Whole-remnant and maximum-voxel SPECT/CT dosimetry in 131I-NaI treatments of differentiated thyroid cancer
(2016) In Medical Physics 43(10). p.5279-5287- Abstract
Purpose: To investigate the possible differences between SPECT/CT based whole-remnant and maximum-voxel dosimetry in patients receiving radio-iodine ablation treatment of differentiated thyroid cancer (DTC). Methods: Eighteen DTC patients were administered 1.11 GBq of 131I-NaI after near-total thyroidectomy and rhTSH stimulation. Two patients had two remnants, so in total dosimetry was performed for 20 sites. Three SPECT/CT scans were performed for each patient at 1, 2, and 3-7 days after administration. The activity, the remnant mass, and the maximum-voxel activity were determined from these images and from a recovery-coefficient curve derived from experimental phantom measurements. The cumulated activity was estimated using... (More)
Purpose: To investigate the possible differences between SPECT/CT based whole-remnant and maximum-voxel dosimetry in patients receiving radio-iodine ablation treatment of differentiated thyroid cancer (DTC). Methods: Eighteen DTC patients were administered 1.11 GBq of 131I-NaI after near-total thyroidectomy and rhTSH stimulation. Two patients had two remnants, so in total dosimetry was performed for 20 sites. Three SPECT/CT scans were performed for each patient at 1, 2, and 3-7 days after administration. The activity, the remnant mass, and the maximum-voxel activity were determined from these images and from a recovery-coefficient curve derived from experimental phantom measurements. The cumulated activity was estimated using trapezoidal-exponential integration. Finally, the absorbed dose was calculated using S-values for unit-density spheres in whole-remnant dosimetry and S-values for voxels in maximum-voxel dosimetry. Results: The mean absorbed dose obtained from whole-remnant dosimetry was 40 Gy (range 2-176 Gy) and from maximum-voxel dosimetry 34 Gy (range 2-145 Gy). For any given patient, the activity concentrations for each of the three time-points were approximately the same for the two methods. The effective half-lives varied (R = 0.865), mainly due to discrepancies in estimation of the longer effective half-lives. On average, absorbed doses obtained from whole-remnant dosimetry were 1.2±0.2 (1 SD) higher than for maximum-voxel dosimetry, mainly due to differences in the S-values. The method-related differences were however small in comparison to the wide range of absorbed doses obtained in patients. Conclusions: Simple and consistent procedures for SPECT/CT based whole-volume and maximumvoxel dosimetry have been described, both based on experimentally determined recovery coefficients. Generally the results from the two approaches are consistent, although there is a small, systematic difference in the absorbed dose due to differences in the S-values, and some variability due to differences in the estimated effective half-lives, especially when the effective half-life is long. Irrespective of the method used, the patient absorbed doses obtained span over two orders of magnitude.
(Less)
- author
- MINGUEZ GABINA, PABLO LU ; Flux, Glenn ; Genollá, José ; Delgado, Alejandro ; Rodeño, Emilia and Sjögreen Gleisner, Katarina LU
- organization
- publishing date
- 2016-10-01
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- I-NaI, differentiated thyroid carcinoma, dosimetry, thyroid bed remnants
- in
- Medical Physics
- volume
- 43
- issue
- 10
- pages
- 9 pages
- publisher
- American Association of Physicists in Medicine
- external identifiers
-
- wos:000385577900003
- pmid:27782699
- scopus:84986557775
- ISSN
- 0094-2405
- DOI
- 10.1118/1.4961742
- language
- English
- LU publication?
- yes
- id
- 39d2ecc1-b746-4dcf-abe6-0f63e781ebc8
- date added to LUP
- 2016-10-03 13:56:00
- date last changed
- 2024-05-03 10:52:48
@article{39d2ecc1-b746-4dcf-abe6-0f63e781ebc8, abstract = {{<p>Purpose: To investigate the possible differences between SPECT/CT based whole-remnant and maximum-voxel dosimetry in patients receiving radio-iodine ablation treatment of differentiated thyroid cancer (DTC). Methods: Eighteen DTC patients were administered 1.11 GBq of <sup>131</sup>I-NaI after near-total thyroidectomy and rhTSH stimulation. Two patients had two remnants, so in total dosimetry was performed for 20 sites. Three SPECT/CT scans were performed for each patient at 1, 2, and 3-7 days after administration. The activity, the remnant mass, and the maximum-voxel activity were determined from these images and from a recovery-coefficient curve derived from experimental phantom measurements. The cumulated activity was estimated using trapezoidal-exponential integration. Finally, the absorbed dose was calculated using S-values for unit-density spheres in whole-remnant dosimetry and S-values for voxels in maximum-voxel dosimetry. Results: The mean absorbed dose obtained from whole-remnant dosimetry was 40 Gy (range 2-176 Gy) and from maximum-voxel dosimetry 34 Gy (range 2-145 Gy). For any given patient, the activity concentrations for each of the three time-points were approximately the same for the two methods. The effective half-lives varied (R = 0.865), mainly due to discrepancies in estimation of the longer effective half-lives. On average, absorbed doses obtained from whole-remnant dosimetry were 1.2±0.2 (1 SD) higher than for maximum-voxel dosimetry, mainly due to differences in the S-values. The method-related differences were however small in comparison to the wide range of absorbed doses obtained in patients. Conclusions: Simple and consistent procedures for SPECT/CT based whole-volume and maximumvoxel dosimetry have been described, both based on experimentally determined recovery coefficients. Generally the results from the two approaches are consistent, although there is a small, systematic difference in the absorbed dose due to differences in the S-values, and some variability due to differences in the estimated effective half-lives, especially when the effective half-life is long. Irrespective of the method used, the patient absorbed doses obtained span over two orders of magnitude.</p>}}, author = {{MINGUEZ GABINA, PABLO and Flux, Glenn and Genollá, José and Delgado, Alejandro and Rodeño, Emilia and Sjögreen Gleisner, Katarina}}, issn = {{0094-2405}}, keywords = {{I-NaI; differentiated thyroid carcinoma; dosimetry; thyroid bed remnants}}, language = {{eng}}, month = {{10}}, number = {{10}}, pages = {{5279--5287}}, publisher = {{American Association of Physicists in Medicine}}, series = {{Medical Physics}}, title = {{Whole-remnant and maximum-voxel SPECT/CT dosimetry in <sup>131</sup>I-NaI treatments of differentiated thyroid cancer}}, url = {{http://dx.doi.org/10.1118/1.4961742}}, doi = {{10.1118/1.4961742}}, volume = {{43}}, year = {{2016}}, }