Quantification and visualization of defects of the functional dopaminergic system using an automatic algorithm.

UNLABELLED: In SPECT, the binding of radiotracers in brain areas is usually assessed by manual positioning of regions of interest (ROIs). The disadvantages of this method are that it is an observer-dependent procedure and that it may not be sensitive for assessing defects significantly smaller than the ROI. To circumvent these limitations, we developed a fully automatic three-dimensional technique that quantifies neuronal radiotracer binding on a voxel-by-voxel basis. METHODS: To build a model of normal 123I-labeled N-omega-fluoropropyl-2beta-carbomethoxy-3beta-(4-iodophenyl) nortropane (FPCIT) binding, 17 studies of healthy volunteers were registered to the same orientation. After registration, the specific-to-nonspecific binding ratio was calculated for each voxel of the striatal volumes of interest (VOIs). The mean and SD of that binding ratio were then calculated on a voxel-by-voxel basis. For the analysis of 10 healthy volunteer studies (control group) and 21 studies of drug-naive patients with Parkinson's disease, the registration and calculation of the specific-to-nonspecific [123I]FPCIT binding ratio were performed by the same method. Subsequently, a voxel of the striata was classified as a diminished [123I]FPCIT binding ratio if its value was lower than the mean -2 x SD. For each subject, the defect size, the relative number of voxels with a diminished binding ratio and the binding ratio of the whole striatal VOIs were calculated and compared with the binding ratio as assessed by the traditional ROI method. RESULTS: The results of the automatic method correlated significantly with the results of the traditional ROI method. Furthermore, for the ipsilateral side, the automatically calculated defect size had less overlap between the patient and the control group than the traditionally calculated binding ratio. CONCLUSION: The method presented quantifies [123I]FPCIT binding ratio automatically on a voxel-by-voxel basis, by comparison with a model of healthy volunteers. We have shown that it is appropriate to use the automatic method as a replacement for the traditional manual method, which enables us to study the localized dopaminergic degeneration process in Parkinson's disease more precisely and without any inter- or intraobserver variability.

Origin and location on the oral activity in sequential salivary gland scintigraphy with 99mTc-pertechnetate.

Conflicting views exist regarding the origin and location of the oral radioactivity seen in salivary gland scintigraphy with 99mTc-pertechnetate. The normal accumulation of oral activity was studied in a series of healthy subjects by sequential scintigraphy (anterior and lateral views) after intravenous injection of 2 mCi of 99mTc-pertechnetate. Ligation of the parotid ducts and/or cannulation of the submandibular ducts, which prevented their secretions from reaching the oral cavity, established that the oral activity was due entirely to radioactive saliva secreted by the parotid and submandibular glands. Pertechnetate mouthwash studies confirmed that radioactive saliva is absorbed to oral mucosa and that adsorption to the lingual mucosa in the major contributor to the oral activity. Pertechnetate uptake in sublingual and minor salivary glands of the oral cavity was not visualized, thereby invalidating scintigraphy in the study of these glands. In the diagnosis of salivary gland disorders, oral activity is a useful indicator of major salivary gland function.

Prevalence of right ventricular involvement in inferior wall infarction assessed with myocardial imaging with thallium-201 and technetium-99m pyrophosphate.

To assess the prevalence and clinical relevance of right ventricular involvement in acute inferior wall infarction, 78 consecutive patients with the latter condition were studied with thallium-201 and technethium-99m pyrophosphate myocardial imaging. Right ventricular involvement was determined from superimposition of the 45 degree left anterior oblique thallium-201 and technetium-99m pyrophosphate images. All 78 patients shoed thallium-201 defects. Sixty-four patients had positive pyrophosphate scans, and 24 of these (37.5 percent) showed right ventricular involvement. None of the patients with right ventricular involvement in this consecutive series showed the classic signs of severe right ventricular failure, although subclinicalright ventricular dysfunction may have been present. There was no significant difference in the incidence of cardiogenic shock between the groups with and without right ventricular involvement. It is concluded that right ventricular involvement in acute inferior wall infarction is relatively frequent but not necessarily associated with severe right-sided pump failure. In patients with acute inferior wall infarction and severe pump failure, dual imaging provides a simple nonivasive method of identifying the subgroup of patients with right ventricular involvement who may benefit from volume loading.

A comparison of rotating slant hole collimator and rotating camera for single photon emission tomography of the heart.

Measurements were made on the tomographic imaging abilities of a rotating slant hole collimator and a rotating scintillation camera system using a standard heart phantom and thallium-201. This allowed a comparison to be made between these and published results for conventional imaging and the seven pinhole technique under standardised conditions. Although better intraplanar resolutions were obtained with the rotating slant hole, the rotating camera was found to give superior definition of a defect and less propagation between reconstructed sections of the phantom.

Influence of high-energy photons from cobalt-57 flood sources on scintillation camera uniformity images.

Cobalt-57 flood sources are often used for system flood-field uniformity checks of scintillation camera performance. Such sources are now available in large sizes and with high activities. Uniformity images using new 57Co sources have shown artefacts which are not present in uniformity images obtained from technetium-99m flood sources of the same activity. The high-energy photons emitted by 57Co and cobalt isotope impurities appear to influence the images obtained. This was investigated in three cameras using three 57Co sources of different age. The flood-field images obtained with the 57Co sources showed non-uniformity patterns that were dependent on the age of the cobalt source, the distance of the source to the collimator, and the specific camera type. Quantification of the uniformity images reflected these findings. Energy spectra of a new 57Co source, obtained with an external 1024-channel analyser connected to the camera, showed a broad tail of high-energy photons above the 122-keV photopeak, due to Compton scatter and collimator penetration. This tail diminished with older sources and with increased source to collimator distance, indicating that in both situations fewer high-energy photons were being measured by the camera system. This tail of high-energy photons contributes to the total count rate, but because this is not obvious from the counts observed in the photopeak window, the camera can unsuspectingly be operated at too high a total countrate where pile-up effects become significant. Caution is therefore advised when using 57Co sources. Problems may be minimized by purchasing low-activity sources (certainly no more than 370 MBq), by placing the source at a distance from the collimator, e.g. 50 cm, by allowing a new source to decay, and by manufacturers producing 57Co sources without detectable radioactive contaminants.

The interrelationship of calcium and magnesium absorption in idiopathic hypercalciuria and renal calcium stone disease.

PURPOSE: A decreased concentration of magnesium in the urine is a risk factor for renal calcium stone disease that may be caused by decreased enteral absorption of magnesium. We analyze the possible reciprocal influences of enteral absorption of calcium and magnesium in patients with renal stone disease. MATERIALS AND METHODS: We measured the fractional enteral absorption of 47calcium and 28magnesium in 11 patients with renal calcium stone disease, including 8 with and 3 without hypercalciuria. Two tests were performed using calcium and magnesium, respectively, followed by another test in which the enteral absorption of calcium and magnesium was measured after both cations were administered together. RESULTS: We noted no clear influence of either cation on the absorption of the other in the 3 patients without hypercalciuria. However, in the 8 hypercalciuric patients enteral calcium absorption decreased after the concurrent administration of magnesium and enteral magnesium absorption increased after the concurrent administration of calcium. Each effect was proportional to the other. CONCLUSIONS: The results of this study indicate that the oral supplementation of magnesium in patients with hyperabsorptive hypercalciuria and renal calcium stone disease is favorable because it decreases calcium absorption and increases magnesium absorption. Both factors may reduce risk factors for renal calcium stone formation.

99m-Tc pertechnetate uptake in the thyroid measured with a scintillation camera: a parameter of thyroid function.

A 99mTc pertechnetate thyroid uptake procedure, using a scintillation camera and a data storage system, is described. After comparison of extrathyroidal activity in several regions below the thyroid, activity in the clavicular regions was preferred for correction of the thyroid uptake measurement. No pertechnetate uptake curve obtained over the initial 15 min after injection was found to be representative of a specific thyroid function, and regional thyroid uptake curves gave only quantitative differences. The 15-min pertechnetate thyroid uptake measurement, with correction for clavicular extrathyroidal activity, correlates well with 131I uptake and is a good parameter of thyroid function, especially in the distinction of euthyroidism and hyperthyroidism.

The influence of dental restorations on salivary gland scintigraphy with 99mTc-pertechnetate.

During sequential salivary gland scintigraphy with 99mTc-pertechnetate, circumscript "cold" areas with less than background activity are sometimes seen in the region of the oral cavity. This phenomenon is due to the presence of extensive dental restorations and should not be misinterpreted in terms of deficient 99mTc-pertechnetate uptake in the minor salivary glands of the oral cavity.

Dosimetry of iodine-123 iodobenzamide in healthy volunteers.

The distribution of the dopamine D2-receptor specific ligand iodine-123 (S)-(-)-2-hydroxy-3-iodo-6-methoxy-N[(1-ethyl-2- pyrrolidinyl)methyl]-benzamide (123I-IBZM) was investigated in human adults from whole-body scans, blood samples and urine collected up to 48 h after injection. Results from the present study performed in six healthy volunteers were combined with those of five volunteers from a previous study. Using the brain, liver, lungs and spleen as source organs, the MIRD method was applied to calculate the absorbed radiation dose of the radioligand in various organs. The thyroid (despite blockage), gallbladder wall, large intestinal walls and spleen received the highest absorbed doses. The average effective dose equivalent of 123I-IBZM for adults was estimated to be 0.034 mSv/MBq. The absorbed dose to the thyroid may be a limiting factor for 123I-IBZM studies in children.

Noninvasive visualization of acute myocardial infarction in man with thallium-201.

Myocardial imaging using 201Tl was performed in 10 patients with supposedly normal myocardial perfusion and in 11 patients with acute myocardial infarction. In all patients with acute myocardial infarction the scintiscan showed an area with diminished radioactivity at the site corresponding the electrocardiographic localization of the infarction. 210Tl seems to be of diagnostic value for recognizing acute myocardial infarction in the very first hours after its onset and for visualizing infarction in patients in whom pre-existing electrocardiographic abnormalities prevent its diagnosis and/or localization.

Thallium-201 scintigraphy in unstable angina pectoris.

Thallium-201 scintigraphy was performed during the pain free period in 98 patients with unstable angina. Scintiscans were positive in 39 patients, questionable in 27 patients and normal in 32 patients. Eighty-one patients responded favorably to treatment (group I). Seventeen patients had complicated courses (group II) and despite maximal treatment with propranolol either developed infarction (six patients) or continued to have angina necessitating coronary surgery (11 patients). In group I during the pain free period 26 of 81 patients had positive thallium-201 scans, whereas 20 patients had an abnormal ECG at that time; during angina 18 patients had transient ECG changes. In group II during the pain free period 13 of 17 patients had positive scans, whereas two patients had abnormal ECG at that time; during angina 12 patients showed transient ECG changes. The sensitivity to recognize group II was 76% for thallium-201 scintigraphy, 11% for ECG during the pain free period; 70% for ECG during angina; 94% for the combination of either positive scans or abnormal ECG. Thus, 1) positive thallium-201 scans occur in patients with unstable angina, 2) positive scans can be obtained during the pain free period, 3) thallium-201 scans are more frequently positive in patients with complicated course.

Value and limitations of thallium-201 scintigraphy in the acute phase of myocardial infarction.

We examined the diagnostic usefulness of thallium-201 scintigraphy in 200 patients with acute myocardial infarction. The scintiscans showed a defect, suggesting infarction in 165. In all 44 patients studied iwthin six hours after onset of symptoms the scintiscans indicated a defect. Frequency of positive scans was significantly higher (90 of 96) in patients studied within 24 hours after onset than in those (75 of 104) studied later (p less than 0.01).

Protocols for selection of cardiac radionuclide studies for use as a data base of normal studies and typical patterns of diseases. COST B2 Working Group II, in association with relevant working/task groups of the European Association of Nuclear Medicine and the European Society of Cardiology.

A data base of clinical studies is required for quality assurance of software used for analysis of radionuclide cardiac imaging procedures. Studies used must be rigorously validated in terms of both the clinical condition of the patient undergoing the procedure and the imaging protocol used. Selection protocols for the creation of a software phantom data base of normal studies and three typical patterns of cardiac disease--recent transmural myocardial infarction, isolated myocardial ischaemia and dilated cardiomyopathy--have been developed by the Cardiac Working Group of the European COST B2 project in association with the Cardiac Task Group of the European Association of Nuclear Medicine and the Working Group on Nuclear Cardiology of the European Society of Cardiology. These protocols include criteria for the interpretation of qualitative and quantitative non-radionuclide data. Compliance of the clinical data with the selection criteria will have to pass scrutiny by an international team for each study used as a software phantom. The radionuclide studies encompass stress and rest myocardial perfusion studies (planar and single photon emission tomography) using thallium-201 and technetium-99m methoxyisobutylisonitrile and rest gated blood pool studies. Methods for acquisition of data are defined for each type of study and for each individual study a portfolio of all clinical data is established. A pilot study is required to investigate the problems and logistics of distributing clinical radionuclide studies between a range of computers and institutes, and to ascertain the procedures necessary for analytical comparison of the results obtained.

Location and size of acute transmural myocardial infarction estimated from thallium-201 scintiscans. A clinicopathological study.

A clinicopathological study was performed in 23 patients who died from acute transmural myocardial infarction and who had been studied with thallium-201 during the acute phase. Twenty patients died within five days and three later than five days after scintigraphy. The scintigraphic location and the estimated size of infarction in vivo were correlated with postmortem findings. There was good agreement in 91% between scintigraphic and postmortem location of infarction and in 70% between the ECG and postmortem findings. The size of infarction as determined from computer-processed schematic drawings of postmortem slices of the heart correlated well with the size determined from processed schematic drawings of the scintiscans (r = 0.91 for anterior infarction, r = 0.97 for inferior infarction, r = 0.86 for anterior-inferior infarction). It is concluded that thallium-201 scintigraphy provided more precise location of infarction than the ECG and that the size of the scintigraphically abnormal area reflected the extent of necrotic myocardium.