Inter-society standards for the performance of brachytherapy: a joint report from ABS, ACMP and ACRO

Transcription

1 Critical Reviews in Oncology/Hematology 48 (2003) 1 17 Inter-society standards for the performance of brachytherapy: a joint report from ABS, ACMP and ACRO Subir Nag a,, Ralph Dobelbower b, Glenn Glasgow c, Gary Gustafson d, Nisar Syed e, Bruce Thomadsen f, Jeffery F. Williamson g a Arthur G. James Cancer Hospital, The Ohio State University, 300 W. 10th Avenue, Columbus, OH, USA b Medical College of Ohio, Toledo, OH, USA c Loyola University, Maywood, IL, USA d William Beaumont Hospital, Detroit, MI, USA e Long Beach Memorial Hospital, Long Beach, CA, USA f University of Wisconsin, Madison, WI, USA g Washington University, St. Louis, MO, USA Accepted 3 February 2003 Contents 1. Introduction Methods Results Clinical process Indications for brachytherapy Contraindications for brachytherapy Pre-treatment patient preparation Applicator placement Ongoing care of the patient during brachytherapy Applicator removal Post brachytherapy management Equipment Brachytherapy sources Applicators Radiation control and QA equipment Ancillary equipment Facilities Manually afterloaded low dose-rate Remotely afterloaded low dose-rate Remotely afterloaded high dose-rate Brachytherapy program Positional and temporal accuracy Numerical, physical and clinical dose delivery accuracy Safety of the patient, public, staff and institution Quality management program for devices Dose specification for prescription and reporting General procedure for designing an integrated QM system for brachytherapy Pretreatment preparation Applicator insertion Imaging Pre-treatment reviews Source loading Corresponding author. Tel.: ; fax: address: nag.l@osu.edu (S. Nag) /$ see front matter 2003 Elsevier Ireland Ltd. All rights reserved. doi: /s (03)00026-x

2 2 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) Treatment delivery Post treatment safety and QA checks Qualifications of personnel involved in brachytherapy Radiation oncologist Medical physicist Radiation therapists and simulation staff Medical dosimetrist Patient support staff Radiation safety officer Radiation safety/protection/control Reviewers Acknowledgements Appendix A. Terms used in brachytherapy (in alphabetical order) References Biographies Abstract Purpose: The proliferation of various brachytherapy modalities for different anatomical sites necessitates the creation of standards for brachytherapy. Methods: A panel consisting of members of The American Brachytherapy Society (ABS), The American College of Medical Physics (ACMP) and The American College of Radiation Oncology (ACRO) developed standards for the clinical practice and quality assurance (QA) of brachytherapy. These were based upon their clinical experience and a review of the literature. Results: Recommended practice standards are presented for clinical processes, treatment planning, equipment, facilities, QA, dose evaluation, dose specification, dose reporting, the training, and credentialing of personnel, and radiation control/safety/protection. Safe and efficacious performance of brachytherapy requires a highly structured QA program and carefully designed treatment delivery processes, as well as a coordinated effort amongst the team members. Conclusion: Standards for clinical brachytherapy are proposed. Practitioners are encouraged to use these standards to design and implement a consistent and efficacious brachytherapy program Elsevier Ireland Ltd. All rights reserved. Keywords: Brachytherapy; Radioisotope; Treatment guidelines; Standards 1. Introduction The term brachytherapy is derived from brachio, the Greek word meaning short. Brachytherapy is a form of radiotherapy that involves treatment with radioactive sources (usually sealed) in contact with or close to the target tissue. The use of brachytherapy began soon after the discovery of radium by Marie Curie in It was discovered that, due to the rapid decrease in dose with distance, the placement of radioactive materials on the surface or implanted into a tumor had the advantage of giving a high dose of radiation to the target volume and limiting dose to the surrounding healthy tissues. Because the healthy tissues received a lower dose than the tumor, there were fewer clinical side effects from treatment. By selective placement of the radioactive sources, the dose distribution could be manipulated to precisely match the shape of the target. Hence, brachytherapy is a form of conformal radiotherapy in which, because the radiation sources are applied directly to the tumor, inaccuracies of treatment due to patient movement are reduced. Sophisticated technological advances have improved the accuracy of brachytherapy. Despite these advances, brachytherapy is regarded by some as more of an art than a science. Because brachytherapy is based upon the principles of both radiotherapy and surgery and has evolved independently in several parts of the world, many different techniques, treatment regimens, dose specification, and treatment planning methods are used. The American Brachytherapy Society (ABS) has published guidelines for brachytherapy at individual treatment sites [1 17], but not on general brachytherapy. The American Association of Physicists in Medicine (AAPM) has published a number of Task Group reports [18 26] primarily with respect to technical, quality assurance (QA), and other brachytherapy physics issues. Similarly, The American College of Radiology (ACR) has published a series of short reports [27 31] on low dose-rate (LDR) and high dose-rate (HDR) brachytherapy and associated physics practices. Since there is no single document for the performance of general clinical brachytherapy The American College of Radiation Oncology (ACRO) Standards Committee felt that a standard of practice for general clinical brachytherapy was required. To obtain broader input, it collaborated with ABS and American College of Medical Physics (ACMP) to produce this report. This document is unique in that it presents a moderately detailed and comprehensive set of practice standards encompassing all conventional brachytherapy modalities addressing both clinical practice guidelines as well as QA and treatment planning issues while synthesizing previously published guidance. This document specifically excludes systemic brachyther-

3 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) apy, intravascular brachytherapy, use of unsealed sources for brachytherapy, and pulsed-dose-rate brachytherapy. Specific recommendations regarding application of brachytherapy to individual sites may be found in brachytherapy textbooks [32 36] and in the various published ABS recommendations [1 17]. (See Appendix A for terms used in brachytherapy.) 2. Methods A panel consisting of members of ABS, ACMP and ACRO performed a literature review. A set of standards for clinical brachytherapy was formulated based on their literature review and aggregate clinical experience. The comments of other experts in the field (listed in the acknowledgment) was incorporated into revisions of the original draft of these standards. The report was then reviewed by the Board of Chancellors of ACRO and the Boards of Directors of ABS and ACMP and their advice was incorporated in the final report. The definition of the recommendation levels used by the panel is as follows: Shall or Must indicates a requirement to be met to ensure a minimum standard of safety and effectiveness. Should or Recommend indicates an important practice standard, but one that may be modified to fit individual patient needs or local practices provided that safety and effectiveness are not compromised. 3. Results The results of the panel s deliberations and the jointly developed standards for general clinical brachytherapy are presented in the following sections Clinical process The patient, the tumor, and the target volume must be evaluated to determine the suitability for brachytherapy. The patient should have a complete clinical assessment that includes history, physical examination, pathological confirmation of the diagnosis, and staging of the tumor. The clinical characteristics of the tumor, i.e., ulcerating, exophytic, or infiltrative, must be noted. Deeply necrotic or ulcerating lesions are less amenable to control, and infiltrative lesions require large implant margins to encompass the disease with brachytherapy. Consideration as to whether the treatment is potentially curative or palliative is important, and determination of whether brachytherapy is to be used alone or in combination with other modalities is necessary Indications for brachytherapy Brachytherapy can be applied to most anatomical sites of the body. It can be used either alone or, more commonly, as part of a multi-modality approach with external beam radiation therapy (EBRT), surgery, and/or chemotherapy. Commonly, brachytherapy is used with EBRT to locally increase the dose to an area at greatest risk for tumor recurrence, such as the original distribution of gross tumor or to the tumor bed at a surgical resection site. EBRT may be used before brachytherapy to shrink bulky tumors and make the site more amenable to brachytherapy application. EBRT is also used to treat gross or microscopic disease in lymphatics or other tissues not suitable for or disposed to brachytherapy application. Conversely brachytherapy can be used to reduce tumor size or to eradicate gross residual disease before application of EBRT, e.g., for HDR brachytherapy of sarcomas or prostate cancer. Brachytherapy can be used as the only treatment modality in several settings: 1. Localized tumors (e.g., organ confined prostate carcinoma). 2. Palliative indications (to improve efficacy and reduce the overall treatment time and morbidity). 3. Tumors recurrent after EBRT where the dose of radiation should be as anatomically circumscribed as possible to minimize dose to previously irradiated normal tissues. 4. Postoperative treatment of the tumor bed where the region at highest risk for recurrence is within the range that can be encompassed by brachytherapy Contraindications for brachytherapy Brachytherapy is generally not used for the following situations, except in special circumstances: 1. Cases in which the diffuse and extensive nature of the disease precludes an adequate brachytherapy application. 2. Patients with distant metastases or diffuse disease without local palliative indications. 3. Patients not medically suitable for anesthesia (if anesthesia is required for the procedure). 4. Tumors that, with current technology, cannot be adequately encompassed by brachytherapy. 5. Patients who are unable to comprehend or comply with radiation safety requirements Pre-treatment patient preparation Informed consent shall be obtained and documented. A preliminary clinical treatment plan based on the tumor assessment should be developed. The treatment plan evaluation should include determination of the target volume and selection of the most suitable type of brachytherapy (such as permanent seeds versus temporary and intracavitary versus interstitial implants). Other important decisions are the dose-rate method (i.e., LDR versus HDR), the type and amounts of radionuclide to be used, and the best applicator to fit the clinical situation. The definition of the target volume, as with surgery and other site-specific treatment modalities, should take into account the need for an anatomical margin of safety in positioning of the therapeutic device. The nature and complexity of the required patient preparations for the process is also specific to the treatment site and the type of brachytherapy utilized. For example,

4 4 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) 1 17 scheduling brachytherapy procedures should be coordinated with the delivery of the necessary sources, taking into consideration the time necessary for source and applicator preparation and sterilization Applicator placement Applicator placement must be performed by an appropriately trained physician, usually, but not necessarily, a radiation oncologist. In some treatment sites, e.g., episcleral eye plaque treatments, specialized surgical expertise is desirable or necessary. However, the radiation oncologist must be responsible for ensuring that the applicators are positioned so as to achieve the treatment goals. The radiation oncologist should work closely with surgical specialists and should be present during applicator placement. The applicator must be suitable for the clinical circumstance and selected on the basis of the distribution of the disease and the anatomy of the individual patient treatment site. Some instruments used in the process may require special credentialing Ongoing care of the patient during brachytherapy A high standard of medical care of the patient (nutrition, hygiene, infection control, anticoagulation, pain control) should be maintained during brachytherapy. The presence of radiation during brachytherapy should not interfere with delivery of necessary medical care. Some patients (for example, those requiring interstitial brachytherapy of the base of tongue, larynx and/or hypopharynx) may require complex processes such as hyperalimentation, tracheostomy, and enteral support. Other patients who have had complex surgical procedures in conjunction with the brachytherapy may require extensive postoperative management. Radiation safety of the caregivers must be considered during delivery of medical care to the patient Applicator removal Most brachytherapy applicators can be safely and comfortably removed in the patient s room without regional or general anesthesia. Consideration should be given to applicator removal in the operating room if (a) the patient s airway is at risk, (b) extensive bleeding is expected or (c) where adequate pain control cannot be expected. Examples of these cases include base of tongue implants and implants deep within the pelvis, abdomen, chest, or the cranium Post brachytherapy management The patients should receive adequate medications for postoperative comfort, organ function, and avoidance of infections. Instructions should be provided regarding care of the treated site and the affected organs. Radiation safety instructions shall be given to patients with permanent implants. Brachytherapy patients should be followed at regular intervals to assess tumor response and treatment related morbidity. If not directly involved in these exams, the radiation oncologist should be informed of the results of follow-up exams Equipment Only the most basic equipment needed to implement a brachytherapy program (BP) is described here. A more comprehensive list of QA, treatment planning and treatment delivery equipment needed for various types of brachytherapy procedures can be found in Appendix C of the AAPM Task Group 56 report [20] Brachytherapy sources Radionuclides commonly used for brachytherapy are listed in Table 1. All photon-emitting sealed brachytherapy sources used for routine treatments shall have calibrations directly or indirectly traceable to air-kerma strength standards of the National Institute of Standards and Technology (NIST), with the following exceptions. For HDR 192 Ir sources, for which primary air-kerma standards are not available, calibrations shall be traceable to the interim secondary standard recommended by the AAPM TG-56 report or superseding document approved by the AAPM [20]. For 90 Sr eye plaques, calibrations shall be traceable to NISTs absorbed dose-rate standard [37]. Dose calculation engines and tools shall be based upon appropriate single-source dose-rate distributions. For interstitial use of 103 Pd, 125 I, and 192 Ir, critically reviewed dosimetric parameters based upon the TG-43 dose calculation formalism should be used [21]. For 103 Pd and 125 I sources, dose calculations should be based upon recent, source-model specific dose-rate measurements that are traceable to the current NIST standard or Monte Carlo calculations [22].For LDR and HDR 137 Cs and 192 Ir sources, classical isotropic Table 1 Radionuclides commonly used for brachytherapy Nuclide (symbol) Approx. half-life Therapeutic emission Energy (kev) Half value layer Common applications Cesium-137 ( 137 Cs) 30 y Gamma mm of lead Intracavitary Cobalt-60 ( 60 Co) 5.26 y Gamma mm of lead Intracavitary Gold-198 ( 198 Au) 2.7 d Gamma mm of lead Interstitial Iodine-125 ( 125 I) 59.4 d X-ray mm of lead Interstitial Iridium-192 ( 192 Ir) 73.8 d Gamma 340* 3 mm of lead Interstitial/intracavitary Palladium-103 ( 103 Pd) 17 d X-ray mm of lead Interstitial Strontium-90 ( 90 Sr/ 90 Y) 28 y Beta 2280 max Minimal Surface y, years; d, days; *, range: kev.

5 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) point-source or Sievert-integral models using appropriate model parameters can provide acceptable accuracy [38]. A brachytherapy source selected for use must be compatible with the treatment site, technique, and applicators employed. Both the radiation oncologist and physicist must be knowledgeable regarding the source characteristics and the methods used for insertion and treatment planning. Before sources are used to treat patients, they must undergo acceptance testing and periodic QA. Experimental or investigational sources, e.g., those not included in the US NRC or an agreement state Sealed Source and Device Registry or those used under supervision of the food and drug administration (FDA) or an Institutional Review Board (IRB), need not satisfy the requirements outlined above. However, the responsible institution and persons must provide calibration procedures, dosimetry data, and assessment of safety, integrity, and biocompatibility that would normally be assured by meeting these regulatory requirements and recommendations of this report Applicators The radiation oncologist must have a fundamental understanding and knowledge of the function and operation of the selected applicator. The applicator (commercial or custom) should meet standard safety constraints equivalent to FDA guidelines/specifications. Before applicators are used to treat patients, they must undergo acceptance review and periodic QA. The radiation oncologist should verify that all the essential applicator components are available, complete, and functional before beginning placement of the applicator Radiation control and QA equipment Every institution practicing brachytherapy shall maintain a system for measuring source strength with secondary traceability for all source types used in its practice [20]. This standard is discussed in more detail later. Facilities performing brachytherapy shall have available both an ion chamber survey meter for performing quantitative radiation surveys and a Geiger Müller detector for qualitative detection of radiation fields. Such instruments should be calibrated annually against an exposure-rate calibration standard bearing an air-kerma strength calibration indirectly traceable to NIST. For 125 I and 103 Pd brachytherapy, a radiation detector should be available to aid in locating individual seeds. Portable shields, L-blocks, shielded source safes, shielded transport containers, as well as source-handling tools as needed to ensure that exposure to personnel and members of the general public fall below applicable regulatory limits shall be available. Additional safety equipment required by remote afterloaders and other specialized treatment delivery equipment is addressed in the specific sections of this document Ancillary equipment Appropriate imaging (planar radiography, fluoroscopy, computerized tomogram (CT), MRI, ultrasound) should be available to aid in placement of the applicator. Additionally, computer treatment planning capability should be available for all brachytherapy procedures and radionuclides (excluding Sr-90 ophthalmic irradiators) used by the physician at a particular institution. Additional equipment as specified in Appendix C of the Task Group 56 report [20] should also be available Facilities The design and construction of a new facility or the selection of an existing facility for performing brachytherapy depends on the number and types of patients to be treated, the funds available, the level of staffing support, and the experience of the radiation oncologist with the methods of brachytherapy. No single brachytherapy technology can be considered the best for treating all types of cancers and for all anatomic sites. The types and number of brachytherapy technologies selected and the clinical sites to be treated strongly influence the extent and kind of facilities required. Generally, all brachytherapy procedures require the following types of physical plant facilities: 1. A secure room to store and prepare radioactive sources. 2. An operating or procedure room for applicator or source placement. 3. Imaging facilities, e.g., conventional X-ray unit, radiotherapy simulator or CT scanner for therapeutic simulation (applicator and source localization). 4. Resources for performing manual and computer-assisted dose computations, treatment planning and treatment evaluation. 5. A facility dedicated for afterloading the radioactive sources into the patient and housing the patient during irradiation (or use of a designated patient s room in the hospital or medical center). Facilities for treatment of brachytherapy patients fall into two different groups: conventional LDR inpatient-based therapy and outpatient-based fractionated HDR brachytherapy. For both manual and remote afterloading, several excellent references are available for guiding the design process and identifying the necessary and desirable facility specifications [39 42]. All facilities in which radioactive sources are stored or used must satisfy the federally mandated limits that the radiation exposure (called dose equivalent in radiation safety) in adjacent unrestricted areas must be (1) less than 0.02 msv in any hour and (2) less than 1 msv annually to members of the general public exposed to radiation from these procedures [43]. In addition, the annual whole body radiation exposure (dose equivalent) of all occupationally exposed personnel, including the brachytherapist, physicist, and support staff is limited to 50 msv. A storage facility used for receipt, control, storage, preparation for use, and

6 6 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) 1 17 disposal of radioactive sources used in brachytherapy shall consist of a lockable room. The room should be equipped with hand-held radiation detectors and survey meters, an area radiation monitor, a storage safe for the sources, some form of source inventory and use record system, equipment for source calibration, devices for handling and transporting sources safely, appropriate shielding devices (e.g. L-block) and a holding area for preparation of sources for decay or disposal [42,44]. The need for local and structural shielding is determined by the workload (total exposure per week or year from handling and storage of radioactive sources) and the proximity of nearby controlled and uncontrolled areas. In the case of HDR brachytherapy, the remote afterloader, which contains the shielded source, may be secured in the treatment room, eliminating the need for a separate storage facility. The type of procedure room depends both on medical intensity of the procedure and logistic factors. Some brachytherapy procedures need to be performed in hospital type operating rooms that support complex regional and general anesthesia and where necessary medical expertise is readily available. Other brachytherapy procedures have lesser anesthesia, operating equipment, space, and medical expertise requirements. The equipment needed for a brachytherapy procedure suite may vary with the level of complexity and can include: (1) equipment and materials for anesthesia or conscious sedation (controlled monitored analgesia); (2) a suction device; (3) guaranteed electrical power for patient monitoring devices and remote display modules; (4) operating room lights; (5) a scrub area; (6) a procedure table; (7) storage for applicators, medical supplies, and applicator fixation devices. Emergency power and lighting systems usually are required. Imaging for applicator placement and simulation can be performed with devices such as an overhead track-mounted X-ray unit with fluoroscopy, a portable C-arm radiography unit, an ultrasound unit, a CT scanner, or some combination of these devices Manually afterloaded low dose-rate For most current forms of temporary LDR manual brachytherapy, the procedure or operating room need only support insertion of non-radioactive applicators. Radioactive source loading and housing of the patient until implant removal take place in an identified inpatient room. This room must be a controlled area of the hospital and staffed by caretakers who are designated as occupationally exposed workers. These personnel, including nurses, must be appropriately trained in managing the resultant radiation hazards. The entire room occupied by an implant patient shall be considered a controlled area. Room selection should also take into consideration the proximity to and occupancy of surrounding uncontrolled areas as well as the structural integrity of the building needed to support the weight of any required structural or portable shielding. The need for structural or portable shielding shall be carefully assessed before placing a brachytherapy treatment room into service. Portable radiation shields should be used, when possible, for high-energy photon-emitting sources to reduce radiation exposure to personnel handling radioactive sources. Emergency source/applicator removal and handling tools, and a shielded source container shall be available in the patient room during the treatment. For those procedures requiring application of radioactive sources in the operating room, e.g., episcleral eye plaque insertions or 137 Cs needle implants, safety practices and precautions similar to those used in the patient s room shall be implemented which limit exposures to operating room staff, recovery personnel, and members of the general public to legally acceptable levels during source transport, sterilization, and insertion Remotely afterloaded low dose-rate Remotely afterloaded LDR facilities usually consist of a hospital room modified to house the LDR device. In addition to the manual brachytherapy requirements described above, such rooms require an independent radiation detector, a redundant patient/nurse communication system, a remote control unit, a door interlock to control the insertion and retraction of radioactive sources, visual and audible device status indicators, and an emergency container for the sources [45] Remotely afterloaded high dose-rate By contrast high radiation dose-rates around HDR units require a structurally shielded vault, unless patients are placed in specially designed locally shielded enclosure. HDR vault wall thicknesses depend on the vault size, the location of the HDR unit in the vault, the type of source, the expected workload as well as the proximity and expected occupancy of surrounding controlled and uncontrolled areas [18,39,40,44,46]. Generally, a concrete wall thickness of cm has been found to be adequate to shield a 370 GBq (10 Ci) 192 Ir source [39,40]. In the United States, regulations require an HDR vault to have all the features previously described for an LDR facility, with the additional requirement of a patient viewing system. An HDR brachytherapy facility can be a simple, intermediate, or dedicated facility. A simple facility consists of an HDR unit in a vault that is shared with an existing megavoltage external beam treatment unit. This cost-effective arrangement is satisfactory if only a few patients are treated weekly. The insertion is performed in a nearby procedure room, the imaging is performed in a simulator near the vault, and the patient is then moved to the vault for treatment. An intermediate HDR facility consists of a dedicated treatment vault, which can be used both for applicator insertion (depending on medical resources needed) and treatment itself. Often it is equipped as a minor procedure or operating room, which minimizes the need to transport the patient from a separate procedure/or room after applicator insertion. An intermediate vault usually lacks a dedicated imaging system, requiring the patient to be moved to the simulator room between applicator insertion and treatment.

7 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) An intermediate level treatment facility is a cost-effective means of increasing throughput when transporting the patient from one room to another does not compromise implant positioning or geometry. In a dedicated HDR facility, the vault is also a fully equipped operating room and has a dedicated imaging device, obviating the need to transfer the patient from one procedure table to another. In these cases, the imaging system may be a digital radiography device, such as the Integrated Brachytherapy Unit (Nucletron Corporation, Columbia, MD), which is designed to automate the treatment planning process or a dedicated CT scanner [47,48]. Another option, which may appeal to institutions with multiple, geographically separated treatment facilities, is a mobile HDR unit that can be transported between facilities. Mobile facilities could be simple (requiring the HDR unit to be moved into a shared treatment vault at each facility), intermediate (the unit is transported in a shielded vehicle which serves as the dedicated procedure room/treatment vault), or complex (the vehicle contains a dedicated imaging system and more complete OR facilities) Brachytherapy program The central goal of the BP is to realize accurately the radiation oncologist s clinical intent for each brachytherapy procedure in a manner that is safe, consistent with limitations of the available resources, and in compliance with applicable standards. In this approach, assuring the quality or accuracy of each task in the treatment planning and delivery process is an essential component of the overall system of planning and administering brachytherapy [19 21,49 52]. An adequate BP has three broad components: 1. Consultation between the radiation oncologist and the medical physicist is meant to assure optimal management of the individual patient s treatment. Selection of the treatment modality, imaging modalities, and ancillary equipment are important considerations. The radiation oncologist prescribes the dose for the treatment, and the medical physicist assists in selecting methods of dose specification, planning, and delivery. The panel emphasizes that a successful BP is not just a physics program, but rather a team effort requiring close collaboration among the physicist, physicians, and other supporting staff. 2. A quality management (QM) program that ensures correct functioning of each device (sources, applicators, computer-assisted planning programs, etc.) and the correct integration of physics supervision into the treatment delivery process. 3. A well-designed treatment delivery program that will ensure an accurate and safe application of the radioactive sources. To achieve the last, a well-organized and appropriately staffed treatment planning and delivery process is required, which must be designed to deliver an accurate, clinically efficacious treatment while ensuring patient safety, cost effectiveness, physician convenience, and efficient patient throughput. To develop a BP that addresses both device function and human factors requires that clinical goals be identified and translated into reality. Every brachytherapy procedure (here procedure points to a specific treatment) consists of an implant design and evaluation process in which the distribution of radioactive sources and the treatment times necessary to administer the prescribed dose distribution are derived, which is followed by the treatment delivery process itself. The radiation oncologist and radiation physicist shall work together to assure accurate treatment delivery meaning that the intended sources are delivered to their intended positions within the correct applicator, and remain there for the correct length of time. Achievement of this goal assumes that the manual or computer-assisted dose calculations correctly predict the treatment times and source positions needed to realize the radiation oncologist s written directive. It also requires that sources and devices have the properties assumed by the design process, and that the applicators and sources are positioned accurately with respect to the target tissue. To assure treatment delivery accuracy, individual QM checks and measurements should be designed to satisfy the endpoints of positional and temporal accuracy, numerical, physical and clinical dose delivery accuracy and safety of the patient, public, staff, and institution Positional and temporal accuracy Temporal accuracy, in the case of removable implants, is achieved if each radioactive source or single-source dwell position remains at its intended location for the time specified by the implant design process within a margin of 2% [50,51]. This tolerance governs the design of tests and QA procedures to ensure that manually afterloaded sources are removed upon completion of dose delivery. It also defines the minimum performance specification for remote afterloader timers, for which the AAPM recommends a tighter 1% accuracy tolerance [25]. Positional accuracy is achieved if the intended sources or dwell position sequence is delivered to the correct location in the applicator within 2 mm [50,51] relative to the source location prescribed directly or indirectly by the radiation oncologist. This tolerance governs tests of coincidence between radiographic markers and the actual radioactive source for each applicator system. While some brachytherapy devices can achieve better positional accuracy under specified conditions, the panel believes that 2 mm is a clinically more realistic and generally achievable tolerance than the 1 mm tolerance endorsed by AAPM for remote afterloading devices [20,25]. The 2 mm positional accuracy target is not a practical criterion for assessing accuracy of applicator location relative to anatomic landmarks or structures. A single tolerance limit for the spatial position of the applicator relative to the anatomy cannot be given. Rather, the applicator or sources

8 8 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) 1 17 should be positioned with sufficient accuracy to meet the dose prescription criteria Numerical, physical and clinical dose delivery accuracy Numerical accuracy of a computer-assisted dose calculation is assessed by comparing its output to independent dose calculations based upon the same algorithm and the input data. A tolerance of 2% should be used for numerical accuracy checks [50,51], compared to 3% recommended by AAPM Task Group 40 [25]. The term, physical dose delivery accuracy, refers to agreement between calculated dose and dose actually delivered under idealized conditions. It is realized if the predicted dose and actual dose absorbed by the medium are equal at reference points specified without positional error relative to the applicator. Physical dose delivery accuracy, for which a tolerance of 6% should be used, essentially specifies the accuracy of single-source dose distributions in homogeneous water. The panel identified 6% as the lowest level of uncertainty, which can be achieved by most source types given currently available dosimetry methods [53]. Physical dose delivery accuracy is influenced by source calibration accuracy, the accuracy of the dose calculation algorithm, and the appropriateness of any user-selected dosimetric parameters. Clinical dose delivery accuracy denotes the agreement between calculated dose and dose actually administered to anatomically defined reference points or surfaces. Assessment of clinical accuracy is difficult because localizing the position of the treatment applicator relative to anatomic landmarks, the ability to image relevant anatomy, and the confounding effects of tissue deformation during the implant are all highly dependent on the implant site and technique used. However, if assessment of applicator placement shows that the prescribed dose cannot be delivered to the target volume with less than 20% deviation from the prescribed dose, then a reassessment of the procedure is required and the following options should be considered prior to initiating therapy: 1. Repositioning of the applicator or sources to fulfill the written directive requirements. 2. Adjustment of the written directive. 3. Aborting the procedure. The methods used to assess clinical accuracy are highly procedure-type dependent. Assessment should occur upon completion of implant imaging or whenever applicator displacement is suspected. The 20% criterion was identified by the panel as a tolerance that most good-quality implant procedures could satisfy, while excluding such phenomena as normal applicator movement. To our knowledge, previously published guidance documents do not address clinical dose delivery accuracy Safety of the patient, public, staff and institution Safety of the public and health care personnel involves controlling radiation exposure of staff and members of the public, insuring the adequacy of the facility shielding barriers, and maintaining control of all radiation sources. Patient safety is achieved by minimizing the risk of catastrophic treatment delivery errors associated with device malfunctions or human errors that may occur during the brachytherapy procedure. Institutional safety is achieved by ensuring that legal and regulatory procedures are strictly followed Quality management program for devices Each brachytherapy practice shall have a QM program for radioactive sources, applicators, remote afterloading devices, treatment accessories, and QM test equipment that adheres to the recommendations of section VI of AAPM s Task Group report 56, Code of practice for brachytherapy physics [20]. The written program should include protocols for the tests needed for initial acceptance testing and commissioning of all equipment, as well as for the periodic daily/each use, quarterly, and annual QM check frequencies recommended by TG-56. According to TG-56, each institution shall maintain the capacity to measure (usually a re-entrant chamber calibrated by an Accredited Dosimetry Calibration Laboratory (ADCL) within 2 years) source strength with indirect traceability to the appropriate NIST primary standard. All vendor-supplied calibrations shall be verified using the above instruments. The recommendations of TG-56 should be followed regarding frequency and fraction of sources to be calibrated. Until such time as a primary standard of air-kerma strength is available for high-intensity 192 Ir sources, either the interim secondary standard recommended by TG-56 [54] or a well chamber calibrated at an ADCL should be used. For other brachytherapy sources lacking primary standards, the recommendations of the AAPM [20] should be followed. When using experimental brachytherapy sources lacking calibration standards to treat human subjects, the physicist is responsible for performing appropriate source strength measurements derived from available primary standards. A QM program for computerized and manual treatment planning systems shall be implemented. At a minimum, this program must confirm accuracy of implant geometry reconstruction tools, accuracy of the dose calculation algorithm, isodose displays, plan quality indices, and input/output devices. This program should comply with recommendations of AAPM TG-53, QA for clinical treatment planning [55], and TG Dose specification for prescription and reporting Whenever possible, treatment prescriptions and assessments of treatment administered should be stated in terms of absorbed dose in water. Where appropriate, e.g., for many interstitial implants, prescribed and reported doses should be based upon minimum dose to a target volume anatomically defined by 3D imaging [56]. As alternatives to the absolute minimum dose, which is difficult to evaluate reproducibly, the minimum dose to a specified fraction of the target volume, e.g., D 90, as determined by a dose-volume histogram

9 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) (DVH), is acceptable [5,6]. Similarly, dose heterogeneity in the treated volume can be specified volumetrically (e.g., the fraction of the target volume receiving a given percentage of the prescribed dose, for example, V 150 or V 200 ), as well as dose administered to critical organs to enable prospective correlation with morbidity [5,6]. However, dose specification based on anatomical landmarks is often not possible or useful. In these cases, dose may be specified to surfaces or points relative to the applicator geometry or anatomic landmarks. For intracavitary treatments, where total source strength and the product of source strength and treatment time are well-established prescription parameters, the quantities air-kerma strength ( Gy m 2 /h) and integrated reference air-kerma (IRAK) with units of Gy m 2, respectively, should be used [57] in place of mgraeq and mg-h, respectively. International Commission for Radiation Units (ICRU) report 58 contains many suggestions on how to report dose homogeneity and other implant quality parameters in the absence of 3D imaging or DVH capabilities [58]. Similarly, ICRU report 38 makes many useful suggestions for specifying dose in intracavitary brachytherapy [59]. Regardless of the dose specification criteria adopted by an institution, the following are to be noted: (1) Dose specification criteria for prescribing treatment, quantifying administered treatment, or quantifying normaltissue doses shall be clearly defined and documented in the appropriate written procedures or the patient s treatment record. The definition must clearly indicate how the speci- fied volume, surface, or points are spatially localized, e.g., how point A coordinates are determined from orthogonal radiographs. (2) The function of specified doses, e.g., vaginal vault surface dose, in constraining treatment or modifying the written directive shall be documented. (3) All personnel involved in planning treatments must understand the importance of consistently and reproducibly applying dose specification criteria to the integrity of treatment system. For brachytherapy treatments that have been empirically validated by patient outcome studies, new dose specification parameters should not be implemented until the correspondence between the old and new criteria is well understood. Similarly, when attempting to reproduce a clinical experience from another institution, the relationship between its dose specification criteria and those to be implemented must be clearly understood. (4) Where practical and appropriate, dose specification criteria endorsed by recognized consensus groups (ICRU, ABS, AAPM etc.) should be used to facilitate inter-institutional communication General procedure for designing an integrated QM system for brachytherapy To implement a new type of brachytherapy procedure in an existing practice, the following procedure is suggested: (A) Definition of procedure flow, identifying each major activity, its location, and type of medical personnel it requires (Fig. 1). Fig. 1. One model of HDR procedure flow diagram.

10 10 S. Nag et al. / Critical Reviews in Oncology/Hematology 48 (2003) 1 17 (B) Identification of vulnerable points in the treatment delivery process where mistakes, misjudgments, or inaccurate data communication can jeopardize the outcome of the procedure. Checks should be designed to identify such errors. The procedure description should describe the check, its acceptance tolerance or tolerance range, when and by whom it is performed, and what action is to be taken if the test result deviates from the expected outcome. The decision to incorporate a redundant check should consider likelihood of the target error and severity of its consequence. (C) Development of written procedures for each type of brachytherapy procedure. Essential patient documentation includes written directive (prescription), plan of treatment (POT), treatment record, treatment volume localization data, along with clinical summaries and consultation notes, computer-based treatment plans and localization films and images. All forms, image data files, and other records bearing data relevant to a specific treatment shall be unambiguously identified in terms of the patient s name and one additional identifier, such as the patient s hospital registration number. For multiple-fraction therapy courses, the date, time, and fraction number of each record component must be clearly identified. In addition, written procedures for each major type of procedure shall be available including the following: 1. Procedure chronology (an expanded and detailed version of procedure flow), including team member functions, QM checks, and forms used for implant description, target volume localization, written directive, and documentation of important safety checks. 2. Technical guidelines, including implant design principles, applicators used, procedure specific target volume localization rules, dose specification criteria, and treatment planning guidelines. 3. Clinical indications in terms of site, stage, and other defining features. 4. Commonly used prescribed doses and loading patterns along with associated external doses. The written directive shall include the treatment site, modality (temporary/permanent, preloaded/manual afterloading/remote afterloading, applicator type), the prescribed dose (or, alternatively, IRAK [52]) and identification of how the dose is specified. For multiple fraction treatment courses, the number of fractions (and, as a check, the absorbed dose per fraction) is needed. The written directive should be signed and dated by a radiation oncologist prior to initiating treatment. For some procedures, the written directive cannot be fully specified prior to loading sources. This occurs for temporary implants when the final dosimetry is not available at the time of loading and for permanent implants for which the number of seeds implanted is not known until completion of the procedure. Incomplete written directives are permitted, so long as the source loading sequence is fully specified and the written directive is completed by the end of the treatment. Any revisions to the written directive shall be clearly stated. The POT shall specify all parameters needed to implement the implant. For all cases, the POT includes: (1) The radionuclide and the source type, the relationship of each applicator to the target volume, the dose at any critical structures and, if appropriate, the identification pattern for catheters or needles (such as the numbering system). (2) For LDR applications: the number and type of sources used; the strengths and locations of the sources in the treatment applicator or implant site; the total treatment duration (or the duration for each source if differential times are used); and proposed insertion and removal times. (3) For HDR applications: the source strength (and treatment unit identification if more than one is available); dwell positions in the applicator; the dwell times; and indexer length settings for all catheters and step size. The treatment record shall indicate the source strength actually used and shall include the following procedure specific information: (1) For temporary LDR brachytherapy applications: the time and date of source insertion; the fraction number; the time and date of source removal; the dose to the target (or IRAK if used for prescribing treatment) or dose specification location; and at the end of the specific treatment, how much of the prescribed treatment course remains to be given. (2) For permanent brachytherapy applications, the time and date of source insertion and number of sources remaining in the patient at the end of the procedure. (3) For HDR applications; the time and date of treatment; the fraction number; the dose, and method of dose specification, for the fraction delivered, and the cumulative dose. (4) For all procedure types: All manual and computerassisted treatment time calculations, isodose plots, and images used for applicator and target localization. For each action requiring documentation of execution, the individual performing the step in question should be documented in the treatment record. All the information in the POT and the treatment record shall be retained in an orderly fashion. Sufficient information shall be retained that an independent expert could reconstruct the treatment. (D) Specification of how target localization data should be documented, including relationship to surrounding normal tissues. (E) Integration of brachytherapy QM into overall Department Quality Improvement program Pretreatment preparation (A) Clinical assessment and target volume definition/localization. When the treatment is based on imaging studies, the physician should determine the target volume and relevant normal anatomy, with the physicist in consultation. Definition of the target volume should use the most effective method (e.g.,