Institute Of Physics And Engineering In Medicine Research Articles

The IPEM code of practice for determination of the reference air kerma rate for HDR 192Ir brachytherapy sources based on the NPL air kerma standard

This paper contains the recommendations of the high dose rate (HDR) brachytherapy working party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a Code of Practice (COP) for the UK for measuring the reference air kerma rate (RAKR) of HDR 192Ir brachytherapy sources. In 2004, the National Physical Laboratory (NPL) commissioned a primary standard for the realization of RAKR of HDR 192Ir brachytherapy sources. This has meant that it is now possible to calibrate ionization chambers directly traceable to an air kerma standard using an 192Ir source (Sander and Nutbrown 2006 NPL Report DQL-RD 004 (Teddington: NPL) http://publications.npl.co.uk). In order to use the source specification in terms of either RAKR, (ICRU 1985 ICRU Report No 38 (Washington, DC: ICRU); ICRU 1997 ICRU Report No 58 (Bethesda, MD: ICRU)), or air kerma strength, SK (Nath et al 1995 Med. Phys. 22 209–34), it has been necessary to develop algorithms that can calculate the dose at any point around brachytherapy sources within the patient tissues. The AAPM TG-43 protocol (Nath et al 1995 Med. Phys. 22 209–34) and the 2004 update TG-43U1 (Rivard et al 2004 Med. Phys. 31 633–74) have been developed more fully than any other protocol and are widely used in commercial treatment planning systems. Since the TG-43 formalism uses the quantity air kerma strength, whereas this COP uses RAKR, a unit conversion from RAKR to air kerma strength was included in the appendix to this COP. It is recommended that the measured RAKR determined with a calibrated well chamber traceable to the NPL 192Ir primary standard is used in the treatment planning system. The measurement uncertainty in the source calibration based on the system described in this COP has been reduced considerably compared to other methods based on interpolation techniques.

Practical experience of using the IPEM 2003 electron code of practice

From 1 January 2007, the Institute of Physics and Engineering in Medicine (IPEM) 2003 code of practice (COP) for electron dosimetry replaces the old air kerma-based Institute of Physics and Engineering in Medicine and Biology 1996 COP as the recommended protocol for the UK. The IPEM 2003 COP requires a secondary standard ionisation chamber calibrated directly in terms of absorbed dose to water. This paper examines the differences between the new and old COP and indicates that the dose measured using the 2003 COP appears to be greater than that using the 1996 COP by approximately 2+/-1%, based on a survey of radiotherapy centres in the UK. The paper also compares the characteristics of the NACP (Scanditronix) and Roos (PTW) chambers recommended by the 2003 COP. No practical difference was found between adopting the NACP or Roos chambers as a secondary standard chamber.

Current issues in nuclear cardiology

Recent technical advances and the introduction of new radiopharmaceuticals have prompted renewed interest in nuclear cardiology. NICE (National Institute for Health and Clinical Excellence) guidelines published in 2003 and 2006 [1, 2] are leading to increased referral rates for both myocardial perfusion imaging (MPI) and MUGA (MUltiple Gated Acquisition) studies. Some departments are experiencing difficulties with this increased throughput and are unlikely to be able to comply with the required 18-week pathway. To provide a forum for discussion of these and other issues, a meeting entitled ‘‘Evolution and Revolution: logistical, technical and scientific developments in nuclear cardiology’’ was organized by the Nuclear Medicine Special Interest Group of the Institute of Physics and Engineering in Medicine (IPEM), and was held at the British Institute of Radiology in February 2007. In this Commentary, we review the main themes raised at the meeting and place them in the context of general advances in cardiac imaging.

Gamma camera scintigraphy of tumours using 195mPt-cisplatin

Platinum enriched with 194Pt was irradiated for 4 days in NRG's TIRO 1 reactor, to produce 195mPt. Spectral analysis of the product was performed using a calibrated hyper pure germanium detector and its constituent radioisotopes were identified as 195mPt, 199Au and 192Ir. Using the detector's intrinsic efficiency calibration, their activities were estimated to be 1049, 133 and 5.8 MBq, respectively. The performance of the gamma camera was tested using quality control procedures recommended by the Institute of Physics and Engineering in Medicine (IPEM) and was found to be satisfactory. A torso phantom was used to determine the minimum detection limit (MDL) of 195mPt in a 2 cm diameter tumour using SPECT acquisitions (32 steps, 60 s per step). The MDL was found to be 8 ppm assuming an administered patient dose of 50 MBq and a total cisplatin dose of 105 mg. This work indicates that 195mPt-cisplatin is suitable for clinical scintigraphy and has led to the development of a clinical protocol that has been approved for a pilot study.

1389 POSTER Quality Assurance (QA) clinical indicators to detect treatment errors and potential overdose in radiotherapy; first results

Background and purpose: This paper compares the quality control checks performed in departments in the United Kingdom with those recommended by the Institute of Physics and Engineering in Medicine (IPEM) in Report 81.Method: The data were gathered by the quality assurance team for the START trial, during visits to individual departments. Data are compared with the frequencies suggested in IPEM report 81. Where applicable, data are also analyzed with respect to machine manufacturer.Results: All departments with linear accelerators check the output at least weekly for both photons and electrons, however 11% of departments do not perform a constancy check of the output on a daily basis. The majority of departments check flatness at gantry zero on a monthly basis. However 27% of departments never check at non-zero gantry angles. In 51% of departments no fluoroscopy checks are performed on simulators on a daily basis.Conclusion: The majority of departments are following the frequencies suggested in IPEM report 81 although there are a number of discrepancies particularly for simulators. Accelerator type needs to be considered when designing quality assurance checks. In many departments more time than is currently allocated is needed on equipment, particularly simulators, to complete all of the checks suggested in Report 81.

The IPEM code of practice for electron dosimetry for radiotherapy beams of initial energy from 4 to 25 MeV based on an absorbed dose to water calibration

This report contains the recommendations of the Electron Dosimetry Working Party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a code of practice for electron dosimetry for radiotherapy beams of initial energy from 4 to 25 MeV. The code is based on the absorbed dose to water calibration service for electron beams provided by the UK standards laboratory, the National Physical Laboratory (NPL). This supplies direct ND,w calibration factors, traceable to a calorimetric primary standard, at specified reference depths over a range of electron energies up to approximately 20 MeV. Electron beam quality is specified in terms of R50,D, the depth in water along the beam central axis at which the dose is 50% of the maximum. The reference depth for any given beam at the NPL for chamber calibration and also for measurements for calibration of clinical beams is 0.6R50,D − 0.1 cm in water. Designated chambers are graphite-walled Farmer-type cylindrical chambers and the NACP- and Roos-type parallel-plate chambers. The practical code provides methods to determine the absorbed dose to water under reference conditions and also guidance on methods to transfer this dose to non-reference points and to other irradiation conditions. It also gives procedures and data for extending up to higher energies above the range where direct calibration factors are currently available. The practical procedures are supplemented by comprehensive appendices giving discussion of the background to the formalism and the sources and values of any data required. The electron dosimetry code improves consistency with the similar UK approach to megavoltage photon dosimetry, in use since 1990. It provides reduced uncertainties, approaching 1% standard uncertainty in optimal conditions, and a simpler formalism than previous air kerma calibration based recommendations for electron dosimetry.

IPEM Report No 84: Guidelines for the Testing and Calibration of Physiotherapy Ultrasound Machines

Institute of Physics and Engineering in Medicine York: IPEM (2001) 67 pp, �20.00, ISBN: 0-904181-98-7 This 67-page soft-cover report has been prepared by an expert group within the Institute of Physics and Engineering in Medicine (IPEM) to provide detailed guidance on the testing and calibration of ultrasound therapy devices. Physiotherapists have long used external energy sources to supplement massage and manipulation for musculo-skeletal therapy. Whilst, recently, there has been a general reduction in use of electrotherapy using radio-frequency radiation, microwaves and interferential devices, ultrasound therapy still remains central to physiotherapy practice. There is now robust evidence that, at least for some injuries, ultrasound accelerates the repair of injured tissue. This has been particularly well demonstrated for bone fracture repair. Managed therapy relies on well-calibrated radiation sources. Unfortunately, there has been less than adequate management of ultrasound output in the past. Several well-documented situations have occurred for which faulty ultrasound equipment has continued in clinical use, either generating no output at all, or, more seriously, operating at maximum power all the time. This report reminds those responsible for managing ultrasound equipment of the need for testing and calibration, and gives detailed advice on procedures for carrying this out. These details are contained in 12 annexes forming the majority of the text. Each annex presents a self-contained aspect of one aspect of testing or calibration, such as the measurement of acoustic power, or an example protocol for machine testing. Each is sufficiently detailed to allow novice technical staff to follow the recommended procedure, or to allow a department to plan to introduce ultrasound field calibration into its practice. Other annexes contain useful additional material, not included in the earlier IPSM Report 58. A procedure for the measurement of effective radiating area, developed by NPL, is carefully described, as is a rapid method for testing the temperature rise due to ultrasound using a simple calorimeter. The next report will, I am sure, consider standardized means to quantify tissue heating and patient dose. Once or twice I felt that quantities were identified but means for their measurement were not specified at the level of detail used elsewhere, for example for beam non-uniformity ratio and rms acoustic pressure. Also, perhaps, the actual problems when using hydrophones in physiotherapy fields were not discussed in sufficient detail, with no mention of the need to carefully control any direct electromagnetic coupling between the transducer and the hydrophone. But these are really minor criticisms. The main (short) text of the report gives rationale, summary of recommendations and guidelines and key references. This is a very practical report, which should be bought and used by all hospital departments with a responsibility for ultrasound therapy equipment, including maintenance departments, physiotherapy departments and medical physics departments. It will underpin competency-based training in medical ultrasound, and will support the NHS National Occupational Standards for Ultrasound Physics and Technology. Being highly practical, I would expect this report to be found in the laboratory or workshop and more rarely in an academic library.

A survey of radiotherapy quality control practice in the United Kingdom for the START trial

Background and purpose: This paper compares the quality control checks performed in departments in the United Kingdom with those recommended by the Institute of Physics and Engineering in Medicine (IPEM) in Report 81. Method: The data were gathered by the quality assurance team for the START trial, during visits to individual departments. Data are compared with the frequencies suggested in IPEM report 81. Where applicable, data are also analyzed with respect to machine manufacturer. Results: All departments with linear accelerators check the output at least weekly for both photons and electrons, however 11% of departments do not perform a constancy check of the output on a daily basis. The majority of departments check flatness at gantry zero on a monthly basis. However 27% of departments never check at non-zero gantry angles. In 51% of departments no fluoroscopy checks are performed on simulators on a daily basis. Conclusion: The majority of departments are following the frequencies suggested in IPEM report 81 although there are a number of discrepancies particularly for simulators. Accelerator type needs to be considered when designing quality assurance checks. In many departments more time than is currently allocated is needed on equipment, particularly simulators, to complete all of the checks suggested in Report 81.