to radiation toxicities, and 6 patients (5.9%) revealed tumour persistence with a GTV exceeding 1.0 cm³. Of 20 patients (19.8%) who died, 8 (7.9%) were tumour-related deaths. Twelve patients (11.9%) suffered from distant metastasis. GTV showed an impact on all endpoints, and treatment delay was associated with reduced odds of eye preservation.

CONCLUSION

LINAC-based fSRS with static conformal beams combined with dynamic conformal arcs and discrete intensity-modulated radiotherapy results in a high tumour control rate. The tumour volume is the most robust physical prognostic marker for local control and disease progression. Avoiding treatment delay improves outcomes.

Magnetic Resonance Imaging in the Clinical Care for Uveal Melanoma Patients-A Systematic Review from an Ophthalmic Perspective

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.

MR-based follow-up after brachytherapy and proton beam therapy in uveal melanoma

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.

Comparison of Magnetic Resonance Imaging-Based and Conventional Measurements for Proton Beam Therapy of Uveal Melanoma

OBJECTIVE

Conventionally, ocular proton therapy (PT) is planned using measurements obtained by an ophthalmologist using ultrasound, fundoscopy, biometry, and intraoperative assessments. Owing to the recent advances in magnetic resonance imaging (MRI) of uveal melanoma (UM), it is possible to acquire high-resolution 3-dimensional images of the eye, providing the opportunity to incorporate MRI in ocular PT planning. In this study, we described how these measurements can be obtained using MRI, compared the MRI-based measurements with conventional ophthalmic measurements, and identified potential pitfalls for both modalities.

DESIGN

Cross-sectional study.

SUBJECTS

Data from 23 consecutive patients with UM treated with PT were retrospectively evaluated.

METHODS

Magnetic resonance imaging-based measurements of axial length, tumor height and basal diameter, and marker-tumor distances were compared with the conventional ophthalmic measurements, and discrepancies were evaluated in a multidisciplinary setting.

MAIN OUTCOME MEASURES

Tumor prominence and basal diameters on MRI and ultrasound, axial length on MRI and biometry, tumor-marker distances on MRI and measured intraoperatively.

RESULTS

The mean absolute differences of the tumor height and basal diameter measurements between ultrasound and MRI were 0.57 mm and 1.44 mm, respectively. Larger absolute differences in height and basal diameter were observed when the full tumor extent was not visible on ultrasound (0.92 mm and 1.67 mm, respectively) compared with when the full tumor extent was visible (0.44 mm and 1.15 mm, respectively). When the full tumor was not visible on ultrasound, MRI was considered more reliable. Tumor-marker distances measured using MRI and intraoperative techniques differed < 1 mm in 55% of the markers. For anteriorly located and mushroom-shaped tumors (25% of the markers), MRI provided more accurate measurements. In flat UM (15% of the markers), however, it was difficult to delineate the tumor on MRI. The mean absolute difference in axial length between optical biometry and MRI was 0.50 mm. The presence of the tumor was found to influence optical biometry in 15 of 22 patients; the remaining patients showed a better agreement (0.30 mm). Magnetic resonance imaging-based biometry was considered more reliable in patients with UM.

CONCLUSIONS

Magnetic resonance imaging allowed for the 3-dimensional assessment of the tumor and surrounding tissue. In specific patients, it provided a more reliable measurement of axial length, tumor dimensions, and marker-tumor distances and could contribute to a more accurate treatment planning. Nevertheless, a combined evaluation remains advised, especially for flat UM.

Local Recurrence in Choroidal Melanomas following Robotic-Assisted Radiosurgery (CyberKnife)

Introduction

Tumor recurrence in choroidal melanoma has been associated with decreased overall survival due to metastatic spreading. To detect risk factors of local recurrence and side effects, we analyzed tumor planning and treatment parameters in patients with recurrence of choroidal melanoma after treatment with robotic-assisted radiosurgery (CyberKnife).

Methods

Six hundred ninety-four patients treated with CyberKnife between 2005 and 2019 were retrospectively reviewed. Age, gender, best-corrected visual acuity, tumor height, and diameter were recorded. Treatment planning and radiation doses were reviewed. Salvage therapy, overall survival, metastasis, and complications were recorded.

Results

Seventy-four patients showed local recurrence. Local recurrence occurred after 42.1 months post CyberKnife treatment (mean; range: 5-100 months). Fourteen out of 74 patients (18.9%) died during follow-up. Recurrence treatment included enucleation in 51 patients (68.9%) and radiosurgery in 19 patients (25.7%). Treatment planning without contrast medium MRI, radiation dose of less than 21 Gy, and insufficient margin delineation were identified as risk factors incrementing local control.

Discussion

Robotic-assisted radiosurgery (CyberKnife) is a suitable treatment option for large choroidal melanoma up to 12 mm. Patients with significantly better visual acuity received repeat CyberKnife treatment as salvage therapy and showed an eye retention rate of 81%.

Automatic Three-Dimensional Magnetic Resonance-based measurements of tumour prominence and basal diameter for treatment planning of uveal melanoma

Background and Purpose

Three-dimensional (3D) Magnetic Resonance Imaging (MRI) is increasingly used to complement conventional two-dimensional ultrasound in the assessment of tumour dimension measurement of uveal melanoma. However, the lack of definitions of the 3D measurements of these tumour dimensions hinders further adaptation of MRI in ocular radiotherapy planning. In this study, we composed 3D MR-based definitions of tumour prominence and basal diameter and compared them to conventional ultrasound.

Materials and methods

Tumours were delineated on 3DT2 and contrast-enhanced 3DT1 (T1gd) MRI for 25 patients. 3D definitions of tumour prominence and diameter were composed and evaluated automatically on the T1gd and T2 contours. Automatic T1gd measurements were compared to manual MRI measurements, to automatic T2 measurements and to manual ultrasound measurements.

Results

Prominence measurements were similar for all modalities (median absolute difference 0.3 mm). Automatic T1gd diameter measurements were generally larger than manual MRI, automatic T2 and manual ultrasound measurements (median absolute differences of 0.5, 1.6 and 1.1 mm respectively), mainly due to difficulty defining the axis of the largest diameter. Largest differences between ultrasound and MRI for both prominence and diameter were found in anteriorly located tumours (up to 1.6 and 4.5 mm respectively), for which the tumour extent could not entirely be visualized with ultrasound.

Conclusions

The proposed 3D definitions for tumour prominence and diameter agreed well with ultrasound measurements for tumours for which the extent was visible on ultrasound. 3D MRI measurements generally provided larger diameter measurements than ultrasound. In anteriorly located tumours, the MRI measurements were considered more accurate than conventional ultrasound.

Comparison between 7 Tesla and 3 Tesla MRI for characterizing orbital lesions

PURPOSE

Characterizing orbital lesions remains challenging with imaging. The purpose of this study was to compare 3 Tesla (T) to 7 T magnetic resonance imaging (MRI) for characterizing orbital lesions.

MATERIALS AND METHODS

This prospective single-center study enrolled participants presenting with orbital lesions from May to October 2019, who underwent both 7 T and 3 T MRI examinations. Two neuroradiologists, blinded to all data, read both datasets independently and randomly. They assessed general characteristics of each orbital lesion as well as image quality and presence of artifacts. Comparison between both datasets was made using Fisher exact test.

RESULTS

Seven patients (4 women, 3 men) with a median age of 52 years were enrolled. Orbital lesion conspicuity was better scored at 7 T compared to 3 T MRI, with 3/7 lesions (43%) scored as very conspicuous at 7 T compared to 0/7 lesion (0%) at 3 T, although the difference was not significant (P = 0.16). Delineation of lesion margins was better scored at 7 T compared to 3 T with 3/7 lesions (43%) scored as very well delineated on 7 T compared to 0/7 lesions (0%) at 3 T, although the difference was not significant (P = 0.34). Details of internal structure were better assessed at 7 T compared to 3 T, with 4/7 lesions (57%) displaying numerous internal details compared to 0/7 lesions (0%) at 3 T (P = 0.10). Internal microvessels were visible in 3/7 lesions (43%) at 7 T compared to 0/7 lesions (0%) at 3 T (P = 0.19).

CONCLUSION

Although no significant differences were found between 7 T and 3 T MRI, assumably due to a limited number of patients, our study suggests that 7 Tesla MRI might help improve the characterization of orbital lesions. However, further studies with more patients are needed.

Imaging of Uveal Melanoma—Current Standard and Methods in Development

Simple Summary

Uveal melanoma is the most prevalent intraocular tumor in adults, derived from melanocytes; the liver is the most common site of its metastases. Due to troublesome tumor localization, different imaging techniques are utilized in diagnostics, i.e., fundus imaging (FI), ultrasonography (US), optical coherence tomography (OCT), single-photon emission computed tomography (SPECT), positron emission tomography/computed tomography (PET/CT), magnetic resonance imaging (MRI), fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), or fundus autofluorescence (FAF). Specialists eagerly use these techniques, but sometimes the precision and quality of the obtained images are imperfect, raising diagnostic doubts and prompting the search for new ones. In addition to analyzing the currently utilized methods, this review also introduces experimental techniques that may be adapted to clinical practice in the future. Moreover, we raise the topic and present a perspective for personalized medicine in uveal melanoma treatment.

Abstract

Uveal melanoma is the most common primary intraocular malignancy in adults, characterized by an insidious onset and poor prognosis strongly associated with tumor size and the presence of distant metastases, most commonly in the liver. Contrary to most tumor identification, a biopsy followed by a pathological exam is used only in certain cases. Therefore, an early and noninvasive diagnosis is essential to enhance patients’ chances for early treatment. We reviewed imaging modalities currently used in the diagnostics of uveal melanoma, including fundus imaging, ultrasonography (US), optical coherence tomography (OCT), single-photon emission computed tomography (SPECT), fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), fundus autofluorescence (FAF), as well as positron emission tomography/computed tomography (PET/CT) or magnetic resonance imaging (MRI). The principle of imaging techniques is briefly explained, along with their role in the diagnostic process and a summary of their advantages and limitations. Further, the experimental data and the advancements in imaging modalities are explained. We describe UM imaging innovations, show their current usage and development, and explain the possibilities of utilizing such modalities to diagnose uveal melanoma in the future.

Eye-specific quantitative dynamic contrast-enhanced MRI analysis for patients with intraocular masses

OBJECTIVE

Dynamic contrast enhanced (DCE)-MRI is currently not generally used for intraocular masses as lesions are small, have an inhomogeneous T₁ and the eye is prone to motion. The aim of this paper is to address these eye-specific challenges, enabling accurate ocular DCE-MRI.

MATERIALS & METHODS

DCE-MRI of 19 uveal melanoma (UM) patients was acquired using a fat-suppressed 3D spoiled gradient echo sequence with TWIST (time-resolved angiography with stochastic trajectories sequence). The analysis consisted of a two-step registration method to correct for both head and eye motion. A T₁ map was calculated to convert signal intensities to concentrations. Subsequently, the Tofts model was fitted voxel wise to obtain K^trans and v_e.

RESULTS

Registration significantly improved the concentration curve quality (p < 0.001). The T₁ of melanotic lesions was significantly lower than amelanotic lesions (888 ms vs 1350 ms, p = 0.03). The average achieved B₁⁺ in the lesions was 91%. The average K^trans was 0.46 min^-1 (range 0.13-1.0) and the average v_e was 0.22 (range 0.10-0.51).

CONCLUSION

Using this eye-specific analysis, DCE of intraocular masses is possible which might aid in the diagnosis, prognosis and follow-up of UM.

Histopathologic and MR Imaging Appearance of Spontaneous and Radiation-Induced Necrosis in Uveal Melanomas: Initial Results

Simple Summary

Uveal melanomas may undergo necrosis, both spontaneously or following radiotherapy. Nowadays radiotherapy is the preferred treatment, whereas enucleation of the eye is used in selected cases. In order to differentiate the effects of radiotherapy from spontaneous degenerative changes in uveal melanomas, we compared the appearance of necrosis, both from a histopathological point of view and from the perspective of MR imaging, in two groups of patients with uveal melanoma: a group who had undergone previous proton beam radiotherapy (secondary enucleation); a control group who had undergone enucleation without any previous radiotherapy treatment (primary enucleation). Irradiated and nonirradiated uveal melanomas differ on the basis of the histological appearance, the MR imaging appearance and the distribution of necrosis. We hope that the findings we observed could be extended to all patients with uveal melanomas treated with radiotherapy, and may enhance the accuracy of radiologists in evaluating MR examinations after radiotherapy.

Abstract

Necrosis in uveal melanomas can be spontaneous or induced by radiotherapy. The purpose of our study was to compare the histopathologic and MRI findings of radiation-induced necrosis of a group of proton beam-irradiated uveal melanomas with those of spontaneous necrosis of a control group of patients undergoing primary enucleation. 11 uveal melanomas who had undergone proton beam radiotherapy, MRI and secondary enucleation, and a control group of 15 untreated uveal melanomas who had undergone MRI and primary enucleation were retrospectively identified. Within the irradiated and nonirradiated group, 7 and 6 eyes with histological evidence of necrosis respectively, were furtherly selected for the final analysis; the appearance of necrosis was assessed at histopathologic examination and MRI. Irradiated melanomas showed a higher degree of necrosis as compared with nonirradiated tumors. Irradiated and nonirradiated lesions differed based on the appearance and distribution of necrosis. Irradiated tumors showed large necrotic foci, sharply demarcated from the viable neoplastic tissue; nonirradiated tumors demonstrated small, distinct foci of necrosis. Radiation-induced necrosis, more pigmented than surrounding viable tumor, displayed high signal intensity on T1-weighted and low signal intensity on T2-weighted images. The hemorrhagic/coagulative necrosis, more prevalent in nonirradiated tumors (4 out of 6 vs. 1 out of 7 cases), appeared hyperintense on T2-weighted and hypointense on T1-weighted images. Our study boosts the capability to recognize radiation-induced alterations in uveal melanomas at MRI and may improve the accuracy of radiologists in the evaluation of follow-up MR examination after radiotherapy.

Clinical Outcomes after International Referral of Uveal Melanoma Patients for Proton Therapy

Simple Summary

This study aims to assess cancer control and preservation of the eye and visual acuity after proton therapy abroad for eye melanoma. For this, medical files were reviewed of Dutch uveal melanoma patients who were treated in Switzerland with proton therapy from 1987 to 2019. The tumours of these patients were too large and/or localised too close to the optic nerve to be treated with local plaque irradiation. There were 103 patients, of whom one had a uveal melanoma in both eyes. The tumours were relatively large and often localised around the central part of the retina. At five years after treatment, proton therapy had controlled the uveal melanomas of 94% of the patients and 81% had preserved their eye. Spread of the cancer beyond the eye was observed in 30% of the patients. Most patients (79%) became blind or had severe visual impairment after proton therapy; a small group of patients had mild or no visual impairment (17%). The size of the tumour, its localisation and the dose of proton therapy were important for the risk of decline in visual acuity. This study shows that proton therapy abroad for uveal melanoma is feasible and yields good results.

Abstract

Objective: To assess oncological and ophthalmological outcomes after international referral of uveal melanoma patients for proton therapy. Materials and Methods: This is a retrospective study among Dutch uveal melanoma patients who were treated in Switzerland with 60.0 CGE proton therapy (in 4 fractions) from 1987 to 2019. All patients were ineligible for brachytherapy due to tumour size and/or proximity to the optic nerve. Time-to-event analyses were performed using Kaplan–Meier’s methodology and Cox proportional hazards models. Results: There were 103 patients (104 eyes) with a median largest tumour diameter of 19 mm (range 6–26 mm). Tumours were localised centrally (11%), mid-peripherally (65%) or peripherally (34%). Median follow-up was 7 years. Five-year local control, distant metastasis-free survival and eye preservation rates were 94%, 70% and 81% respectively. At five years, severe, moderate and mild visual impairment was observed in respectively 79%, 4% and 6% of the patients. Larger tumour volumes and more central tumour localisation were associated with severe visual impairment. After correction for these factors, dose to the macula, optic disc and retina, but not optic nerve was significantly associated with severe visual impairment. Conclusion: International referral for proton therapy yielded good tumour control and eye preservation rates, but risk of distant metastasis and severe visual impairment were substantial, possibly due to the selection of advanced tumour stages and/or central localisation. Dose to the macula may be more relevant than dose to the optic nerve for preservation of visual acuity, which is relevant for the treatment planning of proton therapy.

Role of Structural, Metabolic, and Functional MRI in Monitoring Visual System Impairment and Recovery

The visual system, consisting of the eyes and the visual pathways of the brain, receives and interprets light from the environment so that we can perceive the world around us. A wide variety of disorders can affect human vision, ranging from ocular to neurologic to systemic in nature. While other noninvasive imaging techniques such as optical coherence tomography and ultrasound can image particular sections of the visual system, magnetic resonance imaging (MRI) offers high resolution without depth limitations. MRI also gives superior soft-tissue contrast throughout the entire pathway compared to computed tomography. By leveraging different imaging sequences, MRI is uniquely capable of unveiling the intricate processes of ocular anatomy, tissue physiology, and neurological function in the human visual system from the microscopic to macroscopic levels. In this review we discuss how structural, metabolic, and functional MRI can be used in the clinical assessment of normal and pathologic states in the anatomic structures of the visual system, including the eyes, optic nerves, optic chiasm, optic tracts, visual brain nuclei, optic radiations, and visual cortical areas. We detail a selection of recent clinical applications of MRI at each position along the visual pathways, including the evaluation of pathology, plasticity, and the potential for restoration, as well as its limitations and key areas of ongoing exploration. Our discussion of the current and future developments in MR ocular and neuroimaging highlights its potential impact on our ability to understand visual function in new detail and to improve our protection and treatment of anatomic structures that are integral to this fundamental sensory system. LEVEL OF EVIDENCE 3:   TECHNICAL EFFICACY STAGE 3:  .

An Automatic Framework to Create Patient-specific Eye Models From 3D Magnetic Resonance Images for Treatment Selection in Patients With Uveal Melanoma

PURPOSE

The optimal treatment strategy for uveal melanoma (UM) relies on many factors, the most important being tumor size and location. Building on recent developments in high-resolution 3D ocular magnetic resonance imaging (MRI), we developed an automatic image-processing framework to create patient-specific eye models and to subsequently determine the full 3D tumor shape and size automatically.

METHODS AND MATERIALS

From 15 patients with UM, 3D inversion-recovery gradient-echo (T1-weighted) and 3D fat-suppressed spin-echo (T2-weighted) images were acquired with a 7T MRI scanner. First, the sclera and cornea were segmented from the T2-weighted image by mesh-fitting. The T1- and T2-weighted images were then coregistered. From the registered T1-weighted image, the lens, vitreous body, retinal detachment, and tumor were segmented. Fuzzy C-means clustering was used to differentiate the tumor from retinal detachments. The tumor model was verified and (if needed) edited by an ophthalmic MRI specialist. Subsequently, the prominence and largest basal diameter of the tumor were measured automatically based on the verified contours. These results were compared with manual assessments on the original images and with ultrasound measurements to show the errors in manual analysis.

RESULTS

The framework successfully created an eye model fully automatically in 12 cases. In these cases, a Dice similarity coefficient (mean surface distance) of 97.7%±0.84% (0.17±0.11 mm) was achieved for the sclera, 96.8%±1.05% (0.20±0.06 mm) for the vitreous body, 91.6%±4.83% (0.15±0.06 mm) for the lens, and 86.0%±7.4% (0.35±0.27 mm) for the tumor. The manual assessments deviated, on average, 0.39±0.31 mm in prominence and 1.7±1.22 mm in basal diameter from the automatic measurements.

CONCLUSIONS

The described framework combined information from T1- and T2-weighted images to accurately determine tumor boundaries in 3D. The proposed process may have a direct effect on clinical workflow, as it enables an accurate 3D assessment of tumor dimensions, which directly influences therapy selection.

MR imaging characteristics of uveal melanoma with histopathological validation

Purpose

To evaluate the magnetic resonance imaging (MRI) characteristics of uveal melanoma (UM), to compare them with fundoscopy and ultrasound (US), and to validate them with histopathology.

Methods

MR images from 42 UM were compared with US and fundoscopy, and on 14 enucleated cases with histopathology.

Results

A significant relationship between the signal intensity on T1 and pigmentation on histopathology was found (p=0.024). T1 hyperintense UM were always moderately or strongly pigmented on histopathology, while T1-hypointense UM were either pigmented or non-pigmented. Mean apparent diffusion coefficient (ADC) of the UM was 1.16 ± 0.26 × 10⁻³ mm²/s. Two-thirds of the UM had a wash-out and the remaining a plateau perfusion time-intensity curve (TIC). MRI was limited in evaluating the basal diameter of flat tumors. US tends to show larger tumor prominence (0.5mm larger, p=0.008) and largest basal diameter (1.4mm larger, p<0.001). MRI was good in diagnosing ciliary body involvement, extrascleral extension, and optic nerve invasion, but limited on identifying scleral invasion. An increase of tumor prominence was associated with lower ADC values (p=0.030) and favored a wash-out TIC (p=0.028). An increase of tumor ADC correlated with a plateau TIC (p=0.011).

Conclusions

The anatomical and functional MRI characteristics of UM were comprehensively assessed. Knowing the MRI characteristics of UM is important in order to confirm the diagnosis and to differentiate UM from other intra-ocular lesions and because it has implications for treatment planning. MRI is a good technique to evaluate UM, being only limited in case of flat tumors or on identifying scleral invasion.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00234-021-02825-5.

A Comparison of 3 T and 7 T MRI for the Clinical Evaluation of Uveal Melanoma

Background

Magnetic resonance imaging (MRI) is increasingly being used in the diagnosis and treatment planning of uveal melanoma (UM), the most common primary intraocular tumor. Initially, 7 T MRI was primarily used, but more recently these techniques have been translated to 3 T, as it is more commonly available.

Purpose

Compare the diagnostic performance of 3 T and 7 T MRI of UM.

Study Type

Prospective.

Population

Twenty‐seven UM patients (19% female).

Field Strength/Sequence

3 T: T1‐ and T2‐weighted three‐dimensional (3D) spin echo (SE) and multi‐slice (MS) SE, 7 T: T1‐weighted 3D gradient echo (GE), T2‐weighted 3D SE and MS SE, 3 T and 7 T GE dynamic contrast‐enhanced. T1 weighted images: acquired before and after Gadolinium (Gd) administration.

Assessment

For all sequences, scan and diagnostic quality was quantified using a 5‐point Likert scale. Signal intensities on T1 and T2 relative to choroid and eye muscle respectively were assessed as well as the tumor prominence. Finally, the perfusion time‐intensity curves (TICs) were classified as plateau, progressive, or wash‐out.

Statistical Tests

Image quality scores were compared between both field strengths using Wilcoxon signed‐rank and McNemar tests. Paired t‐tests and Bland–Altman were used for comparing tumor prominences. P < 0.05 was considered statistically significant.

Results

Image quality was comparable between 3 T and 7 T, for 3DT1, 3DT2, 3DT1Gd (P = 0.86; P = 0.34; P = 0.78, respectively) and measuring tumor dimensions (P = 0.40). 2DT1 and 2DT2 image quality were rated better on 3 T compared to 7 T. Most UM had the same relative signal intensities at 3 T and 7 T on T1 (17/21) and T2 (13/17), and 16/18 diagnostic TICs received the same classification. Tumor prominence measurements were similar between field strengths (95% confidence interval: −0.37 mm to 0.03 mm, P = 0.097).

Data Conclusion

Diagnostic performance of the evaluated 3 T protocol proved to be as capable as 7 T, with the addition of 3 T being superior in assessing tumor growth into nearby anatomical structures compared to 7 T.

Level of Evidence

2

Technical Efficacy

Stage 3

Evaluation of intraocular lens position and retinal shape in negative dysphotopsia using high-resolution magnetic resonance imaging

PURPOSE

To assess potential relationships of intraocular lens (IOL) position and retinal shape in negative dysphotopsia (ND).

SETTING

Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.

DESIGN

Case-control study.

METHODS

High-resolution ocular magnetic resonance imaging (MRI) scans were performed in patients with ND and pseudophakic controls, and subsequently used to determine the displacement and tilt of the in-the-bag IOL about the pupil and iris. In addition, anterior segment tomography was used to assess the iris-IOL distance. Furthermore, the retinal shape was quantified from the MRI scans by fitting an ellipse to the segmented inner boundary of the retina. Both the IOL position and retinal shape were compared between groups to assess their potential role in the etiology of ND.

RESULTS

In total, 37 patients with ND and 26 pseudophakic controls were included in the study. The mean displacement and tilt of the IOL were less than 0.1 mm and 0.5 degrees, respectively, in both groups and all directions. The corresponding mean iris-IOL distance was 1.1 mm in both groups. Neither of these values differed statistically significantly between groups (all P values >.6). The retinal shape showed large variations but was not statistically significantly different between the groups in both the left-right (P = .10) and the anterior-posterior (P = .56) directions.

CONCLUSIONS

In this study, the in-the-bag IOL position and retinal shape did not statistically significantly differ between patients with ND and the general pseudophakic population. Given the large variation in retinal shape between subjects, however, it could still be an important factor in a multifactorial origin of ND.

Characterization of the HollandPTC proton therapy beamline dedicated to uveal melanoma treatment and an interinstitutional comparison

PURPOSE

Eye-dedicated proton therapy (PT) facilities are used to treat malignant intraocular lesions, especially uveal melanoma (UM). The first commercial ocular PT beamline from Varian was installed in the Netherlands. In this work, the conceptual design of the new eyeline is presented. In addition, a comprehensive comparison against five PT centers with dedicated ocular beamlines is performed, and the clinical impact of the identified differences is analyzed.

MATERIAL/METHODS

The HollandPTC eyeline was characterized. Four centers in Europe and one in the United States joined the study. All centers use a cyclotron for proton beam generation and an eye-dedicated nozzle. Differences among the chosen ocular beamlines were in the design of the nozzle, nominal energy, and energy spectrum. The following parameters were collected for all centers: technical characteristics and a set of distal, proximal, and lateral region measurements. The measurements were performed with detectors available in-house at each institution. The institutions followed the International Atomic Energy Agency (IAEA) Technical Report Series (TRS)-398 Code of Practice for absolute dose measurement, and the IAEA TRS-398 Code of Practice, its modified version or International Commission on Radiation Units and Measurements Report No. 78 for spread-out Bragg peak normalization. Energy spreads of the pristine Bragg peaks were obtained with Monte Carlo simulations using Geant4. Seven tumor-specific case scenarios were simulated to evaluate the clinical impact among centers: small, medium, and large UM, located either anteriorly, at the equator, or posteriorly within the eye. Differences in the depth dose distributions were calculated.

RESULTS

A pristine Bragg peak of HollandPTC eyeline corresponded to the constant energy of 75 MeV (maximal range 3.97 g/cm2 in water) with an energy spread of 1.10 MeV. The pristine Bragg peaks for the five participating centers varied from 62.50 to 104.50 MeV with an energy spread variation between 0.10 and 0.70 MeV. Differences in the average distal fall-offs and lateral penumbrae (LPs) (over the complete set of clinically available beam modulations) among all centers were up to 0.25 g/cm2 , and 0.80 mm, respectively. Average distal fall-offs of the HollandPTC eyeline were 0.20 g/cm2 , and LPs were between 1.50 and 2.15 mm from proximal to distal regions, respectively. Treatment time, around 60 s, was comparable among all centers. The virtual source-to-axis distance of 120 cm at HollandPTC was shorter than for the five participating centers (range: 165-350 cm). Simulated depth dose distributions demonstrated the impact of the different beamline characteristics among institutions. The largest difference was observed for a small UM located at the posterior pole, where a proximal dose between two extreme centers was up to 20%.

CONCLUSIONS

HollandPTC eyeline specifications are in accordance with five other ocular PT beamlines. Similar clinical concepts can be applied to expect the same high local tumor control. Dosimetrical properties among the six institutions induce most likely differences in ocular radiation-related toxicities. This interinstitutional comparison could support further research on ocular post-PT complications. Finally, the findings reported in this study could be used to define dosimetrical guidelines for ocular PT to unify the concepts among institutions.

3D image-guided treatment planning for Ruthenium-106 brachytherapy of choroidal melanomas

BACKGROUND

Current standard treatment procedures for Ruthenium-106 (Ru-106) brachytherapy for choroidal melanomas do not use 3D image-guided treatment planning. We evaluated the potential impact of introducing 3D treatment planning and quantified the theoretical clinical benefits in terms of tumour control probability (TCP) and normal tissue complication probability (NTCP).

MATERIALS AND METHODS

Treatment plans for thirty-two patients were optimized using 3D image-guided treatment planning and compared to the original 2D clinical plans. Optimization of plans was done in an image-based treatment planning system by optimizing the plaque position and treatment time such that the entire tumour received the prescribed dose of 100 Gy. TCP and NTCP for 2D clinical plans and optimized 3D image-guided plans were estimated from published outcome prediction models and compared within patients using Wilcoxon signed-rank test.

RESULTS

The median minimum tumour dose (D_99% ) for 2D clinical plans was 93 Gy (range: 23-158 Gy), corresponding to 5-year TCP of 75% (IQR 61-86%), while median tumour D_99% for optimized 3D image-guided plans was 115 Gy (range 103-141 Gy), corresponding to TCP of 82% (IQR 80-84%). This was a statistically significant increase in estimated TCP (median increase in TCP 8% (IQR: -5-23, p = 0.006). While the dose to normal tissue increased somewhat, there was no significant change in NTCP.

CONCLUSION

3D treatment planning theoretically allows for improved tumour dose delivery for Ru-106 brachytherapy of choroidal melanomas, resulting in a significant increase in expected tumour control compared to traditional approaches using 2D calculations. The deliverability of optimized plans, and potential increased risk of late complications, will have to be confirmed in future clinical studies.

Diagnostic methods and therapeutic options of uveal melanoma with emphasis on MR imaging-Part II: treatment indications and complications

Therapy of uveal melanoma aims to preserve the eye and its function and to avoid metastatic dissemination. The treatment choice is difficult and must keep into account several factors; the therapeutic strategy of uveal melanoma should therefore be personalized, sometimes requiring to combine different treatment techniques. Nowadays globe-sparing radiotherapy techniques are often preferred to enucleation. Plaque brachytherapy, the most commonly used eye-preserving therapy, is suitable for small- and medium-sized uveal melanomas. Proton beam radiotherapy is indicated for tumours with noticeable size, challenging shape and location, but is more expensive and less available than brachytherapy. Enucleation is currently restricted to advanced tumours, uveal melanomas with orbital or optic nerve involvement, blind and painful eyes because of treatment-related complications (neovascular glaucoma, chronic inflammatory processes). The effect of proton beam therapy on neoplastic tissue is related to direct cytotoxic action of the radiations, impairment of neoplastic vascular supply and immunologic response. Complications after radiotherapy are frequent and numerous and mainly related to tumour thickness, radiation dose and distance between the tumour and optic nerve. The purpose of this pictorial review is to provide the radiologists with awareness about diagnostic methods and therapeutic options of uveal melanoma. In the present second section, we discuss the therapeutic management of uveal melanoma, describing the main ocular-conserving radiotherapic techniques. We subsequently present an overview of the effects of radiations on neoplastic tissue. Lastly, we review ocular complications following radiotherapy that should be evaluated by radiologists during follow-up MRI examinations.

Diagnostic methods and therapeutic options of uveal melanoma with emphasis on MR imaging-Part I: MR imaging with pathologic correlation and technical considerations

Uveal melanoma is a malignant neoplasm that derives from pigmented melanocytes of the uvea and involves, in order of decreasing prevalence, the choroid, ciliary body and iris. Its prognosis is related to histopathologic and genetic features, tumor size and location, extraocular extension. The diagnosis is fundamentally based on clinical evaluation (ophthalmoscopy, biomicroscopy) and ultrasonography. MRI is useful in case of untransparent lens or subretinal effusion. Moreover, MRI has a significant role to confirm the diagnosis, in the evaluation of the local extent of the disease with implications for treatment planning, and in the follow-up after radiotherapy treatment. Uveal melanoma can show different morphologic features (lentiform, dome or mushroom shape) and often determines retinal detachment. MR appearance of uveal melanoma mainly depends on the melanin content. Uveal melanoma typically displays high signal intensity on T1-weighted images and low signal intensity on T2-weighted images. Nevertheless, imaging appearance may be variable based on the degree of pigmentation and the presence of areas of necrosis or cavitation. Differential diagnosis includes other uveal lesions. The radiologists and in particular MRI play a significant role in the clinical management of uveal melanoma. The purpose of this pictorial review is to provide the radiologists with awareness about diagnostic methods and therapeutic options of uveal melanoma. In the present first section we summarize the MR anatomy of the eye and describe ophthalmological and radiological imaging techniques to diagnose uveal melanomas, with emphasis on the role of MR imaging. Additionally, we review MR imaging appearance of uveal melanomas.

Radiation therapy for uveal melanoma: a review of treatment methods available in 2021

PURPOSE OF REVIEW

Radiation therapy has become the standard of care for the treatment of uveal melanoma. We intend to outline the current radiation therapy methods that are employed to treat uveal melanoma. We will outline their relative benefits over one another. We will also provide some background about radiation therapy in general to accustom the ophthalmologists likely reading this review.

RECENT FINDINGS

Four main options exist for radiation therapy of uveal melanoma. Because the eye is a small space, and because melanomas are relatively radioresistant, oncologists treating uveal melanoma must deliver highly focused doses in high amounts to a small space. Therapies incorporating external beams include proton beam therapy and stereotactic radiosurgery. Stereotactic radiosurgery comes in two forms, gamma knife therapy and cyberknife therapy. Radiation may also be placed directly on the eye surgically via plaque brachytherapy. All methods have been used effectively to treat uveal melanoma.

SUMMARY

Each particular radiotherapy technique employed to treat uveal melanoma has its own set of benefits and drawbacks. The ocular oncologist can choose amongst these therapies based upon his or her clinical judgment of the relative risks and benefits. Availability of the therapy and cost to the patient remain significant factors in the ocular oncologist's choice.

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.

Ophthalmic Magnetic Resonance Imaging: Where Are We (Heading To)?

Magnetic resonance imaging of the eye and orbit (MReye) is a cross-domain research field, combining (bio)physics, (bio)engineering, physiology, data sciences and ophthalmology. A growing number of reports document technical innovations of MReye and promote their application in preclinical research and clinical science. Realizing the progress and promises, this review outlines current trends in MReye. Examples of MReye strategies and their clinical relevance are demonstrated. Frontier applications in ocular oncology, refractive surgery, ocular muscle disorders and orbital inflammation are presented and their implications for explorations into ophthalmic diseases are provided. Substantial progress in anatomically detailed, high-spatial resolution MReye of the eye, orbit and optic nerve is demonstrated. Recent developments in MReye of ocular tumors are explored, and its value for personalized eye models derived from machine learning in the treatment planning of uveal melanoma and evaluation of retinoblastoma is highlighted. The potential of MReye for monitoring drug distribution and for improving treatment management and the assessment of individual responses is discussed. To open a window into the eye and into (patho)physiological processes that in the past have been largely inaccessible, advances in MReye at ultrahigh magnetic field strengths are discussed. A concluding section ventures a glance beyond the horizon and explores future directions of MReye across multiple scales, including in vivo electrolyte mapping of sodium and other nuclei. This review underscores the need for the (bio)medical imaging and ophthalmic communities to expand efforts to find solutions to the remaining unsolved problems and technical obstacles of MReye, with the objective to transfer methodological advancements driven by MR physics into genuine clinical value.

Measuring eye deformation between planning and proton beam therapy position using magnetic resonance imaging

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Eye and tumour deformation due to gravity is less than 0.4 mm.

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Conformity index between flexed and supine position for eyes is >0.95.

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Conformity index between flexed and supine position for tumours is >0.85.

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Supinely acquired MR images can be used for PBT planning.

Proton beam therapy (PBT) for uveal melanoma (UM) is performed in sitting position, while the acquisition of the Magnetic resonance (MR)-images for treatment planning is performed in supine position. We assessed the effect of this difference in position on the eye- and tumour- shape. Seven subjects and six UM-patients were scanned in supine and a seating mimicking position. The distances between the tumour/sclera in both positions were calculated. The median distance between both positions was 0.1 mm. Change in gravity direction produced no substantial changes in sclera and tumour shape, indicating that supinely acquired MR-images can be used to plan ocular-PBT.

MRI enables accurate diagnosis and follow-up in uveal melanoma patients after vitrectomy

Supplemental Digital Content is available in the text.

Uveal melanoma (UM), the most common primary intraocular tumour, is often complicated by exudative retinal detachment (RD). Sometimes, this exudative RD is mistaken for a rhegmatogenous detachment and is subsequently treated with vitrectomy with silicone oil (SiOil) tamponade. As SiOil prevents ultrasound imaging, the diagnosis, treatment planning and/or follow-up of UM underlying the detachment are often severely hindered by the SiOil. We aim to develop and evaluate new MRI methods to image UM patients with a SiOil tamponade and evaluate this in vivo. A dedicated MRI protocol for 3 and 7 T was developed and subsequently evaluated in three patients. The MRI protocol developed was evaluated in three patients. In the first patient, SiOil hindered follow-up and therefore MRI was indicated. No tumour recurrence was found after two follow-up scans. The second and third patient underwent vitrectomy with SiOil for assumed rhegmatogenous RD in another hospital, during which a mass was found. In these cases, MRI was used to determine whether the lesion was UM and perform measurements to plan brachytherapy treatment. In general, the proposed workflow is more complicated on 7 T than on 3 T as the off-resonance effects scale linearly with field strength. For example, the shimming procedure needed modifications at 7 T, whereas at 3 T, the automatic shimming sufficed. However, at 7 T, higher resolution images were obtained compared with 3 T (0.6 vs. 0.8 mm³). A dedicated MRI protocol enables high-resolution imaging of vitrectomized eyes with SiOil tamponade, enabling treatment planning or follow-up in UM patients.

Response Evaluation of Choroidal Melanoma After Brachytherapy Using Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI): Preliminary Findings

Purpose: To evaluate the role of diffusion-weighted magnetic resonance imaging (DW-MRI) in the assessment of therapeutic response in patients with choroidal melanoma treated with brachytherapy.

Materials and Methods: We performed a prospective, unicentric study which included patients with choroidal melanoma and indication for brachytherapy. Three DW-MRI examinations were proposed for each patient, one before and two after treatment. The apparent diffusion coefficient (ADC) value was calculated on DW-MRI and compared with local tumor control assessed by ophthalmologic follow-up.

Results: From 07/2018 to 06/2019, 19 patients were recruited, 13 of whom underwent follow-up examinations. Patients' ages ranged from 24 to 78 years and 52.9% were male. At the ocular ultrasound, the mean tumor thickness and diameter were 6.3 and 11.5 mm, respectively. Two patients (15.4%) showed signs of tumor progression during follow-up (7 and 9 months after treatment). There was no statistically significant difference in tumor size between MR before and after treatment, however, there was a significant reduction in mean ADC in patients with progression (p = 0.02).

Conclusion: DW-MRI is a promising method for monitoring patients with choroidal melanoma; reduction in the mean ADC values between pre-treatment MRI and the first post-treatment MRI may be related to the lack of response to brachytherapy and increased risk of disease progression.

The Economic Value of MR-Imaging for Uveal Melanoma

Objective

Uveal melanoma (UM) is the most common primary intra-ocular tumour. Treatment is determined by tumour size and location. Generally, smaller tumours are eligible for brachytherapy unless they are located close to posterior pole. Larger tumours are enucleated or undergo proton beam therapy (PBT), which is more expensive than brachytherapy and less available. Accuracy of tumour size determination is critical for accurate planning and delivery of treatment, particularly to ensure tumour coverage, critical structure sparing, and for the choice of treatment modality. This is particularly the case for tumour dimensions that are close to the cut-off point for a specific type of treatment: in the case of the brachytherapy protocol at our institution, 6-8 mm. Ultrasound is conventionally used, but magnetic resonance imaging (MRI) has recently become an additional available tool. Although more expensive, it enables more accurate measurements and is particularly useful in combination with clinical fundus examination, fundus photography and ultrasound. Our aim in this paper was to determine the economic value of MRI for UM treatment.

Methods

We retrospectively analysed 60 patients' MRI scans acquired as part of a study or for clinical care. For each patient, we assessed whether the extra cost of an MRI generated economic benefit or change in optimal treatment.

Results

MRI indicated a smaller tumour prominence than US in 10% of patients with intermediate tumour size, resulting in a change from PBT to brachytherapy. The costs of MRI, €200-€1000, are significantly lower than the higher costs of PBT compared to brachytherapy, €24,000 difference. In addition, the annual total economic burden of severe vision impairment associated with eye removal is €10,000. Furthermore, for patients where ultrasound was impossible due to previous surgery, MRI enabled eye-preserving treatment.

Conclusion

An additional MRI for specific patients with UM improves economic value as it enables less expensive treatment in a sufficient percentage of patients to compensate for the MRI costs. Value is increased in terms of quality of care as it enables for some a treatment option which spares more vision.

Uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. UMs are usually initiated by a mutation in GNAQ or GNA11, unlike cutaneous melanomas, which usually harbour a BRAF or NRAS mutation. The annual incidence in Europe and the USA is ~6 per million population per year. Risk factors include fair skin, light-coloured eyes, congenital ocular melanocytosis, ocular melanocytoma and the BAP1-tumour predisposition syndrome. Ocular treatment aims at preserving the eye and useful vision and, if possible, preventing metastases. Enucleation has largely been superseded by various forms of radiotherapy, phototherapy and local tumour resection, often administered in combination. Ocular outcomes are best with small tumours not extending close to the optic disc and/or fovea. Almost 50% of patients develop metastatic disease, which usually involves the liver, and is usually fatal within 1 year. Although UM metastases are less responsive than cutaneous melanoma to chemotherapy or immune checkpoint inhibitors, encouraging results have been reported with partial hepatectomy for solitary metastases, with percutaneous hepatic perfusion with melphalan or with tebentafusp. Better insight into tumour immunology and metabolism may lead to new treatments.

Silent volumetric multi-contrast 7 Tesla MRI of ocular tumors using Zero Echo Time imaging

Magnetic Resonance Imaging (MRI) has become a valuable imaging modality in ophthalmology, especially for the diagnosis and treatment planning of patients with uveal melanoma, the most common primary intra-ocular tumor. We aim to develop and evaluate the value of silent Zero Echo Time (ZTE) MRI to image patients with ocular tumors at 7Tesla. Therefore, ZTE and different types of magnetization-prepared ZTE (FLAIR, SPIR, T2 and Saturation recovery), have been developed. After an initial validation with 7 healthy subjects, nine patients with an eye tumor have been evaluated. The ZTE scans were compared to their Cartesian equivalent in terms of contrast, motion-sensitivity, diagnostic quality and patient comfort. All volunteers and especially the patients reported a more comfortable experience during the ZTE scans, which had at least a 10 dB lower sound pressure. The image contrast in the native ZTE was poor, but in the different magnetization-prepared ZTE, the eye lens, cornea and retina were clearly discriminated. Overall the T2-prepared scan yielded the best contrast, especially between tumor and healthy tissue, and proved to be robust against eye motion. Although the intrinsic 3D nature of the ZTE-technique provides an accurate analysis of the tumor morphology, the quality of the ZTE-images is lower than their Cartesian equivalent. In conclusion, the quality of magnetization-prepared ZTE images is sufficient to assess the 3D tumor morphology, but insufficient for more detailed evaluations. As such this technique can be an option for patients who cannot comply with the sound-levels of Cartesian scans, but for other patients the conventional Cartesian scans offer a better image quality.

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.

Assessment of uveal melanomas using advanced diffusion-weighted imaging techniques: value of reduced field of view DWI ("zoomed DWI") and readout-segmented DWI (RESOLVE)

Background

Diffusion-weighted imaging (DWI) has become an important tool for lesion characterization. Advanced techniques of DWI may be used to improve image quality.

Purpose

To evaluate multi-shot segmented DWI (rs-EPI, RESOLVE) and reduced field-of view DWI (rFOV-EPI, “zoomed” EPI) in patients with ocular melanoma and to compare image quality and diagnostic performance in differentiation of melanoma from retinal detachment.

Material and Methods

In this prospective and IRB-approved trial, we examined 26 patients using methods including conventional single-shot echo-planar DWI (ss-EPI), rs-EPI, and rFOV-EPI. Subjective image quality was compared using a four-point score and the maximum tumor length was measured in all sequences. Apparent diffusion coefficient (ADC) measurements were performed using a region-of interest analysis. Tumor delineation and differences in ADC values between melanomas and retinal detachments were compared.

Results

Diffusion restriction was markedly reduced in melanomas in all applied image techniques. Subjective image quality was significantly higher for rFOV-EPI (score = 3.5 ± 0.5) compared with rs-EPI (score = 3.3 ± 0.6) and ss-EPI (score = 2.5 ± 0.9). Regarding tumor diameter measurements, rFOV-EPI showed the best agreement compared with high-resolution conventional sequences. ADC measurements of the tumor and retinal detachment differed significantly ( P < 0.001) with the rFOV-EPI performing best (sensitivities and specificities compared with T1-weighted ss-EPI 61%/82%; rFOV-EPI 86%/92%; rs-EPI 79%/92%, respectively).

Conclusion

rFOV-EPI showed improved image quality compared with ss-EPI and rs-EPI, the most accurate tumor delineation and the best differentiation from retinal detachments in our patients.

Cartesian MR fingerprinting in the eye at 7T using compressed sensing and matrix completion-based reconstructions

PURPOSE

To explore the feasibility of MR Fingerprinting (MRF) to rapidly quantify relaxation times in the human eye at 7T, and to provide a data acquisition and processing framework for future tissue characterization in eye tumor patients.

METHODS

In this single-element receive coil MRF approach with Cartesian sampling, undersampling is used to shorten scan time and, therefore, to reduce the degree of motion artifacts. For reconstruction, approaches based on compressed sensing (CS) and matrix completion (MC) were used, while their effects on the quality of the MRF parameter maps were studied in simulations and experiments. Average relaxation times in the eye were measured in 6 healthy volunteers. One uveal melanoma patient was included to show the feasibility of MRF in a clinical context.

RESULTS

Simulation results showed that an MC-based reconstruction enables large undersampling factors and also results in more accurate parameter maps compared with using CS. Experiments in 6 healthy volunteers used a reduction in scan time from 7:02 to 1:16 min, producing images without visible loss of detail in the parameter maps when using the MC-based reconstruction. Relaxation times from 6 healthy volunteers are in agreement with values obtained from fully sampled scans and values in literature, and parameter maps in a uveal melanoma patient show clear difference in relaxation times between tumor and healthy tissue.

CONCLUSION

Cartesian-based MRF is feasible in the eye at 7T. High undersampling factors can be achieved by means of MC, significantly shortening scan time and increasing patient comfort, while also mitigating the risk of motion artifacts.

MRI of Uveal Melanoma

Uveal Melanoma (UM) is the most common primary malignant ocular tumor. The high soft tissue contrast and spatial resolution, and the possibility of generating 3D volumetric and functional images, make Magnetic Resonance Imaging (MRI) a valuable diagnostic imaging technique in UM. Current clinical MRI protocols, however, are not optimized for UM and therefore lack the quality for accurate assessments. We therefore developed a dedicated protocol at a 3 Tesla MRI, using an eye coil, consisting of multi-slice 2D sequences, different isotropic sequences and diffusion and perfusion-weighted images. This protocol was prospectively evaluated in 9 uveal melanoma patients. The multi-slice 2D sequences had the highest in-plane resolution, being the most suited for lesion characterization and local extension evaluation. The isotropic 3D Turbo-Spin Echo (TSE) sequences were the most suitable for accurate geometric measurements of the tumor and are therefore important for therapy planning. Diffusion and perfusion-weighted images aid in differentiating benign from malignant lesions and provide quantitative measures on tumor hemodynamics and cellularity, which have been reported to be effective in predicting and assessing treatment outcome. Overall, this dedicated MRI protocol provides high-quality imaging of UM, which can be used to improve its diagnosis, treatment planning, and follow-up.

Personalized Anatomic Eye Model From T1-Weighted Volume Interpolated Gradient Echo Magnetic Resonance Imaging of Patients With Uveal Melanoma

PURPOSE

We present a 3-dimensional patient-specific eye model from magnetic resonance imaging (MRI) for proton therapy treatment planning of uveal melanoma (UM). During MRI acquisition of UM patients, the point fixation can be difficult and, together with physiological blinking, can introduce motion artifacts in the images, thus challenging the model creation. Furthermore, the unclear boundary of the small objects (eg, lens, optic nerve) near the muscle or of the tumors with hemorrhage and tantalum clips can limit model accuracy.

METHODS AND MATERIALS

A dataset of 37 subjects, including 30 healthy eyes of volunteers and 7 eyes of UM patients, was investigated. In our previous work, active shape model was successfully applied to retinoblastoma eye segmentation in T1-weighted 3T MRI. Here, we evaluate this method in a more challenging setting, based on 1.5T MRI acquisition and different datasets of awake adult eyes with UM. The lens and cornea together with the sclera, vitreous humor, and optic nerve were automatically segmented and validated against manual delineations of a senior ocular radiation oncologist, in terms of the Dice similarity coefficient and Hausdorff distance.

RESULTS

Leave-one-out cross validation (mixing both volunteers and UM patients) yielded median Dice similarity coefficient values (respective of Hausdorff distance) of 94.5% (1.64 mm) for the sclera, 92.2% (1.73 mm) for the vitreous humor, 88.3% (1.09 mm) for the lens, and 81.9% (1.86 mm) for the optic nerve. The average computation time for an eye was 10 seconds.

CONCLUSIONS

To our knowledge, our work is the first attempt to automatically segment adult eyes, including patients with UM. Our results show that automated active shape model segmentation can succeed in the presence of motion, tumors, and tantalum clips. These results are promising for inclusion in clinical practice.

Plaque brachytherapy for posterior uveal melanoma in 2018: improved techniques and expanded indications

PURPOSE OF REVIEW

Plaque brachytherapy remains the dominant globe-sparing therapy of uveal melanoma. This report highlights recent advances, which have expanded plaque brachytherapy's uses as well as improved the surgical technique.

RECENT FINDINGS

Plaque brachytherapy is effective for tumors that may previously have demanded enucleation. Plaque brachytherapy can be used to control large melanomas as well as melanomas touching the optic nerve. Improvements in planning and design have made plaque therapy simpler for the surgical operator and may reduce collateral radiation damage to normal ocular structures. The COMS implies a required dose of 85 Gy to the tumor apex for treatment of uveal melanoma. However, multiple reports indicate that lower doses may be equally effective for tumor control while reducing radiation dose to uninvolved structures. Vitreoretinal surgeons can be called upon safely to treat long-term side effects of radiation or tumor death such as intractable vitreous hemorrhage or inflammation. Further, vitreoretinal surgeons have employed tumor endoresection as primary local tumor control or in combination with plaque brachytherapy.

SUMMARY

Plaque brachytherapy for uveal melanoma remains highly effective for local tumor control and prevention of metastasis. Indications for plaque brachytherapy have expanded, and the technique has improved.

Multiband diffusion-weighted MRI of the eye and orbit free of geometric distortions using a RARE-EPI hybrid

Diffusion-weighted imaging (DWI) provides information on tissue microstructure. Single-shot echo planar imaging (EPI) is the most common technique for DWI applications in the brain, but is prone to geometric distortions and signal voids. Rapid acquisition with relaxation enhancement [RARE, also known as fast spin echo (FSE)] imaging presents a valuable alternative to DWI with high anatomical accuracy. This work proposes a multi-shot diffusion-weighted RARE-EPI hybrid pulse sequence, combining the anatomical integrity of RARE with the imaging speed and radiofrequency (RF) power deposition advantage of EPI. The anatomical integrity of RARE-EPI was demonstrated and quantified by center of gravity analysis for both morphological images and diffusion-weighted acquisitions in phantom and in vivo experiments at 3.0 T and 7.0 T. The results indicate that half of the RARE echoes in the echo train can be replaced by EPI echoes whilst maintaining anatomical accuracy. The reduced RF power deposition of RARE-EPI enabled multiband RF pulses facilitating simultaneous multi-slice imaging. This study shows that diffusion-weighted RARE-EPI has the capability to acquire high fidelity, distortion-free images of the eye and the orbit. It is shown that RARE-EPI maintains the immunity to B₀ inhomogeneities reported for RARE imaging. This benefit can be exploited for the assessment of ocular masses and pathological changes of the eye and the orbit.

Repeatability of apparent diffusion coefficient and intravoxel incoherent motion parameters at 3.0 Tesla in orbital lesions

OBJECTIVES

To evaluate repeatability of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters in the orbit.

METHODS

From December 2015 to March 2016, 22 patients were scanned twice using an IVIM sequence with 15b values (0-2,000 s/mm2) at 3.0T. Two readers independently delineated regions of interest in an orbital mass and in different intra-orbital and extra-orbital structures. Short-term test-retest repeatability and inter-observer agreement were assessed using the intra-class correlation coefficient (ICC), the coefficient of variation (CV) and Bland-Altman limits of agreements (BA-LA).

RESULTS

Test-retest repeatability of IVIM parameters in the orbital mass was satisfactory for ADC and D (mean CV 12% and 14%, ICC 95% and 93%), poor for f and D*(means CV 43% and 110%, ICC 90% and 65%). Inter-observer repeatability agreement was almost perfect in the orbital mass for all the IVIM parameters (ICC = 95%, 93%, 94% and 90% for ADC, D, f and D*, respectively).

CONCLUSIONS

IVIM appeared to be a robust tool to measure D in orbital lesions with good repeatability, but this approach showed a poor repeatability of f and D*.

KEY POINTS

• IVIM technique is feasible in the orbit. • IVIM has a good-acceptable repeatability of D (CV range 12-25 %). • IVIM interobserver repeatability agreement is excellent (ICC range 90-95 %). • f or D* provide higher test-retest and interobserver variabilities.

9.4T and 17.6T MRI of Retinoblastoma: Ex Vivo evaluation of microstructural anatomy and disease extent compared with histopathology

BACKGROUND

Retinoblastoma is the most common intraocular tumor in childhood with a good prognosis in terms of mortality, but detailed information about tumor morphology and disease extent in retinoblastoma is important for treatment decision making.

PURPOSE

To demonstrate ultrahigh-field MRI tumor morphology and tumor extent in retinoblastoma correlating with in and ex vivo images with histopathology.

STUDY TYPE

Prospective case series.

POPULATION

Six retinoblastoma patients (median age 5.5 months, range 2-14) were prospectively included in this study. Median time between diagnosis and enucleation was 8 days (range 7-19).

FIELD STRENGTH/SEQUENCE

In vivo pre-enucleation at 1.5T MRI with a circular surface coil. Ex vivo imaging (FLASH T₁ -weighted and RARE T₂ -weighted) was performed at field strengths of 9.4T and 17.6T.

ASSESSMENT

After ex vivo imaging, the eyes were histopathologically analyzed and morphologically matched with MRI findings by three authors (two with respectively 14 and 4 years of experience in ocular MRI and one with 16 years of experience in ophthalmopathology).

RESULTS

Small submillimeter morphological aspects of intraocular retinoblastoma were successfully depicted with higher-resolution MRI and matched with histopathology images. With ex vivo MRI a small subretinal tumor seed (300 μm) adjacent to the choroid was morphologically matched with histopathology. Also, a characteristic geographical pattern of vital tumor tissue (400 μm) surrounding a central vessel interspersed with necrotic areas correlated with histopathology images. Tumor invasion into the optic nerve showed a higher signal intensity on T₁ -weighted higher-resolution MRI.

DATA CONCLUSION

Higher-resolution MRI allows for small morphological aspects of intraocular retinoblastoma and extraocular disease extent not visible on currently used clinical in vivo MRI to be depicted.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1487-1497.

Signal Alteration in the Optic Nerve Head on 3D T2-weighted MRI: a Potential Neuroimaging Sign of Glaucomatous Optic Neuropathy

PURPOSE

To investigate whether a signal alteration (SA) in the optic nerve head (ONH) on 3D T2-weighted magnetic resonance imaging (MRI) is associated with glaucomatous optic neuropathy Materials and Methods: A total of 35 patients with bilateral open-angle glaucoma and 31 age-matched controls underwent 3D high-resolution (0.98 × 0.98 × 1 mm³) T2-weighted MRI and detailed ophthalmologic examinations including spectral-domain optical coherence tomography (OCT). Two independent reviewers blinded to subject data determined mild or prominent SA on 3D T2-weighted MRI for the incomplete or complete loss of ocular hypointense continuity in the ONH, respectively. The prevalence of SAs was compared between the two groups with the chi-square test. The OCT measurements were compared among the eyes with a mild or prominent SA and those without an SA using the Kruskal-Wallis test.

RESULTS

Of the 35 eyes with glaucoma, 26 eyes (74.3%) exhibited an SA in the ONH, whereas it was observed in 5 (16.1%) of the 31 controls (P < 0.001). The eyes with a prominent SA had a significantly different average retinal nerve fiber layer thickness (P = 0.002) and the ONH parameters except for the disk area (all P < 0.001) than those without an SA. The eyes with a mild SA had a significantly narrower neural rim area, larger cup volume, and larger average and vertical cup-to-disk ratios compared with those without an SA (P = 0.011, 0.003, 0.004, and 0.004, respectively) Conclusions: The SA in the ONH on 3D T2-weighted MRI was significantly more frequent in eyes with open-angle glaucoma than in the controls.

Investigation into the quantitative and qualitative characteristics of choroidal melanoma through magnetic resonance imaging and B-scan ultrasound

OBJECTIVE

To investigate the homogeneity and vascularity of choroidal melanoma through magnetic resonance imaging (MRI) and brightness modulation (B-mode) ultrasound scan and their correlation with dimensions of tumor, as well as to measure the sensitivity of both modalities in retinal detachment (RD) detection.

MATERIALS AND METHODS

This retrospective chart review included patients diagnosed with choroidal melanoma. All these patients underwent MRI scans using T2-weighted (T2-WI) and T1-weighted (T1-WI) sequences, before and after an intravenous injection of paramagnetic contrast material. The patients were also examined using a B-mode ultrasound scan, and the results from both modalities were compared (tumor homogeneity, tumor height, tumor base diameter, and tumor vascularity).

RESULTS

Forty-two patients (mean age=65.33±12.51 years) with choroidal melanoma were included in the study. Homogeneity was confirmed in 16 patients through ultrasound scan, in 19 patients through T1-WI sequence, in 21 patients through T2-WI sequence, and in 25 patients through T1-WI sequence + contrast (gadolinium). Patients with homogenous tumors presented with lower (P=0.0045) mean height than that of those with nonhomogenous tumors, whereas no statistically significant difference was found for base diameter measurements (P=0.056). Patients with tumors of high vascularity presented with greater mean height (P=0.000638) and greater mean base diameter compared with those with tumors of low vascularity (P=0.019543). RD was detected in 26 patients through T1-WI sequence, in 13 patients through T2-WI sequence, in 26 patients through T1-WI sequence + contrast, and in 32 patients through ultrasound scan, which proved to be the most sensitive modality.

CONCLUSION

The height of choroidal melanoma was positively correlated with tumor's homogeneity. Melanomas of greater height were found to be less homogenous, due to increased degeneration and higher occurrence of intratumoral hemorrhage. In addition, choroidal melanoma's height was also positively correlated with the level of its vascularity. Finally, ultrasound scan was found to be more sensitive than MRI in the detection of RD.

Multi-channel MRI segmentation of eye structures and tumors using patient-specific features

Retinoblastoma and uveal melanoma are fast spreading eye tumors usually diagnosed by using 2D Fundus Image Photography (Fundus) and 2D Ultrasound (US). Diagnosis and treatment planning of such diseases often require additional complementary imaging to confirm the tumor extend via 3D Magnetic Resonance Imaging (MRI). In this context, having automatic segmentations to estimate the size and the distribution of the pathological tissue would be advantageous towards tumor characterization. Until now, the alternative has been the manual delineation of eye structures, a rather time consuming and error-prone task, to be conducted in multiple MRI sequences simultaneously. This situation, and the lack of tools for accurate eye MRI analysis, reduces the interest in MRI beyond the qualitative evaluation of the optic nerve invasion and the confirmation of recurrent malignancies below calcified tumors. In this manuscript, we propose a new framework for the automatic segmentation of eye structures and ocular tumors in multi-sequence MRI. Our key contribution is the introduction of a pathological eye model from which Eye Patient-Specific Features (EPSF) can be computed. These features combine intensity and shape information of pathological tissue while embedded in healthy structures of the eye. We assess our work on a dataset of pathological patient eyes by computing the Dice Similarity Coefficient (DSC) of the sclera, the cornea, the vitreous humor, the lens and the tumor. In addition, we quantitatively show the superior performance of our pathological eye model as compared to the segmentation obtained by using a healthy model (over 4% DSC) and demonstrate the relevance of our EPSF, which improve the final segmentation regardless of the classifier employed.