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  4. ADAM-Pelvic Phantom Update: Using Different Dosimetrydetectors to Measure the Dose by An End-To-End Validation

ADAM-Pelvic Phantom Update: Using Different Dosimetrydetectors to Measure the Dose by An End-To-End Validation

W Johnen1;2*, C Gillmann1;2, M Marot1;2, A Schwahofer1;2;3, A Runz1;2, G Echner1;2, (1) DKFZ, Heidelberg, DE, (2)Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, DE,(3) National Center for Radiation Research in Oncology (NCRO), Heidelberg, DE,

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: radiotherapy, anthropomorphic multimodal phantoms are used to verify new treatment techniques. This work describes an end-to-end test for measuring 3D dose distributions in prostate and rectum in an anthropomorphic pelvis phantom using polymer gel (PG) and thermoluminescent detectors (TLDs).

Methods: existing anthropomorphic pelvic phantom (ADAM) [REF 1 Niebuhr] was modified. Organs as prostate and rectum were 3D printed. The prostate and its connection with the bladder was designed in a way that prostates can be exchanged in between treatment series. Furthermore, the prostate shell is printed in a special process enabling a filling with polymer gel (PG). Dose measurements in the rectum were perfomed with thermoluminescence detectors (TLD). Therefore, a holder was designed (Autodesk Inventor, Autodesk, San Rafael, SA) containing nine bags for TLDs, which are equidistant with three in a row and three in a coloumn. The holder is made of a combination of the 3D printing materials Agilus30TM and VeroClearTM. It was created with the 3D printer Connex3 (Stratasys, Minnesota, US). The treatment plan was based on CT imaging. The whole irradiation process was conducted twice.

Results: 3D printed prostate shells can be filled with PG and placed consecutively in the phantom. The connection within the phantom allows a reproducible replacing of prostate and TLD holder in only 15 minutes.
The dose in the rectum was measured successfully with TLDs with an average dose difference of 0.08 Gy (range: 0.02-0-21 Gy) between measured and calculated dose. For a serial measurement several holders were used.




Conclusion: redesign of the ADAM and the use of new 3D printing techniques and the construction of a specific holder for TLDs allows to integrate dosimetry detectors into anthropomorphic phantoms. It leads to a dose distribution conformal to he measurements.

[1] Niebuhr et al Med Phys 43(2), pp.908-16, 2016

Keywords

Dosimetry, Phantoms, TLDs

Taxonomy

TH- Radiation Dose Measurement Devices: Phantoms for dosimetric measurement

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