Differential regional lung uptake analysis of the lung scan as an adjunct to interpretation of pulmonary embolism.

OBJECTIVE: Differential regional lung uptake (DRLU) analysis of a lung perfusion scan is used to provide information on diversion of the radiotracer from areas supplied by obstructed pulmonary artery branches to areas with patent vessels, which could assist in the diagnosis of pulmonary embolism (PE), especially the intermediate-probability studies. METHODS: Lung perfusion scans performed over 3 years (n=121) were analyzed using a computer overlay of six regions of interest per lung on the posterior view. DRLU was defined for neighboring region pairs as the ratio of the difference in the average count rate to the sum of the count rate in the region pair for a total of 18 region pairs per study. RESULTS: Comparison of the DRLU for high-probability studies (n=30) with normal scans (n=40) showed significant deviation in a least three region pairs per study. For low-probability scans (n=30), there was no significant deviation from the normal. For the intermediate category (n=21), a subgroup (n=7) showed significant deviation in at least three region pairs, which also had a positive computed tomography pulmonary angiography for PE, and another subgroup (n=14) had deviation in two or fewer region pairs with a negative computed tomography pulmonary angiography. CONCLUSION: Using DRLU analysis, intermediate scans for PE could be redefined as low or high probability, on the basis of the number of region pairs showing deviation of DRLU. This could lead to improved diagnostic performance of the study without recourse to additional maneuvers or specialized equipment and would obviate the need for more tests on the patient.

Improved delineation of parathyroid lesions in patients with chronic renal failure using magnified pinhole imaging.

UNLABELLED: (99m)Tc-sestamibi dual-phase scintigraphy is currently established for parathyroid localization. However, the imaging technique is not standardized, and the role of the pinhole collimator, especially, is not fully recognized in the imaging protocol. The aim of this study was to check whether the use of a pinhole collimator in parathyroid scintigraphy would enhance lesion detectability and delineation more than does a parallel-hole collimator or SPECT in patients with secondary hyperparathyroidism due to chronic renal failure with a mixed pattern of abnormalities. METHODS: Thirty-five patients referred for a parathyroid scan were included. Imaging was performed at 10 min and 2 h after injection of 925 MBq (25 mCi) of (99m)Tc-sestamibi using both a pinhole collimator and a high-resolution parallel-hole collimator fitted to a scintillation camera. SPECT was also performed at 1.5 h after injection. The images were reviewed by 2 experienced nuclear medicine physicians, and the results were analyzed. In addition, the contrast of visualized lesions was evaluated. RESULTS: Twenty-three patients (65.7%) had abnormal scan findings. The McNemar test revealed better detection of parathyroid lesions using pinhole imaging than with planar parallel-hole imaging and SPECT (P < 0.001 and P < 0.03, respectively). Both observers showed good agreement in evaluating different imaging techniques (κ = 0.76). Observers were in favor of pinhole imaging because SPECT suffered from noise. Lesion contrast was significantly higher in pinhole imaging than in parallel-hole imaging and SPECT (P < 0.05), with a 16% and 11% improvement in contrast, respectively. CONCLUSION: Pinhole imaging better delineates and detects lesions in parathyroid scintigraphy than does parallel-hole imaging and SPECT. Pinhole imaging increases confidence in image interpretation because of high lesion contrast and better magnification and resolution. The use of this technique is therefore recommended as part of the routine imaging protocol for (99m)Tc-sestamibi parathyroid scintigraphy.

(99m)Tc sulfur colloid and (99m)Tc mebrofenin hepatobiliary functional liver imaging in normal and diabetic rats.

OBJECTIVES: To use (99m)Tc sulfur colloid ((99m)Tc-SC) and (99m)Tc mebrofenin ((99m)Tc-BrIDA) to study liver function in normal and diabetic rats. MATERIALS AND METHODS: Radionuclide imaging was performed on 2 groups of rats, using (99m)Tc-SC for one group and (99m)Tc-BrIDA for the other (20 rats per group) before and after induction of diabetes mellitus (DM) using streptozotocin administration (55 mg/kg i.p.). Dynamic acquisition was obtained for 1 h after the injection of 37 MBq of radiotracer. For the (99m)Tc-SC group, organ/tissue uptake was determined by drawing regions of interest (ROI) over the heart, liver, spleen and also the whole body (WB). The ratio of the ROI of each organ to the WB ROI was calculated. For (99m)Tc-BrIDA, ratios of cumulative count rates in liver, liver parenchyma, biliary tree and abdomen ROI to a WB ROI were also calculated. Statistical analysis was performed to compare the ratios of organ/tissue uptake to WB uptake before and after DM induction using the paired t test. RESULTS: (99m)Tc-SC uptake ratios (means ±SD) showed a lower liver-to-WB uptake ratio (0.75 ± 0.05) in the rats after DM induction compared to baseline (0.81 ± 0.06), while the cardiac blood pool showed higher uptake ratios in the rats after DM induction (p = 0.026). For (99m)Tc-BrIDA, there was no significant difference in radiotracer uptake ratios obtained from the rats before and after DM induction (p = 0.41). CONCLUSION: Using functional liver imaging, there was a statistically significant decrease in the liver phagocytic/reticuloendothelial system function after DM induction, as evidenced by decreased (99m)Tc-SC liver uptake and increased blood pool compared to prediabetes, while the hepatobiliary function remained unchanged after DM induction using (99m)Tc-BrIDA imaging.

Optimal imaging positions for 3-phase bone scanning of patients with bony pathology of the feet.

UNLABELLED: The aim of the study was to optimize imaging positions of (99m)Tc-methylene diphosphonate ((99m)Tc-MDP) 3-phase bone scanning for the accurate localization of foot pathology in patients with trauma and diabetes-related complications. METHODS: (99m)Tc-MDP 3-phase bone scanning was performed for 26 controls and 27 patients with foot pathology. Flow was acquired in 1 of the following projections: anterior-posterior, medial-lateral, or plantar. Blood-pool and delayed images were acquired in a set of 5 projections (anterior, posterior, medial, lateral, and plantar). Images from the control group were checked for the views that best visualized individual bones or regions of the foot. These views were cross-correlated with images from the patient group to see whether they localized the exact site of the foot lesion. RESULTS: In the controls, the plantar view was the best view for visualization of the forefoot region. The mid foot was best assessed on the anterior view. Medial-lateral views were best suited for imaging the hind foot, and the posterior view was the best for the ankle joint. In the subjects with foot pathology, lesions were accurately assigned to the affected bone using the imaging criteria derived from the controls. In a few cases, however, additional views were needed because of overlap or shine-through of activity, particularly in mid-foot lesions. CONCLUSION: Optimal imaging positioning of the foot by bone scanning can be achieved using 5 views, which can yield accurate localization of a particular structure or bone, thereby improving the diagnostic accuracy of the procedure.

Treatment of renal calculi by lithotripsy: minimizing short-term shock wave induced renal damage by using antioxidants.

Treatment with extracorporeal shock wave lithotripsy (ESWL), the preferred method of treating kidney stones <3 cm in size, has been shown to induce silent and often self-limiting acute and chronic lesions in the kidneys and adjacent organs. We conducted a randomized clinical trial to determine whether ESWL produces ischaemia and reperfusion injury in the kidneys and whether oral administration of antioxidants reduces the degree of short-term renal injury in patients treated with ESWL. The study included 120 patients with renal stones (1-3 cm in size) treated with ESWL. The patients were divided into three groups--patients in group A (n=39) served as a control group and were not given any antioxidants; patients in group B (n=41) were given two capsules of antioxidants "Nature Made R: " 2 h before ESWL, and 2 and 8 h after ESWL; and patients in group C (n=40) were given two capsules of the antioxidants 2 and 8 h after ESWL. Double 'J' stents were inserted in patients before treatment with ESWL. Blood and urine samples were obtained from all patients just before the start of treatment with ESWL, and at 2 and 24 h and on 7th and 28th day after ESWL. Serum levels of malondialdehyde (MDA), alpha-tocopherol, cholesterol, albumin and ascorbic acid, and alpha-tocopherol/cholesterol ratio were determined. Urinary levels of albumin and beta(2) microglobulin were also determined as measures of renal tubular injury. At 24 h after ESWL, patients given antioxidants (groups B + C) had significantly reduced mean serum concentration of MDA (P<0.001); higher levels of serum ascorbic acid (P<0.001) and serum albumin (P<0.001); lower alpha-tocopherol/cholesterol ratio, lower urinary albumin and beta(2 )microglobulin levels compared with patients who did not receive antioxidants (group A). These findings suggest that treatment with ESWL generates free radicals through ischaemic/reperfusion injury mechanism, and that oral administration of antioxidant may protect these patients from short term renal injury caused by ESWL.

Post-test probability for pulmonary embolism after ventilation-perfusion scan assessed by nuclear medicine physicians.

OBJECTIVE: The objective of this prospective study was to compare assessments of pre- and post-ventilation-perfusion (V/Q) scan probabilities for pulmonary embolism (PE) by the nuclear medicine physician and the referring physician. MATERIALS AND METHODS: Seventy-nine patients (41 females, 38 males, mean age 49 years) referred for V/Q scans over a period of 6 months and suspected of PE were included in the study. The pre-test likelihood was determined independently by a consultant nuclear physician and a referring physician prior to the V/Q scan. The scan was performed according to a standard protocol using 8 view technetium-99m diethylenetriamine pentaacetic acid aerosol ventilation study followed by a technetium-99m macroaggregated albumin perfusion study. The scan was interpreted according to prospective investigation of pulmonary embolism diagnosis criteria. The post-scan probability was calculated. The probability of PE was quoted as low, intermediate and high. Agreement or disagreement in assessing the pre- and post-scan probability was classified according to the degree of difference (no difference: 0; minor difference: 1, and major difference: 2 grades). RESULTS: The agreement between the nuclear medicine and referring physicians on clinical probability of PE was moderate (63%) before the scan and good (90%) after the scan. The disagreement in assessing the clinical probability between the referring physician and the nuclear medicine physician was predominantly minor. Only 5 and 1% of the disagreement was major in pre-scan and post-scan probabilities, respectively. CONCLUSION: The data show that nuclear medicine physicians can use the assessment of pre-scan clinical likelihood to determine the post-scan probability of PE.

Nonosseous abnormalities on bone scans.

Although bone scanning is a test primarily concerned with skeletal abnormalities, important nonosseous findings are occasionally present on the images. To gauge the significance of such nonosseous uptake and, in particular, to determine whether these findings contain useful diagnostic information, the technical and medical staff in nuclear medicine must recognize the various patterns of nonbony uptake and understand their causes. The objectives of this article are to demonstrate the appearances of nonosseous uptake on bone scans, to categorize the forms of soft-tissue uptake, to emphasize technical artifacts leading to soft-tissue uptake, and to highlight the clinical significance of pathologic soft-tissue uptake.

Minimizing radiation exposure from patients treated with iodine-131 for hyperthyroidism using a lead collar: a simple and effective approach.

OBJECTIVE: To construct a lead collar useful for shielding the electromagnetic radiation from the thyroid of patients treated with radioiodine (131)I for hyperthyroidism, thereby reducing the radiation emitted from these patients. MATERIALS AND METHODS: A specially designed cervical lead collar was used to shield radiation exposure from 'hot thyroids' of 20 patients treated with iodine-131 for hyperthyroidism. The collar was made of lead strips stacked together around a plastic neck support fastened around the patient's neck. Measurements of the radiation exposure rate were obtained at increasing distances from the patients (50, 100, 200 cm), with and without the lead collar, at various times after (131)I treatment. RESULTS: Radiation exposure measurements over 3 weeks showed relatively high exposure rates in the first week after treatment. The radiation exposure from the patients wearing the lead collar was half that found in the same patients not wearing the collar. CONCLUSION: The use of the lead collar significantly reduced the radiation exposure of patients' surroundings. It was particularly useful in patients who could not abide strictly to the standard restrictive protocols after treatment with (131)I.

Salivary gland scintigraphy: the use of semiquantitative analysis for uptake and clearance.

OBJECTIVE: Quantitative analysis of (99m)Tc-pertechnetate salivary gland scintigraphy has been used in the evaluation of salivary gland function, but so far no one method can be considered optimal for this task. In this study, a semiquantitative method providing 2 functional parameters for objective assessment of salivary gland function by scintillation camera imaging was tested. METHODS: Twenty-one patients referred for (99m)Tc-pertechnetate thyroid scanning were studied. Two patients with salivary complaints were also included. Dynamic imaging of the anterior head using a scintillation camera was started after a bolus intravenous injection of 185 MBq (5 mCi) (99m)Tc-pertechnetate at 1 frame per 30 s for 30 min. At 15 min after injection, diluted lemon juice was administered orally. Analysis of the dynamic study included time-activity curves of 4 salivary glands (right and left parotid and right and left submandibular). Two parameters of function were defined: uptake rate, taken as the value of the initial slope of the time-activity curve, and washout fraction, which was the relative mobilizable radioactivity from each salivary gland after ingestion of the sialogogue. A parametric image of the washout fraction was also generated. RESULTS: The images showed gradual uptake in the parotid and submandibular glands. Washout was noted immediately after ingestion of the lemon juice. The pattern of the time-activity curve in all glands showed an early fast-rising part followed by a slow-rising component to nearly a plateau within 6-10 min after injection. The mean value of the uptake rate parameter was 0.10 +/- 0.09 cps/s. There was no significant difference between the parotid and submandibular glands or the right and left sides. Uptake in the parotid gland was 1.5-2 times that in the submandibular gland. The washout fraction was 1.40 +/- 1.60 for the parotid glands and 0.77 +/- 0.41 for the submandibular glands (P = 0.005). CONCLUSION: The quantitative analysis method including the uptake rate and the washout fraction parameters would enable objective assessment of salivary function and provide a reproducible means for follow-up of functional impairment in certain diseases.

A mathematical model of optimized radioiodine-131 therapy of Graves' hyperthyroidism.

BACKGROUND: The current status of radioiodine-131 (RaI) dosimetry for Graves' hyperthyroidism is not clear. Recurrent hyperthyroidism and iatrogenic hypothyroidism are two problems which interact such that trying to solve one leads to exacerbation of the other. Optimized RaI therapy has therefore begun to be defined just in terms of early hypothyroidism (ablative therapy) as physicians have given up on reducing hypothyroidism. METHODS: Optimized therapy is evaluated both in terms of the greatest separation of cure rate from hypothyroidism rate (non-ablative therapy) or in terms of early hypothyroidism (ablative therapy) by mathematical modeling of outcome after radioiodine and critically discussing the three common methods of RaI dosing for Graves' disease. RESULTS: Cure follows a logarithmic relationship to activity administered or absorbed dose, while hypothyroidism follows a linear relationship. The effect of including or omitting factors in the calculation of the administered I-131 activity such as the measured thyroid uptake and effective half-life of RaI or giving extra compensation for gland size is discussed. CONCLUSIONS: Very little benefit can be gained by employing complicated methods of RaI dose selection for non-ablative therapy since the standard activity model shows the best potential for cure and prolonged euthyroidism. For ablative therapy, a standard MBq/g dosing provides the best outcome in terms of cure and early hypothyroidism.