Apical dose versus volume dose of Ruthenium-106 brachytherapy for uveal melanoma.

OBJECTIVE: Ruthenium-106 brachytherapy is commonly used to treat uveal melanomas. Most centres prescribe a radiation dose to the tumour apex that is calculated with the tumour located in the centre of the plaque. Recent work suggests that D99%-the minimum radiation dose delivered to 99% of tumour volume-may be a better predictor of tumour control than apex dose. Both dosing regimens may be affected by tumour and treatment variables differently. We explored the effect of differences in these variables on volume and apex dose using a 3-dimensional planning model. METHODS: The time required to deliver 100 Gy to the tumour apices of representative tumours ranging from 2- to 6-mm thickness with central plaque positioning was calculated in Plaque Simulator™. This treatment time was used for further calculations, including D99% with central plaque placement, and apical and tumour volume doses when tumour and plaque characteristics were altered, including eccentric plaque placement, either away from (tilt) or along (offset) scleral surface, tumour shape, and plaque type. RESULTS: D99% was always greater than the apex dose when plaques were placed centrally, and the difference increased with tumour thickness. Increasing degrees of tumour offset reduced apical dose and D99%, with a greater effect on apical dose for thicker and D99% for thinner tumours, respectively. Differences in tumour shape and plaque type had idiosyncratic effects on apical and volume dosing. CONCLUSION: D99% and apex dose are affected by tumour and treatment characteristics in different ways, highlighting the complexity of radiation delivery to uveal tumours.

Adaptive optics imaging in inherited retinal diseases: A scoping review of the clinical literature.

Adaptive optics (AO) imaging enables direct, objective assessments of retinal cells. Applications of AO show great promise in advancing our understanding of the etiology of inherited retinal disease (IRDs) and discovering new imaging biomarkers. This scoping review systematically identifies and summarizes clinical studies evaluating AO imaging in IRDs. Ovid MEDLINE and EMBASE were searched on February 6, 2023. Studies describing AO imaging in monogenic IRDs were included. Study screening and data extraction were performed by 2 reviewers independently. This review presents (1) a broad overview of the dominant areas of research; (2) a summary of IRD characteristics revealed by AO imaging; and (3) a discussion of methodological considerations relating to AO imaging in IRDs. From 140 studies with AO outcomes, including 2 following subretinal gene therapy treatments, 75% included fewer than 10 participants with AO imaging data. Of 100 studies that included participants' genetic diagnoses, the most common IRD genes with AO outcomes are CNGA3, CNGB3, CHM, USH2A, and ABCA4. Confocal reflectance AO scanning laser ophthalmoscopy was the most reported imaging modality, followed by flood-illuminated AO and split-detector AO. The most common outcome was cone density, reported quantitatively in 56% of studies. Future research areas include guidelines to reduce variability in the reporting of AO methodology and a focus on functional AO techniques to guide the development of therapeutic interventions.

Quantifying the effect of eccentric ruthenium plaque placement on tumor volume dose.

Purpose: Ruthenium-106 brachytherapy is a common treatment for small to medium-sized uveal melanomas. In certain clinical contexts, plaques may be placed eccentrically to tumor center. The effect of plaque decentration, a common radiation dose measurement in radiotherapy: D98%, the percentage of the tumor volume receiving at least 98% of the prescribed dose (a commonly used term in radiation oncology), is unknown. We investigated this using two commonly used plaques (CCA and CCB; Eckert & Ziegler, BEBIG GmbH) in silico. Material and methods: Using a Plaque Simulator™ (Eye Physics) plaque modelling software, treatment time required to deliver 100 Gy D98% with central plaque placement was calculated for both plaque models, treating tumors with basal dimensions of 10 mm (CCB plaque only) and 7 mm (CCA and CCB plaques), and a range of thicknesses. D98% was calculated for plaque-tumor edge distances of 0-5 mm. Additionally, we defined minimum plaque-tumor edge distances, at which D98% fell by 10% and 5% (safety margins). Results: D98% decreased as plaque-tumor edge distance decreased, i.e. as plaque eccentricity increased. Minor (< 1 mm) plaque decentration caused minimal D98% changes across tumor thicknesses. Safety margins did not follow a consistent pattern. Conclusions: Eccentric plaque placement reduces the radiation dose delivered to choroidal tumors. Both tumor (thickness, diameter) and plaque (size, location) characteristics are important D98% modulators. Further investigation of the effect of these characteristics and dose to organs at risk is essential.

Ultra-low dose external beam radiotherapy for presumed choroidal lymphoma: a case report.

Primary choroidal lymphoma is a rare, slowly progressive intraocular malignancy. Most are low grade B cell lymphomas, often involving tissues adjacent to the choroid such as the subconjunctival space, lacrimal gland or orbit. Ideally, these lesions are biopsied to establish histopathological diagnosis. The most accessible ocular structure is biopsied. Obtaining tissue by transvitreal choroidal biopsy imparts a small but significant risk of ocular morbidity, including the need for multiple surgeries, retinal detachment and vision loss.External beam radiotherapy (EBRT) is a common and effective treatment of low-grade lymphomas. EBRT has been found to very successfully treat primary marginal zone lymphomas of the ocular adnexa, which are typically of the same cell type as most primary choroid lymphomas. Ultra-low dose EBRT, most commonly using a total dose of 4 Gy, has been shown to be as effective as higher doses of radiotherapy for follicular or marginal zone lymphomas. The use of this low dose regimen for conjunctival lymphomas has been recently explored. The role of EBRT, and especially ultra-low dose EBRT, for treatment of primary choroidal lymphoma has been confined to case reports.We describe a case of presumed primary choroidal lymphoma diagnosed on clinical findings alone as the risks of ocular biopsy were deemed too high, and report outcome following treatment with ultra-low dose EBRT.

A pilot study of the pharmacokinetics of continuous magnesium infusion in critically ill patients.

Objective: The pharmacokinetics and haemodynamic effect of continuous magnesium infusion in non-cardiac intensive care unit (ICU) patients are poorly understood. We aimed to measure serum and urine magnesium levels during bolus and continuous infusion in critically ill adults, compare serum levels with those of a control population, and assess its haemodynamic effect. Design: Pharmacokinetic study Setting: A single tertiary adult ICU. Participants: Mechanically ventilated adults requiring vasopressor support. Intervention: A 10 mmol bolus of magnesium sulfate followed by 1.5-3 mmol/h infusion for 24 hours. Main outcome measures: The primary outcome was the change in total serum magnesium concentration. The main secondary outcome was mean arterial pressure (MAP)- adjusted vasopressor dose. Results: We matched 31 treated patients with 93 controls. Serum total magnesium concentration increased from a median 0.94 mmol/L (interquartile range [IQR], 0.83-1.10 mmol/L) to 1.38 mmol/L (IQR, 1.25-1.69 mmol/L; P < 0.001) and stabilised between a median 1.64 mmol/L (IQR, 1.38-1.88 mmol/L) at 7 hours and 1.77 mmol/L (IQR, 1.53-1.85 mmol/L) at 25 hours. This was significantly greater than in the control group (P < 0.001). The MAP-adjusted vasopressor dose decreased during magnesium infusion (P < 0.001). Conclusion: In critically ill patients, a magnesium sulfate bolus followed by continuous infusion achieved moderately elevated levels of total serum magnesium with a decrease in MAP-adjusted vasopressor dose. Trial registration number: ACTRN12619000925145.

Anterior Insular Cortex is Critical for the Propensity to Relapse Following Punishment-Imposed Abstinence of Alcohol Seeking.

Humans with alcohol use disorder typically abstain because of the negative consequences associated with excessive drinking, and exposure to contexts previously associated with alcohol use can trigger relapse. We used a rat model that captures a characteristic of this human condition: namely voluntary abstinence from alcohol use because of contingent punishment. There is substantial variability in the propensity to relapse following extended periods of abstinence, and this is a critical feature preventing the successful treatment of alcohol use disorder. Here we examined relapse following acute or prolonged abstinence. In male alcohol preferring P rats, we found an increased propensity to relapse in Context B, the punishment context after prolonged abstinence. Next, we found that neither alcohol intake history nor the motivational strength of alcohol predicted the propensity to relapse. We next examined the putative circuitry of context-induced relapse to alcohol seeking following prolonged abstinence using Fos as a marker of neuronal activation. The anterior insular cortex (AI) was the only brain region examined where Fos expression correlated with alcohol seeking behavior in Context B after prolonged abstinence. Finally, we used local infusion of GABAA and GABAB receptor agonists (muscimol + baclofen) to show a causal role of the AI in context-induced relapse in Context B, the punishment context after prolonged abstinence. Our results show that there is substantial individual variability in the propensity to relapse in the punishment-associated context after prolonged abstinence, and this is mediated by activity in the AI.SIGNIFICANCE STATEMENT A key feature of alcohol use disorder is that sufferers show an enduring propensity to relapse throughout their lifetime. Relapse typically occurs despite the knowledge of adverse consequences including health complications or relationship breakdowns. Here we use a recently developed rodent model that recapitulates this behavior. After an extended period of abstinence, relapse propensity is markedly increased in the "adverse consequence" environment, akin to humans with alcohol use disorder relapsing in the face of adversity. From a circuitry perspective, we demonstrate a causal role of the anterior insular cortex in relapse to alcohol seeking after extended abstinence following punishment imposed voluntary cessation of alcohol use.

Reduced alcohol-seeking in male offspring of sires exposed to alcohol self-administration followed by punishment-imposed abstinence.

Emerging evidence has demonstrated that paternal alcohol use can modify the behavior of offspring, particularly male offspring. However, preclinical studies to date have not used voluntary self-administration of alcohol to examine alcohol-related behaviors in offspring. Here, we tested the hypothesis that paternal alcohol self-administration followed by punishment-imposed abstinence alters alcohol consumption and seeking in male offspring. Male inbred alcohol preferring iP rats were trained to self-administer alcohol in one context followed by punishment-imposed suppression of alcohol-seeking in a different context using contingent footshock. Following this, all rats were bred with alcohol naïve female iP rats. F1 offspring were then trained to self-administer alcohol in an identical operant paradigm as sires. Alcohol intake and self-administration behaviors of alcohol-sired offspring were compared to control-sired offspring whose fathers had not been exposed to the alcohol operant conditioning experience. We found that paternal alcohol self-administration reduced context-induced relapse to alcohol-seeking in male offspring. These findings indicate that voluntary paternal alcohol experience, operant conditioning, and punishment can result in intergenerational changes in offspring behavior, and that this effect may protect against the vulnerability to relapse after alcohol use. We also noted reduced alcohol responding in the punishment-associated context in alcohol-sired offspring, suggesting altered perception of punishment sensitivity or the anxiogenic response to footshock. Collectively, these findings provide evidence that paternal alcohol abuse can impact alcohol-related behaviors in male offspring.