Abstract
Purpose: To evaluate the additional radiation exposure in terms of effective dose incurred by patients in the CT (computed tomography) portion of 123 I-MIBG (123II-metaiodobenzylguanidine) study with SPECT/CT (Single photon emission computed tomography associated to computed tomography) in some pediatric patients of our department. Methods: Data from 123II-MIBG scans comprising 50 children were presented in this study. The contribution of total effective dose imparted by the nuclear tracer and patient's age was calculated. Effective dose from the CT portion of the examination is also estimated.SPECT acquisitions were performed with a dual-headed SPECT unit with an integrated 2-slice CT scanner (Symbia T E-Cam, Siemens Medical Systems, Erlangen, Germany). The CT acquisition were performed using a tube current modulation system (Care Dose 4D). Parameters used were: tube current of 30 - 60 mAs, slice thickness of 3-5 mm, and tube voltage of 110 kV. Results: Our results show that SPECT dosimetry depends on administered activity and patient’s age and weight. For CT scan, effective dose is affected by tube current (mA), tube potential (kVp), rotation speed, pitch, slice thickness, patient mass, and the exact volume of the patient that is being imaged. Conclusion: For children, 123II-MIBG study with SPECT/CT should be performed using the lowest available voltage and current. A sensible choice of these two parameters used can significantly reduce radiation dose, without any compromise in the quality of the diagnostic information.
Highlights
Metaiodobenzylguanidine (MIBG) is used for scintigraphic imaging of the adrenomedullary tumors pheochromocytoma and neuroblastoma in children
The use of I23I-l for labeling takes advantage of the better physical properties of I23I for imaging, allows higher activities to be administered with favorable radiation dosimetry and greater photon flux resulting in higher count, higher quality planar images and permits the performance of the single photon computed tomography (SPECT).[1,2,3]
While for SPECT, dosimetry is dependent on administered activity and the patient’s age and weight; for CT scan, there are many factors which affect dosimetry
Summary
Metaiodobenzylguanidine (MIBG) is used for scintigraphic imaging of the adrenomedullary tumors pheochromocytoma and neuroblastoma in children. The interpretation of scintigraphic images can be confounded by physiological uptake, which can be better identified with SPECT/CT. It results in a significant increase of patient dose. The average radiopharmaceutical effective dose varies from tens to thousands of mSv for some nuclear medicine exams.[4] the introduction of CT in nuclear diagnostic process results in a significant increase of the patient dose. Some authors have questioned the need to reduce doses in children.[7,8]
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