Helical tomotherapy planning
Patient will dress the diving suit (3 mm thick) to create bolus effect. AccuFix™ Cantilever
Board™ with shoulder depression and thermoplastic fixation were used for head and shoulder
immobilization. BlueBagTM immobilization system (Medical Intelligence) was used to fix main
trunk and extremities. Both immobilization systems provide a consistent treatment position
from the initial computed tomography (CT) scanning, pretreatment megavoltage CT (MVCT)
imaging to final treatment delivery. For tomotherapy treatment planning, a CT image set of
the whole body was required. The patients were scanned in a large bore (75 cm) CT scanner
(Siemens, SOMATOM Definition, Dual source computed tomography system). Because most critical
organs are located in the central part of the body, therefore two image sets were scanned
with 2.5 mm and 5 mm for upper and lower part, respectively. The level at 15 cm above knee
was used as a reference point to separate the upper and lower set. The geometric edges of
both fields were abutted at the HT treatment's 50% isodose plane.
Both image sets were restored on a Pinnacle workstation using the Pinnacle Launch Pad
Restore utility then using the Philips Pinnacle3 treatment planning system for contouring
because the HT planning system has no such capability. After that, the plan was transferred
to the Tomotherapy Hi Art Planning system (Tomotherapy, Inc., Madison, Wisconsin, USA). The
clinical target volume (CTV) included the entire body surface system with subcutaneous 0.5
cm. To account for set-up variability and breathing motion, a planning target volume (PTV)
was generated with a 0.5 cm margin The prescription dose was 75 cGy/fraction in 4 times/wk
for total skin area and for tumor area. Total doses of 30 Gy to 95% of the PTV are delivered
to the total skin area and tumor part, respectively. The normal tissue dose constraints
utilized were based on the results of the survey of the clinical outcome of the target dose
and dose limits to various organs at risk (OARs) such as the brain, optic chiasm, optic
nerves, lenses, eyes, parotid glands, oral cavity, thyroid gland, bilateral lungs,
esophagus, heart, liver, spleen, pancreases, kidneys, bowel, bladder, uterus and vagina.
Maximum importance was given to target dose coverage. The constraints on dose and penalty
were adjusted accordingly during optimization. The field width, pitch, and modulation factor
(MF) used for the treatment planning optimization were 2.5, 0.287 cm, and 3.5, respectively.
The dose volume histograms (DVHs) were calculated for the target and individual OARs.
Toxicity of treatment was scored according to the Common Terminology Criteria for Adverse
Events v4.0 (CTCAE v4.0).
Daily check of patient positioning was performed by the MVCT system integrated in the
tomotherapy machine. Briefly, before every treatment, MVCT scans were taken in selected
regions using the normal mode (4 mm slice thickness) of the body and fused with the
treatment planning CT scan using bony anatomy and soft tissue images such as the lungs.
Three sets of MVCT scan (scan 1, orbits to T4; scan 2, T10 to the ischial tuberosities; scan
3, 15 cm above knee to 15 cm below knee) were performed to the check the patient's whole
body alignment. MVCT scans were obtained. Image fusions were evaluated by the attending
physician and physicist. Any translational shifts suggested by the image fusion results were
applied to the final patient setup before treatment delivery. The tolerance of setup error
allowed only a 5-mm difference between the three scans in any of the three translation
directions and 1° of difference in roll. Additional selected MVCT scans were performed after
treatment to verify patient immobilization.
Observational Model: Case-Only, Time Perspective: Retrospective
Skin lesions size
every month from treatment up to half year
Taiwan: Institutional Review Board
FEMH No. 101115-E