99mTc-interleukin-2 scintigraphy in normal subjects and in patients with autoimmune thyroid diseases: a feasibility study

Purpose  Radiolabelled interleukin-2 is a radiopharmaceutical used for the study of chronic inflammatory processes. ¹²³I-labelled interleukin-2 has successfully been used in a large number of patients affected by several immune-mediated diseases. ¹²³I, however, is expensive and not readily available. We have, therefore, developed a method for labelling interleukin-2 with ^99mTc to high specific activity based on the use of an N₃S bifunctional chelating agent. In this paper, we describe the results obtained with ^99mTc-interleukin-2 in a series of eight normal subjects and of 12 patients with autoimmune thyroid diseases. Methods  Biodistribution, pharmacokinetics, haematological and systemic toxicity, radiation absorbed dose and in vivo targeting were studied. Results  Results showed rapid plasma clearance of ^99mTc-interleukin-2 with retention mainly in the kidneys. Biodistribution and kinetics were similar to that observed for ¹²³I-interleukin-2. No acute systemic toxicity was found; a small decrease in peripheral blood lymphocytes was observed in the first hours only in patients, but it was mild and transient. ^99mTc-interleukin-2 accumulated, to varying extents, in the thyroid of all patients affected by autoimmune thyroid diseases but not in the thyroid of normal subjects. The effective dose equivalent of a diagnostic activity of ^99mTc-interleukin-2 (185 MBq) was 1.35 mSv. No correlation was observed between thyroid autoantibodies and uptake of ^99mTc-interleukin-2. Conclusions  The use of ^99mTc-interleukin-2 is safe and simple; the favourable dosimetry and biodistribution and the rapid clearance make it potentially useful for the study of chronic inflammatory diseases such as autoimmune thyroid disease.     

99mTc-interleukin-2 scintigraphy for the in vivo imaging of vulnerable atherosclerotic plaques

Purpose Several histopathological studies have demonstrated that vulnerable plaques are enriched in inflammatory cells. The aims of this study were: (1a) to test the ability of ^99mTc-labelled interleukin-2 (^99mTc-IL2) to bind to IL2R-positive (IL2R+) cells in carotid plaques and (1b) to correlate the plaque uptake of ^99mTc-IL2, measured in vivo, with the number of IL2R+ cells within the plaque, measured ex vivo by histology (transversal study, TS), and (2) to evaluate changes in ^99mTc-IL2 uptake in plaques, before and after treatment with a statin or a hypocholesterolaemic diet (longitudinal study, LS).Methods Ultrasound scan was performed for plaque characterisation and localisation. Fourteen patients (16 plaques) eligible for endoarterectomy were recruited for the TS and underwent ^99mTc-IL2 scintigraphy before surgery. Nine patients (13 plaques) were recruited for the LS; these patients received atorvastatin or a standard hypocholesterolaemic diet and ^99mTc-IL2 scintigraphy was performed before and after 3 months of treatment.Results The degree of ^99mTc-IL2 uptake was expressed as the plaque/background (T/B) ratio. In patients from TS, T/B ratios correlated with the percentage of IL2R+ cells at histology (r=0.707; p=0.002) and the number of IL2R+ cells at flow cytometry (r=0.711; p=0.006). No correlations were observed between ultrasound scores and either scintigraphic or histological findings. In patients from the LS, the mean ^99mTc-IL2 uptake decreased in statin-treated patients (1.75±0.50 vs 2.16±0.44; p=0.012), while it was unchanged in the patients on the hypocholesterolaemic diet (2.33±0.45 vs 2.34±0.5).Conclusion ^99mTc-IL2 accumulates in vulnerable carotid plaques; this accumulation is correlated with the amount of IL2R+ cells and is influenced by lipid-lowering treatment with a statin.     

99mTc-HMPAO labelled leucocyte scintigraphy in the diagnosis of pelvic inflammatory disease

BACKGROUND: Scintigraphy using leucocytes labelled with 99mTc hexamethylpropyleneamine oxime (99mTc-HMPAO) is widely used for the localization of inflammatory foci and abscesses in cases of acute pelvic inflammatory disease, which is one of the serious health problems of women of child-bearing age. Early diagnosis and effective management of this condition can preserve fertility and prevent serious complications, such as peritonitis and sepsis. AIM: To evaluate the importance of scintigraphy using 99mTc-HMPAO labelled leucocytes in the early diagnosis of patients with pelvic inflammatory disease. METHODS: Fifteen women (mean age 29.2+/-8 years, range 25-46 years) with suspicion of pyogenic pelvic inflammatory disease based on gynaecological examinations, clinical findings and blood tests were included in this study. The patients received 555 MBq 99mTc-HMPAO labelled leucocytes, by injection, and were scanned by scintigraphy 0.5-1, 3 and 24 h later in the anterior abdominal projection. Ten of the patients were then evaluated by abdominal or transvaginal ultrasonography, four by computed tomography and two by both ultrasound and computed tomography. The final diagnosis was made by surgical intervention. RESULTS: Scintigraphy detected pelvic inflammatory disease in five of the patients. In three of them the disease was apparent on the scans taken at 0.5-1 h, and in the other two it was apparent at 3 h. There were no false negative results, and one false positive result. The scan accurately reflected the absence of pelvic inflammatory disease in nine patients showing non-pathological tracer uptake in the lower abdominal region. CONCLUSION: We showed that scintigraphy with 99mTc-HMPAO labelled leucocytes had a sensitivity of 100%, specificity of 90%, overall accuracy of 93%, positive predictive value of 83%, and negative predictive value of 100%. Therefore, we conclude that 99mTc-HMPAO labelled leucocyte scans provide a rapid and highly accurate method for diagnosing pelvic inflammatory disease in women of child-bearing age. This adds an important contribution to the diagnosis of infection and helps determine further operative or conservative treatment.     

Clinical assessment of 99mTc-HMPAO scintigraphy in thoracic tumors]

99mTc-hexamethylpropylene amineoxime (99mTc-HMPAO) scintigraphy was performed in 15 malignant tumors in 11 patients and a patient with bronchopneumonia. A high 99mTc-HMPAO affinity for the tumors was observed on SPECT, however, the mean tumor/contralateral normal lung ratios of 99mTc-HMPAO activity (1.26) was lower than that of 201Tl-chloride (2.29). 99mTc-HMPAO uptake was seen not only in the tumors but also in the bronchopneumonia, atelectasis, and irradiated lung (containing radiation fibrosis). Moreover, a diffuse uptake in the lung was seen in a patient received repeated chemotherapy. Therefore, it is emphasized that there is a non-specific 99mTc-HMPAO uptake in those various pulmonary conditions.     

The assessment of 99mTc-HMPAO tumor scintigraphy using VX-2 tumors in rabbits]

Tumor scintigraphy using 99mTc-hexamethyl-propyleneamine oxime (99mTc-HMPAO) was performed in VX-2 tumors implanted in the muscles of the lower limbs of rabbits to evaluate the possibility that this agent could be used to estimate the blood perfusion of the tumor. The distribution of 99mTc-HMPAO in the tumor immediately after the intravenous injection of this radiopharmaceutical exhibited almost the same distribution on the static image 1 hour after administration. Tumor time-activity curve for 99mTc-HMPAO revealed initial peak after the injection followed by fading of 99mTc-HMPAO activity and subsequent gradual decrease in activity over the next 1 hour. The ratio of 99mTc-HMPAO activity in the tumor to that in normal muscle tissue during this next 1 hour was high and independent of time. These findings indicate that static 99mTc-HMPAO scintigraphy can provide qualitative but not quantitative data useful in the estimation of tumor blood perfusion. Moreover, comparison of distribution of 99mTc-HMPAO on the static images and angiographic, histological findings also suggest that static 99mTc-HMPAO images accurately reflect tumor blood perfusion.     

Diagnosis of pyogenic pelvic inflammatory diseases by 99mTc-HMPAO leucocyte scintigraphy

Pelvic inflammatory disease (PID) is one of the major health problems of women of child-bearing age. Among the most serious complications of PID is the formation of a tubo-ovarian abscess (TOA). Early diagnosis of this condition may prevent serious surgical complications such as peritonitis and sepsis, which may be fatal. The purpose of this study was to investigate the efficacy of technetium-99m hexamethylpropylene amine oxime (HMPAO) leucocyte scintigraphy in the diagnosis of TOA. Twenty women with high clinical suspicion of TOA underwent ^99mTc-HMPAO leucocyte scintigraphy. The labelling of leucocytes with ^99mTc-HMPAO was performed according to a standard protocol. Scans were obtained at 1, 3 and 24 h following the injection of the labelled leucocytes. In eight cases the early and/or late scan was positive, in 11 cases it was negative, and in one case of ovarian cyst torsion, confirmed by laparoscopy, it showed slight uptake in the capsule of the cyst (false-positive). The sensitivity of ^99mTc-HMPAO leucocyte scintigraphy was 100%, specificity 91.6%, positive predictive value 89%, negative predictive value 100% and overall accuracy 95%. It is concluded that leucocyte scintigraphy is a non-invasive, safe, physiological and accurate procedure for the diagnosis of TOA. The 24-h scan is crucial, since in some cases the abscess was not clearly visualized on the early scan. Leucocyte scintigraphy may reduce the need for CT, diagnostic laparoscopy and unnecessary invasive surgical procedures.     

Diagnosis of pyogenic pelvic inflammatory diseases by 99mTc-HMPAO leucocyte scintigraphy

Pelvic inflammatory disease (PID) is one of the major health problems of women of child-bearing age. Among the most serious complications of PID is the formation of a tubo-ovarian abscess (TOA). Early diagnosis of this condition may prevent serious surgical complications such as peritonitis and sepsis, which may be fatal. The purpose of this study was to investigate the efficacy of technetium-99m hexamethylpropylene amine oxime (HMPAO) leucocyte scintigraphy in the diagnosis of TOA. Twenty women with high clinical suspicion of TOA underwent 99mTc-HMPAO leucocyte scintigraphy. The labelling of leucocytes with 99mTc-HMPAO was performed according to a standard protocol. Scans were obtained at 1, 3 and 24 h following the injection of the labelled leucocytes. In eight cases the early and/or late scan was positive, in 11 cases it was negative, and in one case of ovarian cyst torsion, confirmed by laparoscopy, it showed slight uptake in the capsule of the cyst (false-positive). The sensitivity of 99mTc-HMPAO leucocyte scintigraphy was 100%, specificity 91.6%, positive predictive value 89%, negative predictive value 100% and overall accuracy 95%. It is concluded that leucocyte scintigraphy is a non-invasive, safe, physiological and accurate procedure for the diagnosis of TOA. The 24-h scan is crucial, since in some cases the abscess was not clearly visualized on the early scan. Leucocyte scintigraphy may reduce the need for CT, diagnostic laparoscopy and unnecessary invasive surgical procedures.     

The value of 99mTc-HMPAO labelled white blood cell scintigraphy in acute appendicitis patients with an equivocal clinical presentation

Various imaging studies can be performed in the evaluation of patients with a clinical presentation equivocal for acute appendicitis. One of these studies is technetium-99m hexamethylpropylene amine oxime (HMPAO) labelled white blood cell (WBC) scintigraphy. The aim of this study was to evaluate the accuracy and clinical value of 99mTc-HMPAO WBC scintigraphy in the aforementioned group of patients. Forty-one patients who had acute right lower quadrant abdominal pain with a clinical presentation equivocal for acute appendicitis were included in the study. The anterior abdomen and pelvis were imaged up to 4 h after the injection of 125-300 MBq 99mTc-HMPAO WBCs and the results were immediately reported to the surgeon before a decision was taken on whether to perform laparotomy. Diagnostic accuracy was established by the intra-operative findings and the histopathology in operated patients. In non-operated patients, absence of abdominal symptoms 1 month after scintigraphy and/or identification of another cause of abdominal pain was used to rule out acute appendicitis. There were 16 patients with positive scintigraphy and 81% of these patients were positive within 2 h post injection. There were no false-positive or false-negative results. We operated on 17 (41.4%) patients, and only one patient (5.9%) underwent unnecessary laparotomy. We conclude that 99mTc-HMPAO WBC scintigraphy is a rapid, highly accurate method for the exclusion of acute appendicitis and that its use can lower the unnecessarily high laparotomy rate in patients with an equivocal clinical presentation.     

The value of 99mTc-HMPAO labelled white blood cell scintigraphy in acute appendicitis patients with an equivocal clinical presentation

Various imaging studies can be performed in the evaluation of patients with a clinical presentation equivocal for acute appendicitis. One of these studies is technetium-99m hexamethylpropylene amine oxime (HMPAO) labelled white blood cell (WBC) scintigraphy. The aim of this study was to evaluate the accuracy and clinical value of ^99mTc-HMPAO WBC scintigraphy in the aforementioned group of patients. Forty-one patients who had acute right lower quadrant abdominal pain with a clinical presentation equivocal for acute appendicitis were included in the study. The anterior abdomen and pelvis were imaged up to 4 h after the injection of 125-300 MBq ^99mTc-HMPAO WBCs and the results were immediately reported to the surgeon before a decision was taken on whether to perform laparotomy. Diagnostic accuracy was established by the intra-operative findings and the histopathology in operated patients. In non-operated patients, absence of abdominal symptoms 1 month after scintigraphy and/or identification of another cause of abdominal pain was used to rule out acute appendicitis. There were 16 patients with positive scintigraphy and 81% of these patients were positive within 2 h post injection. There were no false-positive or false-negative results. We operated on 17 (41.4%) patients, and only one patient (5.9%) underwent unnecessary laparotomy. We conclude that ^99mTc-HMPAO WBC scintigraphy is a rapid, highly accurate method for the exclusion of acute appendicitis and that its use can lower the unnecessarily high laparotomy rate in patients with an equivocal clinical presentation.     

Scintigraphic findings on99mTc-MDP,99mTc-sestamibi and99mTc-HMPAO images in Gaucher's disease

Gaucher's disease is an autosomal recessive lysosomal storage disease characterized by the specific deficiency of glucocerebrosidase that leads to accumulation of insoluble glucocerebroside in the reticuloendothelial system, particularly the bone marrow, liver, spleen and lymph nodes. Direct scintigraphic visualization of lipid deposits in Gaucher's disease has recently been described, based on the use of the lipid-soluble xenon-133. We report here on the use of the lipophilic cat-ionic complex technetium-99m sestamibi (^99mTc-MIBI), employed as an indicator of increased cellular density and metabolic activity, to evaluate Gaucher cell infiltrates in the bone marrow;^99mTc-hexametazime (^99mTc-HMPAO) was also employed, as a pure indicator of lipidic infiltration in the bone marrow. A 67-year-old patient with known type 1 Gaucher's disease presented with a painful left hip and knee and difficulty in gait subsequent to traumatic fracture of the left femoral neck that had required implant of a fixation screw-plaque. Bone scan with^99mTc-methylene diphosphonate revealed reduced uptake at the distal metaphyseal-epiphyseal femoral region. In addition, whole-body maps and spot-view acquisitions of the thighs and legs were recorded at both 30 min and 2.5 h after the injection of^99mTc-MIBI: the scintigraphic pattern clearly showed increased uptake at several sites involved by Gaucher deposits in the bone marrow (both knees, with variable intensity in different areas), matching the bone changes detected by conventional x-ray. The target to non-target ratios slowly decreased with time, from an average value of 2.25 in the early scan to an average value of 2 in the delayed scan. The lipid-soluble agent^99mTc-HMPAO exhibited a superimposable scintigraphic pattern of accumulation at the involved sites, though with lower target to non-target ratios (1.27–1.48). The results obtained in this patient suggest a potential role of^99mTc-MIBI in the scintigraphic evaluation of Gaucher's lipid deposits in the bone marrow. If the results are confirmed in other patients, this radiopharmaceutical would offer clear advantages over¹³³Xe because of its wider availability and greater practicality (i.v. administration of^99mTc-MIBI versus inhalation of¹³³Xe, and use of a single gamma camera instead of two as with¹³³Xe).     

Technetium-99m hexamethylpropylene amine oxime labelled leucocyte scintigraphy in ulcerative colitis and Crohn's disease

Technetium-99m hexamethylpropylene amine oxime labelled leucocyte scintigraphy (LS) was performed on 45 occasions in 30 patients with ulcerative colitis and on 53 occasions in 34 patients with Crohn's disease. Serial images were taken following re-injection of the labelled leucocytes. The segmental extent of the inflammation and the grade of the leucocyte uptake were calculated, and compared with the laboratory results and colonoscopy findings. The sensitivity and specificity of LS proved higher in ulcerative colitis (87% and 93%) than in Crohn's disease (53% and 89% in cases with large intestine involvement, and 82% and 100% in cases with small intestine involvement). The activity of the process determined by LS correlates with the ₂ globulin level (r=0.47), fibrinogen level (r=0.50), fS iron level (r=–0.57), sedimentation (r=0.44), leucocyte count (r=0.38), platelet count (r=0.34) and Best index (r=0.31) in ulcerative colitis, but not in Crohn's disease. Correspondence to: M. Papós     

99mTc-interleukin-2 scintigraphy as a potential tool for evaluating tumor-infiltrating lymphocytes in melanoma lesions: a validation study.

Cutaneous melanoma is often characterized by the presence of tumor-infiltrating lymphocytes (TILs). The degree of such infiltration and cell activation are considered significant prognostic factors reflecting the host's immune response to the tumor; thus, patients with peritumoral infiltration may have a better prognosis and may also achieve a better response to interleukin-2 (IL2) immunotherapy. There is evidence that the expression of cluster designation (CD) 25 antigen (IL2 receptor [IL2R]) is a good marker of activity of T lymphocytes against melanoma cells. The aim of this study was to evaluate in vivo the binding of 99mTc-IL2 to lymphocytes infiltrating cutaneous melanoma and to determine whether such uptake correlates with immunologic and histologic data, thus providing useful prognostic information for IL2 therapy in patients with advanced disease. METHODS: Thirty patients with cutaneous lesions suspected of being melanoma were studied. Planar gamma-camera images over known tumor sites were acquired 1 h after the injection of 111-185 MBq of 99mTc-IL2. Tumor uptake of 99mTc-IL2 was measured as a target-to-background (T/B) radioactivity ratio. All patients underwent surgery, and histologic evaluation of the resected lesion was performed. The percentage of different peripheral blood lymphocyte subsets (CD3, CD4, CD8, CD16, CD25) and the percentage of IL2R-positive tumor cells on histologic sections were also measured. RESULTS: At final histology, 21 lesions were found to be melanoma and 9 were classified as benign. In 15 of 21 (71%) melanomas and 2 of 9 (22%) benign cutaneous lesions, we found uptake of 99mTc-IL2. The calculated T/B ratios correlated significantly with the number of IL2R-positive TILs. CONCLUSION: 99mTc-IL2 scintigraphy provides a means of in vivo measurement of the extent of tumor infiltration of IL2R-positive cells, thereby providing valuable prognostic information for selection of patients who may benefit from IL2 immunotherapy.     

Measurement of cerebral perfusion volume and 99mTc-HMPAO uptake using SPECT in controls and patients with Alzheimer's disease

Methods for quantifying the changes in brain function observed in single photon emission computed tomography (SPECT) using hexamethylenepropylene amine oxime (HMPAO) for patients with Alzheimer's disease have the potential of improving the diagnostic accuracy of the procedure and its ability to monitor response to treatment. The absolute percentage uptake of HMPAO and the cerebral perfusion volume (CPV) of the brain were assessed using SPECT in 26 patients with mild to moderate Alzheimer's disease (AD) and 24 control subjects. A subset of 15 control subjects, which was age-matched to the AD patients, was selected to allow fair statistical comparison of parameters between groups. The percentage of brain volume with reduced perfusion (R) and a volume loss index (VLI), given by /CPV, were also calculated. Eight of the control subjects were studied on a second occasion after a mean period of 6 months. There was no significant difference in percentage uptake between controls and AD patients, the mean value being 5.8%. Cerebral perfusion volume in controls was found to depend on sex (mean value in males and females being 1327 ml and 1222 ml, respectively) and on age. The volume loss index corrected for age and sex provided good discrimination between controls and AD subjects giving a sensitivity and specificity of 81% and 96%, respectively. The repeatability coefficient, the 95% confidence limit for the difference between repeat measurements, on controls was 67 ml (5%). The measurement of cerebral perfusion volume and related indices may be of value in identifying patients with early Alzheimer's disease and in following their response to treatment.     

Comparison of quantitative 99mTc-HMPAO and 67Ga citrate lung scans in patients with active diffuse infiltrative lung disease

Diffuse infiltrative lung disease (ILD) is a heterogeneous group of disorders that predominantly affect the lung parenchyma and spare the airway. To objectively assess the degree of pulmonary vascular endothelium damage in active ILD, lung/liver uptake ratios (L/L ratios) on 99mTc hexamethylpropylene amine oxime (99mTc-HMPAO) lung scans were determined in 21 patients with active ILD. Meanwhile, the 67Ga citrate uptake index (GUI) on 67Ga lung scans was measured in order to evaluate the severity of lung inflammation in active ILD. The results show there were statistically significant differences between normal controls and patients with active ILD, as shown in the L/L ratio and GUI. However, when the patients were divided into two groups: (1) eight patients with normal chest X-ray findings, and (2) 13 patients with abnormal X-ray findings, there was no significant difference between groups 1 and 2 for the results of L/L ratio and GUI. In addition, no correlation between the degree of damage to the pulmonary vascular endothelium and the severity of lung inflammation was found. In conclusion, L/L ratios on 99mTc-HMPAO lung scans and GUI on 67Ga lung scans are different to the findings of chest X-rays and have the potential to objectively detect the degree of damage to the pulmonary vascular endothelium and the severity of lung inflammation in active IDL. However, the relationship between L/L ratio and GUI in active ILD is not significant.     

Clinical need for both scintigraphy with technetium-99m GSA and per-rectal portal scintigraphy in some patients with chronic liver disease

Scintigraphy with 99mTc-diethylenetriaminepentaacetate with galactosyl human serum albumin (99mTc-GSA) and per-rectal portal scintigraphy are useful for evaluating hepatic functional reserve and portal circulation, respectively. We did the procedures simultaneously in some patients to examine the relationship between hepatic functional reserve and portal circulation in chronic liver disease. Scintigraphy with 99mTc-GSA was done in 10 healthy subjects, 45 patients with chronic hepatitis, and 165 patients with cirrhosis. Fifty-seven patients (13 with hepatitis and 44 with cirrhosis) also underwent per-rectal portal scintigraphy with 99mTc-pertechnetate within two weeks. A receptor index was calculated by dividing the radioactivity of the liver region of interest (ROI) by that of the liver-plus-heart ROI at 15 min after the injection of 99mTc-GSA. The index of blood clearance was calculated by dividing the radioactivity of the heart ROI at 15 min by that of the heart ROI at 3 min. A solution containing 99mTc-pertechnetate was instilled into the rectum, and serial scintigrams were taken while radioactivity curves for the liver and heart were recorded sequentially. A per-rectal portal shunt index was determined by calculating the ratio of counts for the liver to counts for the heart integrated for 24 seconds immediately after the appearance of the liver time-activity curve. The median receptor index was lower for more severe liver disorders, increasing in the order of chronic hepatitis, compensated cirrhosis and decompensated cirrhosis, and the median index of blood clearance was higher. The median receptor index was significantly lower when a complication (varices, ascites, or encephalopathy) was present, and the median index of blood clearance was higher. The shunt index was correlated significantly with the two other indices, but these values for some one-third of the patients disagreed in either indices. Scintigraphy with 99mTc-GSA and per-rectal portal scintigraphy with 99mTc-pertechnetate are both needed for accurate assessment of the severity of chronic liver disease before treatment-making decisions, because in some patients, results are not correlated.     

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

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.     

Scintigraphy with 99mTc-HMPAO labeled leukocytes in acute cholecystitis

99mTc-HMPAO labeled leukocyte scanning was performed on 38 patients with clinically suspected acute cholecystitis (AC) to evaluate its diagnostic value. The typical finding was an increasing accumulation of the tracer in the gallbladder wall in a 4 hour series of scintigrams. Leukocyte scan was positive in 16 of 17 patients with surgically and histologically confirmed AC. There were no false-positive findings. The sensitivity, specificity, and accuracy of scintigraphy were 94, 100, and 96%, respectively. In 2 patients with acute acalculous cholecystitis true-positive findings were observed. Scintigraphy with 99mTc-HMPAO labeled leukocytes is a valuable new imaging method in AC.