Compatibility of 3D printing materials and printing techniques with PAGAT gel dosimetry

Elter, A.; Dorsch, S.; Mann, P.; Runz, A.; Johnen, W.; Karger, Christian P.

doi:10.1088/1361-6560/aafef0

Cited by 17 publications

(19 citation statements)

References 23 publications

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“…As an example, the new 3D printed prostate organ surrogate could be filled with polymer dosimetry gel instead of tissue surrogate. The compatibility of polymer dosimetry gel with the 3D print material of the prostate has already been demonstrated by Elter et al 27 This combination would allow for additional 3D dose measurements in the target, which was not possible with the ADAM phantom. An upcoming study will further elaborate on this point.…”

Section: E Potential Applications In Image Guided Radiotherapy Plamentioning

confidence: 93%

Technical Note: ADAM PETer – An anthropomorphic, deformable and multimodality pelvis phantom with positron emission tomography extension for radiotherapy

et al. 2020

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Objective: To develop an anthropomorphic, deformable and multimodal pelvis phantom with positron emission tomography extension for radiotherapy (ADAM PETer). Methods: The design of ADAM PETer was based on our previous pelvis phantom (ADAM) and extended for compatibility with PET and use in 3T magnetic resonance imaging (MRI). The formerly manually manufactured silicon organ surrogates were replaced by 3D printed organ shells. Two intraprostatic lesions, four iliac lymph node metastases and two pelvic bone metastases were added to simulate prostate cancer as multifocal and metastatic disease. Radiological properties (computed tomography (CT) and 3T MRI) of cortical bone, bone marrow and adipose tissue were simulated by heavy gypsum, a mixture of Vaseline and K 2 HPO 4 and peanut oil, respectively. For soft tissues, agarose gels with varying concentrations of agarose, gadolinium (Gd) and sodium fluoride (NaF) were developed. The agarose gels were doped with patientspecific activity concentrations of a Fluorine-18 labelled compound and then filled into the 3D printed organ shells of prostate lesions, lymph node and bone metastases. The phantom was imaged at a dual energy CT and a 3T PET/MRI scanner. Results: The compositions of the soft tissue surrogates are the following (given as mass fractions of agarose[w%]/NaF[w%]/Gd[w%]): Muscle (4/1/0.027), prostate (1.35/4.2/0.011), prostate lesions (2.25/4.2/0.0085), lymph node and bone metastases (1.4/4.2/0.025). In all imaging modalities, the phantom simulates human contrast. Intraprostatic lesions appear hypointense as compared to the surrounding normal prostate tissue in T2-weighted MRI. The PET signal of all tumors can be localized as focal spots at their respective site. Activity concentrations of 12.0 kBq/mL (prostate lesion), 12.4 kBq/mL (lymph nodes) and 39.5 kBq/mL (bone metastases) were measured. Conclusion: The ADAM PETer pelvis phantom can be used as multimodal, anthropomorphic model for CT, 3T-MRI and PET measurements. It will be central to simulate and optimize the technical workflow for the integration of PET/MRI-based radiation treatment planning of prostate cancer patients.

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Section: E Potential Applications In Image Guided Radiotherapy Plamentioning

confidence: 93%

Technical Note: ADAM PETer – An anthropomorphic, deformable and multimodality pelvis phantom with positron emission tomography extension for radiotherapy

et al. 2020

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“…Therefore, all workflows for dosimetry studies are well established at our institution. 7,14,21,22,24…”

Section: Methodsmentioning

confidence: 99%

“…Slight discrepancies (maximum 5%) between measured and planned doses were observed only on the edges of the prostate organ surrogate. These discrepancies could potentially result from the wall effect 21 , on the other hand they appear to have a non-random structure on the gamma maps (Figure 4). Further measurements should be done to investigate this effect.…”

Section: Methodsmentioning

confidence: 99%

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Technical Note: On the feasibility of performing dosimetry in target and organ at risk using polymer dosimetry gel and thermoluminescence detectors in an anthropomorphic, deformable, and multimodal pelvis phantom

et al. 2021

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Objective To assess the feasibility of performing dose measurements in the target (prostate) and an adjacent organ at risk (rectum) using polymer dosimetry gel and thermoluminescence detectors (TLDs) in an anthropomorphic, deformable, and multimodal pelvis phantom (ADAM PETer). Methods The 3D printed prostate organ surrogate of the ADAM PETer phantom was filled with polymer dosimetry gel. Nine TLD600 (LiF:Mg,Ti) were installed in 3 × 3 rows on a specifically designed 3D‐printed TLD holder. The TLD holder was inserted into the rectum at the level of the prostate and fixed by a partially inflated endorectal balloon. Computed tomography (CT) images were taken and treatment planning was performed. A prescribed dose of 4.5 Gy was delivered to the planning target volume (PTV). The doses measured by the dosimetry gel in the prostate and the TLDs in the rectum (“measured dose”) were compared to the doses calculated by the treatment planning system (“planned dose”) on a voxel‐by‐voxel basis. Results In the prostate organ surrogate, the 3D‐γ‐index was 97.7% for the 3% dose difference and 3 mm distance to agreement criterium. In the center of the prostate organ surrogate, measured and planned doses showed only minor deviations (<0.1 Gy, corresponding to a percentage error of 2.22%). On the edges of the prostate, slight differences between planned and measured doses were detected with a maximum deviation of 0.24 Gy, corresponding to 5.3% of the prescribed dose. The difference between planned and measured doses in the TLDs was on average 0.08 Gy (range: 0.02–0.21 Gy), corresponding to 1.78% of the prescribed dose (range: 0.44%–4.67%). Conclusions The present study demonstrates the feasibility of using polymer dosimetry gel and TLDs for 3D and 1D dose measurements in the prostate and the rectum organ surrogates in an anthropomorphic, deformable and multimodal phantom. The described methodology might offer new perspectives for end‐to‐end tests in image‐guided adaptive radiotherapy workflows.

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“…Especially, it is necessary to carry out the experimental dosimetric verification before radiotherapy treatments, and generally phantoms have been used for the verification because it is difficult to directly measure actual 3D dose distribution at the target volume inside human body. Recent investigations have demonstrated that additive manufacturing enables us to fabricate the desired shape of phantoms (Takeshi et al 2017;Forte et al 2016;Elter et al 2019;Pantelis et al 2018;Leonard et al 2018;Fabian et al 2016). Due to the irradiated regions in polymer gels becoming visibly opaque with absorbed dose, polymer gels have been considered as an alternative to water as material of phantoms.…”

Section: Introductionmentioning

confidence: 99%

3D printable inter cross-linking network (ICN) gels for reversible transparency control with water content

et al. 2019

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A patient-specific phantoms, which are equivalent to human tissues, is needed in the experimental dosimetric verification before radiotherapy treatments. Most of the shape of gel phantoms have been structurally limited because of the fabrication method using mold technique. The present study focuses on direct freeform fabrication of gel phantom with the customized optical 3D gel printing system. Life-sized gel phantoms were replicated using conventional mold techniques, the 3D printer with two-step sequential free-radical polymerization process and inter cross-linking network gels as 3D printing materials. The gel phantoms are ultraviolet light-sensitive instead of radiation. The ultraviolet sensitivity of the gel phantoms (using mold techniques) with different molar ratios were experimentally evaluated with transmittance measurements, and were theoretically estimated by curve fitting to the observed data. This measurement gave us the insight that more vinyl monomers in the gel phantoms caused rapid polymerization and visibly opaque as well as conventional gel dosimeters. We confirmed that inter cross-linking network gel was 3D printable with the customized 3D printer, with resolution of fabrication 500 lm, as pre-finger-shaped phantom. The cross section of 3D printed gel phantom showed the distribution of opacity, that is, the distribution of UV irradiation. We expect that the 3D printer specialized gel materials and ICN gels are feasible for practical fabrication method of 3D gel phantom.

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Compatibility of 3D printing materials and printing techniques with PAGAT gel dosimetry

Cited by 17 publications

References 23 publications

Technical Note: ADAM PETer – An anthropomorphic, deformable and multimodality pelvis phantom with positron emission tomography extension for radiotherapy

Technical Note: ADAM PETer – An anthropomorphic, deformable and multimodality pelvis phantom with positron emission tomography extension for radiotherapy

Technical Note: On the feasibility of performing dosimetry in target and organ at risk using polymer dosimetry gel and thermoluminescence detectors in an anthropomorphic, deformable, and multimodal pelvis phantom

3D printable inter cross-linking network (ICN) gels for reversible transparency control with water content

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