Radiation Dose Assessment for I-131 Therapy of Thyroid Cancer Using I-124 PET Imaging

Erdi, Yusuf E.; Macapinlac, Homer A.; Larson, Steven M.; Erdi, Alev K.; Yeung, Henry; Furhang, E; Humm, John L.

doi:10.1016/s1095-0397(99)00004-7

Cited by 74 publications

(42 citation statements)

References 9 publications

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“…Using the reference approach (5 PET measurement points from 4 to 96 h), the present study found broadly similar radioiodine kinetics to those observed by other groups investigating 124 I PET dosimetry, albeit we noted wider ranges and higher maximum values than did those groups (3)(4)(5) The clinical course of DTC is often favorable, and standardized radioiodine therapy is well established and frequently successful. In selected patients, an individual therapy needs to be performed at the limits, and prospective dosimetry is required.…”

Section: Discussionsupporting

confidence: 87%

Optimized ¹²⁴I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Jentzen¹,

Freudenberg²,

Eising³

et al. 2008

J Nucl Med

150

117

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Iodine kinetics and lesion dose per administered 131 I activity (LDpA) of differentiated thyroid cancer metastases were determined using 124 I PET. These data were analyzed to derive an optimized dosimetry protocol. Methods: We evaluated the timeactivity-concentration curves of 37 lesions in 17 patients who had undergone thyroidectomies. LDpA determination involved 124 I PET images acquired at 4, 24, 48, 72, and 96 h after intake of a capsule containing 20-40 MBq of 124 I. A combination of a linear and a monoexponential or a monoexponential function only parameterized the time-activity-concentration curves. The LDpAs, calculated using data from all 5 PET time points, served as reference. The lesions were classified into 3 groups, according to potential for cure with 131 I therapy: low (#5 Gy GBq 21 ; n 5 14), medium (between 5 and 10 Gy GBq 21 ; n 5 9), or high LDpAs (.10 Gy GBq 21 ; n 5 14). Using the reference approach, the differences in the empiric kinetic parameters within the LDpA groups were evaluated. The reference LDpAs were compared with those derived from only 2, 3, or 4 PET data points and from 1 adapted 2-point approach. Lin's concordance correlation coefficient (r c ) and the mean absolute percentage deviation in LDpAs were used to assess agreement between simplified and reference approaches. Results: The effective 124 I half-life, linear activity-concentration rate (a), and 24-h activity concentration (CpA) (the latter 2 per administered 124 I activity) differed significantly among the LDpA groups (P , 0.05). LDpAs correlated with 24-h CpAs (r 5 0.94, P , 0.001). Using the 4-, 24-, and 96-h measurements, a r c value of greater than or equal to 0.90 was found, and the mean absolute percentage deviation was less than or equal to 16%. Similar statistical values were obtained for the adapted approach, which was based on 24-and 96-h PET data points only. Conclusion: Lesion classification into LDpA groups was feasible using a single PET scan at ;24 h. Because of the highly variable kinetics, 1 additional measurement at ;96 h was needed to obtain a sufficiently reliable LDpA estimate. The adapted 24-96-h approach appears to be the optimal 124 I protocol and is a reliable simplification of the 5-point protocol.Key Words: PET; radionuclide therapy; dosimetry; iodine-124; differentiated thyroid cancer Several groups (1-5) have successfully used 124 I PET alone and with CT to guide postsurgical treatment and, in particular, radioiodine therapy in patients with differentiated thyroid carcinoma (DTC). Preradiotherapeutic 124 I PET is valuable in restaging disease; dosimetric analysis of the imaging data can identify the patients most likely to benefit from radioiodine therapy and can determine safe and effective individualized therapeutic activities of radioiodine.Our original ;20, and ;44 h after 124 I administration; sometimes a fourth scan was acquired at 96-144 h. However, to our knowledge, no group has yet published the results of any systematic investigation to determine the number and timing of PET sca...

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Section: Discussionsupporting

confidence: 87%

Optimized ¹²⁴I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Jentzen¹,

Freudenberg²,

Eising³

et al. 2008

J Nucl Med

150

117

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“…Compared with 131 I SPECT, 124 I PET imaging offers a higher image spatial resolution, increased counting rate sensitivity, and higher quantitative capacity, resulting in the application of pretherapeutic 124 I PET/CT-based lesion dosimetry (12)(13)(14)(15)(16)(17).…”

mentioning

confidence: 99%

Dose–Response Relationship in Differentiated Thyroid Cancer Patients Undergoing Radioiodine Treatment Assessed by Means of ¹²⁴I PET/CT

et al. 2016

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The dose-response relationship in a fixed-activity approach generally applied in the treatment of differentiated thyroid cancer was assessed using 124 I PET/CT. Methods: Pretherapeutic 124 I PET/ CT images of 47 patients scheduled for radioiodine therapy were retrospectively analyzed. 124 I PET/CT images were acquired 24 and 96 h after oral administration of approximately 28 MBq of 124 I-sodium iodide. Lesions were identified as thyroid remnants or metastases (lymph node, lung, bone). After a neoteric segmentation technique allowing accurate volume estimation down to the 124 I PET spatial resolution of 0.15 mL was applied, lesions were divided into a known-volume group and a small-volume group. For the known-volume group, average lesion-absorbed dose (AD) values were calculated, whereas for the small-volume group a minimum lesion AD was estimated. Lesion response was determined on the basis of 124 I PET/CT and 131 I SPECT/CT follow-up images. A lesion not detectable on any of the follow-up images was considered a completely responding lesion. Differences in lesion AD estimations between completely and incompletely responding lesions were evaluated by Mann-Whitney U test. Moreover, receiver-operating-characteristic curves were used to test the performance of pretherapeutic 124 I PET/CT lesion AD for prediction of complete lesion response. Results: In the approach of fixed radioiodine activity (3.0 ± 1.0 GBq), 89% of thyroid remnants and 69% of metastases responded completely. Except for the small-volume groups, the lesion AD of completely responding lesions was significantly higher than that of incompletely responding lesions. Using receiver-operating-characteristic curve analysis, it was shown that for the known-volume group, pretherapeutic 124 I PET/CT lesion dosimetry can be used as a prognostic tool to predict lesion-based 131 I therapy response with an area under the curve of 0.76 for remnants and 0.97 for metastases. The corresponding lesion AD threshold value maximizing correct complete response prediction was 90 Gy for remnants and 40 Gy for metastases. Conclusion: In a fixed-activity approach, a statistically significant dose-response relationship for both thyroid remnants and metastases using pretherapeutic 124 I PET/CT lesion dosimetry was found. The findings may be useful in patient management. Radi oiodine therapy is the standard adjuvant therapy after total thyroidectomy in patients with differentiated thyroid cancer (DTC) (1,2). The purpose of radioiodine therapy is 2-fold: ablation of thyroid remnants and treatment of radioiodine-avid metastases.The generally accepted threshold for lesion-absorbed dose (AD) to achieve high therapy response is 85 Gy for metastases and 300 Gy for thyroid remnants (3,4). To predict therapy response, a reliable AD estimation requires, inter alia, accurate lesion volume determination, which is hampered by the often small lesion volumes with respect to the spatial resolution of 131 I scintigraphy and lesion segmentation difficulties encountered in ultrasonography, CT, ...

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“…Several groups have reported promising results using 124 I as a diagnostic agent (6,7). 124 I is a positron emitter and can be imaged using PET, with resolution, sensitivity, and quantitation superior to those obtainable with the use of 131 I in scintigraphy or SPECT.…”

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confidence: 99%

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

et al. 2015

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Radioiodine therapy with 131 I is used for treatment of suspected recurrence of differentiated thyroid carcinoma. Pretherapeutic 124 I PET/CT with a low activity (∼1% of 131 I activity) can be performed to determine whether uptake of 131 I, and thereby the desired therapeutic effect, may be expected. However, false-negative 124 I PET/CT results as compared with posttherapeutic 131 I SPECT/CT have been reported by several groups. The purpose of this study was to investigate whether the reported discrepancies may be ascribed to a difference in lesion detectability between 124 I PET/CT and 131 I SPECT/CT and, hence, whether the administered 124 I activity is sufficient to achieve equal detectability. Methods: Phantom measurements were performed using the National Electrical Manufacturers Association 2007 image-quality phantom. As a measure of detectability, the contrast-to-noise ratio was calculated. The 124 I activity was expressed as the percentage of 131 I activity required to achieve the same contrast-to-noise ratio. This metric was defined as the detectability equivalence percentage (DEP). Results: Because lower DEPs were obtained for smaller spheres, a relatively low 124 I activity was sufficient to achieve similar lesion detectability between 124 I PET/CT and 131 I SPECT/CT. DEP was 1.5%, 1.9%, 1.9%, 4.4%, 9.0%, and 16.2% for spheres with diameters of 10, 13, 17, 18, 25, and 37 mm, respectively, for attenuation-and scatter-corrected SPECT versus point-spread function (PSF) model-based and time-of-flight (TOF) PET. For no-PSF no-TOF PET, DEP was 3.6%, 2.1%, 3.5%, 7.8%, 15.1%, and 23.3%, respectively. Conclusion: A relatively low 124 I activity of 74 MBq (∼1% of 131 I activity) is sufficient to achieve similar lesion detectability between 124 I PSF TOF PET/CT and 131 I SPECT/CT for small spheres (#10 mm), since the reported DEPs are close to 1%. False-negative 124 I PET/CT results as compared with posttherapeutic 131 I SPECT/CT may be ascribed to differences in detectability for large lesions (.10 mm) and for no-PSF no-TOF PET, since DEPs are greater than 1%. On the basis of DEPs of 3.5% for lesion diameters of up to 17 mm on no-PSF no-TOF PET, 124 I activities as high as 170 MBq may be warranted to obtain equal detectability.

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Radiation Dose Assessment for I-131 Therapy of Thyroid Cancer Using I-124 PET Imaging

Cited by 74 publications

References 9 publications

Optimized ¹²⁴I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Optimized ¹²⁴I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Dose–Response Relationship in Differentiated Thyroid Cancer Patients Undergoing Radioiodine Treatment Assessed by Means of ¹²⁴I PET/CT

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

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Radiation Dose Assessment for I-131 Therapy of Thyroid Cancer Using I-124 PET Imaging

Cited by 74 publications

References 9 publications

Optimized 124I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Optimized 124I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Dose–Response Relationship in Differentiated Thyroid Cancer Patients Undergoing Radioiodine Treatment Assessed by Means of 124I PET/CT

Quantitative Comparison of 124I PET/CT and 131I SPECT/CT Detectability

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Optimized ¹²⁴I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Optimized ¹²⁴I PET Dosimetry Protocol for Radioiodine Therapy of Differentiated Thyroid Cancer

Dose–Response Relationship in Differentiated Thyroid Cancer Patients Undergoing Radioiodine Treatment Assessed by Means of ¹²⁴I PET/CT

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability