Medical Physics
Current Activities
An outstanding feature of the year was the Department’s leading role (with the strong assistance of the Department of Radiation Oncology) in the hosting of the inaugural Modelling Of Tumour Development Behaviour and Response to Treatment in Clinical Oncology meeting in Adelaide. The feedback from all attendees was highly positive and Adelaide was encouraged to offer a second meeting in 18 months time.
Another strong development was the creation, again in conjunction with the Department of Radiation Oncology, of a 5 year strategic plan (2004 to 2009) for radiotherapy services in South Australia. The plan highlighted and addressed issues of medical physics staffing, infrastructure, training, continued professional development as well as the opportunities to provide the best technology for cancer radiotherapy services. This strategic plan has been put to the Department of Health for consideration while every effort is being made to achieve the desired outcomes within the current constrained resources.
Professional activities remain a strong feature of the Department with major input into the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM). As well as continuing with heavy contributions to the local branch seminar programs and production of the College’s journal, staff members help constitute the organizing committee for the national medical physics conference to be held in Adelaide next year. With 2005 being the United Nations Year of Physics, the conference should be a spectacular event.
However, routine service provision is the core business of the Department and reports from the individual sections follow.
Linear Accelerator Quality Assurance, Dosimetry and External Beam Therapy
The system of linear accelerator Quality Assurance (QA) has been developed intensively over the last 5 years, as a result of new technologies and equipment implemented in that time. Examples of new QA procedures introduced include: regular beam profile scanning of multi-leaf collimators, electronic portal imaging devices and enhanced dynamic wedges.
Upgrades have been performed to the quality assurance and treatment planning software (MUCalc), SXRT section in particular. This is to improve the clarity of the data input and to prevent miscalculation incidents leading to wrong patient treatments.
Determination of absorbed dose delivered by linear accelerators and other radiation devices is one of the most essential tasks carried out by any medical physics department. The absolute dose calibration is always performed according to the national and international protocols.
The Radiotherapy Interest Group (RIG) of ACPSEM adopted the new IAEA protocol during the EPSM conference in Perth, 2001. A three year transition period was given to all radiotherapy departments to implement the protocol into their calibration procedures. Subsequently, a plan was developed to transfer the absolute dose calibration based on TRS 277 to TRS 398. Once a thorough understanding of differences between the two protocols has been established, a series of measurements have been performed to compare the two calibration procedures. On completion of protocol comparison measurements, all photon beams were recalibrated according to new TRS 398 protocol in June-July 2004 followed by recalibration of all electron beams in September-October 2004. The new TRS 398 protocol means an improvement in absolute dose determination for megavoltage photon and electron beams. Simplification of several steps in the protocol also makes the measurements more straightforward and reduces the risk of potential set up and calculation errors.
A new digital radiography system, the Kodak DirectView CR850, was installed and commissioned during 2004. The improved clarity of the images produced with this system, compared to the standard “wet” developing process, greatly enhances identification and delineation of treatment targets, thus increasing accuracy of patient set up and treatment delivery. Also, the digital manipulation facility allows for a “poor” quality image to be digitally enhanced to a satisfactory standard, thus eliminating the need to repeat the x-ray, and so reducing the amount of radiation received by patients.
This year, the Medical Physics department was involved in Total Body Irradiation (TBI) of 11 patients. Apart from planning data confirmation, physicists have been responsible for in-vivo patient dosimetry in order to confirm that a correct dose has been delivered to patients.
Seventeen patients were treated in 2004 with Stereotactic Radio-Surgery (SRS) and fractionated Radio-Therapy (SRT). Treatment planning and an accurate treatment set up for these patients were provided by the medical physics staff as well as pre-treatment quality assurance for SRS.
Computing Quality Assurance, Isotopes, Brachytherapy and Information System Section
Transperineal permanent implant of the prostate with Iodine-125 seeds has been successfully implemented as a multidisciplinary project with the RAH Departments of Radiation Oncology and Urology. This form of brachytherapy for early stage prostate cancer has been internationally accepted as having good survival rates with a lower incidence of patient complications than other forms of treatment. Our initial involvement included the writing of specifications for tender, assessing the offered systems and then the commissioning of the selected ultrasound, stepper and treatment planning equipment. Our ongoing involvement includes collaborating with Radiation Oncology and Urology staff in prostate volume assessment, treatment pre-planning, theatre procedures and post-treatment CT based planning and assessment. We continue to refine our treatment planning techniques to achieve an optimum dose distribution for each patient.
Apart from the introduction of permanent seed implant low dose rate (LDR) brachytherapy, this year has seen an increase in the use of the LDR Selectron unit in Ward B6 and a doubling in the number of patients treated on the HDR unit.
The ‘hot lab’ by our staff to conform with modern EPA standards for the safe and clinically clean handling of radioisotopes. We specified and acquired a complete set of equipment to store, calibrate and handle loose and stranded Iodine-125 seeds and to enable the safe sterile loading of implant needles. Some equipment was designed and manufactured in our RE workshop at considerable saving in cost. PC software developed in the department displays each calibration and records it in a secure database.
Radioactive Ruthenium eye plaques are used for treatment of eye tumours at the RAH. A new set of plaques for the ophthalmologists’ use was purchased this year. The plaques were checked for integrity, calibrated and commissioned for clinical use.
Software and hardware quality assurance is essential with radiotherapy planning systems and forms a major component of this section’s work. We facilitated the hardware upgrading of one of the workstations and the server to higher performance in readiness for a new intensity modulated radiotherapy software version expected in 2005. Software development and enhancement activities also required modifications to the PVStats source code to allow for archiving of patient records as the patient database had become large. These modifications made the software more reliable and user-friendly.
Radiation Engineering Section
During the year Radiation Engineering section continued providing high quality services to Radiation Oncology Department. While the number of serious faults has dropped slightly from 53 to 44, the minor problem component has risen from 180 up to 290 calls. This increase can be explained by aging of the two Varian accelerators, which can no longer be considered new, working under heavy load. As RE has managed to keep most of the calls within minor breakdown 30-minute time frame, average downtime per major faults was also reduced from 1.62 hours to 1.29. The latest represents further 20% improvement in RE efficiency which has almost doubled since 2001.
The following table illustrates statistics of accelerators breakdowns and RE performance during the last four years.
TS1 |
TS2 |
TS3 |
TS4 |
TS5 |
Total major |
Total minor |
Total |
||
| 2001 | Repair time | 40.5 |
27.5 |
21.6 |
7.0 |
19.0 |
115.6 |
- |
|
| Number of breakdowns | 17 |
12 |
13 |
4 |
8 |
54 |
170 |
224 |
|
| Time per breakdown | 2.4 |
2.3 |
1.7 |
1.7 |
2.4 |
2.2 |
<0.5 |
||
| 2002 | Repair time | 23.7 |
40.8 |
10.6 |
9.5 |
3.2 |
87.8 |
- |
|
| Number of breakdowns | 13 |
18 |
8 |
7 |
3 |
49 |
190 |
239 |
|
| Time per breakdown | 1.8 |
2.3 |
1.3 |
1.4 |
1.1 |
1.8 |
<0.5 |
||
| 2003 | Repair time | 37.5 |
16.0 |
15.0 |
17.5 |
n/a |
86.0 |
- |
|
| Number of breakdowns | 17 |
15 |
10 |
11 |
n/a |
53 |
180 |
233 |
|
| Time per breakdown | 2.21 |
1.07 |
1.5 |
1.59 |
n/a |
1.62 |
<0.5 |
||
| 2004 | Repair time | 21.8 |
8.75 |
14.5 |
11.5 |
n/a |
56.55 |
- |
|
| Number of breakdowns | 18 |
11 |
8 |
7 |
n/a |
44 |
290 |
335 |
|
| Time per breakdown | 1.21 |
0.8 |
1.81 |
1.64 |
n/a |
1.29 |
<0.5 |
Through the years RE adopted a practice to repair all modules of linear accelerators and ancillary equipment down to component level wherever it was possible. This year was not any different and no costly replenishment of existing spare PSB stock was required. RE keeps purchasing of spare parts from accelerator manufacturers to a minimum. This has proven to be very cost effective and has a potential to save thousands of dollars every year. For example, sourcing out an OEM supplier of MLC motors brought $12,000 saving on the cost of 20 failed motors in the past year.
Bargaining is another option for cost cutting. In certain circumstances vendors become more flexible in their pricing policy and offer significant discounts. Utilization of such circumstances to negotiate the best possible price gave us $7000 saving on purchasing a new magnetron for the low energy Varian machine.
12 projects for Medical Physics and Radiation Oncology were carried out by the RE Mechanical Workshop this year. Estimated savings of these is in excess $10,000.
RE provides in-house preventative maintenance services and repairs to five linear accelerators, which also included two MLCs and two EPI devices, one simulator, two X-ray units, HDR brachytherapy unit and auxiliary equipment. New equipment that was recently acquired and will be looked after by RE includes Mobile Image Intensifier, Ultrasound Station and Computer Radiography System. RE has also been looking after the following equipment on a first line repair basis: Film Processor, CT scanner and LDR brachytherapy unit.
Conclusion
The Department of Medical Physics has had a very successful year in many ways. The demands on the staff have been high and they have responded well. Many new activities are expected in the new year with the installation of new accelerators, an information system and hopefully the ability to conduct image guided radiotherapy.