Biodistribution and radiation dosimetry of 99mTc-HMPAO-labeled monocytes in patients with rheumatoid arthritis.

UNLABELLED: Rheumatoid arthritis (RA) involves the accumulation of monocyte-derived macrophages in the affected synovial tissue. This process of cell migration could be portrayed scintigraphically to monitor noninvasively the effects of therapy on the progress of the disease. For this purpose, labeling of purified autologous monocytes with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) at very high specific radioactivity has recently been developed. The aim of this study was to assess the biodistribution and radiation dosimetry of 99mTc-HMPAO-labeled monocytes in adult patients with RA. METHODS: In 8 patients with RA, monocytes were isolated from 100 mL of blood and labeled with 99mTc-HMPAO to a yield of 10 Bq/cell. Multiple whole-body scans were performed up to 20 h after reinjection of an average of 200 MBq of 99mTc-HMPAO-labeled monocytes. Urine and blood samples were collected. The fraction of administered activity in 7 source organs was quantified from the attenuation-corrected geometric mean counts in conjugate views. Radiation-absorbed doses were estimated with OLINDA/EXM software. RESULTS: Autologous monocytes labeled with 99mTc-HMPAO at high intracellular yields showed in vivo kinetics comparable with labeled leukocytes, with initial trapping in the lungs followed by distribution into the liver, spleen, and bone marrow. The radiation-absorbed estimates for 99mTc-HMPAO-labeled monocytes were comparable with those for 99mTc-HMPAO-labeled mixed white blood cells, with an effective dose of 0.011 mSv/MBq. CONCLUSION: 99mTc-HMPAO-labeled monocytes have biodistribution and radiation dosimetry similar to those of 99mTc-HMPAO-labeled mixed white blood cells and might therefore be used for in vivo monitoring of immunomodulating therapy in patients with RA.

Radiopharmaceutical management of 90Y/111In labeled antibodies: shielding and quantification during preparation and administration.

BACKGROUND: The combined application of potent beta-emitting isotopes for therapy with remitting isotopes for scintigraphy requires a profound regimen concerning team member safety and radionuclide quantification. METHODS: We have developed materials and methods for a proper and easy manipulation of 90Y during preparation and administration of 90Y/111In pharmaceuticals used for radioimmunotherapy. RESULTS: The efficacy of the shielding measures is documented. Protocols for the calibration of gamma-dose calibrators with respect to 90Y are extended to the assessment of quench-corrected liquid scintillation counting of 90Y. The contribution of 90Y backscatter to 111 In counting is quantified. Newly developed shielding equipment allows an adequate administration of relatively large volumes (100 ml) of 90Y/111In labeled pharmaceuticals to patients. CONCLUSIONS: The procedures described combine pharmaceutical (Good Manufacturing Practice) and radiation safety requirements with an accurate logging of relevant data.

Volume measurements in nuclear medicine gated SPECT and 4D echocardiography: validation using a dynamic cardiac phantom.

PURPOSE: A dynamic cardiac phantom was used as a reference to compare volumes measured with gated SPECT and 4D echocardiography. MATERIAL AND METHODS: Gated SPECT data were acquired with a standard single-head gamma camera, and the volume reconstructions were carried out using the Mirage software by Segami. 4D echocardiography used a new prototype of rotating scan head to acquire ultrasound images during a cardiac cycle, used to reconstruct the volume deformations as a function of time. End-diastolic volume, end-systolic volume, and ejection fraction were measured using both gated SPECT and 4D echocardiography. RESULTS: The results obtained showed a good correlation between volumes measured with the two modalities, but a slight overestimation of volumes with gated SPECT. The influence of filtering and pixel size parameters on the measured volumes was quantified for gated SPECT, in order to correct the overestimation. CONCLUSION: The agreement between gated SPECT (after correction) and 4D echocardiography confirmed the relevance of the comparisons. This study was an initial step before conducting clinical trials to compare exhaustively left ventricular volumes obtained with the two modalities.

Influence of collimator choice and simulated clinical conditions on 123I-MIBG heart/mediastinum ratios: a phantom study.

PURPOSE: (123)I presents imaging problems owing to high-energy photon emission. We investigated the influence of collimators on (123)I-MIBG heart/mediastinum ratios (H/M ratios). Secondly, we assessed the influence on H/M ratios of different activity concentrations, simulating clinical conditions. Thirdly, the value of scatter correction was assessed. METHODS: The AGATE cardiac phantom was filled with (123)I in three sequential conditions: A, heart and mediastinal activity; B, adding lung activity; and C, adding liver activity (protocol I). In protocol II, myocardium and liver were filled with different activities ranging from low to high. For each condition, static anterior planar and single-photon emission computed tomography studies were acquired on a Siemens e.cam (SI) and a General Electric Millennium VG (GE) system, using low-energy high-resolution and medium-energy (ME) collimators for protocol I and only ME collimators for protocol II . For the SI camera, a triple energy window (TEW) scatter correction was applied. RESULTS: Planar H/M ratios were influenced by scatter and septal penetration from increasing amounts of liver activity. These effects were less pronounced for ME collimators. Although the TEW scatter correction increased ratios overall, TEW correction did not improve the relative differences between the ratios. TEW correction therefore does not add any benefit to obtain an accurate reflection of myocardial activity concentrations. CONCLUSION: For straightforward implementation of semi-quantitative (123)I-MIBG myocardial studies, we recommend the use of ME collimators without scatter correction.