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Scalp Dose Measurement for Single Fraction Stereotactic Radiotherapy Patients

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S Singh

S Singh1*, K Jassal2 , B Sarkar3 , U Giri4 , S pal5 , K Vittal6 , s osman7 , (1) fortis memorial research institute, Gurgaon, haryana, (2) Fortis Memorial Research Institute, Gurgaon, ,(3) AMRI Cancer Centre, Kolkata, ,(4) ,,,(5) RML, Lucknow, Lucknow, Uttar Pradesh, (6) Fortis Memorial Research Institute, Gurgaon, Haryana, (7) Fortis Momerial Research Institute, Gurgaon, Haryana


SU-I-GPD-T-592 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Dosimetry measurements of scalp for alopecia in SRS patients with hypo fractionated regimens

Methods: A skull phantom was constructed to measure the scalp dose for Stereotactic radiotherapy (SRS) patients. Skull was filled with the Bee wax having relative density of 0.958 g/cm3 which was equivalent to relative density of water 1 g/cm3. Phantom was immobilized with the SRS mask. For making the scalp of skull modeling wax was used having relative density equivalent to 0.900 g/cm3. Thickness of wax used was equivalent to 3.5 mm in thickness, to simulate the scalp of the patient. Phantom was scanned with Phillips CT (Philips Gemini TOF PET-CT, Amsterdam) scanner with 1.5 mm slice thickness. Patients selected were already contoured and treated. All the contours were transferred on the skull phantom after image fusion using point registration method on Monaco V5.11.01. The original plan were copied to phantom and same were delivered on the phantom. VMAT plan were generated to give a total dose of 25 Gy in single fraction. To measure the scalp dose, optically stimulated luminescence Nano dots were placed inside the scalp and on the surface of scalp.

Results: The measured mean scalp dose for a prescription dose of 25 Gy in single fraction for 5 patients inside and outside the scalp were 7.3±0.05 Gy, 6.45±0.45 Gy, 6.84±0.40 Gy, 6.7±0.1 Gy, 6.25±0.08 Gy.

Conclusion: The constructed skull phantom was proved to be the best tool for evaluation of scalp dose. The dose measured using phantom and OSL agreed to the dose that is sufficient for temporary alopecia.

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