$468 Posters

1117 poster

Verification of set up deviation with BeamCath stereotactic technique using electronic portal imaging in cl inical practice

C. Ekh 1, Z. Khoshbakht ~, K. Annerstedt - Klasson ~, A. BjSreland 2, L. Franz6n 1

~ Sundsvalls Hospital, Department of Radiotherapy, Sundsvall, Sweden 2Sundsvalls Hospital, Department of Hospital Physics, Sundsvall, Sweden Background: In May 2002 a new radiotherapy department was established in Sundsvall in central Sweden. One of the most common treatments given today in Sundsvall is dose- escalated radiotherapy of prostate cancer using the BeamCathD stereotactic method.

The BeamCathLJ method involves a special urethral catheter with markers to visualize the prostatic urethra with portal imaging. With this technique accurate localization of the prostate can be achieved allowing dose-escalation to 78 Gy without increased complications compared to doses U 70 Gy given with conventional or 3D conformal radiotherapy.

The aim of this study was to determine set-up deviations during the first 2-4 treatment sessions with the BeamCathL~ stereotactic method using an Electronic Portal Imaging (EPI) system (Elekta, iViewGT).

Material and methods: Treatment simulation in Sundsvall is done using virtual simulation. The patient fixation, CT- scanning and target definition are made in Sundsvall, using the virtual simulation system GE, advantage SIM or the treatment planning system Nucletron OTP. The CT-data containing target and OAR information is then sent to Ume~ for dose calculation. The setup parameters from the dose calculation system are then stored in the common database for use in Sundsvall. The dose plan is also exported to the virtual simulation system in Sundsvalt for creation of reference DRR:s for the EPI system

Setup verification is made using an EPI system with an amSi detector. Image matching is made by comparing the field DRR from the virtual simulation system to the EPI using the digital matching tools in the EPID system and the projected cross hair from the DRR as the aiming device. Each EPI requires only a small portion of the total fraction dose. If the initial EPI indicates a set up deviation of 2 mm or more in either direction the patient is moved and another EPI is taken to verify the new position.

35 patients have been treated with BeamCath[] stereotactic technique since September 2003 and were enrolled in this study.

Results: The mean setup deviation and the corresponding standard deviation (1 SD) of the systematic and random errors for this technique were measured in the: plane orthogonal to the beam axis. The result decided from the initial EPI was 5.9 U 2.6 mm, excluding treatments within the tolerable limits already on this first EPI. The result from the EPI taken immediately before the major part of the field MU:s where given was 1.5 [] 1.0 mm including all treatments. Patient position adjustments were necessary in ca. 40 % of the treatments.

Conclusions: These results show that set-up deviations in prostate cancer patients treated with this technique are negligible in clinical practice. Patient fixation and immobilization techniques together with experience and skill of the treatment staff is crucial in minimizing random errors.

1118 poster

The e-volution of continuing education and communication in radiotherapy using modern technology B.M. Newelf, C. Pan De 2, H. Zandbergen 2, F.M. Gescher 1, P.C. Levendag 2

l Leyenburg Hospital, Radiotherapy, The Hague,, The Netherlands 2Erasmus MC, Radiotherapy, Rotterdam, The Netherlands

Introduction: We are at the beginning of a new era, which will revolutionise the potential of e-learning and interactive communication within the health service making the pool of knowledge available far greater than was ever thought possible. We can now share diagnostic x-rays, slides under the microscope, simple or complicated treatment plans, to name but a few of the ever-growing possibilities. Not only can we share the same on-screen images, but we can also take over the cursor and change or correct, or show a specific area to our colleagues, many miles away. Imagine the advantages of being continuously on-line and being able to consult with sharp up to date images, instead of just words. Reports can be typed and directly corrected and checked; an accurate manner of passing on and corroborating information. The time saved is immeasurable.

Methods: Each department has a well-equipped conference room with PC's and projection possibilities. We can quickly send large amounts of information such as radiotherapy CAT scans with isodose curves or diagnostic X-ray investigations by using the really fast speed offered by broadband communication. The security is guaranteed by using a Virtual Private Network (VPN) between the locations. Various software programs make the communication and sharing possible.

The financial support of the organisation is an essential pre- requisite.

Results: The RT technicians took this opportunity to set up a regular continuing education program. One of the more important aspects is the 'sharing' of continuing education. Our aim is not only to teach but also to share in the daily practices of each department hereby broadening and heightening the knowledge and expertise of the RT technicians. The total quality of the treatment is continuously raised to a higher standard The patients and the RT professions all gain from this investment. New techniques can be more efficiently demonstrated and explained. The departments can also help each other to optimize the workflow and the quality of the end product.

Conclusion: We no longer need to travel backwards and forwards in order to discuss a patient case or to give a lecture. Once setup, the connection is straightforward. The learning potential for all levels of staff is enormous. The financial aspects should not be a stumbling block for something that will soon be as necessary as a phone call. This new technology offers many great possibilities for the future, but this can only be realized with enthusiasm, good organizational support and ICT backup

1119 poster

I.O.R.T. using a non dedicated linac: operating procedures

G. Brusadin, R. Berto/i, E. Celotti Baldi, R. Bares, G. Fedato

CRO Aviano, Radiotherapy, A~,iano PN, Italy Introduction: In the latter half of 1998, at the Department of Radiotherapy of the Aviano Cancer Centre, a IORT Project was initiated with a view to clinically implementing the IORT

Posters S469

modality using a non-dedicated Linac (Varian 2100C; 6-9- 12-16-20 MeV electrons). The Radiation Therapist Technologists (RTT) were involved in the IORT project and they actively participated in the determination of IORT operating procedures. The first IORT treatment was delivered on April 1 "t, 1999.The present presentation reports on our 5- year experience with IORT, which, up to the present time, numbers over 150 treatments. The presentation gives also an account of the problems dealt with and of the actions taken thereof.

Problems and requires' : In the initial phase of the IORT project the following issues were addressed:

- Adequate training Of the RTTs. The RTTspart icipated in indoor multidisciplinary meetings and they visited several Institutions where the IORT modality had been already implemented. In addition, the RTTs. had a specific training in the routine activities of an operating room.

- Careful planning and scheduling of the IORT intervention within the routine activities of the Radiotherapy department. The suspension of ordinary treatments was carefully scheduled to allow the delivery of the IORT treatment.

- Pre-treatment dosimetric measurements (including various electrons energies) were made.

Finally, arrangements were made for the pre-treatment sanitisation of the Linac bunker prior to IORT delivery and for the isolation of the route between the operating room and the non-dedicated Linac.

Operating procedures: The indoor training involved all the health personnel who participated in the IORT Project. After six months of training, including simulation of the IORT treatment, of the route between the operating room and the non-dedicated Linac, and docking, the operating procedures were established.

The presentation details those procedures.

Conclusions: From our experience, we find that to carry out these procedures safely, these requirements are needed:

• Perfect acquaintance of the procedures and the equipments by all involved health care professionals.

• Training of a work group.

In the IORT modality using a non-dedicated Linac the primary organisational aspect to arrange is the suspension of the every day radiating treatments. We estimate in about two hours the time needed to carry out the procedures in the Linac room. This means a delay for the patients attending for the every day external treatment. This delay is well accepted if the patients are informed, in an exhausting way, why they have to wait.

1121 poster

A qua l i ty assurance protocol for cone-beam CT for the radiation therapy technologist

R. de Jon,q, D. Minkema, J.J. Sonke, M. Herk van, P. Remeijer

Netherlands Cancer Institute, Radiotherapy, Amsterdam, The Netherlands

Introduction: With the introduction of Cone-Beam CT (CBCT) in our department we aim to reduce the geometrical uncertainties, like organ motion, organ shape variations and patient setup errors. As a result of the increasing accuracy narrower margins can be used, so there will be more room for dose escalation with less normal tissue complications. As a first step, we started using CBCT as a replacement of portal imaging for the correction of setup errors in February

2004. Within the proces of treatment planning and radiation, we distinguish 4 isocenters: conventional or planning CT, Linac, lasers and CBCT. These 4 isocenters must be the same when using image guided radiotherapy. The conventional CT, Linac and lasers are already checked routinely, however an additional check is needed for the CBCT. We therefore developed a simple method to check this calibration on a regular basis.

Methods and mater ia ls: The Cone-Beam system consists of two retractable arms mounted on the Linac at 90 ° of the MV- source. On one arm an amorphous silicon flat panel detector is mounted and on the other arm a kV-source. The most important difference with a conventional CT is that the whole CT volume is scanned in one rotation, because CBCT uses a cone shaped beam instead of a fan shaped beam, and a 2- dimensial detector of 41.5x41.5 cm instead of a single row of detectors.

For this CBCT isocenter check an in-house developed phantom with ball bearings for the alignment, and PVC rods for matching was used. The alignment of the phantom was checked with portal images (acquired on the Linac) matched with DRR's generated from the reference scan. Next, the alignment was determined by matching a CBCT scan with the reference scan. If the isocenters of the Linac and the CBCT are the same, than the shift (=outcome of both matches) should be the same.

Results: Performing this QA test takes about 15 minutes, including a warm up procedure for the kV source. Our first results from 14 checks, over almost three months, are in the next table:

! .......................... ~Difference in portal image center and CBCT scan center

......... :~ '~!~(mm) Ay (mm) ~Az Cmm)

Average~-0.1 1.2 0.2

!~t5 . . . . ~0.6 0.4 0.4

The value of hy is above our limi{s (1 mm) and recently we found a stability problem in the position of the kV-source, that might explain this systematic error. This stability problem has been solved,

Conclusions: This new quality assurance protocol for the verification of the kV and MV isocenter is now used on a weekly basis by the RTT working on the CBCT machine, and has revealed a small construction error in the system.

1122 poster

Radiotherapy process redesign and their consequences for radiation technologists in BVI, The Netherlands

M.E. van Oosterbaan, A. Hol, T.C. van der Klooster, A.E.M. Koolen, J.M. van Lieshout, M.E.M. van der Made, C.G. Schasfoort, J.B.W. Smits, N. van de Wiel

Dr. Bernard Verbeeten Instituut, Radiotherapy, Tilburg, The Netherlands

Introduction: The Bernard Verbeeten Institute currently does not fulfil the conditions of national waiting-time conventions for radiotherapy. For the coming years, a constant growth has been expected with respect to the amount of BVI radiotherapy Patients. By use of the current management, this will result in both emotional and physical avoidable damagel This damage is caused by a lack of capacity.

In order to cope with this situation in a suitable and qualitative responsible manner, it has been decided to analyse the radiotherapy process and to redesign it with the methodology of Business Process Redesign.