An international multi-center investigation on the accuracy of radionuclide calibrators in nuclear medicine theragnostics.

BACKGROUND: Personalized molecular radiotherapy based on theragnostics requires accurate quantification of the amount of radiopharmaceutical activity administered to patients both in diagnostic and therapeutic applications. This international multi-center study aims to investigate the clinical measurement accuracy of radionuclide calibrators for 7 radionuclides used in theragnostics: 99mTc, 111In, 123I, 124I, 131I, 177Lu, and 90Y. METHODS: In total, 32 radionuclide calibrators from 8 hospitals located in the Netherlands, Belgium, and Germany were tested. For each radionuclide, a set of four samples comprising two clinical containers (10-mL glass vial and 3-mL syringe) with two filling volumes were measured. The reference value of each sample was determined by two certified radioactivity calibration centers (SCK CEN and JRC) using two secondary standard ionization chambers. The deviation in measured activity with respect to the reference value was determined for each radionuclide and each measurement geometry. In addition, the combined systematic deviation of activity measurements in a theragnostic setting was evaluated for 5 clinically relevant theragnostic pairs: 131I/123I, 131I/124I, 177Lu/111In, 90Y/99mTc, and 90Y/111In. RESULTS: For 99mTc, 131I, and 177Lu, a small minority of measurements were not within ± 5% range from the reference activity (percentage of measurements not within range: 99mTc, 6%; 131I, 14%; 177Lu, 24%) and almost none were outside ± 10% range. However, for 111In, 123I, 124I, and 90Y, more than half of all measurements were not accurate within ± 5% range (111In, 51%; 123I, 83%; 124I, 63%; 90Y, 61%) and not all were within ± 10% margin (111In, 22%; 123I, 35%; 124I, 15%; 90Y, 25%). A large variability in measurement accuracy was observed between radionuclide calibrator systems, type of sample container (vial vs syringe), and source-geometry calibration/correction settings used. Consequently, we observed large combined deviations (percentage deviation > ± 10%) for the investigated theragnostic pairs, in particular for 90Y/111In, 131I/123I, and 90Y/99mTc. CONCLUSIONS: Our study shows that substantial over- or underestimation of therapeutic patient doses is likely to occur in a theragnostic setting due to errors in the assessment of radioactivity with radionuclide calibrators. These findings underline the importance of thorough validation of radionuclide calibrator systems for each clinically relevant radionuclide and sample geometry.

Comparison of Intraoperative γ-Probe Imaging and Postoperative SPECT/CT in Detection of Sentinel Nodes Related to the Ovary.

Tracer injection into ovarian ligaments has been shown to detect sentinel nodes (SNs) in patients with ovarian cancer. To determine the possibility that SNs are missed, this feasibility study compared their detection during surgery with their detection on postoperative SPECT/CT. METHODS: In 8 patients (with either ovarian or endometrial cancer), after a staging lymphadenectomy including resection of SNs related to the ovary, SPECT/CT was performed within 24 h. RESULTS: SPECT/CT identified hotspots in 4 patients at sites where SNs were resected. In 6 patients, additional sites were found, mainly in the pelvic region. CONCLUSION: Discrepancies between the γ-probe and SPECT/CT may be due to missed SNs during surgery, but with respect to pelvic hotspots, in most cases they are more probably related to remnants of tracer at injection sites. With respect to sites where SNs were resected, remaining hotspots may have been caused by residual lymphatic flow after resection.

The detection of sentinel nodes in ovarian cancer: a feasibility study.

UNLABELLED: Few sentinel node (SN) studies in ovarian cancer have been reported, mainly because of the risk of tumor dissemination associated with the injection of tracers into the ovarian cortex. To our knowledge, the injection of tracers into the ovarian ligaments has not been explored. The aim of this study was to determine the feasibility of the SN procedure in ovarian cancer with tracer injection into the ovarian ligaments and to establish whether the procedure is safe for the healthcare workers. METHODS: The study included patients who were at high risk of ovarian malignancy. Blue dye and radioactive colloid were injected into the proper ovarian ligament and suspensory ligament of the ovary. To measure professional radiation exposure, ring dose meters were worn by the surgeon, theater nurse, and pathologist during 3 procedures. RESULTS: An SN procedure was performed in 21 patients, and at least 1 SN location was identified in all patients using the γ probe before retroperitoneal exploration. SNs were located in the paraaortic and paracaval regions only in 67% of the patients, in the pelvic region only in 9%, and in both the paraaortic/paracaval and the pelvic regions in 24%. All but 2 SNs were found on the ipsilateral side. In 6 patients who underwent retroperitoneal exploration, 1-4 SNs were identified using the γ probe and resected. Blue-stained SNs were detected in 2 patients. Positive SNs were detected in 1 patient with lymph node metastases. The amount of radiation exposure to the surgeon, theater nurse, and pathologist did not exceed the safe limit. CONCLUSION: The identification of SNs in all cases suggests that the SN procedure performed by injection of tracers in the ovarian ligaments is feasible and promising. The procedure is safe for the involved personnel. Further investigation is necessary to determine the clinical application of this new technique.

Sentinel node in ovarian cancer: study protocol for a phase 1 study.

BACKGROUND: The concept of sentinel lymph node surgery is to determine whether the cancer has spread to the very first lymph node or sentinel node. If the sentinel node does not contain cancer, then there is a high likelihood that the cancer has not spread to other lymph nodes. The sentinel node technique has been proven to be effective in different types of cancer. In this study we want to determine whether a sentinel node procedure in patients with ovarian cancer is feasible when the tracers are injected into the ovarian ligaments. METHODS/DESIGN: Patients with a high likelihood of having an ovarian malignancy in whom a median laparotomy and a frozen section analysis is planned and patients with endometrial cancer in whom a staging laparotomy is planned will be included.Before starting the surgical staging procedure, blue dye and radioactive colloid will be injected into the ligamentum ovarii proprium and the ligamentum infundibulo-pelvicum. In the analysis we calculate the percentage of patients in whom it is feasible to identify sentinel nodes. Other study parameters are the anatomical localization of the sentinel node(s) and the incidence of false negative lymph nodes. TRIAL REGISTRATION: Approval number: NL40323.068.12Name: Medical Ethical Committee Maastricht University Hospital, University of MaastrichtAffiliation: Maastricht University HospitalBoard Chair Name: Medisch Ethische Commissie azM/UM.

An HPLC-based assay of adenylosuccinate lyase in erythrocytes.

ADSL deficiency is a disorder of purine metabolism with a broad clinical spectrum. A rapid and simple HPLC-based assay to measure ADSL activity in erythrocytes was developed. The suitability of DBSs was assessed. ADSL activity was measured in erythrocyte lysates and DBS using succinyl-AMP as the substrate. Detection and quantification were performed using isocratic ion-pairing reversed-phase HPLC with UV-detection. Reference values in erythrocyte lysates were established. The intra- and interassay variations were 2% and 8%, respectively. ADSL deficiency was easily recognized. ADSL activity in DBS was highly unstable, disqualifying DBS for diagnostic procedures.