Optimization of Equipment and Methodology for Whole Body Activity Retention Measurements in Children Undergoing Targeted Radionuclide Therapy

Abstract

Accurate measurements of whole-body activity retention of patients during radionuclide therapy are essential for two reasons: First, they enable the correct radiation protection advice to be given and second, they permit the accurate determination of the absorbed whole-body dose delivered during therapy. This, in turn, allows treatment planning to be carried out for future radionuclide therapy on an individual patient basis, and also enables the investigation of the potential correlation of absorbed dose with treatment outcome in groups of patients. There are significant difficulties associated with taking whole-body retention measurements of children, especially when they are very young and/or unwell. It is essential to carry these out in a way that minimises disturbance to the child while still providing good quality data. To accomplish this, we have aimed to optimize the following aspects of the procedure: (i) the environment in which the measurements are performed; (ii) the equipment--which includes the recent installation of a specially designed whole-body activity monitoring system for these patients; and (iii) the methodology for calculating the absorbed dose. These improvements have allowed large numbers of accurate and reproducible whole-body measurements to be collected following patient administrations. This has enabled the identification of more phases of radionuclide excretion during therapy than had previously been observed. These data have been used for radiation protection advice and treatment planning. Two (2) patients were given multiple radionuclide treatments and we were able to compare the whole-body doses delivered.

Whole-Body Dosimetry for Individualized Treatment Planning of 131I-MIBG Radionuclide Therapy for Neuroblastoma

“…Line of equality is also shown. Error bars indicate uncertainty in absorbed dose due to random errors generated during data acquisition and were calculated using method described by Chittenden et al (19). into account other patient-specific factors, such as kidney function (24).…”

“…For therapy, patients were isolated within a purpose-built room with adjacent toilet facilities (19). Parents and caretakers were allowed limited access to the patient when suitably protected against contamination with a gown, an apron, gloves, and overshoes but were otherwise separated from the child by a shielded wall, lead screens, or lead glass.…”

“…For the tracer study, measurements were obtained using a shielded (3 cm of lead; diameter, 5 cm; thickness, 5 cm) NaI detector fixed into the ceiling space 2 m directly above the patient's bed (19). Sufficient counts were acquired to ensure that the Poisson noise was below 5%.…”

Compartmental Model for 223Ra-Dichloride in Patients With Metastatic Bone Disease From Castration-Resistant Prostate Cancer

“…A measurement immediately after administration and before any patient voiding was used to convert measured patient counts to injected activity. Optimization of the equipment and methodology for whole-body activity retention measurements was performed according to Chittenden et al 26 and guidelines published by Hindorf et al 27 Regular measurements were performed every 2 hours on day 1, and additional (twice per day) readings were taken until the patient was discharged at approximately 48 hours postadministration. Further measurements were performed at 96 and 144 hours postadministration.…”

Molecular radiotheranostics for neuroendocrine tumours

“…This is a challenging procedure that can be addressed by performing whole-body dosimetry as a surrogate measure, which can be derived accurately from external measurements (gamma camera whole-body imaging). 37 Varying patient biokinetics lead to a wide range of reported absorbed whole-body doses. 38,39 An even wider range of absorbed doses is delivered to tumours for all therapy procedures.…”