AAPM recommendations on medical physics practices for ocular plaque brachytherapy: Report of task group 221.

The American Association of Physicists in Medicine (AAPM) formed Task Group 221 (TG-221) to discuss a generalized commissioning process, quality management considerations, and clinical physics practice standards for ocular plaque brachytherapy. The purpose of this report is also, in part, to aid the clinician to implement recommendations of the AAPM TG-129 report, which placed emphasis on dosimetric considerations for ocular brachytherapy applicators used in the Collaborative Ocular Melanoma Study (COMS). This report is intended to assist medical physicists in establishing a new ocular brachytherapy program and, for existing programs, in reviewing and updating clinical practices. The report scope includes photon- and beta-emitting sources and source:applicator combinations. Dosimetric studies for photon and beta sources are reviewed to summarize the salient issues and provide references for additional study. The components of an ocular plaque brachytherapy quality management program are discussed, including radiation safety considerations, source calibration methodology, applicator commissioning, imaging quality assurance tests for treatment planning, treatment planning strategies, and treatment planning system commissioning. Finally, specific guidelines for commissioning an ocular plaque brachytherapy program, clinical physics practice standards in ocular plaque brachytherapy, and other areas reflecting the need for specialized treatment planning systems, measurement phantoms, and detectors (among other topics) to support the clinical practice of ocular brachytherapy are presented. Expected future advances and developments for ocular brachytherapy are discussed.

A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry.

INTRODUCTION: In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detector's response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E¯(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality indexQ(BT)(E¯), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, Dw, around BT sources. MATERIALS AND METHODS: While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT)(E¯)=TPR10(20)(E¯) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT)(E¯)=Dprim(r=2cm,θ0=90°)/Dprim(r0=1cm,θ0=90°), utilizing precise primary absorbed dose data, Dprim, from source reference databases, without additional MC-calculations. RESULTS AND DISCUSSION: For BT photon sources used clinically, Q(BT)(E¯) enables to determine the effective mean linear attenuation coefficient µ¯(E) and thus the effective energy of the primary photons Eprim(eff)(r0,θ0) at the TG-43 reference position Pref(r0=1cm,θ0=90°), being close to the mean total photon energy E¯tot(r0,θ0). If one has calibrated detectors, published E¯tot(r) and the BT radiation quality correction factor [Formula: see text] for different BT radiation qualities Q and Q0, the detector's response can be determined and Dw(r,θ) measured in the vicinity of BT photon sources. CONCLUSIONS: This novel brachytherapy photon radiation quality indexQ(BT) characterizes sufficiently accurate and precise the primary photon's penetration probability and scattering potential.

Comparison of different adjuvant radiotherapy approaches in childhood bladder/prostate rhabdomyosarcoma treated with conservative surgery.

BACKGROUND AND PURPOSE: Multimodality treatment approaches provide high local control and satisfying overall survival (OS) for children with localized bladder and/or prostate rhabdomyosarcoma (BP-RMS). However, current strategies including surgery and conventional radiotherapy are compromised by high rates of long-term genitourinary adverse effects. Therefore, a planning study combining organ preserving surgery with three different innovative adjuvant radiotherapy approaches was performed. PATIENTS AND METHODS: A case of a 21-month-old boy with BP-RMS treated with polychemotherapy according to the CWS 2002-P protocol, prostatectomy, partial cystectomy, and adjuvant high dose rate brachytherapy (HDR-BT) was used to perform a planning study comparing HDR-BT with intensity-modulated radiotherapy (IMRT) and intensity-modulated proton therapy (IMPT) planning. RESULTS: All modalities provide good coverage of the target volume and spare critical normal tissues. Rectum doses could be reduced by 2/3 using IMPT and by 1/3 using BT compared to IMRT. In terms of sparing the pelvis growth plates, BT and IMPT are also superior to IMRT. CONCLUSION: All modalities provide good sparing of normal tissue. BT and IMPT are superior to IMRT with regard to doses on rectum and growth plates. BT is equivalent to IMPT in adequately selected tumors.

Radiation protection of persons living close to patients with radioactive implants.

BACKGROUND: Permanent interstitial brachytherapy is--in certain cases--a very successful therapeutic option, but application of radioactive implants always results in only gradually diminishing radiation exposure of persons in the patient's immediate surroundings. MATERIAL AND METHODS: Using patients with clinically localized prostate cancer treated with iodine-125 ((125)I) or palladium-103 ((103)Pd) as an example, it is shown how a patient, if necessary or wished by him, can, by wearing commercially available X-ray protection shorts, reduce radiation exposure of family members in such a way that at a distance r from the patient a given dose per year is not exceeded. RESULTS: The computational procedures necessary for the determination of the individual periods of wearing X-ray protection clothing are provided in the form of formulae and graphics. All considerations and calculations can also be applied to other radiotherapeutic interventions involving the use of (125)I, (103)Pd or other gamma-sources. CONCLUSION: If necessary, a patient with permanent radioactive implants can reduce radiation exposure of family members by wearing special X-ray protection clothing for a limited period of time. This kind of radiation protection is very efficient and considerably simpler to accomplish than a reduction of exposure time or an increase of the distance between the patient and family members.

Clinical quality assurance for 106Ru ophthalmic applicators.

BACKGROUND AND PURPOSE: Episcleral brachytherapy using 106Ru/106Rh ophthalmic applicators is a proven method of therapy of uveal melanomas sparing the globe and in many cases sparing the vision. In the year 2001, an internal clinical quality assurance procedure revealed that part of the ophthalmic applicators leaked and that the calibration was erroneous. Consequently, the producer modernized its production procedures and, in May 2002, introduced a dose rate calibration that is traceable to the NIST standard. This NIST calibration confirmed that the previous calibration had been incorrect. In order to study the effects of the producer's new internal quality assurance procedures on the ophthalmic applicators, applicators of this new generation were submitted to a newly improved internal clinical acceptance test. PATIENTS AND METHODS: The internal clinical acceptance test consists of a leakage test and a dosimetric test of the ophthalmic applicators. The leakage test simulates contact of the ophthalmic applicators with chloride containing body fluid. The dosimetric tests measure depth dose curves and dose rate with a plastic scintillator dosimetric system and compare them with the indications in the producer's certificate. Furthermore, the depth dose profile of the most frequently used applicator (type CCB) was compared with published data. RESULTS: The internal clinical leakage test showed that all of the tested ophthalmic applicators belonging to the new generation (n=17) were tight and not contaminated. The dosimetric acceptance tests applied to seven different types of applicators revealed that the relative depth dose profiles in the therapeutically relevant range (up to a depth of

On the actual state of industrial quality assurance procedures with regard to (106)Ru ophthalmic plaques.

BACKGROUND: In radiotherapy of intraocular tumors, e. g., in the case of malign choroid melanomas, episcleral brachytherapy with (106)Ru ophthalmic plaques has proven to be successful. In a study, the authors reported on the discovery of the following shortcomings in industrial quality assurance, which are relevant to therapy, during the course of an internal clinical acceptance test of (106)Ru ophthalmic plaques, manufactured by the company Bebig from Berlin, Germany. This consisted of inconsistent dose rate specifications in the manufacturer's certificate, covering a range of 111% and with the risk of leakage of the plaques. Bebig was called upon to adapt state-of-the-art production methods with regard to (106)Ru ophthalmic plaques. MATERIAL AND METHODS: In the meantime, Bebig has modernized production of (106)Ru ophthalmic plaques and adopted all the quality assurance procedures proposed by the authors. Moreover, the requested traceability of the calibration of activity and dose rate of the (106)Ru ophthalmic plaques to standards of the federal authorities in charge of measurement procedures has been implemented. RESULTS: In the year 2002, Bebig updated, among other things, the ASMW (GDR) calibration of the dose rate of the (106)Ru ophthalmic plaques from the years 1987-1989 by a calibration of the NIST (USA). The current NIST calibration, together with the new equipment for the measurement of the depth dose curves, led to the consequence that the new NIST 2001 dose rate values show, in the mean, a deviation of 0.75 times (plaque type CCC) up to 2.06 times (plaque types CCX, CCY, and CCZ) compared to the dose rate values that had been indicated so far in Bebig's certificate, based on the ASMW 1987 calibration. For the 95% confidence interval, Bebig estimated the measurement uncertainty to be +/- 25%. If one takes into consideration the minimal and maximal values in such 95% confidence intervals, it follows that the new NIST 2001 dose rate values deviate between 0.56 times (plaque type CCC) and 2.58 times (plaque types CCX, CCY, and CCZ) from the Bebig certificate (ASMW calibration 1987). As regards leakage, no objections arose in the case of the (106)Ru ophthalmic plaques produced according to the new quality standards. CONCLUSION: Legislation has to make sure that the use of radioactive material on humans be, among other things, permitted as a matter of principle only, if the dose rate calibration can be traced to standards of a federal authority of measurement procedures. Furthermore, special leakage tests for radiation sources which come into direct contact with body fluids should be established. A historical retrospect reveals that the greatest changes have taken place in the indication of the dose rates of (125)I sources. Since the beginning of the use of (125)I sources in brachytherapy in the late 1960s, the dose rate indications, so far, have had to be reduced in small steps over a period of about 35 years by nearly a factor of 2. As regards the (106)Ru ophthalmic plaques, the NIST 2001 calibration has resulted in a comparable reduction of the dose rate indications of up to a factor of 2 within the period of about several months. Thus, in the previous history of radiotherapy this case must be regarded as unique, because for the first time ever, an urgently needed recalibration has been protracted for such an unduly long period of time.

[Physical and technical quality assurance and radiation protection in transperineal interstitial permanent prostate brachytherapy with 125-iodine seeds]. / Physikalisch-technische Qualitätssicherung und Strahlenschutz bei der Monotherapie der Prostata mit Jod-125-Seeds.

BACKGROUND: Early stage prostate cancer can be treated successfully by interstitial brachytherapy with 125-iodine seeds. A quality-assurance programme is presented that was designed for this purpose for internal clinical use. Furthermore the requirements of the new German Ordinance Governing Radiation Protection (StrlSchV) that came into force on August 1, 2001, are taken into account. MATERIAL AND METHODS: For the 125-iodine monotherapy of the prostate we used RAPID STRANDS (Amersham Health, Braunschweig, Germany). According to the guidelines of the new Ordinance Governing Radiation Protection, the determination of the body dose of the staff is made to rely on the new measurement quantities H(p) (10) and H(p) (0.07). The nominal air kerma rate of the seeds is measured with a calibrated well-chamber of the type HDR 1000 Plus and an electrometer of the type MAX 4000 (Standard Imaging Inc., USA). The ultrasound images of the prostate are produced by an ultrasound device of the type Falcon 2101 (B-K Medical, Denmark). For treatment planning the programme VariSeed (Varian, Darmstadt, Germany) was employed. Correct loading of the needles is controlled by autoradiography before implantation. After the implantation radiation-protection measurements in the operating room are carried out. RESULTS: As regards the personnel, for the depth personal dose equivalent Hp(10) and relating to two applications each, measurement values between 0 microSv and 14 microSv resulted. The control of the radiation exposure of the hands revealed superficial personal dose values H(p) (0.07) of up to 1 mSv. The nominal air kerma rates of the RAPID STRANDS were all lying within the 95% confidence interval guaranteed by the producer. The autoradiographs documented -- except for one case -- the correct loading of the needles. The interstitial transperineal prostate implantation of the 125-iodine seeds succeeded as planned with all patients. Until now no contamination of the operating room was detected by the radiation-protection measurements. CONCLUSION: The physical-technical quality assurance programme presented here covers the whole physical-technical range of the internal clinical quality assurance and could be integrated into the course of the treatment without any problems. It has th following advantages: The autoradiographic documentation of the correctly loaded needles serves as proof that the prerequisite for the production of the prescribed physical dose distribution is fulfilled. The internal clinical determination of the nominal air kerma rate is the basis for a correct dose application.

[Physical basics and clinical realization of interstitial brachytherapy of the prostate with iodine 125]. / Physikalische Grundlagen und klinische Durchführung der interstitiellen Brachytherapie der Prostata mit Jod-125.

BACKGROUND: Interstitial brachytherapy with I-125 seeds can be used for successful treatment of early stage prostate cancer. There is presented the technique of permanent transperineal implantation of I-125 seeds with intraoperative treatment planning which is suited for the treatment of prostate cancer up to the clinical stage of T2a. MATERIAL AND METHODS: Some weeks before the implantation of the seeds the prostate volume is determined using transrectal ultrasound (TRUS) so as to estimate the required number of I-125 seeds. At the outset of the treatment the prostate is stabilized by two perineally inserted needles. Subsequently there is carried out an ultrasound guided treatment planning that allows to optimize the distribution of the seeds within the prostate. In interstitial brachytherapy we use RAPID STRANDS((R)), i. e. the I-125 seeds are embedded in vicryl suture at distances of 1 cm. During implantation of the I-125 seeds the transversal placement of the applicator needles is controlled by TRUS and the cranio-caudal placement of the applicator needles is controlled using the fluoroscopic unit as well as TRUS. About 4 weeks after the implantation of the seeds there is carried out a postoperative computation of the dose distribution of the implant using CT imaging. RESULTS: The procedure possesses the advantage that ultrasound imaging, treatment planning and seed implantation are carried out with the prostate remaining in an unaltered position. During implantation the combined imaging of TRUS and fluoroscopy allows a safe placement of the seeds with in the prostate. CONCLUSION: The methods for the calculation of the actually attained dose distribution must still be optimized, because the postoperative examination of the individual results has so far been possible only with difficulties resulting from methodological inconveniences.

[Optimal intravascular brachytherapy: safety and radiation protection, reliability and precision guaranteed by guidelines, recommendations and regulatory requirements]. / Optimale intravaskuläre Brachytherapie. Sicherheit und Strahlenschutz, Zuverlässigkeit und Präzision gewährleistet durch Leitlinien, Empfehlungen und Verordnungen.

BACKGROUND: The success of intravascular brachytherapy relies entirely on the interdisciplinary approach. Interventional cardiologists, radiation oncologists and medical physicists must form a team from day 1. All members of the team need special knowledge and regular training in the field of vascular radiation therapy. Optimization of intravascular brachytherapy requires the use of standardized methods of dose specification, recording and reporting. This also implies using standardized methods of source calibration in terms of absorbed dose to water and having methods for simple internal control of the dosimetric quantities of new or replaced sources. Guidance is offered by international recommendations (AAPM TG 60, DGMP Report 16, NCS and EVA GEC-ESTRO). LEGAL REQUIREMENTS FOR RADIATION PROTECTION--WHAT'S NEW?: In Europe, new legal requirements on radiation protection issues have to be fulfilled. For Germany, the revised "Strahlenschutzverordnung" has been released recently. Nearly all organizational and medical processes are affected. For intravascular brachytherapy, several changes of requirements have to be considered. However, to follow these requirements does not cause serious problems. DGMP REPORT 16: GUIDELINES FOR MEDICAL PHYSICAL ASPECTS OF INTRAVASCULAR BRACHYTHERAPY: Evaluation of clinical results by comparison of intravascular brachytherapy treatment parameters is possible only if the prescribed dose and the applied dose distribution are reported clearly, completely and uniformly. The DGMP guidelines thus recommend to prescribe the dose to water at the system related reference point PRef at 2 mm radial distance for intracoronary application (and at 5 mm for peripheral vessels). The mean dose at 1 mm tissue depth (respectively at 2 mm) should be reported in addition. To safely define the planning target volume from the injured length, safety margins of at least 5 mm (10 mm) have to be taken into account on both ends. Safety margins have also to be considered for multisegmental treatment, to omit underdosage. IVUS based localization will support precise planning, avoid a geographic miss and edge effects and will allow for later evaluation. These DGMP recommendations are also included in the EVA GEC ESTRO recommendations and in the draft for an up-date of the AAPM TG 60 report. CONCLUSION: Medical physical quality management of intravascular brachytherapy is a necessary condition for optimal and safe treatment. Procedures, devices, and sources should fulfill the same degree of precision and safety as common in radiotherapy.

Clinical beta radiation dosimetry for brachytherapy in terms of absorbed dose to water: ISO new work item proposal for international standardization.

PURPOSE: Beta radiation has found increasing interest in intravascular brachytherapy for successfully overcoming the severe problem of restenosis after interventional treatment of arterial stenosis. Prior to initiating procedures applying beta radiation there is a common need to specify methods for the determination and specification of the absorbed dose to water or tissue and their spatial distributions. The DIN-NAR standardization in radiology task group Dosimetry has initiated an international ad hoc working group for an ISO new work item proposal on the standardization of procedures in clinical beta radiation dosimetry. METHODS: The intent of this standard is to review methods and to give recommendations for the calibration of therapeutic beta sources, a code of practice for clinical beta radiation dosimetry and guidance for estimating the uncertainty of the absorbed dose to water delivered. The standard will be confined to "scaled" radioactive sources such as single seeds, source trains, line, shell and volume sources for which only the beta radiation emitted is of therapeutic relevance. The topics will include dosimetric quantities; source data; calibration and traceability; general principles and requirements for absorbed dose measurements; in phantom dosimetry; theoretical modeling; presentation of dose distributions; clinical dosimetry; clinical quality control; irradiation treatment planning; as well as uncertainties. The document is geared to organizations wishing to establish reference methods in dosimetry aiming at clinical demands for appropriate small measurement uncertainties. Existing normative documents as well as international recommendations, such as those from AAPM, DGMP, ESTRO, NCS, ICRU, or IAEA will be taken into account. RESULTS: The first meetings of the new international working group took place in March and September 2002 at Essen, Germany [IAEA-cn-96-73, 2002]. CONCLUSIONS: Based on the DGMP Report 16, the AAPM TG 60 up-date draft, other recommendations and normative documents, the DIN-NAR project has collected and prepared detailed material on the calibration and dosimetry of beta radiation brachytherapy sources in terms of absorbed dose to water. The ISO new work item proposal will be completed in spring 2003.