Remote afterloading for neutron brachytherapy using californium-252.
BACKGROUND
Despite a pronounced technical process attained in radiotherapy of malignant neoplasms, no remarkable improvement in the treatment results has been achieved. The reason for this stagnation is the interaction between tumor cell and photon radiation. Tumor resistance against photon bombardment can be broken down by applying high linear energy transfer (LET) radiation-based treatment. The discovery of californium-252 ((252)Cf) nuclide, a source of gamma neutron radiation, established a precondition for using neutrons in tumor brachytherapy. The design of a remote afterloading device using (252)Cf sources remains an unsolved problem.


METHODS
The afterloading device has been designed as a stationary radiator which is composed of three mutually interconnected units: 1. the control and drive unit consisting of a control computer and a motor-driven bowden system carrying the (252)Cf source; 2. the source which is housed in a watertight concrete vessel-storage strong room, situated in the ground at a depth of 25 cm beneath the patient's bed; 3. the afterloading application module installed in the irradiation room.


RESULTS
Remote afterloading allows simple, inexpensive and highly efficient radiation protection and work safety for the operating personnel. The sources may be moved arbitrarily during treatment with a position accuracy of 0.5-1.0 mm within a distance of 520 cm from the source storage position in the strong room to the application position. Both afterloading systems' unused indexer outputs are protected electronically and mechanically against any unintentional movement of the source outside the application tubes.


CONCLUSIONS
The technologic concept of the present automatic afterloading device for neutron brachytherapy represents a possible option from the range of conceivable design variants, which - while minimizing technologic and economic requirements - provides the operating personnel with optimum protection and work safety, thus extending the applicability of high LET radiation-based treatment methods in clinical practice.
Tacev
Taco
T
Masaryk Memorial Cancer Institute, Brno, Czech Republic. tacev@procoms.cz
Grigorov
Grigor
G
Papírek
Tomás
T
Kolarík
Vladimír
V
D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D002142:Californium / Q000627:therapeutic use*; D004867:Equipment Design; D006801:Humans; D018499:Linear Energy Transfer; D009502:Neutrons / Q000627:therapeutic use*; D011835:Radiation Protection
D002142:Californium