Alana Hudson

Cobalt, Linac, or Other: What Is the Best Solution for Radiation Therapy in Developing Countries?

The international growth of cancer and lack of available treatment is en route to become a global crisis. With >60% of cancer patients needing radiation therapy at some point during their treatment course, the lack of available facilities and treatment programs worldwide is extremely problematic. The number of deaths from treatable cancers is projected to increase to 11.5 million deaths in 2030 because the international population is aging and growing. In this review, we present how best to answer the need for radiation therapy facilities from a technical standpoint. Specifically, we examine whether cobalt teletherapy machines or megavoltage linear accelerator machines are best equipped to handle the multitudes in need of radiation therapy treatment in the developing world.

Implementation of a high-dose-rate brachytherapy program for carcinoma of the cervix in Senegal: a pragmatic model for the developing world.

West Africa has one of the highest incidence rates of carcinoma of the cervix in the world. The vast majority of women do not have access to screening or disease treatment, leading to presentation at advanced stages and to high mortality rates. Compounding this problem is the lack of radiation treatment facilities in Senegal and many other parts of the African continent. Senegal, a country of 13 million people, had a single (60)Co teletherapy unit before our involvement and no brachytherapy capabilities. Radiating Hope, a nonprofit organization whose mission is to provide radiation therapy equipment to countries in the developing world, provided a high-dose-rate afterloading unit to the cancer center for curative cervical cancer treatment. Here we describe the implementation of high-dose-rate brachytherapy in Senegal requiring a nonstandard fractionation schedule and a novel treatment planning approach as a possible blueprint to providing this technology to other developing countries.

Evaluation of target and cardiac position during visually monitored deep inspiration breath-hold for breast radiotherapy

A low-resource visually monitored deep inspiration breath-hold (VM-DIBH) technique was successfully implemented in our clinic to reduce cardiac dose in left-sided breast radiotherapy. In this study, we retrospectively characterized the chest wall and heart positioning accuracy of VM-DIBH using cine portal images from 42 patients. Central chest wall position from field edge and in-field maximum heart distance (MHD) were manually measured on cine images and compared to the planned positions based on the digitally reconstructed radiographs (DRRs). An in-house program was designed to measure left anterior descending artery (LAD) and chest wall separation on the planning DIBH CT scan with respect to breath-hold level (BHL) during simulation to determine a minimum BHL for VM-DIBH eligibility. Systematic and random setup uncertainties of 3.0 mm and 2.6 mm, respectively, were found for VM-DIBH treatment from the chest wall measurements. Intrabeam breath-hold stability was found to be good, with over 96% of delivered fields within 3 mm. Average treatment MHD was significantly larger for those patients where some of the heart was planned in the field compared to patients whose heart was completely shielded in the plan (p < 0.001). No evidence for a minimum BHL was found, suggesting that all patients who can tolerate DIBH may yield a benefit from it. PACS number(s): 87.53.Jw, 87.53.Kn, 87.55.D.A low‐resource visually monitored deep inspiration breath‐hold (VM‐DIBH) technique was successfully implemented in our clinic to reduce cardiac dose in left‐sided breast radiotherapy. In this study, we retrospectively characterized the chest wall and heart positioning accuracy of VM‐DIBH using cine portal images from 42 patients. Central chest wall position from field edge and in‐field maximum heart distance (MHD) were manually measured on cine images and compared to the planned positions based on the digitally reconstructed radiographs (DRRs). An in‐house program was designed to measure left anterior descending artery (LAD) and chest wall separation on the planning DIBH CT scan with respect to breath‐hold level (BHL) during simulation to determine a minimum BHL for VM‐DIBH eligibility. Systematic and random setup uncertainties of 3.0 mm and 2.6 mm, respectively, were found for VM‐DIBH treatment from the chest wall measurements. Intrabeam breath‐hold stability was found to be good, with over 96% of delivered fields within 3 mm. Average treatment MHD was significantly larger for those patients where some of the heart was planned in the field compared to patients whose heart was completely shielded in the plan (p < 0.001). No evidence for a minimum BHL was found, suggesting that all patients who can tolerate DIBH may yield a benefit from it. PACS number(s): 87.53.Jw, 87.53.Kn, 87.55.D‐

A Novel Translational Total Body Irradiation Technique

A novel translating bed total body irradiation treatment delivery technique that employs dynamically shaped beams is presented. The patient is translated along the floor on a moving bed through a stationary radiation beam and the shape of the radiation beam is changed dynamically as the patient is moved through it, enabling compensation for local variations in patient thickness and tissue density. We demonstrate that the use of dynamically shaped beams results in greatly improved dose homogeneity compared with standard techniques, which use a single static beam shape. Along a representative dose profile through the lungs of a mock-human body, the maximum range of dose deviation from the average is 5.6% (from +2.7% to -2.9%) for the dynamic beam technique compared with 12.8% (from +3.6% to -9.2%) for the static beam technique. A novel, dual-interlock system that prevents bed motion when the radiation beam is stopped and stops the radiation beam when the bed motor is stopped has also been developed. The dual-interlock not only enhances the safety of the treatment but also ensures accuracy in the delivery of the treatment.

A framework for the implementation of new radiation therapy technologies and treatment techniques in low-income countries

We present a practical, generic, easy-to-use framework for the implementation of new radiation therapy technologies and treatment techniques in low-income countries. The framework is intended to standardize the implementation process, reduce the effort involved in generating an implementation strategy, and provide improved patient safety by reducing the likelihood that steps are missed during the implementation process. The 10 steps in the framework provide a practical approach to implementation. The steps are, 1) Site and resource assessment, 2) Evaluation of equipment and funding, 3) Establishing timelines, 4) Defining the treatment process, 5) Equipment commissioning, 6) Training and competency assessment, 7) Prospective risk analysis, 8) System testing, 9) External dosimetric audit and incident learning, and 10) Support and follow-up. For each step, practical advice for completing the step is provided, as well as links to helpful supplementary material. An associated checklist is provided that can be used to track progress through the steps in the framework. While the emphasis of this paper is on addressing the needs of low-income countries, the concepts also apply in high-income countries.

165: A Practical Energy Modulation Technique to Avoid Enucleation for Advanced Periocular Cancers

Purpose: Consider a 2x2x1.5 cm basal cell cancer invading right medial canthus periocular embryonic fusion plane. Usual techniques fail: an irregular PTV 4x4x2.5 cm deep, a concave surface, a deep tumour, and adjacent ocular structures. Oculoplastics/Mohs risk enucleation. Electrons with an internal eye shield require bolus and limit energy to 9 MeV. High energy conformal RT risks medial retinal damage. Systemic agents may palliate but do not cure. We describe low energy electron RT (e) with an orthovoltage (ortho) bump. “Bump” modulates energy by replacing some e-dose with ortho to increase surface dose and optimize dose distribution. Bump applies to any anatomic location to a depth of 2-3 cm. Bump can use ewith a tungsten eye shield and ortho for maximal eye-sparing. With orbit invaded, morbidity follows. Radiotherapy may be the best eyepreserving option. Methods and Materials: Central-axis dose calculation using measured % depth dose were compared with central and offcentral axis dose calcs using kVDoseCalc, a dose engine validated in kV cone-beam and ortho therapy; and Monte Carlo for eoffaxis dose calc. We compare conformal RT, arcs, and bump, for periocular cancer cases. We compared central axis data for a 4x4 cm field with: 1) 9 MeV alone; 2) 9 MeV with 0.7 cm custom wax; 3) 9 MeV, 80% of dose, 100 kV DXR bump, SSD 10 cm, 20% of dose; 4) 9 MeV, 80% of dose, 200 kV DXR bump, SSD 50 cm, 20% of dose. Patients treated at our institution in 10 or 20 treatments received 8 or 16 electron treatments (prescribed to account for REB of electrons) and 2 or 4 photons treatments, for a total dose of 45 Gy in 10 fractions, or 50 Gy in 20 fractions. Results: For the case above tables based on measured dose give: Surface dose (1) 86%; (2) 90%; (3) 100%; (4) 94% Dmax (100%) (1) 2.0 cm; (2) 1.3 cm; (3) 2.0 cm; (4) 2.0 cm Dose @ 2.7 cm (1) 89%; (2) 58%; (3) 87%; (4) 91% Surface and depth refer to skin surface. Dose is normalized: Dmax = 100%. REB and geometry are not included. Comparing dynamic conformal ARCs, VMAT, electrons +/bolus or tantalum mesh, and bump show the benefits of 9 MeV with 100-200 kV bump. Dose drop off is swift at ~40%/cm beyond D90%. Dose spares eye. Low SSD, low kV bump results in best homogeneity and surface dose; high kV bump gives best dose at depth. Patients can be scanned with a 3D printer wax replica eye shield to reduce artifact and enable accurate dose calculation. Actual patient results are illustrated with isodose distributions; for three clinical cases, the dose above 80% to retina was 2.5 cc for conformal treatment, 1.0 cc for dynamic conformal arc and < 0.5 cc for bumps, demonstrating excellent shielding for the bump technique. Conclusions: Energy modulation with ortho and electrons can result in improved dose distribution. Benefits include: increased treatment depth, improved dose homogeneity, no bolus, increased shield effectiveness, and reduced penumbra; important when treating near the eye.

Sci-Thur PM - Colourful Interactions: Highlights 08: ARC TBI using Single-Step Optimized VMAT Fields

Purpose: This work outlines a new TBI delivery technique to replace a lateral POP full bolus technique. The new technique is done with VMAT arc delivery, without bolus, treating the patient prone and supine. The benefits of the arc technique include: increased patient experience and safety, better dose conformity, better organ at risk sparing, decreased therapist time and reduction of therapist injuries. Methods: In this work we build on a technique developed by Jahnke et al. We use standard arc fields with gantry speeds corrected for varying distance to the patient followed by a single step VMAT optimization on a patient CT to increase dose inhomogeneity and to reduce dose to the lungs (vs. blocks). To compare the arc TBI technique to our full bolus technique, we produced plans on patient CTs for both techniques and evaluated several dosimetric parameters using an ANOVA test. Results and Conclusions: The arc technique is able reduce both the hot areas to the body (D2% reduced from 122.2% to 111.8% p<0.01) and the lungs (mean lung dose reduced from 107.5% to 99.1%, p<0.01), both statistically significant, while maintaining coverage (D98% = 97.8% vs. 94.6%, p=0.313, not statistically significant). We developed a more patient and therapist-friendly TBI treatment technique that utilizes single-step optimized VMAT plans. It was found that this technique was dosimetrically equivalent to our previous lateral technique in terms of coverage and statistically superior in terms of reduced lung dose.

SU-F-P-02: A New Framework for the Equipment Donation Program

PURPOSE The Equipment Donation Sub-Committee has developed a new, formalized process for both donating and requesting donated equipment. The purpose of the framework is to increase the likelihood that available, working-order equipment is put to good use at functional, deserving clinics. METHODS A consensus approach was used to develop a fresh approach to equipment donation and requesting equipment for donation. The committee developed specific forms for people who wish to donate equipment and for those who are seeking specific donated equipment. The forms include a summary of the equipment as well as questions designed to inform the committee with respect to the condition of the equipment, the resources of the clinic that is requesting equipment, the specific need for requested equipment, whether or not additional components or software are required for its proper functioning, and ancillary considerations such as regulatory and import rules that may affect the donation. Following submission of the forms the equipment, or request, are entered into a database, reviewed by the committee, and compatibility matches are proposed. RESULTS This is the first time a formalized, consensus-based approach has been used by the Equipment Donation Sub-Committee. Forms are available on the aapm.org website and should be emailed to equipment.donation@aapm.org. The first applications using this new process will be summarized and discussed. CONCLUSION We anticipate this process will facilitate and expedite the process of equipment donation and will serve as a tool for assessing and improving the program.

Poster — Thur Eve — 39: Feasibility of Commissioning HybridArc with the Delta 4 two plane diode phantom: comparisons with Gafchromic Film.

HybridArc is a relatively novel radiation therapy technique which combines optimized dynamic conformai arcs (DCA) and intensity modulated radiation therapy (IMRT). HybridArc has possible dosimetry and efficiency advantages over stand alone DCA and IMRT treatments and can be readily implemented on any linac capable of DCA and IMRT, giving strong motivation to commission the modality. The Delta4 phantom (Scandidos, Uppsala, Sweden) has been used for IMRT and VMAT clinical dosimetric verification making it a candidate for HybridArc commissioning. However the HybridArc modality makes use of several non co-planar arcs which creates setup issues due to the geometry of the Delta4, resulting in possible phantom gantry collisions for plans with non-zero couch angles. An analysis was done determining the feasibility of using the Delta4 fixed at 0° couch angle compared with results obtained using Gafchromic ETB2 film (Ashland, Covington Kentucky) in an anthropomorphic phantom at the planned couch angles. A gamma index analysis of the measured and planned dose distributions was done using Delta4 and DoseLab Pro (Mobius Medical Systems, Houston Texas) software. For both arc and IMRT sub-fields there is reasonable correlation between the gamma index found from the Delta4 and Gafchromic film. All results show the feasibility of using the Delta4 for HybridArc commissioning.

Poster — Thur Eve — 49: Unexpected Output Drops: Pitted Blackholes in Tungsten

During the daily measurement of radiation output of a 6 MV beam on a Varian Trilogy Linear Accelerator the output dropped below 2% and initiated a call to action by physics to determine the cause. Over the course of weeks the cause of the issue was diagnosed to be a defect in the target, resulting in a drop in output and an asymmetry of the beam. Steps were taken to return the machine to clinical service while parts were on order while ensuring the safety of patient treatment. The machine target was replaced and the machine continues to operate as expected. A drop in output is usually a rarity and a defect in the target is possibly more rare. This experience demonstrated the importance of routine QC measurement, recording and analyzing daily output and symmetry values. In addition, this event showcased the importance of a multi-disciplinary approach in a high-pressure situation to effectively troubleshoot unique events to ensure consistence, safety patient treatment.