J.A. Santos-Miranda

Feasibility of integrating a multi-camera optical tracking system in intra-operative electron radiation therapy scenarios

Intra-operative electron radiation therapy (IOERT) combines surgery and ionizing radiation applied directly to an exposed unresected tumour mass or to a post-resection tumour bed. The radiation is collimated and conducted by a specific applicator docked to the linear accelerator. The dose distribution in tissues to be irradiated and in organs at risk can be planned through a pre-operative computed tomography (CT) study. However, surgical retraction of structures and resection of a tumour affecting normal tissues significantly modify the patients geometry. Therefore, the treatment parameters (applicator dimension, pose (position and orientation), bevel angle, and beam energy) may require the original IOERT treatment plan to be modified depending on the actual surgical scenario. We propose the use of a multi-camera optical tracking system to reliably record the actual pose of the IOERT applicator in relation to the patients anatomy in an environment prone to occlusion problems. This information can be integrated in the radio-surgical treatment planning system in order to generate a real-time accurate description of the IOERT scenario. We assessed the accuracy of the applicator pose by performing a phantom-based study that resembled three real clinical IOERT scenarios. The error obtained (2 mm) was below the acceptance threshold for external radiotherapy practice, thus encouraging future implementation of this approach in real clinical IOERT scenarios.

Surgery and intraoperative electron radiotherapy in recurrent or metastatic oligotopic extrapelvic cancer: Long-term outcome

PURPOSE To evaluate the feasibility and long-term outcome of surgery combined with intraoperative electron radiotherapy (IOERT) as rescue treatment in patients with recurrent and/or metastatic oligotopic extrapelvic cancer. METHODS AND MATERIALS From April 1996 to April 2010, we treated 28 patients using 34 IOERT procedures. The main histopathology findings were adenocarcinoma (39%) and squamous cell carcinoma (29%). The original cancer sites were gynecologic (67%), urologic (14%) and colorectal (14%). The location of recurrence was the para-aortic region in 53.5% of patients. RESULTS Median follow-up was 39 months (1-84 months), during which time 14% of patients experienced local recurrence and 53.5% developed distant metastasis. Overall survival at 2 and 5 years was 57% and 35% respectively. At the time of the analysis, 13 patients were alive, 6 for more than 55 months of follow-up. Local control was not significantly affected by the following histopathologic characteristics of the resected surgical specimen: number of fragments submitted for pathology study (1 to >6), maximal tumor dimension (≤ 2 to ≥ 6 cm), rate of involved nodes (0-100%) and involved resection margin (local recurrence 23% vs 7%; p = 0.21). Local recurrence was significantly affected by microscopic cancer in more than 50% of specimen fragments (38% vs 9%, p = 0.02). CONCLUSIONS IOERT for recurrence of oligotopic extrapelvic cancer increased long-term survival in patients with controlled cancer and appears to compensate for some adverse prognostic features in local control. Individualized treatment strategies for this heterogeneous category of patients with recurrent cancer will make it possible to optimize results.

Feasibility assessment of the interactive use of a Monte Carlo algorithm in treatment planning for intraoperative electron radiation therapy.

This work analysed the feasibility of using a fast, customized Monte Carlo (MC) method to perform accurate computation of dose distributions during pre- and intraplanning of intraoperative electron radiation therapy (IOERT) procedures. The MC method that was implemented, which has been integrated into a specific innovative simulation and planning tool, is able to simulate the fate of thousands of particles per second, and it was the aim of this work to determine the level of interactivity that could be achieved. The planning workflow enabled calibration of the imaging and treatment equipment, as well as manipulation of the surgical frame and insertion of the protection shields around the organs at risk and other beam modifiers. In this way, the multidisciplinary team involved in IOERT has all the tools necessary to perform complex MC dosage simulations adapted to their equipment in an efficient and transparent way. To assess the accuracy and reliability of this MC technique, dose distributions for a monoenergetic source were compared with those obtained using a general-purpose software package used widely in medical physics applications. Once accuracy of the underlying simulator was confirmed, a clinical accelerator was modelled and experimental measurements in water were conducted. A comparison was made with the output from the simulator to identify the conditions under which accurate dose estimations could be obtained in less than 3 min, which is the threshold imposed to allow for interactive use of the tool in treatment planning. Finally, a clinically relevant scenario, namely early-stage breast cancer treatment, was simulated with pre- and intraoperative volumes to verify that it was feasible to use the MC tool intraoperatively and to adjust dose delivery based on the simulation output, without compromising accuracy. The workflow provided a satisfactory model of the treatment head and the imaging system, enabling proper configuration of the treatment planning system and providing good accuracy in the dosage simulation.

RADIANCE—A planning software for intra-operative radiation therapy

In the last decades accumulated clinical evidence has proven that intra-operative radiation therapy (IORT) is a very valuable technique. In spite of that, planning technology has not evolved since its conception, being outdated in comparison to current state of the art in other radiotherapy techniques and therefore slowing down the adoption of IORT. RADIANCE is an IORT planning system, CE and FDA certified, developed by a consortium of companies, hospitals and universities to overcome such technological backwardness. RADIANCE provides all basic radiotherapy planning tools which are specifically adapted to IORT. These include, but are not limited to image visualization, contouring, dose calculation algorithms—Pencil Beam (PB) and Monte Carlo (MC), DVH calculation and reporting. Other new tools, such as surgical simulation tools have been developed to deal with specific conditions of the technique. Planning with preoperative images (preplanning) has been evaluated and the validity of the system being proven in terms of documentation, treatment preparation, learning as well as improvement of surgeons/radiation oncologists (ROs) communication process. Preliminary studies on Navigation systems envisage benefits on how the specialist to accurately/safely apply the pre-plan into the treatment, updating the plan as needed. Improvements on the usability of this kind of systems and workflow are needed to make them more practical. Preliminary studies on Intraoperative imaging could provide an improved anatomy for the dose computation, comparing it with the previous pre-plan, although not all devices in the market provide good characteristics to do so. DICOM.RT standard, for radiotherapy information exchange, has been updated to cover IORT particularities and enabling the possibility of dose summation with external radiotherapy. The effect of this planning technology on the global risk of the IORT technique has been assessed and documented as part of a failure mode and effect analysis (FMEA). Having these technological innovations and their clinical evaluation (including risk analysis) we consider that RADIANCE is a very valuable tool to the specialist covering the demands from professional societies (AAPM, ICRU, EURATOM) for current radiotherapy procedures.

Does Radiotherapy Have to Justify its Use in Hodgkin's Disease?

In 1902, Pusey performed and published the ® rst treatment with radiotherapy (RT) in a patient with Hodgkin’s disease (HD). Later, Gilbert, in 1931, formulated the need of a systematic plan of irradiation on all affected nodal regions while insisting on the need to achieve remission of all the lesions with the ® rst treatment used. Beginning in the 1950s, Kaplan and the Stanford group, in the megavolt era, de® ned the modern techniques of RT and established the principles of RT planning in HD that are still applicable today (1). In 1994, Lee stated that RT, applied on its own, was still the best treatment for HD in the initial stages (2). More than 50 study series with follow-ups of more than 20 years support this statement (3 ± 8). Nevertheless, in routine practice as well as in the development of protocols and clinical trials, an almost unanimous abandonment of RT as the single treatment in HD is emerging. Combined treatment (CT) is becoming standard practice without, as Gustafsson (9, 10) and Ng & Mauch (11) have recently stated, bibliographic support demonstrating signi® cant improvements in overall survival. The reasons for RT losing ground in initial-stage treatment have been debated and:or, justi® ed on the basis of:

Semi-automatic Segmentation of Sacrum in Computer Tomography Studies for Intraoperative Radiation Therapy

Intra-Operative Radiation Therapy (IORT) is a technique that combines surgery and adjuvant radiation. It is applied directly to a post-resected tumor bed by means of a specific applicator docked to the linear accelerator. IORT’s primary purpose is to reduce local cancer recurrence. Separating healthy tissues from the tumor bed is essential in order to maximize treatment efficacy and to avoid damage to organs at risk. Current image segmentation during planning procedures is done manually, using computed tomography studies, by an expert radiation oncologist. This procedure can be time consuming. The authors present an automated procedure that would expedite the process of segmentation, specifically tested in rectal cancer cases where the sacrum is the area at risk. A segmentation algorithm was developed based on the creation of an averaged image (template) that was manually segmented. The algorithm geometrically transforms template segmentation by registering it to the input images. Preliminary results demonstrate the feasibility of the proposed approach.

Optical Tracking System Integration into IORT Treatment Planning System

Intra-Operative Radiation Therapy (IORT) is a technique that combines surgery and adjuvant radiation directly applied to a post-resected tumor bed by means of a specific applicator docked to the linear accelerator. An IORT Treatment Planning System (TPS) allows radiation oncologists to plan the treatment using computed tomography (CT) images of the patients. The integration of an optical tracking system into the IORT scenario would allow guiding the radiation applicator according to the planned treatment. In this paper the complete integration of an optical tracking system into the TPS and the experimental set-up in the real IORT scenario is described, showing the feasibility of applicator guidance in IORT procedures.