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Programme implementation
Radiotherapy
Introduction
The medical physics involvement in the implementation of a radiotherapy program are multi-faceted. Issues that need to be addressed include the design of the facility, specification and selection of equipment, acceptance and commissioning of equipment including software systems, staffing levels and staff training, establishment of a quality assurance programme, compliance with radiation protection and safety regulations, and regular independent auditing of the service.
It is widely acknowledged that the clinical aspects (diagnosis, treatment decision making, indications for treatment and follow-up), as well as the procedures related to the physical and technical aspects of patient treatment, must be carefully controlled and planned to ensure safe, high-quality radiotherapy. More recently, the radiation oncology community has acknowledged that a systematic approach is necessary for all steps within the clinical, safety and technical aspects of radiotherapy programmes.
The medical physics involvement in the implementation of a radiotherapy program are multi-faceted. Issues that need to be addressed include the design of the facility, specification and selection of equipment, acceptance and commissioning of equipment including software systems, staffing levels and staff training, establishment of a quality assurance programme, compliance with radiation protection and safety regulations, and regular independent auditing of the service.
It is widely acknowledged that the clinical aspects (diagnosis, treatment decision making, indications for treatment and follow-up), as well as the procedures related to the physical and technical aspects of patient treatment, must be carefully controlled and planned to ensure safe, high-quality radiotherapy. More recently, the radiation oncology community has acknowledged that a systematic approach is necessary for all steps within the clinical, safety and technical aspects of radiotherapy programmes.
Site planning
Planning for a new radiotherapy facility requires a systematic approach. Therefore, a master plan for the construction of a radiotherapy facility is required. Such a plan would incorporate information on the environmental, legal, technical and professional aspects related to developing a concept plan for the establishment of a radiotherapy service.
Legal issues include the right to the site and the regulatory infrastructure to support the safety of the radiotherapy programme. Environmental issues could include geotechnical surveys to confirm flood lines, earthquake zones and ground conditions, e.g. high water tables and soil characteristics. Technical issues include facility design, consideration of electrical and fire services, and the overall risk assessment of the project. Provision of services for both brachytherapy and external beam radiotherapy should be addressed. Professional aspects include a plan for the education and training of staff prior to the arrival of radiotherapy equipment. Time frames for completing each aspect of the master planning process should be developed.
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Radiation shielding
The safety of patients, staff and the general public is a primary consideration in the implementation of a radiation treatment programme. If not properly managed, the radiation sources used in radiotherapy have the potential to injure those within or in the proximity of the facility. Radiation safety has two primary components: an intrinsically safe facility design with adequate shielding and other physical safety and security measures to prevent accidental and unintended exposure. Radiation safety includes policies and procedures which, when followed, will ensure that the radiation exposure to staff is kept as low as reasonably achievable, social and economic factors being taken into account. In almost all jurisdictions the use of ionising radiation for any purpose, including therapeutic, is tightly regulated. The first step in planning a radiotherapy facility, or changing equipment or practice in an existing facility, is to consult with the appropriate national regulatory authority. Regulations will provide the minimum design criteria, requirements on annual and instantaneous dose equivalent rates, required interlocks, and other radiation safety measures. Next, the architectural design of the facility may then be commenced. The shielding design is both complex and critical. It is essential that a clinically qualified medical physicist competent to perform this calculation is involved, in collaboration with the radiation oncology team. Consideration should be given to the number of daily treatments as well as the different radiotherapy treatment techniques offered at the facility. If there are plans to implement high monitor unit treatment techniques, such as Intensity Modulated Radiation Therapy and Stereotactic Body Radiation Therapy, the recent peer reviewed literature should be referred to during facility design. Construction can only commence once regulatory approval has been obtained.
Equipment selection
Radiotherapy equipment specification and selection should be included in the planning of radiotherapy services. Consideration of the national needs and available resources is required when establishing, maintaining and upgrading a radiotherapy service. The general approach in performing a needs assessment is to examine what is available in the facility, region or country, and compare it to what should be available, considering the particular demand and situation of the catchment area or target group.
Radiotherapy equipment is commonly procured through a tender process. The tender document needs to include the detailed technical, clinical and performance specification of the required equipment. It is the responsibility of the clinically qualified medical physicists to prepare the specification in consultation with other radiotherapy health professionals.
Radiotherapy equipment includes external beam treatment units (linear accelerators, Cobalt 60 machines etc.), immobilisation and positioning devices, dosimetry and quality control equipment, conventional and CT simulators, treatment planning systems (TPS), oncology information systems (OISs) as well as record and verify systems (RVSs), brachytherapy systems and patient imaging systems.
The features of a modern TPS are diverse, including modules for virtual simulation, image registration, target and organ at risk segmentation, interfacing to RVSs and OISs, complex photon and electron beam models for dose distribution calculation and inverse planning modules for IMRT and VMAT. A specification for a TPS needs to carefully consider that all these components are aligned with the department’s needs.
The RVS and OIS need to be seamlessly integrated with the treatment units and the TPSs. Additional OIS functionality including image review, clinical assessment, dosimetry records, scheduling of activities and alerts, and electronic patient records and appointments need to be considered.
For selection and specification of a CT simulator, consideration needs to be given to the integrated movable or fixed laser system to enable patient set- and mark-up and the flat radiolucent couch top with indexing appropriate to the immobilization and positioning devices as needed.
Additional space could be needed for the preparation of patient treatment devices and storage. This could include the following: a manual or automated hot wire cutter, low melting point alloy blocks, consumable supplies of foam blocks, an alloy dispenser, a fume cupboard, lead sheets, bolus material (wax and/or gel), a water heating bath, consumable supplies of immobilisation thermoplastics, supplies of vacuum bags and a compression pump.
Staffing levels
The IAEA recommends that it is necessary to define overall staffing requirements, including those of medical physicists, to provide appropriate radiotherapy services and support efficient and safe care of patients.
Medical physics staffing levels have usually been calculated based on patient numbers or radiotherapy equipment numbers. However, it is now recognised that these simple methods of calculating medical physics staffing levels are not adequate to capture the different case mix and levels of complexity of service amongst radiotherapy centres. An activity-based approach to identify the required staffing levels has been designed by the IAEA. The developed staffing algorithm requires inputs on patient numbers, equipment, complexity of treatment techniques, as well as percentages of time spent on non-clinical responsibilities including teaching, management and research.
External beam radiotherapy techniques
Radiotherapy techniques can be described as two-dimensional (2D), three dimensional conformal (3D CRT) or intensity–modulated radiotherapy (IMRT). 2D radiotherapy involves the planning of treatments based on two dimensional images such as radiographs and information on patient external anatomical references from physical measurements. Dose calculation can be manual or computerized. In 3D CRT, treatment planning is computerized and based on three dimensional CT-based images of the patient. The target is defined in 3D and the beams shaped to conform to the target while avoiding healthy tissues as much as possible. IMRT builds on 3D CRT to improve the conformality of the dose distribution within the target through modulation of the beam intensity.
The WHO and IAEA have defined three different equipment packages of radiotherapy equipment based on the capacity of the health system to deliver a comprehensive package of cancer interventions. These packages with increasing complexity from Package 1 to Package 3 assist health administrators and radiotherapy health professionals in need of assessment for radiotherapy. More information about these packages can be found in the WHO/IAEA publication, “Technical specifications of radiotherapy equipment for cancer treatment”.
Furthermore, when establishing a new EBRT service, consideration needs to be given at an early planning stage as to whether to include a single external beam treatment unit or two . Single machine departments may suffer from being unable to treat patients in the event of machine breakdown and inability to meet an increased demand for services in the future.
To establish a radiotherapy service in an institution, a number of steps should be taken. These include defining the programme scope, developing staffing needs, training, acceptance testing and commissioning of the equipment and developing and implementing a dedicated comprehensive QA programme. The close collaboration and expertise of an appropriately trained multidisciplinary team, including radiation oncologists, medical physicists, and radiation technologists, is a requisite.
A complete understanding of all steps is necessary before one can successfully begin a new programme. It is important to allow sufficient time for medical physics staff to carry out acceptance testing and commissioning. Only radiation oncology departments that have extensive experience with 3D CRT are advised to transition to IMRT. Detailed clinical and imaging protocols need to be developed. Training in IMRT technology for all members of the team is essential prior to the initiation of such a programme. The team members also need to be trained on the actual equipment that they plan to use for IMRT.
HDR Brachytherapy techniques
2D brachytherapy is usually based on planar imaging, treatment plan libraries, point dose prescription and dose reporting. This brachytherapy technique is mainly used for the treatment of gynaecologic cancers. Access to volumetric imaging in the form of CT, MR and ultrasound allows the possibility of 3D brachytherapy treatment planning with volumetric images, contouring of the target and organs at risk, and the possible use of an optimization algorithm to optimize the treatment plan. This allows for a more individualised approach to treatment planning and may reduce treatment toxicity and provide better treatment outcomes, however it is much more resource intensive.
Therefore, the first step in 3D brachytherapy is to consider the resource implications. New equipment, new procedures, additional staff, and training of staff may be required.??Detailed clinical and imaging protocols need to be developed and a thorough commissioning process is required to initiate 3D treatment planning and volume dose reporting in brachytherapy.
Introduction to IGRT into clinical practice
In conventional radiotherapy, set-up uncertainties are reduced through patient immobilization and careful positioning, and internal motion is estimated based on the study of analogous patient populations having in mind that target position and motion varies from patient to patient and from day to day. Portal imaging using the treatment beam can facilitate the identification of patient misalignment. However, the target is not always visible on portal images, and the surrounding anatomy can be a poor surrogate for target localisation. Since the 1990s, technological advances have resulted in the use of integrated imaging systems for treatment delivery, leading to the concept of image guided radiotherapy (IGRT). Improvements in treatment accuracy and precision can be achieved with IGRT as documented in literature, based on both phantom and patient studies.
Although there is no uniformly accepted definition as to where conventional verification imaging ends and IGRT begins, there is general agreement that the key features of IGRT are:
(a) The availability of high-quality imaging equipment in the treatment room;
(b) The ability to visualize key anatomical structures, including the target, with the patient in the treatment position, with the main objective being to inform beam placement. Appropriate surrogates may be used for soft tissue positioning (e.g. fiducial markers) and to infer the locations of organs relative to each other;
(c) A protocol to act on the findings. This could be done on-line (i.e. prior to turning on the radiation beam) or off-line (i.e. between fractions).
An IGRT programme should be built on a firm foundation of expertise in 3D CRT performed with portal imaging. Some prerequisites for IGRT are therefore the availability of volumetric imaging for treatment planning, a treatment planning system capable of generating reference images and a treatment machine with an integrated imaging system. A record and verify system is also needed to record, as a minimum, that the planned 3D CRT or IMRT treatment is delivered as prescribed and that the appropriate reference images are available at the treatment unit. Additional human resources are needed to provide an IGRT service owing to the additional complexity in the imaging and treatment process.
The logistical consecutive steps necessary to establish an IGRT programme include the following:
(a) Appointing an IGRT implementation committee;
(b) Defining the scope of the programme, including preparing a structured timeline;
(c) Identifying the necessary equipment, including software;
(d) Considering the possible impact on patient throughput;
(e) Development of a programme budget, by performing market research of IGRT equipment before purchasing equipment;
(f) Developing staffing needs for the programme and hire new staff;
(g) Allowing a reasonable timeline to perform installation, acceptance testing and commissioning;
(h) Training of all personnel involved in the programme;
(i) Developing the necessary guidelines, policies and procedures;
(j) Developing and implementing a comprehensive quality assurance programme for IGRT.