Modernization of safety environment for a dedicated beamline for proton ocular therapy.

Background: Proton therapy is an effective treatment for ocular melanoma, and other tumors of the eye. The fixed horizontal beamline dedicated to ocular treatments at Massachusetts General Hospital was originally commissioned in 2002, with much of the equipment, safety features, and practices dating back to an earlier implementation at Harvard Cyclotron in the 1970s.

Purpose: To describe the experience of reevaluation and enhancement of the safety environment for one of the longest continuously operating proton therapy programs.

A Systematic Comparison of Dose Distributions Delivered in I Plaque Brachytherapy and Proton Radiation Therapy for Ocular Melanoma.

Purpose: To characterize dose distributions with I plaque brachytherapy compared with proton radiation therapy for ocular melanoma for relevant clinical scenarios, based on tumor base diameter (d), apical height (h), and location.

Methods And Materials: Plaque and proton treatment plans were created for 4 groups of cases: (1) REF: 39 instances of reference midsize circular-base tumor (d = 12 mm, h = 5 mm), in locations varying by retinal clock hours and distance to fovea, optic disc, and corneal limbus; (2) SUP: 25 superiorly located; (3) TEMP: 25 temporal; and (4) NAS: 25 nasally located tumors that were a fixed distance from the fovea but varying in d (6-18 mm) and h (3-11 mm). For both modalities, 111 unique scenarios were characterized in terms of the distance to points of interest, doses delivered to fovea, optic disc, optic nerve at 3 mm posterior to the disc (ON@3mm), lens, and retina.

A Comparison of Treatment Outcomes after Standard Dose (70 Gy) versus Reduced Dose (50 Gy) Proton Radiation in Patients with Uveal Melanoma.

Objective: To compare outcomes in a large patient cohort with small-medium tumors located within 1 disc diameter (DD) of the optic nerve and/or fovea treated with 50 Gy or 70 Gy proton therapy.

Design: Retrospective cohort study.

Subjects: A total of 1120 patients with uveal melanomas ≤ 15 mm in largest basal diameter, ≤ 5 mm in height, located within 1 DD of the optic nerve and/or fovea, who received primary treatment with protons between 1975 and 2016 at Massachusetts Eye and Ear/Massachusetts General Hospital.

Characterization of an Iodinated Rectal Spacer for Prostate Photon and Proton Radiation Therapy.

Purpose: Conventional rectal spacers (nonI-SPs) are low-contrast on computed tomography (CT), often necessitating magnetic resonance imaging for accurate delineation. A new formulation of spacers (I-SPs) incorporates iodine to improve radiopacity and CT visualization. We characterized placement, stability, and plan quality of I-SPs compared to nonI-SPs.

Proton beam irradiation of uveal melanoma involving the iris, ciliary body and anterior choroid without surgical localisation (light field).

Aims: To assess treatment outcomes after proton beam irradiation (PBI) without surgical localisation of uveal melanomas involving the iris, ciliary body and anterior choroid.

Methods: Retrospective chart review of 125 patients evaluated at Massachusetts Eye and Ear and treated with PBI using a light field set-up without localisation surgery between November 1975 and April 2017. The tumours were characterised as follows: iris (n=18, 14.

Predicting Patient-specific Dosimetric Benefits of Proton Therapy for Skull-base Tumors Using a Geometric Knowledge-based Method.

Purpose: To predict the organ at risk (OAR) dose levels achievable with proton beam therapy (PBT), solely based on the geometric arrangement of the target volume in relation to the OARs. A comparison with an alternative therapy yields a prediction of the patient-specific benefits offered by PBT. This could enable physicians at hospitals without proton capabilities to make a better-informed referral decision or aid patient selection in model-based clinical trials.

Practice Patterns Analysis of Ocular Proton Therapy Centers: The International OPTIC Survey.

Purpose: To assess the planning, treatment, and follow-up strategies worldwide in dedicated proton therapy ocular programs.

Methods And Materials: Ten centers from 7 countries completed a questionnaire survey with 109 queries on the eye treatment planning system (TPS), hardware/software equipment, image acquisition/registration, patient positioning, eye surveillance, beam delivery, quality assurance (QA), clinical management, and workflow.

Results: Worldwide, 28,891 eye patients were treated with protons at the 10 centers as of the end of 2014.

Visual Outcomes after Proton Beam Irradiation for Choroidal Melanomas Involving the Fovea.

Purpose: To report visual outcomes in patients undergoing proton beam irradiation of tumors located within 1 disc diameter of the fovea.

Design: Retrospective review.

Participants: Patients with choroidal melanoma involving the fovea treated with proton beam therapy between 1975 and 2009.

[18F]-Fluoromisonidazole positron emission tomography/computed tomography visualization of tumor hypoxia in patients with chordoma of the mobile and sacrococcygeal spine.

Purpose: To investigate [18F]-fluoromisonidazole positron emission tomography/computed tomography (FMISO-PET/CT) detection of targetable hypoxic subvolumes (HSVs) in chordoma of the mobile or sacrococcygeal spine.

Methods And Materials: A prospective, pilot study of 20 patients with primary or locally recurrent chordoma of the mobile or sacrococcygeal spine treated with proton or combined proton/photon radiation therapy (RT) with or without surgery was completed. The FMISO-PET/CT was performed before RT and after 19.

Evaluation of the dosimetric impact of interfractional anatomical variations on prostate proton therapy using daily in-room CT images.

Purpose: To quantify interfractional anatomical variations and their dosimetric impact during the course of fractionated proton therapy (PT) of prostate cancer and to assess the robustness of the current treatment planning techniques.

Methods: Simulation and daily in-room CT scans from ten prostate carcinoma patients were analyzed. PT treatment plans (78 Gy in 39 fractions of 2 Gy) were created on the simulation CT, delivering 25 fractions to PTV1 (expanded from prostate and seminal vesicles), followed by 14 boost fractions to PTV2 (expanded from prostate).

Monte Carlo calculation of imaging doses from diagnostic multidetector CT and kilovoltage cone-beam CT as part of prostate cancer treatment plans.

Purpose: To calculate imaging doses to the rectum, bladder, and femoral heads as part of a prostate cancer treatment plans, assuming an image guided radiation therapy (IGRT) procedure involving either the multidetector CT (MDCT) or kilovoltage cone-beam CT (kV CBCT).

Methods: This study considered an IGRT treatment plan for a prostate carcinoma patient involving 50.4 Gy from 28 initial fractions and a boost of 28.

A case study in proton pencil-beam scanning delivery.

Purpose: We completed an implementation of pencil-beam scanning (PBS), a technology whereby a focused beam of protons, of variable intensity and energy, is scanned over a plane perpendicular to the beam axis and in depth. The aim of radiotherapy is to improve the target to healthy tissue dose differential. We illustrate how PBS achieves this aim in a patient with a bulky tumor.

Life, liberty, and the pursuit of protons: an evidence-based review of the role of particle therapy in the treatment of prostate cancer.

Proton beam therapy (PBT) has been in use for a number of decades, though interest in PBT for localized prostate cancer has grown substantially in recent years. Protons offer the theoretical potential of achieving dose escalation and decreasing toxicity by capitalizing on unique physical dose deposition characteristics to avoid normal tissue. Although it has proven effective in a number of malignancies including as a means for dose escalation in prostate cancer, there is little published clinical data to support its comparative superiority over alternative forms of conformal radiation for prostate cancer.

Advanced-technology radiation therapy in the management of bone and soft tissue sarcomas.

Background: For patients with sarcomas, radiotherapy can be used as neoadjuvant, adjuvant, or primary local therapy, depending on the site and type of sarcoma, the surgical approach, and the efficacy of chemotherapy.

Methods: The authors review the current status of advanced technology radiation therapy in the management of bone and soft tissue sarcoma.

Results: Advances in radiotherapy have resulted in improved treatment for bone and soft tissue sarcomas.

A treatment planning comparison of intensity modulated photon and proton therapy for paraspinal sarcomas.

Purpose: A comparative treatment planning study has been undertaken between intensity modulated (IM) photon therapy and IM proton therapy (IMPT) in paraspinal sarcomas, so as to assess the potential benefits and limitations of these treatment modalities. In the case of IM proton therapy, plans were compared also for two different sizes of the pencil beam. Finally, a 10% and 20% dose escalation with IM protons was planned, and the consequential organ at risk (OAR) irradiation was evaluated.

Viscosity as an experimental tool in studying the mechanism of stereoselective and product-selective chemical transformations through frictional impositions.

In the present Account, we examine the viscosity dependence as a function of temperature, pressure, and solvent polarity for the double inversion in the photolytic azoalkane denitrogenation, the thermal isomerization of housanes, and stereochemical memory versus Curtin-Hammett behavior in radical-cation rearrangements. The analysis of these stereoselective and product-selective viscosity studies in terms of the simple free-volume model demonstrates the utility of frictional effects for the elucidation of complex reaction mechanisms in molecular transformations.

Viscosity-dependent diastereoselectivity and product selectivity in the photodenitrogenation of a spirocyclopropane-substituted, DBH-type azoalkane.

In the photodenitrogenation of the spirocyclopropane-substituted azoalkane 1 in alcoholic solvents of various viscosity (from 0.6 to 89.2 cP) to the diastereomeric housanes 2 (major product) and bicyclo[3.

Stereochemical memory versus Curtin-Hammett behavior in the rearrangement of 1,3-cyclopentanediyl radical cations derived from housanes through structural effects on conformational control.

The electron-transfer-catalyzed rearrangement of the housanes 1 affords regioselectively the two cyclopentenes 2 and 3 by 1,2-migration of a group at the methano bridge. Appropriate ring annelation in the intermediary cyclopentane-1,3-diyl radical cation 1(*+) changes the stereochemical course of the rearrangement from complete stereoselectivity (stereochemical memory) for the structurally simple housane 1b to partial loss of stereoselectivity through competing conformational interconversion for the tricyclic housane 1c. Additional cyclohexane annelation, as in the tetracyclic housane 1a, results in complete loss of stereocontrol through Curtin-Hammett behavior, as substantiated by the viscosity dependence on the product ratio of the rearrangement.

Viscosity dependence of the denitrogenation quantum yield in azoalkane photolysis: experimental evidence for reversible formation of the diazenyl diradical.

[reaction: see text] Experimental evidence is reported for the reversible formation of the singlet diazenyl diradical ((1)DZ), photolytically generated from the structurally elaborate DBH-type azoalkane. Reversiblity of the (1)DZ formation manifests itself through the decrease of the photodenitrogenation quantum yield over a ca. 40-fold viscosity variation (from 0.

On the chemiluminescence in the oxidation of tetravalent uranium to the uranyl ion by dimethyldioxirane.

The reaction of the tetravalent uranium [U(IV)] with dimethyldioxirane (DMD) in strongly acidic water-acetone solutions is accompanied by chemiluminescence (CL) in the visible (Vis) and infra-red (IR) regions. At least three independent reaction pathways are involved in the U(IV)-DMD oxidation: the first entails the non-chemiluminescent oxidation of U(IV) to the uranyl ion (UO(2) (2+)); the second involves the catalytic decomposition of DMD by U(IV) to afford singlet oxygen, as manifested by its characteristic IR-CL; and in the third process, slow Vis-CL (510-540 nm) is emitted, following DMD consumption.

Viscosity-controlled, product-selective rearrangement of the cyclopentane-1,3-diyl radical cation derived from an annelated housane by electron transfer: a case of Curtin-Hammett behavior.

The fractional-power viscosity dependence of the product ratio [2]/[3] approximately eta(alpha(3)-alpha(2)) manifests the different free-volume requirements for the methylene (k(3) approximately eta(alpha)(3)) versus methyl (k(2) approximately eta(alpha)(2)) migrations. The syn/anti-conformational changes (k(1), k(-1)) in the radical cation 1(*+) proceed faster than the structural transformations (k(2), k(3)), which constitutes the first Curtin-Hammett case in radical-cation rearrangements.

Photochemical versus thermal skeletal inversion: viscosity-controlled photodenitrogenation of a bridgehead-substituted DBH-type azoalkane and thermal syn-to-anti housane isomerization.

Upon photochemical nitrogen extrusion, azoalkane 1b yields the diastereomeric housane products syn-2b (inversion) and anti-2b (retention), whose syn-to-anti isomerization (k(iso)) is observable already at room temperature. From the similar viscosity dependence of the k(inv)/k(ret) data for the photolysis of the azoalkane 1b and the k(iso) data for the thermolysis of the housane syn-2b, we conclude that these skeletal inversions are subject to frictional impediments and these determine the stereoselectivity.