End-to-end empirical validation of dose accumulation in MRI-guided adaptive radiotherapy for prostate cancer using an anthropomorphic deformable pelvis phantom

Bohoudi, O.; Lagerwaard, Frank J.; Bruynzeel, A.; Niebuhr, Nina I.; Johnen, W.; Senan, Suresh; Slotman, Ben J.; Pfaffenberger, A.; Palacios, Miguel

doi:10.1016/j.radonc.2019.09.014

Cited by 27 publications

(34 citation statements)

References 41 publications

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“…Hoffmanns et al 8 demonstrated that the ADAM‐phantom was suitable for end‐to‐end testing in MR‐guided online adaptive radiotherapy. In addition, Bohoudi et al 7 used the ADAM phantom to perform an end‐to‐end empirical validation of dose accumulation in MRI‐guided adaptive radiotherapy simulating six MR‐guided prostate SBRT treatment courses. However, in the ADAM phantom, dosimetry measurements were limited to films in distinct pockets at the surface of bladder and rectum.…”

Section: Discussionmentioning

confidence: 99%

“…The ADAM phantom was optimized to mimic human image contrast at 1.5T MRI and CT. 6 Organ motion and deformation can be simulated by varying bladder and rectum fillings. 7 For dosimetry measurements, imaging marker points and pockets for dosimetry films are implemented at the surface of rectum and bladder organ surrogates. Hoffmanns et al demonstrated the suitability of the ADAM phantom for end-to-end tests in MR-guided radiotherapy.…”

Section: Introductionmentioning

confidence: 99%

“…8 Bohoudi et al used the phantom for an end-to-end empirical validation of dose accumulation in MRI-guided adaptive radiotherapy for prostate cancer. 7 In the present note, we describe the extension of the ADAM phantom for compatibility with PET and use in 3T MRI. To allow for a safe and easy incorporation of radioactive isotopes, the design of the phantom was changed towards a completely modular structure.…”

Section: Introductionmentioning

confidence: 99%

“…Hoffmanns et al demonstrated the suitability of the ADAM phantom for end‐to‐end tests in MR‐guided radiotherapy 8 . Bohoudi et al used the phantom for an end‐to‐end empirical validation of dose accumulation in MRI‐guided adaptive radiotherapy for prostate cancer 7 …”

Section: Introductionmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…MRI phantoms have been developed primarily as standard reference objects or calibration tools used to validate the accuracy of in vivo measurements. Phantoms are built for a wide range of applications including geometric distortion, 2-4 motion correction, [5][6][7] Abbreviations used: 2D, two-dimensional; 3D, three-dimensional; ADC, apparent diffusion coefficient; B 0 , static magnetic field; B 1 , applied magnetic field; BW, bandwidth; CPMG, Carr- relaxometry, 8-10 perfusion, [11][12][13] diffusion, [14][15][16] chemical characterization [17][18][19] and MR-guided therapeutics, [20][21][22] all of which attempt to model a standard in vivo environment.…”

Section: Introductionmentioning

confidence: 99%

A strategy to prevent a temperature‐induced MRI artifact in warm liquid phantoms due to convection currents

2021

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MRI phantom studies often fail to mimic the temperature of the human body, which can negatively impact accuracy. An artifact induced by increasing temperature in liquid phantoms was observed, presenting a significant challenge to temperature‐controlled experiments. In this study we characterize and provide a solution to eliminate this temperature‐induced MRI artifact. Low concentration (0.5–2.5 mM) agar phantoms were prepared. Utilizing a temperature‐controlled phantom holder, T1‐ and T2‐weighted structural images were acquired at 7 T along with quantitative B0, B1, T1, T2 and ADC maps at both 25 and 37°C. Additionally, computer simulations were conducted to demonstrate the fluid flow and thermal flux patterns in water to provide an insight into the origins of the artifact. Evidence from computer simulation and quantitative MRI strongly suggest the artifact was caused by heat transfer in the form of natural convection leading to structured patterns of signal loss in MR images. The artifact was present up to agar concentrations of 1.5 mM (T1 = 3068 ± 16 ms, T2 = 1052 ± 20 ms, ADC = 2.29 ± 0.36 × 10−3 mm2/s at 25°C; T1 = 3928 ± 44 ms, T2 = 1122 ± 24 ms, ADC = 2.64 ± 0.49 × 10−3 mm2/s at 37°C), above which point increased sample viscosity no longer allows for convection currents, thereby eliminating the artifact. The methodology described in this work simplifies quantitative MR acquisition of liquid phantoms at physiological temperature by suppressing convection currents with relatively small changes to intrinsic MR parameters (T1 increased by 1.4% and T2 decreased by 17% for 1.5 mM agar at 25°C).

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Dosimetric considerations for moldable silicone composites used in radiotherapy applications

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et al. 2022

J Applied Clin Med Phys

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Due to their many favorable characteristics, moldable silicone (MS) composites have gained popularity in medicine and recently, in radiotherapy applications. We investigate the dosimetric properties of silicones in radiotherapy beams and determine their suitability as water substitutes for constructing boluses and phantoms. Two types of silicones were assessed (𝜌 = 1.04 g/cm 3 and 𝜌 = 1.07 g/cm 3 ). Various dosimetric properties were characterized, including the relative electron density, the relative mean mass energy-absorption coefficient, and the relative mean mass restricted stopping power. Silicone slabs with thickness of 1.5 cm and 5.0 cm were molded to mimic a bolus setup and a phantom setup, respectively. Measurements were conducted for Co-60 and 6 MV photon beams, and 6 MeV electron beams. The doses at 1.5 cm and 5.0 cm depths in MS were measured with solid water (SW) backscatter material (D MS-SW ), and with a full MS setup (D MS-MS ), then compared with doses at the same depths in a full SW setup (D SW-SW ). Relative doses were reported as D MS-SW /D MS-SW and D MS-MS /D SW-SW . Experimental results were verified using Monaco treatment planning system dose calculations and Monte Carlo EGSnrc simulations. Film measurements showed varying dose ratios according to MS and beam types. For photon beams, the bolus setup D MS-SW /D SW-SW exhibited a 5% relative dose reduction. The dose for 6 MV beams was reduced by nearly 2% in a full MS setup. Up to 2% dose increase in both scenarios was observed for electron beams. Compared with dose in SW, an interface of MS-SW can cause relatively high differences. We conclude that it is important to characterize a particular silicone's properties in a given beam quality prior to clinical use. Because silicone compositions vary between manufacturers and differ from water/SW, accurate dosimetry using these materials requires consideration of the reported differences.

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End-to-end empirical validation of dose accumulation in MRI-guided adaptive radiotherapy for prostate cancer using an anthropomorphic deformable pelvis phantom

Cited by 27 publications

References 41 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

A strategy to prevent a temperature‐induced MRI artifact in warm liquid phantoms due to convection currents

Dosimetric considerations for moldable silicone composites used in radiotherapy applications

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