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Katarina Sjögreen Gleisner

Professor

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Whole-remnant and maximum-voxel SPECT/CT dosimetry in 131I-NaI treatments of differentiated thyroid cancer

Författare

  • PABLO MINGUEZ GABINA
  • Glenn Flux
  • José Genollá
  • Alejandro Delgado
  • Emilia Rodeño
  • Katarina Sjögreen Gleisner

Summary, in English

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.

Avdelning/ar

  • Medicinsk strålningsfysik, Lund

Publiceringsår

2016-10-01

Språk

Engelska

Sidor

5279-5287

Publikation/Tidskrift/Serie

Medical Physics

Volym

43

Issue

10

Dokumenttyp

Artikel i tidskrift

Förlag

American Association of Physicists in Medicine

Ämne

  • Radiology, Nuclear Medicine and Medical Imaging
  • Other Physics Topics

Nyckelord

  • I-NaI
  • differentiated thyroid carcinoma
  • dosimetry
  • thyroid bed remnants

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0094-2405