Development and evaluation of a kit formulation for the preparation of 99mTc-DMP-HSA, a new tracer agent for radionuclide ventriculography.

This study presents the development of a kit formulation for the preparation of 99mTc-DMP-HSA, followed by a comparison of such kit-prepared 99mTc-DMP-HSA to 99mTc-RBCs in a volunteer. Reconstitution of the labeling kits with up to 5.55 GBq 99mTc afforded 99mTc-DMP-HSA preparations with a > 95% radiochemical purity for up to 8 h. Only minor differences were observed in the global distribution of both tracer agents, whereas the calculated ejection fractions were almost identical. The effective dose equivalent of 99mTc-DMP-HSA is 8.68 microSv/MBq.

Stabilisation of high-activity 99mTc-d,l-HMPAO preparations with cobalt chloride and their biological behaviour.

It has been reported that the stability of a 1.11-GBq (30 mCi) technetium-99m d,l-hexamethyl-propylene amine oxime (HMPAO) preparation can be improved to up to 5 h by the addition of 200 micrograms CoCl2.6H2O within 2 min after reconstitution. However, it is not clear whether this method is also efficient for high-activity preparations (5.55 GBq) and whether this modified 99mTc-d,l-HMPAO has the same biological properties and can safely be used. We have now studied CoCl2-stabilised 99mTc-d,l-HMPAO preparations containing different amounts of "in-house" HMPAO ligand and SnCl2 and reconstituted with activities from 1.11 GBq to 5.55 GBq 99mTc. The characteristics of the generator eluates were also divergent, ranging from fresh eluates from a generator eluted less than 2 h previously to 4-h-old eluates from a generator not eluted during the preceding 72 h. Preparations containing up to 5.55 GBq 99mTc and as low as 2 micrograms SnCl2.2H2O can be efficiently stabilised for at least 6 h by the addition of CoCl2 shortly after reconstitution. Interestingly, it was found that the stabilisation method is not efficient if the cobalt ions are added prior to reconstitution of the preparation. This implies that the cobalt chloride cannot be incorporated in the labelling kit. Also, preparations with amounts of the ligand lower or higher than 0.5 mg formed the 99mTc-d,l-HMPAO complex with low radiochemical yield or showed rapid degradation. Therefore, combination of a subdivision and storage of Ceretec kits in fractions (as reported in the literature) is contra-indicated with this CoCl2 stabilisation method. CoCl2-stabilised Ceretec kits reconstituted with 5550 MBq 99mTcO4- and used 4-5 h after preparation retain the diagnostic usefulness of the fresh 1110-MBq preparation with regard to leucocyte labelling and brain imaging. Although baboon brain uptake of the stabilised preparation was 6%-9% lower, this small difference could not be distinguished in the tomographic images. The data obtained with both inhouse prepared d,l-HMPAO and Ceretec kits suggest that the eluate restrictions recommended by the Ceretec manufacturer can be neglected if the preparation is stabilised with Co2+ ions. Studies with 57Co-spiked CoCl2 added to d,l-HMPAO preparations demonstrated that the Co2+ ions clearly interact with the d,l-HMPAO ligand, probably to form one or more complexes. From biodistribution studies in mice it became evident that the toxicological profile of the Co2+ ions in the presence of d,l-HMPAO should be more favourable than that of cobaltous ions. For these reasons, it seems justifiable that CoCl2-stabilised 99mTc-d,l-HMPAO preparations should undergo rigorous studies to elucidate their clinical usefulness and pharmacological safety.

Tomographic and planar quantitation of perfusion defects on technetium 99m-labeled sestamibi scans: evaluation in patients treated with thrombolytic therapy for acute myocardial infarction.

BACKGROUND: Our segmentation algorithm for single-photon emission computed tomographic perfusion studies was tested in 244 patients treated by thrombolysis within 5 hours after onset of symptoms. This algorithm uses radial slices to approximate true three-dimensional gradients, determines the apex and basal plane, and creates a perfusion and volume polar map. METHODS AND RESULTS: Perfusion defect size was compared with enzymatic infarct size and global and regional function. All patients underwent rest planar and tomographic 99mTc-labeled sestamibi scanning, contrast coronary angiography, and ventriculography 10 to 14 days after the start of treatment. Manual correction had to be performed in only 10% of the cases and presented no problems. The correlation coefficients (r) between planar and relative tomographic perfusion defects versus enzymatic infarct size were 0.71 and 0.73. A negative correlation was found with left ventricular ejection fraction: r = -0.65 and r = -0.60. A comparable correlation was also found between regional wall motion and perfusion defect size. Most correlations were higher in the case of anterior infarction. An excellent correlation was found between planar and tomographic defect size (r = 0.83). CONCLUSIONS: In most cases, our segmentation algorithm delineates myocardial edges and basal plane automatically. A good correlation was found between perfusion defect size, enzymatic infarct size, and global and regional ventricular function.

Whole body skeletal imaging with [18F]fluoride ion and PET.

Using our recently reported whole body PET imaging technique, we performed whole body PET studies of the skeletal system with [18F]fluoride ion in 19 patients with a range of malignant and benign skeletal conditions and in 19 normal male volunteers. The technique produces two-dimensional projection images of the entire skeletal system ("a PET bone scan"), in addition to coronal, sagittal, and axial tomographic images of the skeletal system. The tomographic images had a 13% higher lesion detection sensitivity than the projection images. Whole body PET skeletal imaging with [18F]fluoride ion is technically feasible, provides images of excellent quality, and may be coupled with more quantitatively precise kinetic PET [18F]fluoride ion studies (over limited regions of the body) when numerical estimates of skeletal [18F]fluoride ion uptake are desired. The method is potentially useful in clinical applications where the high resolution and numerical precision of PET are of particular value (e.g., in accurately defining the anatomic location and extent of lesions and in assessing changes in bone metabolism on serial studies).