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Skin dose for head and neck cancer patients treated
with intensity-modulated radiation therapy( IMRT )
Hsiao-Ju Fu ; Yuk-Wah Tsang ; Chih-Chia Chang
Departament of Radiation Oncology, Dimanson Medical Foundation Chia-Yi Christian Hospital, Taiwan
Purpose
This research focused on the reliability of thermoluminescent dosimeters (ultrathin TLD) and
ISP Gafchromic EBT film to measure the surface dose in phantom and the skin dose in headand-neck patients treated with intensity-modulated radiation therapy technique (IMRT).
Materials and Methods
Seven-field treatment plans with prescribed dose of 180cGy were performed on Eclipse
treatment planning system (version8.1) which utilized pencil beam calculation algorithm(PBC).
In calibration test, the variance coefficient of the ultrathin TLDs is within 3%. The points on the
calibration curve of the Gafchromic film are within 1% variation. Five measurements were taken
on phantom using ultrathin TLD and EBT film respectively. The measured mean surface doses
between ultrathin TLD or EBT film are within 5% deviation. Skin doses of 6 patients were
measured for initial 5 fractions and the mean dose per-fraction was calculated.
Results
If the extrapolated doses for 30 fractions were below 4000cGy, the skin reaction grading
observed according to Radiation Therapy Oncology Group (RTOG) was either grade 1 or grade
2 ( in figure 1 and 2). If surface dose exceeded 4500cGy in 31 fractions, then grade 3 to 4 ( in
figure 3 and 4) skin reaction was observed.
Fig. 1 The skin reaction grading: grade 1
Fig. 2 The skin reaction grading: grade 2
Fig. 3 The skin reaction grading: grade 3
Fig. 4 The skin reaction grading: grade 3 to 4
Conclusions
In future study, more patients should be enrolled and establish the relationship between
skin doses and skin reactions more precisely.