We have located links that may give you full text access.
Journal Article
Multicenter Study
The Italian multicentre dosimetric study for lesion dosimetry in (223)Ra therapy of bone metastases: Calibration protocol of gamma cameras and patient eligibility criteria.
Physica Medica : PM 2016 December
PURPOSE: The aims of this work were to explore patient eligibility criteria for dosimetric studies in (223)Ra therapy and evaluate the effects of differences in gamma camera calibration procedures into activity quantification.
METHODS: Calibrations with (223)Ra were performed with four gamma cameras (3/8-inch crystal) acquiring planar static images with double-peak (82 and 154keV, 20% wide) and MEGP collimator. The sensitivity was measured in air by varying activity, source-detector distance, and source diameter. Transmission curves were measured for attenuation/scatter correction with the pseudo-extrapolation number method, varying the experimental setup. (223)Ra images of twenty-five patients (69 lesions) were acquired to study the lesions visibility. Univariate ROC analysis was performed considering visible/non visible lesions on (223)Ra images as true positive/true negative group, and using as score value the lesion/soft tissue contrast ratio (CR) derived from (99m)Tc-MDP WB scan.
RESULTS: Sensitivity was nearly constant varying activity and distance (maximum s.d.=2%). Partial volume effects were negligible for object area ⩾960mm(2). Transmission curve measurements are affected by experimental setup and source size, leading to activity quantification errors up to 20%. The ROC analysis yielded an AUC of 0.972 and an optimal threshold of CR of 10, corresponding to an accuracy of 92%.
CONCLUSION: The minimum calibration protocol requires sensitivity and transmission curve measurements varying the object size, performing a careful procedure standardisation. Lesions with (99m)Tc-MDP CR higher than 10, not overlapping the GI tract, are generally visible on (223)Ra images acquired at 24h after the administration, and possibly eligible for dosimetric studies.
METHODS: Calibrations with (223)Ra were performed with four gamma cameras (3/8-inch crystal) acquiring planar static images with double-peak (82 and 154keV, 20% wide) and MEGP collimator. The sensitivity was measured in air by varying activity, source-detector distance, and source diameter. Transmission curves were measured for attenuation/scatter correction with the pseudo-extrapolation number method, varying the experimental setup. (223)Ra images of twenty-five patients (69 lesions) were acquired to study the lesions visibility. Univariate ROC analysis was performed considering visible/non visible lesions on (223)Ra images as true positive/true negative group, and using as score value the lesion/soft tissue contrast ratio (CR) derived from (99m)Tc-MDP WB scan.
RESULTS: Sensitivity was nearly constant varying activity and distance (maximum s.d.=2%). Partial volume effects were negligible for object area ⩾960mm(2). Transmission curve measurements are affected by experimental setup and source size, leading to activity quantification errors up to 20%. The ROC analysis yielded an AUC of 0.972 and an optimal threshold of CR of 10, corresponding to an accuracy of 92%.
CONCLUSION: The minimum calibration protocol requires sensitivity and transmission curve measurements varying the object size, performing a careful procedure standardisation. Lesions with (99m)Tc-MDP CR higher than 10, not overlapping the GI tract, are generally visible on (223)Ra images acquired at 24h after the administration, and possibly eligible for dosimetric studies.
Full text links
Related Resources
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app