A totally integrated simulation technique for three-field breast treatment using a CT simulator.
A method was devised to simulate patients with breast cancer in the actual treatment position utilizing a diagnostic CT spiral scanner, 3-D Image Workstation for virtual simulation, and a laser coordinate system to transfer planning parameters to the patient's skin. It was desired to produce non-divergent tangential beams through the lung as well as a matched line for tangential and supraclavicular fields. The patients were immobilized in an Alpha CradleTM cast. Radio-opaque markers were placed on the superior, inferior, medial, and lateral margins of the field so as to afford appropriate initial field set-up approximations. The patient was scanned. The data set was then transferred to the workstation where an isocenter was chosen. The patient was marked. Virtual simulation was then performed. This method employed a half beam technique for the posterior edge of the tangential fields. Table rotation and blocking of the superior margin of the tangential fields were used to produce a vertical edge to match a supraclavicular field. Using a beam's eye view the lateral tangent was matched to the medial exit. A digitally reconstructed radiograph was created to define the tangent fields and place the supraclavicular block. Our initial experience with 50 patients verifies that this is a reproducible and accurate technique. Time required for immobilization and tangential field simulation is approximately 30 minutes. Data is available for 3-D treatment planning or 2-D treatment planning on a reconstructed transverse slice angled to match the collimator angle through the patient. Using a CT simulator for simulation of breast cancer affords accuracy of at least equal magnitude to conventional simulators as determined by beam films and ease of set-up. This technique also affords greater ease in changing treatment parameters without having to resimulate the patient.
Butker
E K
EK
Department of Radiation Oncology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Helton
D J
DJ
Keller
J W
JW
Hughes
L L
LL
Crenshaw
T
T
Davis
L W
LW
D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed