ESTRO 36 Abstract Book

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S404 ESTRO 36
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Material and Methods
Five different TL materials TLD100, TLD100H, TLD200,
TLD400 and TLD500, were investigated. Each type of TL
dosimeter was irradiated to the eight different qualities
of x-radiation. Mean of the response of the 5 dosimeters
for a certain x-radiation with effective energy Eeff was
taken as the energy dependent TL response of that type
of TL dosimeter. For each type of TL detector, energy
dependence curves were determined by fitting the
experimental results with a polynomial function. Tandem
curve pairs for six different combinations were generated;
;1.TLD100H, TLD200, TLD400, 2.TLD100H, TLD200,
TLD500, 3.TLD100H, TLD400, TLD500, 4.TLD100H,
TLD200, TLD400,5.TLD100, TLD200, TLD500 and
6.TLD100, TLD400, response ratios at different
energies was calculated and compared with two TL
material tandem systems.
Results
All Tandem curves exhibited maximum TL response ratio,
Emax, at approximately 45 keV, with reduction in TL
response ratios at energies above and below this energy
level. All tandem combinations, except the combinations
(1) and (4) showed that at energies in the 30 to 80 keV
range, where the TL response ratio of tandem pair (i) is
same, TL response ratio tandem pair (ii) differs by 20-30%,
Figure 2. This will help in determining whether the
effective energy of radiation beam is less than or greater
than the Emax.
Conclusion
This work presents some possible TLD tandem systems
consisting of three types TL materials which are better
able to estimate effective energy of a radiation beam in
the 30 to 100 keV range than the presently used two TL
material tandem systems. This can potentially improve
dosimetry in situations where information about the
effective energy of radiation is crucial such as personal
monitoring. Considering the high sensitivity TLD100H, the
TL material increasingly being used in personal dosimetry,
tandem combinations of TLD100H,TLD200 & TLD500 or
TLD100H, TLD400 & TLD500 are recommended for x or
gamma radiation energy discrimination in the 30 to 120
keV range.
PO-0765 Preparation and Fabrication of a Full-scale
Patient-specific 3D-Printed Radiotherapy Phantom
D. Craft1, R. Howell1
1The University of Texas MD Anderson Cancer Center,
Radiation Physics, Houston- TX, USA
Purpose or Objective
Phantoms are used in a wide variety of ways for
radiotherapy research and quality assurance. Generally,
however, these phantoms are limited in size and
complexity to represent only small treatment areas or
generalized patients. 3D printing technology can make the
fabrication and design of patient-specific phantoms simple
and inexpensive, but has also been limited by size and
complexity due to the limited size of most 3D printers and
the tendency of materials to warp while being printed. We
aimed to overcome these limitations by developing an
effective 3D printing workflow that could be used to
design and fabricate large, full-scale, patient-specific
phantoms with negligible material warping errors. To
demonstrate the viability of our technique we produced a
full-scale phantom of a post-mastectomy patient treated
at our institution.
Material and Methods
The clinical CT data for a post-mastectomy patient at our
institution was converted into a 3D model, and then
trimmed to remove the patient’s head and arms to
simplify printing. The model was next sliced into eleven
2.5-cm-thick sagittal slices, which fit better and have less
warping relative to axial slices. Each slice was printed
using polylactic acid to represent all body tissues at 100%
infill. Air cavities and lower density regions like the lungs
were left open and unfilled. The slices were printed on an
inexpensive and commercially available 3D printer with