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2013-8

2013-8

“Development and Application of new Rotational Radiotherapeutic Techniques using Gravity Oriented Absorbers and Films”

Danciu Claudia(1)
(1)European Medical Physics School, University of Patras, Greece


ABSTRACT
A short historical review on the conception and evolution of the synchronous protection technique is presented.
The idea of synchronous protection of the Organs At Risk (OARs) in rotational therapy was first conceived by Professor Proimos in 1957. Then, the beam was immobile and horizontal. The patient was rotating around a vertical axis, which was meeting the central ray of the beam. This idea was further developed in the early ’60s for the presently usual case, in which the patient is horizontal and immobile and the source rotates on a vertical plane about the patient. In this case, the protectors are gravity oriented.
During the next two decades (1960s and 1970s), the gravity oriented protectors were designed, built and applied for several cases such as cancer of larynx and esophagus with protection of spinal cord, cancer of cervix with protection of bladder and rectum, eccentric tumors, cancer of antrum or other targets with eye protection as well as lymph node irradiation.
Although these techniques offer very good physical results, they were not so widely adopted and applied by the radiotherapeutic community, mainly because the imaging equipment and techniques (CT, ultrasound, etc.) were not so much developed as they are now.
The investigation of concrete physicogeometric problems and to propose practical and simple solutions for the application of such gravity oriented protectors, was later introduced by Danciu C in her PhD Thesis (Patras, 2001).
As a result, new techniques were developed and they refer to:
(a) modulating and filtering the rotating beam for targets near or around the spinal cord;
(b) shaping continuously the parallel to the axis of rotation sides of the rotating beam;
(c) irradiation of small irregular tumours with protection of small neighbours under high geometric accuracy;
(d) treatment of cervix cancer with simultaneous protection of the bladder, the rectum, the femurs and the spinal cord and (e) tomography by the rotating beam using a bank of parallel films oriented by gravity. These techniques have been applied on home-made solid phantoms of unit density material and on commercially available anthro-pomorphic phantoms (e.g. Alderson phantoms) in connection with film dosimetry and ion chamber measurements.
A radiodosimetric investigation of three types of films has preceded the physical investigation of these new dynamic conformal external beam techniques.