Selective Internal Radiation Therapy With Yttrium-90 Glass Microspheres: Biases and Uncertainties in Absorbed Dose Calculations Between Clinical Dosimetry Models

Mikell, Justin; Mahvash, Armeen; Siman, Wendy; Baladandayuthapani, Veera; Mourtada, Firas; Kappadath, S. Cheenu

doi:10.1016/j.ijrobp.2016.07.021

Cited by 31 publications

(29 citation statements)

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“…The mean error in mean tumor absorbed doses between the Monte Carlo and 90Y‐SurePlan algorithms was determined to be less than 3% with a range of −9% to +14%. The mean error in dosimetry between different Monte Carlo packages has been reported to be around 5% . Other sources of uncertainty for absorbed dose calculations following 90 Y‐SIRT include the accuracy of the dose calibrator in determining the administered 90 Y activity (< 5%) and the uncertainties in SPECT quantification of the in vivo 90 Y distribution (< 20%).…”

Section: Discussionmentioning

confidence: 99%

“…90 Y SPECT images (counts/ml) for each patient were converted to activity concentration (Bq/ml) using SPECT self‐calibration. The self‐calibration approach used to determine the 90 Y activity concentration from 90 Y SPECT/CT images following 90 Y‐SIRT has been previously described . Briefly, the counts in each reconstructed SPECT voxel (counts/ml) were first normalized by the total counts in a prescribed SPECT FOV and then multiplied by the net administered 90 Y‐microsphere activity to compute the 90 Y activity concentration in that SPECT voxel (Bq/ml).…”

Section: Methodsmentioning

confidence: 99%

“…The self-calibration approach used to determine the 90 Y activity concentration from 90 Y SPECT/CT images following 90 Y-SIRT has been previously described. [9][10][11] Briefly, the counts in each reconstructed SPECT voxel (counts/ml) were first normalized by the total counts in a prescribed SPECT FOV and then multiplied by the net administered 90 Y-microsphere activity to compute the 90 Y activity concentration in that SPECT voxel (Bq/ml). The different approaches for 90 Y SPECT self-calibration stem from different definitions of the SPECT VOI used to determine the total SPECT counts associated with the 90 Y activity.…”

Section: B Spect Self-calibrationmentioning

confidence: 99%

“…Investigators have reported on the positive role of 90 Y planar and 90 Y bremsstrahlung SPECT/CT in disease management after 90 Y‐SIRT . Furthermore, 90 Y SPECT/CT also facilitates dosimetry at the voxel level that allows for investigations into the volume distribution of absorbed doses in tumors and normal liver tissue . A number of approaches have been described in the literature for generation and quantitation of 90 Y bremsstrahlung SPECT/CT, as described in a recent review article .…”

Section: Introductionmentioning

confidence: 99%

“…8 Furthermore, 90 Y SPECT/CT also facilitates dosimetry at the voxel level that allows for investigations into the volume distribution of absorbed doses in tumors and normal liver tissue. [9][10][11] A number of approaches have been described in the literature for generation and quantitation of 90 Y bremsstrahlung SPECT/CT, as described in a recent review article. 12 Some of the approaches for 90 Y SPECT quantitation include Monte Carlo-based modeling of SPECT corrections and reconstructions 13,14 to multiple energy window-based scatter compensations.…”

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confidence: 99%

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Characterization of ⁹⁰Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following ⁹⁰Y‐microsphere selective internal radiation therapy

Balagopal

Kappadath

2017

Medical Physics

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The mean error of < 3% for commercial software can be considered clinically acceptable for Y-SIRT dosimetry. Absorbed dose quantification using Y-SPECT self-calibration with the chest-abdomen contour was equivalent to that calculated using the SPECT FOV, but self-calibration with the total liver contour yielded substantially higher (~70%) dose values. The large biases revealed by our study suggest that consistent absorbed dose calculation approaches are essential when comparing Y-SIRT dosimetry between different clinical studies.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: B Spect Self-calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Characterization of ⁹⁰Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following ⁹⁰Y‐microsphere selective internal radiation therapy

Balagopal

Kappadath

2017

Medical Physics

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Dose volume histogram‐based optimization of image reconstruction parameters for quantitative ⁹⁰Y‐PET imaging

et al. 2018

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Purpose: 90 Y-microsphere radioembolization or selective internal radiation therapy is increasingly being used as a treatment option for tumors that are not candidates for surgery and external beam radiation therapy. Recently, volumetric 90 Y-dosimetry techniques have been implemented to explore tumor dose-response on the basis of 3D 90 Y-activity distribution from PET imaging. Despite being a theranostic study, the optimization of quantitative 90 Y-PET image reconstruction still uses the mean activity concentration recovery coefficient (RC) as the objective function, which is more relevant to diagnostic and detection tasks than is to dosimetry. The aim of this study was to optimize 90 Y-PET image reconstruction by minimizing errors in volumetric dosimetry via the dose volume histogram (DVH). We propose a joint optimization of the number of equivalent iterations (the product of the iterations and subsets) and the postreconstruction filtration (FWHM) to improve the accuracy of voxel-level 90 Y dosimetry. Methods: A modified NEMA IEC phantom was used to emulate clinically relevant 90 Y-PET imaging conditions through various combinations of acquisition durations, activity concentrations, sphere-to-background ratios, and sphere diameters. PET data were acquired in list mode for 300 min in a single-bed position; we then rebinned the list mode PET data to 60, 45, 30, 15, and 5 min per bed, with 10 different realizations. Errors in the DVH were calculated as root mean square errors (RMSE) of the differences in the image-based DVH and the expected DVH. The new optimization approach was tested in a phantom study, and the results were compared with the more commonly used objective function of the mean activity concentration RC. Results: In a wide range of clinically relevant imaging conditions, using 36 equivalent iterations with a 5.2-mm filtration resulted in decreased systematic errors in volumetric 90 Y dosimetry, quantified as image-based DVH, in 90 Y-PET images reconstructed using the ordered subset expectation maximization (OSEM) iterative reconstruction algorithm with time of flight (TOF) and point spread function (PSF) modeling. Our proposed objective function of minimizing errors in DVH, which allows for joint optimization of 90 Y-PET iterations and filtration for volumetric quantification of the 90 Y dose, was shown to be superior to conventional RC-based optimization approaches for imagebased absorbed dose quantification. Conclusion: Our proposed objective function of minimizing errors in DVH, which allows for joint optimization of iterations and filtration to reduce errors in the PET-based volumetric quantification 90 Y dose, is relevant to dosimetry in therapy procedures. The proposed optimization method using DVH as the objective function could be applied to any imaging modality used to assess voxel-level quantitative information.

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Systematic and random errors of PET‐based ⁹⁰Y 3D dose quantification

et al. 2020

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PurposeThe objective was to characterize both systematic and random errors in Positron Emission Tomography (PET)‐based 90Y three‐dimensional (3D) dose quantification.MethodsA modified NEMA‐IEC phantom was used to emulate 90Y‐microsphere PET imaging conditions: sphere activity concentrations of 1.6 and 4.8 MBq/cc, sphere‐to‐background ratios of 4 and 13, and sphere diameters of 13, 17, and 37 mm. PET data were acquired using a GE D690 PET/CT scanner for 300 min on days 0–11. The data were downsampled to 60–5 min for multiple realizations to evaluate the count starvation effect. The image reconstruction algorithm was 3D‐OSEM with PSF + TOF modeling; the parameters were optimized for dose‐volume histogram (DVH), as a 90Y 3D dose quantification. 90Y‐PET images were converted to dose maps using the local deposition method, then the sphere DVHs were calculated. The ground truth for the DVH was calculated using convolution method. Dose linearity was evaluated in decaying 90Y activity (reduced count rate and total count) and decreasing acquisition durations (reduced total count only). Finally, the impacts of the low 32‐ppm positron yield on PET‐based 3D 90Y‐dose quantification were evaluated; the bias and variability of resulting DVHs were characterized.ResultsWe observed nonlinear errors that depended on the 90Y activity (count rate) and not on the total true prompt counts. These nonlinear errors in mean dose underestimated the measured mean dose by> 20% for a measured dose range of 40–230 Gy; although the shapes of the DVH were not altered. Compensation based on empirical models reduced the nonlinearity errors to be within 5% for measured dose range of 40–230 Gy. In contrast, the errors due to nonuniformity introduced by image noise dominated the systematic errors in the DVH and stretched the DVH on both tails.For the 37‐mm sphere, the magnitude of errors in D80 increased from −25% to −36% when acquisition duration was decreased from 300 to 10 min. The effect of image noise on DVH was more extensive in smaller spheres; for the 17‐mm sphere, the magnitude of errors in D80 increased from −29% to −45% acquisition duration was decreased from 300 to 10 min. For the 37‐mm sphere, the errors in D20 increased from +3.5% to only +10.5% when the acquisition duration was decreased from 300 to 10 min; in the 17‐mm sphere, the errors in D20 were 6.5% for both 300‐ and 10‐min sphere images.ConclusionsCount‐starved 90Y‐PET data introduce both systematic and random errors. The systematic error increases the apparent nonuniformity of the DVH, while the random error increases the uncertainty in the DVH. The systematic errors were larger than the random errors. Lower count rate of 90Y‐PET also introduces systematic bias, which is scanner specific. The errors of bias‐compensated mean tumor dose were <10% when 90Y‐PET scan time was >15 min/bed for tumors >37 mm. Dmedian and Dmean were the most stable dose metrics. An acquisition duration of 30 min is recommended to keep the random errors < 10% for a typical tumor with sphere equivalent diameter >17 mm and average tumor dose >40 Gy.

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Selective Internal Radiation Therapy With Yttrium-90 Glass Microspheres: Biases and Uncertainties in Absorbed Dose Calculations Between Clinical Dosimetry Models

Cited by 31 publications

References 28 publications

Characterization of ⁹⁰Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following ⁹⁰Y‐microsphere selective internal radiation therapy

Characterization of ⁹⁰Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following ⁹⁰Y‐microsphere selective internal radiation therapy

Dose volume histogram‐based optimization of image reconstruction parameters for quantitative ⁹⁰Y‐PET imaging

Systematic and random errors of PET‐based ⁹⁰Y 3D dose quantification

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Selective Internal Radiation Therapy With Yttrium-90 Glass Microspheres: Biases and Uncertainties in Absorbed Dose Calculations Between Clinical Dosimetry Models

Cited by 31 publications

References 28 publications

Characterization of 90Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following 90Y‐microsphere selective internal radiation therapy

Characterization of 90Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following 90Y‐microsphere selective internal radiation therapy

Dose volume histogram‐based optimization of image reconstruction parameters for quantitative 90Y‐PET imaging

Systematic and random errors of PET‐based 90Y 3D dose quantification

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Characterization of ⁹⁰Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following ⁹⁰Y‐microsphere selective internal radiation therapy

Characterization of ⁹⁰Y‐SPECT/CT self‐calibration approaches on the quantification of voxel‐level absorbed doses following ⁹⁰Y‐microsphere selective internal radiation therapy

Dose volume histogram‐based optimization of image reconstruction parameters for quantitative ⁹⁰Y‐PET imaging

Systematic and random errors of PET‐based ⁹⁰Y 3D dose quantification