Dynamic conical conformal radiotherapy using a C-arm-mounted accelerator: dose distribution and clinical application.
OBJECTIVE
The aim of this study was to solve anisotropy in the dose distributions from rotational conformal radiotherapy (RCRT) by using a C-arm-mounted accelerator.


METHODS
The linac head was designed to move along the C-arm with a maximum angle of 60 degrees (from a vertical position toward the gantry). Simultaneous rotation of the gantry creates a dynamic conical irradiation technique. Dynamic conical conformal radiation therapy (Dyconic CRT) was developed by combining the technique with continuous motion of a multileaf collimator. Dose distributions were measured in phantoms using film densitometry and compared with conventional RCRT. Dose distributions in actual radiation therapy patients are also presented.


RESULTS
Dyconic CRT enabled the precise delivery of noncoplanar beams without rotating the table. The measurements showed that three-dimensionally isotropic dose falloff was achieved with Dyconic CRT. Dose inhomogeneity in the sagittal direction with Dyconic CRT was compensated for by use of wedge filters.


CONCLUSIONS
The drawbacks of the dose distributions produced by RCRT were overcome with the use of Dyconic CRT.
Nakagawa
Keiichi
K
Department of Radiology, University of Tokyo Hospital, Tokyo, Japan. nakagawa-rad@umin.ac.jp
Aoki
Yukimasa
Y
Tago
Masao
M
Ohtomo
Kuni
K
D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy; D008268:Macular Degeneration; D010315:Particle Accelerators / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011832:Radiation Injuries / Q000517:prevention & control; D011874:Radiometry; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D012399:Rotation; D012449:Safety