Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials

Kemerink, Gerrit J.; Visser, M. G. W.; Franssen, R.; Beijer, Emiel; Zamburlini, M.; Halders, Serve; Brans, Boudewijn; Mottaghy, Felix M.; Teule, G. J. J.

doi:10.1007/s00259-011-1732-1

Cited by 43 publications

(36 citation statements)

References 13 publications

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“…In addition, the radioisotope 18 F has noteworthy physical advantages over other common radioisotopes used in SSTR imaging, yielding PET images of high resolution and quality, enabling a highly sensitive and efficient detection of neuroendocrine tumors. In studies in which quantification of uptake might be required, this approach is likely superior to that using 68 Ga-labeled peptides because of the significantly higher maximum energy of 68 Ga positrons as compared with those from 18 F (1,899 keV and 644 keV, respectively) (33). The longer half-life of 18 F is also a major advantage, as it will allow for distribution of the tracer over longer distances in the same manner as 18 F-FDG, to reach PET centers not equipped with a 68 Ge/ 68 Ga generator or able to locally perform 18 F-labeling.…”

Section: Discussionmentioning

confidence: 99%

In Vivo Evaluation of ¹⁸F-SiFAlin–Modified TATE: A Potential Challenge for ⁶⁸Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

et al. 2015

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Radiolabeled peptides for tumor imaging with PET that can be produced with kits are currently in the spotlight of radiopharmacy and nuclear medicine. The diagnosis of neuroendocrine tumors in particular has been a prime example for the usefulness of peptides labeled with a variety of different radionuclides. Among those, 68 Ga and 18 F stand out because of the ease of radionuclide introduction (e.g., 68 Ga isotope) or optimal nuclide properties for PET imaging (slightly favoring the 18 F isotope). The in vivo properties of good manufacturing practice-compliant, newly developed kitlike-producible 18 F-SiFA-and 18 F-SiFAlin-(SiFA 5 silicon-fluoride acceptor) modified TATE derivatives were compared with the current clinical gold standard 68 Ga-DOTATATE for high-quality imaging of somatostatin receptor-bearing tumors. Methods: SiFA-and SiFAlin-derivatized somatostatin analogs were synthesized and radiolabeled using cartridge-based dried 18 F and purified via a C18 cartridge (radiochemical yield 49.8% ± 5.9% within 20-25 min) without high-performance liquid chromatography purification. Tracer lipophilicity and stability in human serum were tested in vitro. Competitive receptor binding affinity studies were performed using AR42J cells. The most promising tracers were evaluated in vivo in an AR42J xenograft mouse model by ex vivo biodistribution and in vivo PET/CT imaging studies for evaluation of their pharmacokinetic profiles, and the results were compared with those of the current clinical gold standard 68 Ga-DOTATATE. Results: Synthetically easily accessible 18 F-labeled silicon-fluoride acceptor-modified somatostatin analogs were developed. They exhibited high binding affinities to somatostatin receptor-positive tumor cells (1.88-14.82 nM). The most potent compound demonstrated comparable pharmacokinetics and an even slightly higher absolute tumor accumulation level in ex vivo biodistribution studies as well as higher tumor standardized uptake values in PET/CT imaging than 68 Ga-DOTATATE in vivo. The radioactivity uptake in nontumor tissue was higher than for 68 Ga-DOTATATE. Conclusion: The introduction of the novel SiFA building block SiFAlin and of hydrophilic auxiliaries enables a favorable in vivo biodistribution profile of the modified TATE peptides, resulting in high tumorto-background ratios although lower than those observed with 68 Ga-DOTATATE. As further advantage, the SiFA methodology enables a kitlike labeling procedure for 18 F-labeled peptides advantageous for routine clinical application.

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Section: Discussionmentioning

confidence: 99%

In Vivo Evaluation of ¹⁸F-SiFAlin–Modified TATE: A Potential Challenge for ⁶⁸Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

et al. 2015

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“…Respiratory motion in the lung blurred the activity and made the size of PMs appear larger in the image (19). Another reason was the increased positron range in lung tissue (20), resulting in an additional overestimation of the functional volume. An observed single PM of 0.9 mL yielded a response index of -10%.…”

Section: Response Assessment Of Known-volume Groupmentioning

confidence: 99%

“…The observation of a response rate of 100% implies that the actual ADs are notably larger than the minimum ADs. Again, one obvious explanation is that the actual diameters of the 24 PMs are considerably smaller than 11.5 mm, but respiratory motion-related blurring and positron range effects also further enhance the AD underestimation (19,20).…”

Section: Response Assessment Of Small-volume Groupmentioning

confidence: 99%

Assessment of Lesion Response in the Initial Radioiodine Treatment of Differentiated Thyroid Cancer Using ¹²⁴I PET Imaging

et al. 2014

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124 I PET/CT images from differentiated thyroid cancer patients were retrospectively analyzed to assess the relationship between absorbed radiation dose (AD) to lesions and their response after radioiodine therapy. Methods: Patients received serial 124 I PET/CT scans before and after their first radioiodine treatment. The pretherapy PET data were used to segment the lesion volumes and to predict the therapy-delivered ADs after administration of the therapeutic 131 I activity. The segmentation method's lower volume limit of determinability was a sphere of 0.80 mL, which classified the lesions into a known-volume group (.0.80 mL) or a small-volume group (#0.80 mL) with their respective average and minimum ADs. The posttherapy PET data were used to assess the lesion-based therapy success. In the known-volume group, the response rate was calculated on the basis of lesions that received average ADs above the generally accepted threshold of 85 Gy for metastases and 300 Gy for thyroid remnants (TRs) and was expressed as the percentage of completely responding lesions. In the small-volume group, the metastasis and TR responses were evaluated for 3 minimum-AD groups: 5 to 10 Gy (TR, 5 to 30 Gy), .10 to 85 Gy (TR, .30 to 300 Gy), and .85 Gy (TR, .300 Gy). Their response rates were calculated in terms of the percentage of completely responding lesions in each minimum-AD group. Results: In total, 59 lesions in 17 patients were amenable to reliable volume estimation. The response rates were 63%, 88%, and 90% for lymph node metastases (LMs), pulmonary metastases, and TRs, respectively. The response rates of 168 small lesions in 34 patients were more than 82% for LMs and more than 91% for TRs in each of the 3 minimum-AD groups; all small pulmonary metastases responded completely. Conclusion: In the known-volume group, the response rate for TRs matched well with historical data derived using 131 I scintigraphy imaging, whereas the response rate for LMs was not as high as expected, which may be explained by too short a follow-up time for a few LMs and a higher sensitivity of PET imaging. Small lesions were treated effectively, suggesting that they are considerably smaller than 0.80 mL. Radi oiodine therapy has been established in the management of differentiated thyroid cancer (DTC) after total thyroidectomy (except for patients at very low risk, such as those with papillary microcarcinoma). Radioiodine treatment is used primarily to eliminate tumor tissue, that is, locoregional lymph node metastases (LMs), distant metastases such as pulmonary metastases (PMs) and bone metastases (BMs), and secondarily to ablate thyroid remnants (TRs). In particular, the successful treatment of metastases is relevant because patients with metastases that completely respond have considerably higher survival rates than patients with incompletely responding metastases (1).The established quantity of radiation that mediates successful therapy is the absorbed radiation dose (AD) to lesions. Historically, the relationship between AD and response succe...

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“…Nevertheless, 68 Ga-PET imaging is not widely available because of the limited daily availability of 68 Ga (;50 mCi) and the lack of Food and Drug Administration-approved 68 Ge/ 68 Ga generators (20). 18 F-fluoride presents several attractive properties for imaging (21,22) and is produced on a daily basis in large quantities in hundreds of cyclotrons in hospitals and radiopharmacies worldwide. Yet the challenges of labeling peptides with 18 F-fluoride are significant: the low chemical reactivity of 18 F-fluoride in water (23) and short half-life (109.8 min) challenge 18 F labeling of peptides that are generally soluble only in water or aqueous cosolvents.…”

mentioning

confidence: 99%

Preclinical Evaluation of a High-Affinity ¹⁸F-Trifluoroborate Octreotate Derivative for Somatostatin Receptor Imaging

et al. 2014

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Recent studies have highlighted the high sensitivity of PET imaging with 68 Ga-labeled octreotide derivatives for the detection and staging of neuroendocrine tumors. A somatostatin receptor ligand that is easily radiolabeled with 18 F-fluoride could improve the availability of PET imaging of neuroendocrine tumors. We report an alkyltrifluoroborateoctreotate conjugate that is radiolabeled in a 1-step 18 F exchange reaction in high yield and with high specific activity. Methods: We conjugated a new alkyltrifluoroborate to octreotate to obtain AMBF 3 -TATE, which was stored in 50-nmol aliquots for radiolabeling. 18 F labeling was performed by 18 F-19 F isotope exchange with 18 F-fluoride, and the tracer was purified by C18 cartridge separation. The radiochemical yield was 20%-25%. PET imaging and biodistribution were performed on mice bearing AR42J tumor xenografts. Results: AMBF 3 -TATE bound the somatostatin receptor subtype 2 with high affinity (inhibition constant, 0.13 ± 0.03 nM). Starting with 29.6-37 GBq (0.8-1 Ci) of 18 F-fluoride, more than 7.4 GBq (.200 mCi) of 18 F-AMBF 3 -TATE were obtained in 25 min (n 5 5) with greater than 99% radiochemical purity at high specific activity (.111 GBq [3 Ci]/μmol). 18 F-AMBF 3 -TATE was stable in plasma. PET imaging and biodistribution showed rapid renal excretion with low liver activity. High tumor uptake (10.11% ± 1.67% injected dose/g, n 5 5) was detected at 60 min after injection. Bone uptake was negligible. Tumor-to-liver, tumor-to-blood, tumor-to-muscle, and tumor-to-bone ratios (at 60 min) were 26.2 ± 0.8, 25.1 ± 1.0, 89.0 ± 3.1, and 21.3 ± 3.6, respectively. Conclusion: 18 F-AMBF 3 -TATE was radiolabeled in high yield and at high specific activity, did not require high-performance liquid chromatography purification, exhibited unexpectedly high binding affinity to somatostatin receptor subtype 2, and showed excellent pharmacokinetic properties in vivo, with high tumor uptake and high contrast ratios.

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Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials

Cited by 43 publications

References 13 publications

In Vivo Evaluation of ¹⁸F-SiFAlin–Modified TATE: A Potential Challenge for ⁶⁸Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

In Vivo Evaluation of ¹⁸F-SiFAlin–Modified TATE: A Potential Challenge for ⁶⁸Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

Assessment of Lesion Response in the Initial Radioiodine Treatment of Differentiated Thyroid Cancer Using ¹²⁴I PET Imaging

Preclinical Evaluation of a High-Affinity ¹⁸F-Trifluoroborate Octreotate Derivative for Somatostatin Receptor Imaging

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Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials

Cited by 43 publications

References 13 publications

In Vivo Evaluation of 18F-SiFAlin–Modified TATE: A Potential Challenge for 68Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

In Vivo Evaluation of 18F-SiFAlin–Modified TATE: A Potential Challenge for 68Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

Assessment of Lesion Response in the Initial Radioiodine Treatment of Differentiated Thyroid Cancer Using 124I PET Imaging

Preclinical Evaluation of a High-Affinity 18F-Trifluoroborate Octreotate Derivative for Somatostatin Receptor Imaging

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In Vivo Evaluation of ¹⁸F-SiFAlin–Modified TATE: A Potential Challenge for ⁶⁸Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

In Vivo Evaluation of ¹⁸F-SiFAlin–Modified TATE: A Potential Challenge for ⁶⁸Ga-DOTATATE, the Clinical Gold Standard for Somatostatin Receptor Imaging with PET

Assessment of Lesion Response in the Initial Radioiodine Treatment of Differentiated Thyroid Cancer Using ¹²⁴I PET Imaging

Preclinical Evaluation of a High-Affinity ¹⁸F-Trifluoroborate Octreotate Derivative for Somatostatin Receptor Imaging