Assessment of absorbed dose to thyroid, parotid and ovaries in patients undergoing Gamma Knife radiosurgery

Abstract

Stereotactic radiosurgery was originally introduced by Lars Leksell in 1951. This treatment refers to the noninvasive destruction of an intracranial target localized stereotactically. The purpose of this study was to identify the dose delivered to the parotid, ovaries, testis and thyroid glands during the Gamma Knife radiosurgery procedure. A three-dimensional, anthropomorphic phantom was developed using natural human bone, paraffin and sodium chloride as the equivalent tissue. The phantom consisted of a thorax, head and neck and hip. In the natural places of the thyroid, parotid (bilateral sides) and ovaries (midline), some cavities were made to place TLDs. Three TLDs were inserted in a batch with 1 cm space between the TLDs and each batch was inserted into a single cavity. The final depth of TLDs was 3 cm from the surface for parotid and thyroid and was 15 cm for the ovaries. Similar batches were placed superficially on the phantom. The phantom was gamma irradiated using a Leksell model C Gamma Knife unit. Subsequently, the same batches were placed superficially over the thyroid, parotid, testis and ovaries in 30 patients (15 men and 15 women) who were undergoing radiosurgery treatment for brain tumours. The mean dosage for treating these patients was 14.48 +/- 3.06 Gy (10.5-24 Gy) to a mean tumour volume of 12.30 +/- 9.66 cc (0.27-42.4 cc) in the 50% isodose curve. There was no significant difference between the superficial and deep batches in the phantom studies (P-value < 0.05). The mean delivered doses to the parotid, thyroid, ovaries and testis in human subjects were 21.6 +/- 15.1 cGy, 9.15 +/- 3.89 cGy, 0.47 +/- 0.3 cGy and 0.53 +/- 0.31 cGy, respectively. The data can be used in making decisions for special clinical situations such as treating pregnant patients or young patients with benign lesions who need radiosurgery for eradication of brain tumours.

Response of l-alanine and 2-methylalanine minidosimeters for K-Band (24GHz) EPR dosimetry

“…4 and 5 it can be seen that our system (minidosimeter/K-Band spectrometer) is able to detect doses of the order of 10 Gy, unlike the work of Mack et al [39] whose minimum dose was 150 Gy to obtain an X-Band EPR spectrum with good S/N ratio with an L-alanine minidosimeter. It is important to note that dose values typically found in radiosurgery treatments are 10 Gy [40,41] making our system, a potential candidate to be used in radiosurgery dosimetry.…”

Dosimetry and verification of 60Co total body irradiation with human phantom and semiconductor diodes

“…In order to check the accuracy in dose delivery, a human phantom which had three sections (head and neck, trunk, hip) was used. [13] A 0.3-cc ion chamber (TM31013, PTW-Freiburg) was imbedded in the phantom at the prescribed point (umbilicus) and the delivered dose was measured.…”

“…The validity of these algorithms was investigated using the human phantom. [13] Surface doses were measured by diodes and the positioning of these detectors was carefully carried out in order to avoid a shadowing effect. Midplane doses were measured with the 0.3 cc ionization chamber (TM31013).…”

Consideration of the radiation dose delivered away from the treatment field to patients in radiotherapy

“…Hasanzadeh et al . [45] constructed an anthropomorphic phantom and undertook TLD measurements of dose in untargeted organs for Gamma-Knife radiosurgery. Petti et al .…”

“…[45] The subplot is a ratio plot of the 6-field CRT and IMRT deliveries compared to the 4-field CRT delivery (monitor units were 1260, 1308 and 2850, respectively). Difference between achieving a 14×14-cm 2 field with a static MLC or with a sliding-window technique [adapted from Sharma et al .…”