Usefulness of 99mTc-ciprofloxacin (infecton) scan in diagnosis of chronic orthopedic infections: comparative study with 99mTc-HMPAO leukocyte scintigraphy.

UNLABELLED: 99mTc-labeled ciprofloxacin (infecton) has been developed for detecting infectious foci, which localize in high concentrations in living bacteria. Other studies performed with various infections in animals and humans have found that infecton is a promising agent with better specificity for bacterial infections than white blood cell (WBC) scans. In this study, we evaluated the efficacy of infecton scintigraphy for detecting chronic bone and joint infections. METHODS: Fifty-six sites with suspected bone or joint infection were examined with 99mTc-WBC and infecton scans in 51 patients. Of these patients, 21 had prosthetic implant materials. Biochemical, radiologic, and microbiologic data and clinical outcomes also contributed, along with the results from scintigraphic techniques, in determining the presence or absence of infection. Scintigraphic images were produced at 1 and 4 h after injection of 370-400 MBq infecton or 185-200 MBq 99mTc-hexamethylpropyleneamine oxime (HMPAO)-WBCs. For each patient, there were at least 2 d and at most 7 d between scintigraphic studies. RESULTS: There were 30 true-positive, 4 false-positive, 20 true-negative, and 2 false-negative results with infecton. With 99mTc-HMPAO-WBCs, the results were 20, 1, 23, and 12, respectively. Values for sensitivity, specificity, and accuracy were 94%, 83%, and 89%, respectively, with the infecton scan and 63%, 96%, and 77%, respectively, with WBC scanning. Differences between the two agents were statistically significant (P < 0.001). Infecton and WBC scan results were in general concordance for 43 of 56 sites (77%). Infecton results for vertebral infections were the most notable findings in this study, despite the limited number of patients with this condition. Infecton scans were positive for hot spots in five of six patients with vertebral osteomyelitis. WBC scans showed photon-deficient areas in four of these same patients and normal distribution in the remaining two patients. CONCLUSION: Infecton is a useful agent for detecting infectious foci in bones and joints. Moreover, the infecton scan seems to be a more powerful tool in diagnosing vertebral infections than WBC scintigraphy.

Impact of initial surgical treatment on survival of patients with differentiated thyroid cancer: experience of an endocrine surgery center in an iodine-deficient region.

This retrospective clinical study was designed to analyze the impact of the initial surgical procedure on the survival of 1000 patients with differentiated thyroid cancer of follicular cell origin who had a thyroid operation and were followed for the 30 years between 1968 and 1998 (median 14 years) in an iodine-deficient region where goiter is endemic. There were 753 women and 247 men with a mean age of 42.8 +/- 6.7 years (range 17-86 years). Patients were divided into three groups. All patients had undergone thyroxine treatment and thyroid-stimulating hormone (TSH) suppression, and most had had iodine-131 treatment postoperatively. Group A consisted of 336 patients with differentiated thyroid cancer (DTC) who were treated with bilateral subtotal thyroidectomy in our institution or elsewhere. Group B consisted of 158 patients with DTC who were treated initially with unilateral total lobectomy and contralateral subtotal lobectomy in our institution or elsewhere and underwent reoperation in our department. Group C consisted of 506 patients with DTC who were treated initially with total or near-total thyroidectomy in our department. Kaplan-Meyer survival analysis was used. Recurrence was seen in 23% and death in 8% of the patients. The 20-year survival rates were 76%, 85%, and 92% for groups A, B, and C, respectively. The survival difference among the patients of group A and groups B and C was found to be statistically different (p < 0.001). Long-term survival of patients with differentiated thyroid cancer living in endemic areas for goiter can be influenced by the initial surgical treatment. Patients treated initially with total or near-total thyroidectomy appear to have a better prognosis.

Correlation of technetium-99m MIBI and thallium-201 retention in solitary cold thyroid nodules with postoperative histopathology.

A comparative prospective study of technetium-99m methoxyisobutylisonitrile (MIBI) and thallium-201 with early (15 min) and delayed (90 min for MIBI, 3 h for 201Tl) imaging in the differentiation of thyroid lesions is presented. Forty patients with cold thyroid nodules visualised on 99mTc-pertechnetate scan and with dyskaryotic or atypical epithelial cells verified by fine needle aspiration biopsy underwent MIBI and 201Tl scintigraphy at 3-day intervals. Subsequent thyroidectomies were carried out in all patients. Semiquantitative analysis was performed using a lesion to non-lesion ratio on early (ER) and delayed images (DR). Additionally, a retention index (RI) was calculated using the formula RI=(DR-ER) x 100/ER. The reproducibility of the method for the early and delayed measurements was tested by analysing intra- and inter-observer variability and repeatability coefficients. Histopathologically, the nodules were found to be well-differentiated thyroid cancer in 21 patients and benign in 19 patients. There was no significant difference in the ER between malignant and benign lesions for either 201Tl or MIBI (P>0.05). However, for both agents significant differences were found between malignant and benign lesions with regard to DR (P<0.01 for 201Tl and P<0.001 for MIBI) and RI (P<0.001 for both agents). Statistical comparison of the two agents showed no significant differences (P>0.05) except with regard to DR and RI in malignant nodules (P<0.05). A receiver operating characteristic analysis was performed to determine threshold levels for the differentiation of malignant from benign nodules. Following this analysis, ER, DR and RI levels of 1.03, 1.54 and 2 for MIBI and < or =1.42, 1.24 and 5 for 201Tl were selected. Using these threshold levels, the sensitivity, specificity and accuracy of the study were 90.5%, 36.8% and 65% for ER MIBI, 61.9%, 94.7% and 77.5% for DR MIBI, 95.2%, 89.4% and 92.5% for RI MIBI, 85.7%, 47.3% and 67.5% for ER 201Tl, 80.9%, 73.6% and 77.5% for DR 201Tl, and 90.5%, 94.7% and 92.5% for RI 201Tl. In conclusion, the DR for MIBI and 201Tl is superior to the ER in detecting malignant nodules, and the RI for both MIBI and 201Tl is more valuable than the DR in differentiating malignant from benign thyroid nodules.

Comparison of 99mTc-methoxyisobutyl isonitrile and 201T1 scintigraphy in visualization of suppressed thyroid tissue.

UNLABELLED: Both (201)TI and (99m)Tc-methoxyisobutyl isonitrile (MIBI) have been used in the visualization of suppressed thyroid tissue in patients with autonomously functioning thyroid nodules (AFTNs). It has been suggested that thyroid-stimulating hormone (TSH) control is not a major determinant of both tracers. However, the mechanism of thyroid uptake of these agents is controversial. In this study, we compared (201)TI and MIBI in the visualization of suppressed thyroid tissue in patients with a solitary toxic AFTN. METHODS: Thirty-two patients (13 triiodothyronine [T3] and 19 T3 + levorotatory thyroxine [T4] hyperthyroid patients) with toxic AFTNs visualized on (99m)Tc-pertechnetate scanning were included in the study. All patients underwent MIBI and (201)TI thyroid scintigraphy within a 3-d interval. The scintigrams were analyzed both visually and semiquantitatively. For the semiquantitative analysis, regions of interest (ROIs) were generated over the nodule (N) and contralateral normal lobe (E), and the mean counts in each ROI were calculated. RESULTS: The N/E uptakes (mean +/- SD) for pertechnetate, MIBI, and (201)TI were 11.37 +/- 4.53, 4.76 +/- 1.38, and 1.63 +/- 0.15, respectively, in T3 + T4 hyperthyroid patients and 9.46 +/- 3.64, 2.73 +/- 0.63, and 1.57 +/- 0.23, respectively, in T3 hyperthyroid patients. Our results showed that (201)TI uptake of suppressed thyroid tissue compared with AFTN was more prominent and significantly higher than that of MIBI for both groups of patients (P = 1.08E-05 for T3 and 6.15E-09 for T3 + T4 hyperthyroidism). There was no significant difference for either pertechnetate or (201)TI (P > 0.05) when the N/E uptakes of both groups of patients were compared. However, the N/E uptake of MIBI in T3 + T4 hyperthyroid patients was significantly higher than that in T3 hyperthyroid patients (P = 6.69E-06). CONCLUSION: Clear visualization of suppressed thyroid tissue with both (201)TI and MIBI in patients with low serum concentrations of TSH suggests that TSH is not a major factor in the thyroid uptake of either agent. (201)TI is superior to MIBI in the visualization of suppressed thyroid tissue in patients with a toxic thyroid nodule. An increased rate of metabolism in the follicular cells of AFTNs in T3 + T4 hyperthyroid patients compared with that in T3 hyperthyroid patients might be responsible for the higher N/E for MIBI compared with that for (201)TI.

The role of 99Tcm-tetrofosmin in the evaluation of thyroid nodules.

Various radionuclides, including 67Ga, 201Tl and 99Tcm-sestamibi, have been used to differentiate benign from malignant thyroid nodules. 99Tcm-tetrofosmin, a lipophilic cationic radiotracer, and 99Tcm-sestamibi have also been reported to accumulate in thyroid tumours. In this study, we evaluated the role of 99Tcm-tetrofosmin in the differentiation of malignant from benign thyroid nodules. Seventy-nine patients with solitary non-functioning thyroid nodules were included in the study. Fine-needle aspiration biopsy was performed in all patients. Sixty patients were subsequently operated on and 19 patients refused surgery. After the injection of 370 MBq 99Tcm-tetrofosmin, static images at 5, 30, 60, 120 and 180 min were acquired. Both visual and semi-quantitative analysis was performed. On visual interpretation, the nodules with late retention were classified as positive for malignancy and nodules without late retention were classified as negative for malignancy. In the semi-quantitative analysis, regions of interests were drawn over the nodule and contralateral normal thyroid tissue. The average number of counts was recorded and tumour-to-normal thyroid tissue ratios calculated. Post-operative histology revealed 19 malignant and 41 benign nodules. Of the benign nodules, adenomas behaved similarly to the malignant nodules with late retention of tracer, while adenomatous nodules revealed no late retention on delayed images and could be differentiated from malignant tumours. In the semi-quantitative analysis, there was a significant difference in tumour-to-normal tissue ratios for adenomatous nodules and malignant tumours as well as adenomas. We conclude that it is not possible to differentiate between malignant and benign thyroid nodules with 99Tcm-tetrofosmin. However, 99Tcm-tetrofosmin scintigraphy is helpful in selecting nodules that can be cured by surgical intervention.

Single-photon emission computed tomographic myocardial perfusion imaging in patients with mitral valve prolapse.

The possibility of exercise-induced myocardial ischemia due to mitral valve prolapse (MVP) in the absence of coronary artery disease was evaluated with single-photon emission computed tomographic analysis using thallium-201 and technetium-99m sestamibi in 72 patients with MVP. Exercise electrocardiography was positive in 5 patients (8%), but single-photon emission computed tomography was found to be normal in all patients, and exercise-induced chest pain, electrocardiographic changes, and arrhythmias were found not to be related to myocardial ischemia in patients with MVP.

The effect of P-glycoprotein function inhibition with cyclosporine A on the biodistribution of Tc-99m sestamibi.

PURPOSE: The failure to cure persons with cancer is caused primarily by the development of drug resistance by overexpression of p-glycoprotein. Diverse groups of drugs have been identified, including cyclosporine A, which can reverse drug resistance by inhibiting P-glycoprotein transport. Tc-99m sestamibi is a substrate for P-glycoprotein. P-glycoprotein is normally expressed in biliary canalicular surfaces of hepatocytes and is responsible for the excretion of cationic metabolites from the liver. The aim of the current study was to evaluate the effect of cyclosporine A on the biological distribution of Tc-99m sestamibi in vivo. METHODS: Five patients with alopecia and two renal transplant patients who were treated with cyclosporine A were selected for the study. All patients were examined before and at least 2 weeks after administration of cyclosporine A. Tc-99m sestamibi scintigraphy was performed by obtaining planar abdominal images at 5, 30, 60, 120, and 180 minutes after injection, and the liver-heart ratios were calculated. RESULTS: Plasma cyclosporine A, bilirubin levels, liver enzymes, and creatinine clearance values were obtained from all patients. In three, the plasma cyclosporine A level was increased to more than 400 pg/dl. The liver-heart ratio was increased significantly after cyclosporine A administration (P < 0.01). After cyclosporine A administration Tc-99m sestamibi excretion was delayed and the uptake in the liver was increased. The difference was 17% at 5 minutes and 38% at 180 minutes. Liver retention was greatest in patients with cyclosporine A toxicity. CONCLUSIONS: With a limited number of patients, this study suggests that Tc-99m sestamibi excretion from the liver is mediated by P-glycoprotein, and inhibition of P-glycoprotein transport not only delays liver excretion but also increases the liver uptake of Tc-99m sestamibi. Because this observation deserves further investigation, the inhibition of P-glycoprotein function with nontoxic multidrug-resistance reversing agents may be used as an intervention to increase the tumor uptake of Tc-99m sestamibi and to increase the sensitivity of Tc-99m sestamibi tumor imaging.

A method to evaluate microcirculatory vascular patency of full thickness burn in an animal model.

BACKGROUND: In cases of thermal injuries it is always difficult to predict the extent of necrosis to the peripheral ischemic zone. Practically, full-thickness skin burn also affects the underlying muscle, panniculus carnosus, which adheres tightly to the skin. In this proposed model, the muscle which was always partly damaged also covers the ischemic zone of full-thickness burn injury. To evaluate the deeper levels of injury, the status of the micro circulation of thermally affected muscle was evaluated by counting the accumulated radioactive agent, 99mTc methoxyisobutylisonitril (MIBI) in the muscle cells. METHODS: 370 MBq/kg (10 mCi/kg) MIBI was administered intravenously to the animals having burn injuries by a comb device as described in previous literature. Then, 20 minutes after injection, whole burned areas were excised and placed under a gamma camera. Each thermally injured area showed four rectangular defects with lower tracer uptakes than the three adjacent interspaces. The tracer uptake of the burned sites and interspaces was analyzed from the acquired images on a computer, and the degree of injury could be assessed quantitatively. Additionally, specimen counts were obtained from selected burned stripes, interspaces and normal tissue for comparison. RESULTS: Burned sites were evident with lower tracer uptakes whereas interspaces with higher uptakes. Captured activity in interspaces indicated that capillary patency mostly maintained and it permitted the arrival of the radiopharmaceutical to the muscle cells. CONCLUSIONS: Muscle layer, where just below the burn area and tightly attached to the skin, could be assessed as a representative of the extension of the injury.

Prospective validation of single plasma sample 99mTc-ethylenedicysteine clearance in adults.

UNLABELLED: 99mTc-L,L-ethylene, L, dicysteine (EC) clearance shows strong correlation with orthoiodohippurate clearance, and it is possible to estimate effective renal plasma flow from 99mTc-EC clearance. In routine clinical studies, it is practical to use the one or two plasma sample method instead of multiple plasma samples for clearance determination. A single-sample technique was developed for 99mTc-EC, and a regression formula was generated. A prospective study tested the validity of this regression formula. METHODS: The study population was composed of 26 patients with a wide range of renal function. Multiple plasma sample 99mTc-EC clearances were calculated from all patients using the open two-compartment model. Single plasma sample clearances were also determined from the 54-min plasma sample using the regression formula published previously. RESULTS: The multiple-sample plasma clearance of 99mTc-EC ranged from 46 to 668 mL/min with a mean of 300.76 +/- 150.73 mL/min. The clearances obtained from the 54-min plasma sample ranged from 49 to 699 mL/min, with a mean of 297.39 +/- 152.23 mL/min. There was an excellent correlation between the clearances obtained by the two techniques (r = 0.99, slope = 0.9911). The standard error of estimation was found to be 25.9 mL/min. CONCLUSION: This study suggests that 99mTc-EC clearance can be estimated from 54-min plasma samples with an acceptable error of estimation for most routine clinical studies.

Simplified technetium-99m-EC clearance in adults from a single plasma sample.

UNLABELLED: Technetium-99m-EC has recently been introduced as an alternative renal tubular agent to 131I-ortho iodohippurate (OIH). It has been shown that 99mTc-EC clearance shows strong correlation with OIH clearance and it is possible to estimate effective renal plasma flow. In routine clinical studies, it is practical to use one or two plasma sample methods instead of multiple plasma samples for clearance determination. An attempt was made to determine 99mTc-EC clearance with one sample method. METHODS: Data from 72 subjects were collected. To increase the range of renal function, two anuric hemodialysis patients were also included. Clearances were determined by the open two-compartment model. RESULTS: The clearance range was 12 ml/min to 660 ml/min with a mean of 275 +/- 117 ml/min. Analysis of correlation was made by Tauxe's method. The least standard error of estimation (s.e.e. = 32.71 ml/min) and the best correlation (r = 0.97) between the theoretical volume distribution and the clearance estimations were obtained from the 54-min plasma sample. CONCLUSION: This study suggests that EC clearance could be determined by a simplified single-sample method with an acceptable s.e.e.

Effects of allopurinol, ibuprofen and cyclosporin A on local microcirculatory disturbance due to burn injuries.

This experiment was designed to study the reactions in the surrounding area of burn injury that may lead to further necrosis in 24 h. To prevent extension of burn size into the tissue adjacent to burn injury, it was attempted to reduce progressive microvascular damage by different drugs (ibuprofen, allopurinol or cyclosporin A (CyA)) in a rat model. The burn model consisted of a row of four 10 x 20 mm burn areas separated by three unburned 5 x 20 mm skin bridges (interspaces). To evaluate microcirculation and perfusion of panniculus carnosus muscle which is beneath the burned area of skin, the radioactive agent, technetium-99m methoxyisobutylisonitrile (99Tc01-MIBI) was used 24 h after the burn. Capillary permeability of injured tissue was assessed by the wet and dry weight technique. In all study groups, interspaces showed higher uptakes of 99Tc01-MIBI between 40 and 95 per cent, in comparison with burn sites in the first 24 h following burn. Among the treated rats better results were obtained by allopurinol and CyA treatment that commenced before burn than ibuprofen. Wet and dry ratios were found to be significantly lower in interspaces in rats pretreated with allopurinol and CyA. Results of this experiment showed that neutrophils and free radical-mediated injury may be involved in the pathogenesis of local response to thermal injury, and allopurinol and CyA have some effects to prevent progressive ischemia, capillary compromise and oedema.

Evaluation of external radiation exposure rate from radioiodine-treated hyperthyroid patients and radiation safety considerations.

Hyperthyroid patients treated with radioiodine (131I) pose an external radiation risk to individuals who come into close contact with them. In order to determine changes in levels of external radiation with time in relation to the dose administered, 38 hyperthyroid patients being treated with 131I were evaluated Thyroid uptake, plasma T3, T4 and TSH levels were measured prior to treatment. Using a Geiger-Muller probe, levels of external radiation were measured at distances of 0.3, 0.6, 1.0 and 2.0 m from the patient -at the level at which the maximum activity was recorded -30 min, 1, 3, 7 and 10 days post-therapy. The patients were split into two groups. Group I comprised 22 patients treated with < or = 370 MBq 131I, 5 (23%) of whom registered > 0.46 mC kg-1 at a distance of 1.0 m 30 min post-therapy. Group II comprised 16 patients treated with > 370 MBq 131I, 13 (81%) of whom registered 0.46 mC kg-1 at a distance of 1.0 m one day post-therapy. At 3 days in Group I and 7 days in Group II, the estimated total radiation exposure rates were found to exceed the 1994 US Nuclear Regulatory Commission dose limits for children and pregnant women. Based on the results obtained, we present some guidelines intended to prevent the public from unnecessary radiation exposures.

Cerebellar and subcortical blood flow abnormalities in children with partial epilepsy.

Cerebellar and cerebral subcortical blood flow in 41 children with partial epilepsy and 6 normal controls was investigated during the interictal state using single photon emission computed tomography with technetium-99m hexamethylpropyleneamineoxime. Seventeen of 41 patients had been treated with antiepileptic drugs (AEDs) for 4.65 +/- 3.80 years (range 0.2-12) and 24 patients were drug-free. Unilateral hypoperfusion of cerebellum and cerebral subcortical gray matter was demonstrated in 11 (28%) and 16 (40%) patients, respectively. Most of them also had focal cerebral cortical perfusion abnormalities, ipsilateral or contralateral to the cerebellar and cerebral subcortical hypoperfusion. The mean asymmetry indices of cerebellar blood flow in the medicated and the unmedicated patients were significantly higher than in the control cases (P < 0.02 and P < 0.04), whereas the differences in the asymmetry indices in cerebral subcortical areas were insignificant. AED therapy did not affect the perfusion of cerebellum and cerebral subcortical regions (P > 0.05 and P > 0.05). Our results suggest that functional alterations on anatomically connected remote areas in patients with partial epilepsy are not related to the drug effect and probably due to primary epileptogenic activity.

Technetium-99m-MIBI scintigraphy in pulmonary tuberculosis.

UNLABELLED: We investigated the usefulness of 99mTc-methoxyisobutylisonitrile scintigraphy in patients with known or suspected pulmonary tuberculosis (PTB) in comparison with radiological and bacteriological findings. METHODS: Thirty-six patients aged 13-59 yr were scanned 15 and 60 min after intravenous injection of 370 MBq (10 mCi) 99mTc-methoxyisobutylisonitrile. Twenty-four patients had active PTB proven by chest radiograph and sputum examinations, two had miliary tuberculosis and ten were suspected of having relapsed PTB with negative sputum examinations and indeterminate chest radiographs. In 12 patients 99mTc-MIBI imaging was repeated 1-3 mo after chemotherapy. RESULTS: Of 24 patients with active localized PTB, 22 (92%) showed increased focal uptake of 99mTc-MIBI, but two patients with minimal infiltration on chest radiographs had no accumulation of 99mTc-MIBI. Both patients with miliary PTB showed diffuse 99mTc-MIBI uptake in the lungs. Among 10 patients with suspicion of relapse, 99mTc-MIBI scans were true-positive in 4 of 5 patients (80%) with culture-proven tuberculosis and false-positive in 2 of 5 (40%) patients with negative sputum cultures. For repeat imaging, 6 of 10 patients with active localized PTB showed reduced MIBI uptake, which correlated with chest radiograph findings, and one patient had increased MIBI uptake again concordant with clinical and radiological findings which were suggestive of resistance to first line chemotherapy of tuberculosis. The other three patients showed no significant scintigraphic changes despite clinical and partial radiological regression. CONCLUSION: Active PTB granulomas generally present considerable 99mTc-MIBI uptake that is most probably related to disease activity. Therefore, 99mTc-MIBI scanning could be used in the detection and follow-up of active PTB as a complement to routine techniques.

Evaluation of technetium-99m-ethylenedicysteine in renal disorders and determination of extraction ratio.

UNLABELLED: This article evaluates the clinical usefulness of 99mTc-ethylenedicysteine (EC) in patients with various renal disorders. In addition, extraction ratios of 99mTc-EC in five volunteers were also determined. METHODS: Twenty patients were intravenously injected with 200 MBq 99mTc-EC and 2.5 MBq [131I]orthoiodohippurate (OIH) simultaneously and 11 blood samples were withdrawn within 60 min. Plasma clearance was determined on the basis of a two-compartment model. Imaging was performed in the posterior projection by acquiring three sets of images. Extraction ratios were determined from the blood samples obtained from the renal vein and abdominal aorta. RESULTS: Renal clearance of 99mTc-EC was significantly lower than that of OIH (p = 0.0003) with good correlation (r = 0.93). Volume distributions of 99mTc-EC and OIH were 26584 +/- 10807 ml/1.73 m2 and 23148 +/- 7602 ml/1.73 m2, respectively (p = 0.047). The clearance half-lives of 99mTc-EC and OIH were 98 +/- 54 min and 74 +/- 54 min, respectively (p = 0.049). Protein binding of 99mTc-EC (33 +/- 3.2%) was significantly less than that of OIH (62 +/- 2.8%) (p < 0.0001). Red blood cell binding of 99mTc-EC was almost negligible (5.7 +/- 4.3%). Similar extraction ratios were obtained from blood (0.68 +/- 0.08) and plasma (0.70 +/- 0.07) (p = 0.062). The 60-min excretion fractions were similar for 99mTc-EC and OIH, with values of 50% +/- 20% and 51% +/- 19%, respectively (p = 0.9). CONCLUSION: Technetium-99m-EC is a suitable radiopharmaceutical for routine renal dynamic studies. Although the biological behavior of 99mTc-EC seems to be different from that of OIH, their clearances demonstrate high correlation. Technetium-99m-EC provides excellent quality images and has high potential in the evaluation of quantitative renal functions.

Brain SPECT evaluation of the visual cortex in amblyopia.

UNLABELLED: In amblyopia, the number of visual cortical neurons are reduced and abnormal or absent sensitivity to retinal light stimulation of the amblyopic eye is demonstrated. Ten amblyopic patients were studied to evaluate the response of the visual cortex to visual stimulation. METHODS: All patients with unilateral amblyopia received 500-550 MBq 99mTc-HMPAO during visual stimulation. Strobe light flashing was used as the stimulus for five patients and a checkerboard pattern reversal was used in the other five patients, closing one eye. For both groups a 2-Hz frequency was used. One week later, the same procedure was repeated with the opposite eye closed. SPECT images were reconstructed with prefiltering techniques and sliced along the orbitomeatal line. RESULTS: For all patients, the amblyopic eye demonstrated less radioactivity in the visual cortex than in the normal eye. The mean cerebral-to-cerebellar ratios were 0.95 +/- 0.05 and 1.09 +/- 0.07 for amblyopic and normal eyes, respectively (p < 0.0001). CONCLUSION: Visual cortex response of the amblyopic eye to light stimulation was severely reduced when compared to the normal eye.

Clinical comparison of technetium-99m-EC, technetium-99m-MAG3 and iodine-131-OIH in renal disorders.

UNLABELLED: Technetium-99m-ethylenedicysteine has recently been developed for renal function studies. The pharmacokinetics of 99mTc-EC were studied by constant infusion technique and compared with 99mTc-MAG3 and 131I-OIH in 11 patients with various renal disorders. METHODS: After giving a 7.4 MBq 131I-OIH and 90-110 MBq 99mTc-EC or 99mTc-MAG3 bolus, a constant infusion (1MBq/ml 99mTc-agent and 0.07 MBq/m 131I-OIH was started. Sixteen blood and five urine samples were obtained over three hr. RESULTS: The renal clearance of 99mTc-EC was higher than that of 99mTc-MAG3. The 99mTc-EC/OIH and 99mTc-MAG3/OIH ratios were 0.75 +/- 0.05 and 0.55 +/- 0.10 (p = 0.00087), respectively. The distribution volume of 99mTc-EC was also higher than that of 99mTc-MAG3 (15722 +/- 4644 and 9509 +/- 2788 ml/1.73m2, respectively; p = 0.072). The 99mTc-EC/OIH and 99mTc-MAG3/OIH distribution volume ratios were 1.03 +/- 0.14 and 0.55 +/- 0.10, respectively (p = 0.0003). The 60-min excretion values of 99mTc-EC and 99mTc-MAG3 were compared to that of OIH. The 99mTc-EC/OIH and 99mTc-MAG3/OIH excretion ratios were 0.96 +/- 0.06 and 1.07 +/- 0.10, respectively (p = 0.162). The protein binding of 99mTc-EC and OIH were found to be 34% +/- 4 and 66% +/- 5, respectively (p < 0.0001). The red cell binding of 99mTc-EC was negligible (3% +/- 1.2) in comparison to OIH (27% +/- 3; p < 0.0001). CONCLUSION: This limited study demonstrates the pharmacokinetic and renal clearance properties of 99mTc-EC. This agent has good potential for renal function evaluation.