Donor leucocyte imaging in patients with AIDS: a preliminary report

Four patients with the acquired immunodeficiency syndrome (AIDS) and fever were investigated using donor leucocyte scans. The lung/liver and lung/spleen uptake ratios in these patients were compared with the uptake ratios in donor leucocyte scans in seven neutropenic (non-AIDS) patients and five patients who had autologous leucocyte scans performed over the same time period. For all scans indium-111-oxime-labelled leucocytes were used, except for one AIDS patient in whom technetium-99m hexamethyl-propylene amine oxide (HMPAD)-labelled donor leucocytes were used. There were no adverse reactions to the donor cell infusions. Two patients had repeat studies 8 weeks apart (from different donors) without ill effect. There were no differences in the 111In uptake ratios between the three groups. There were three positive studies in the patients with AIDS, and these elucidated the cause of the pyrexia in all three. The negative case is more difficult to confirm, but the clinical course and the absence of focal disease on post-mortem have been taken to support the scan findings. There was no difference in the acceptability of the technique or the distribution of the labelled leucocytes between the AIDS and non-AIDS patients. Donor leucocyte imaging of patients with AIDS is probably more effective and considerably less hazardous for technical staff than autologous leucocyte methods. This study demonstrates that the technique can be applied successfully to patients with AIDS.     

Evaluation of white cell scintigraphy using indium-111 and technetium-99m labelled leucocytes

Indium-111 oxine labelled leucocyte (¹¹¹In oxine leucocyte) scintigraphy is the test of choice in detecting occult infection and localising focal inflammation. ¹¹¹In oxine labelling is technically difficult and expensive and leucocyte labelling with technetium-99m stannous colloid (^99mTc Sn colloid) has been considered to be an alternative. Leucocytes from 40 cases referred for investigation of occult infection or localisation of inflammation were simultaneously labelled with ¹¹¹In oxine and ^99mTc Sn colloid with dual isotope acquisition performed at 1, 3 and 24 h. Twenty-four hour ^99mTc Sn colloid scans were corrected for ¹¹¹In downscatter. Each case was independently interpreted by two experienced observers. Twentyone patients demonstrated positive ¹¹¹In oxine leucocyte scans. Using ¹¹¹In oxine leucocyte scans as the gold standard, ^99mTc Sn colloid leucocyte scanning had an overall sensitivity of 86% and a specificity of 95%. Clinical follow-up verified that three patients had false negative ^99mTc Sn colloid leucocyte scans and one patient had a false positive. Further clinical evaluation of ^99mTc Sn colloid labelled leucocytes is required before they can become a reliable replacement for ¹¹¹In oxine leucocytes. Correspondence to: S. Boyd     

Indium-111 labelled white blood cell scintigraphy in cranial and spinal septic lesions

Cranial and spinal infections are severe events that require timely diagnosis and treatment. Physical and neurological examination, laboratory tests and radiological imaging may be insufficient for assessing cranial and spinal septic lesions. This study aimed to evaluate the accuracy of indium-111 white blood cell (WBC) scan in assessing the presence of leucocytes in intracranial and spinal lesions, and in the diagnosis, management and follow-up of primary, post-traumatic and post-surgical infections. One hundred and twenty-four subjects were included in the study (48 with post-traumatic or post-surgical lesions, 73 with primary cerebral lesions, and 3 with spinal lesions). All patients underwent a diagnostic work-up including planar scans with 111In-labelled WBCs, at 4 and 24 h post tracer injection. All subjects underwent surgical treatment. Patients who did not recover from the infection as suggested by clinical evolution underwent further treatment (up to three times) and further WBC scans (up to four times). WBC scintigraphy correctly identified all the areas of leucocyte accumulation, as confirmed after surgery. WBC scintigraphy also correctly excluded the presence of leucocytes in all other lesions, as demonstrated at surgery. The results of this study confirm the accuracy of WBC scan for the assessment of patients with cranial and spinal lesions, in whom the demonstration of leucocyte accumulation can ease the diagnosis of infection, and indicate that the method is also accurate for the follow-up and management of neurosurgical patients.     

Simultaneous administration of111In-human immunoglobulin and99mTc-HMPAO labelled leucocytes in inflammatory bowel disease

Technetium-99m hexamethylpropylene amine oxime (HMPAO) labelled leucocytes and indium-111 polyclonal immunoglobulin (IgG) were simultaneously injected into a group of 27 patients routinely referred for the investigation of inflammatory bowel disease (IBD). Ten-minute anterior abdomen and tail on detector views were obtained at 30 min, 4 h and 24 h p.i. of both tracers. The diagnosis of IBD was obtained in all cases by endoscopy with biopsy and/or surgery. Images were blindly evaluated by two experienced observers who only knew of the clinical suspicion of IBD. IBD was confirmed in 20 patients (12 with Crohn's disease and eight with ulcerative colitis). Sensitivity, specificity and accuracy were 100%, 85% and 96% respectively for labelled leucocytes and 70%, 85% and 74% for IgG. Both IgG and leucocyte scans were normal in six out of seven patients in whom a diagnosis of IBD was excluded; the remaining patient, with ischaemic colitis, was falsely positive with both agents. As far as disease extension is concerned, the IgG study localized 27 diseased segments, whereas 49 were seen with the leucocyte study. Eighty-four segments were normal and 25 showed tracer uptake with both agents. Twenty-four were positive only with the leucocyte study and two were positive only with the IgG study. Agreement between the agents was 80.7%. These results confirm that¹¹¹In-human polyclonal scintigraphy is less sensitive than^99mTc-HMPAO scintigraphy both for the diagnosis of IBD and in the evaluation of disease extension. Nevertheless, if leucocyte labelling is not available, labelled IgG can be used only for diagnostic purposes.     

Quantification of pulmonary uptake of indium-111 labelled granulocytes in inflammatory bowel disease

This study describes a method for quantifying the pulmonary trapping of indium-111 labelled polymorphonuclear (PMN) cells in patients with inflammatory bowel disease (1131) in comparison to non-inflamed controls. Twenty patients with extensive IBD were studied by ¹¹¹In-PMN scintigraphy. Gamma-camera images were obtained at 2.5–4 h (early) and 20–25 h (late) after the injection of autologous PMNs labelled in plasma with ¹¹¹In-tropolonate. Local uptake in the chest, iliac bone marrow, spleen and liver was quantified as the counts per pixel per second per MBq of injected ¹¹¹In for both early and late scans. Fourteen subjects without inflammatory disease were studied as controls. IBD patients showed significantly greater loss of splenic activity between early and late scans compared with controls (mean ± SD: –35.7% ± 16.6% versus –4.5% ± 6.1%, P < 0.001). There was no significant difference between control and IBD groups with respect to liver and bone marrow uptake on both early and late scans. Chest uptake was significantly higher in patients with 11313 on both early (6.4 ± 1.6 cps/MBq/pix) and late (5.6 ± 1.5cps/MBq/pix) scans, compared with the controls (4.8 ± 1.3 cps/MBq/pix, P < 0.005 and 3.4 ± 1.0 cps/MBq/pix, P < 0.001 respectively). The chest uptake in the control group on the late scans demonstrated a significant linear correlation with iliac uptake (y=0.23x + 0.41, r=0.87, n=14). Assuming in controls that there is no parenchymal uptake of ¹¹¹In, this regression enables an estimate to be made, based on iliac counts, of the count rate from bone marrow in the chest wall. After subtraction of this from the total chest count rate, the true parenchymal uptake was derived, which averaged (2.86 ± 0.91) cps/MBq/pix in the IBD group compared to zero assumed in the control group. The higher lung ¹¹¹In-PMN uptake on the early scans in IBD compared to controls is suggested to reflect a combination of increased margination, compared to controls, and early migration, whilst the excess ¹¹¹In-PMN retention on late scans represents extravascular migration only. The bone marrow correction technique for quantification of pulmonary migration of ¹¹¹In-PMNs should prove useful for the evaluation of PMN kinetics in disease. Correspondence to: A.M. Peters     

99Tcm-labelled leucocyte imaging in active rheumatoid arthritis

A simplified technique of labelling leucocytes with technetium-99m is described and applied to patients with active rheumatoid arthritis. The clinically active and less active knees in seven patients were imaged and the uptake of labelled leucocytes was measured. The measurements were repeated after local steroid injection into nine painful knees. A 50-80% reduction in leucocyte uptake localized to the region of the synovium was demonstrated in the eight knees which showed clinical responses and a rise of 8% in the non-responder. There was a variable response in the knees that were not injected. 99Tcm leucocyte imaging in rheumatoid arthritis is able to assess objectively joint inflammation and its response to treatment.     

Indium-111 labelled white blood cell scintigraphy in cranial and spinal septic lesions

Cranial and spinal infections are severe events that require timely diagnosis and treatment. Physical and neurological examination, laboratory tests and radiological imaging may be insufficient for assessing cranial and spinal septic lesions. This study aimed to evaluate the accuracy of indium-111 white blood cell (WBC) scan in assessing the presence of leucocytes in intracranial and spinal lesions, and in the diagnosis, management and follow-up of primary, post-traumatic and post-surgical infections. One hundred and twenty-four subjects were included in the study (48 with post-traumatic or post-surgical lesions, 73 with primary cerebral lesions, and 3 with spinal lesions). All patients underwent a diagnostic work-up including planar scans with ¹¹¹In-labelled WBCs, at 4 and 24 h post tracer injection. All subjects underwent surgical treatment. Patients who did not recover from the infection as suggested by clinical evolution underwent further treatment (up to three times) and further WBC scans (up to four times). WBC scintigraphy correctly identified all the areas of leucocyte accumulation, as confirmed after surgery. WBC scintigraphy also correctly excluded the presence of leucocytes in all other lesions, as demonstrated at surgery. The results of this study confirm the accuracy of WBC scan for the assessment of patients with cranial and spinal lesions, in whom the demonstration of leucocyte accumulation can ease the diagnosis of infection, and indicate that the method is also accurate for the follow-up and management of neurosurgical patients.     

99mTc-human immunoglobulin (HIG)--first results of a new agent for the localization of infection and inflammation

Technetium (99mTc) labelled, polyclonal human immunoglobulin (HIG) is a new agent that detects focal infection and inflammation. This new agent was compared in 40 patients with the accepted standard, namely 111In-oxine-labelled leucocytes. This comparison resulted in a sensitivity of 94% and a specificity of 96% for 99mTc-HIG when 111In-oxine leucocytes were defined as giving the true result. The new agent was shown to localize both sepsis and active inflammatory bowel disease (IBD). There was 100% concordance in the 16 patients with IBD who were imaged with both 99mTc-HIG and 111In-oxine leucocytes. Discordant results were obtained in one case of suspected osteomyelitis, which was false-positive on the 99mTc-HIG scan, and one case of pyrexia of unknown origin when the 99mTc-HIG was false-negative and the 111In-oxine leucocyte scan demonstrated accumulation of tracer in the caecum at 24 h post-injection. Normal distribution for 99mTc-HIG demonstrated activity in the kidneys and bladder and that 50% of the tracer is cleared through the kidneys during the first 24 h post-injection. There were no major or minor side-effects.     

In vivo viability of 111In-labelled granulocytes demonstrated in a sham-dialysis model

In seven febrile patients undergoing regular dialysis treatment, sham-dialysis with a dialyzer equipped with a cuprophane membrane was performed during a routine 111In-oxine white blood cell scan with "pure" granulocytes isolated on a discontinuous gradient (Percoll/plasma: n = 5; Metrizamide/plasma: n = 2). The patients were in contact with the cuprophane membrane over 45 or 90 min. Twenty-five (+/- 5) minutes after the start of the dialysis, the peripheral leucocyte count (59 +/- 22%) and the 111In activity in the peripheral blood decreased to a minimum of their initial range (64 +/- 21%) because of leucocyte activation. The activity over both lungs increased symmetrically (29 +/- 15%), the spleen activity decreased (14.8 +/- 8%) and the liver activity remained constant. At the end of the dialysis (45-90 min post-injection), the number of circulating neutrophils, peripheral 111In activity and activity distribution in the organs regained their initial level. In conclusion, these data confirm previously described data concerning the sequestration of neutrophils into the lung during dialysis treatment. The data demonstrate the origin of the activated neutrophils in the circulation and the spleen. The identical behaviour of 111In-oxine-labelled and unlabelled granulocytes is demonstrated. Additionally, the accumulation of activity in the spleen is due not to opsonized cells but to sequestrated neutrophils, which are able to migrate from the spleen after adequate activation. The migration of activated cells into the lung explains the diagnostic difficulties posed by diffuse lung uptake in leucocyte scans in patients with leucocyte-activating diseases.     

99Tcm and 111In leucocyte scintigraphy in inflammatory bowel disease.

A comparative study of 99Tcm-hexamethylpropyleneamine oxime (HMPAO) and 111In leucocyte scintigraphy was performed in inflammatory bowel disease. Two hundred and thirty-four patients were studied, 146 had 99Tcm-HMPAO, 82 had 111In and six had both. The sensitivity, specificity and accuracy of the 99Tcm leucocyte scan were 96, 97 and 97%, respectively, and 96, 97 and 97%, respectively, for the 111In leucocyte scan. 99Tcm-HMPAO leucocytes demonstrated similar diagnostic accuracy to 111In-labelled leucocytes with improved image quality and reduced radiation dose.     

Evaluation of 111In leukocyte whole body scanning.

Indium-111 oxine, polymorphonuclear cells isolated and labeled with 111In were used for studying absecesses and inflammatory conditions. There were 64 total scans done in 59 patients, 32 male and 27 female, aged 3-81 years (average, 51). The original clinical diagnosis was abscess in 33 patients. The whole blood cell scan was abnormal in 12 (36%) of these, and a good clinical correlation was obtained in 11 of the 12. In the 21 with a normal scan, 18 had no evidence of abscess, yielding one false-positive and three false-negative interpretations in the abscess group. Thirteen patients had fever of unknown origin, nine had negative scans and no subsequent evidence of abscess, and four had positive scans with good correlation in three. Acute bone and joint infections were positive on scan (4/4), whereas chronic osteomyelitis was negative (0/2). Three patients with acute myocardial infarction and three of four with subacute bacterial endocarditis had normal scans. All three studies in renal transplant rejection showed positive uptake in the pelvic kidneys. Indium-111 white blood cell scans have proved useful to diagnose or exclude a diagnosis of abscess or inflammatory condition infiltrated with polymorphonuclear leukocytes.     

Scintigraphic evaluation of the painful prosthetic joint: a comparison of gallium-67 citrate and indium-111 labelled leucocyte imaging

The radiopharmaceuticals gallium-67 and indium-111 labelled leucocytes have been compared in 15 patients with a painful joint prosthesis in an attempt to identify those patients with periprosthetic infection. Gallium-67 images were abnormal in five out of six patients with periprosthetic infection and normal in seven out of nine without evidence of infection. Indium-111 leucocyte images were abnormal in three out of six patients with infection and normal in all nine patients without infection. Indium-111 labelled leucocyte imaging is technically more difficult to perform than gallium-67 imaging. This, combined with the higher sensitivity of gallium-67 imaging for infection around a prosthetic joint, leads us to conclude that gallium-67 imaging is superior to indium-111 leucocyte imaging in identifying infection as a cause of a painful prosthetic joint.     

Indium-111-labeled autologous platelets for location of vascular thrombi in humans

Twenty-two patients suspected of having either venous or arterial thrombi were studied with In-111-labeled autologous platelets. Whole-body scans were performed 3, 24, and 48 hr following i.v. injection. Twelve patients studied with saline-washed platelets had unsatisfactory 15-min recovery and biologic half-time. When the labeling was carried out in plasma, these values compared favorably with normal values reported for Cr-51-labeled autologous platelets. Of ten patients studied using platelets labeled in plasma, three had normal scans, six had abnormal scans, and one had an equivocal scan. All six abnormal scans were confirmed with corresponding positive findings in either the venogram, arteriogram, or lung scan. J Nucl Med 19: 626-634, 1978.     

Immunoscintigraphy using 111Indium-labeled antimyosin in suspected myocarditis

111Indium-monoclonal antimyosin scans were carried out in 21 patients with suspected myocarditis, confirmed by reduced ejection volume, pericardial effusion and clinical follow up in 12 patients. Coronary heart disease was excluded angiographically in all cases. Quantitative evaluation of myocardial 111In-antimyosin accumulation 48 hours after injection showed a pathological uptake in 10/12 patients with increased heart/lung ratios (Q48 greater than 1.58). Ratios were also elevated in 2 patients with cardiomyopathy, 2 suffering from vasculitis and 1 with dermatomyositis. Four patients without proven cardiac disease had normal ratios (Q48 less than or equal to 1.58). Examination after 24 hours was of limited value, depending on the residual blood pool activity. Visual analysis of the scans showed a high interobserver variation despite a positive correlation with quantitative analysis (48 h p.i.: r = 0.72; p less than 0.001), and is not recommended. The results show the value of the 111In-antimyosin scan as a screening method prior to myocardial biopsy. However, scintigraphy cannot definitely elucidate the cause of myocardial damage. Therefore, myocardial biopsy is still recommended after positive antimyosin scans.     

Utility of 111In-labelled leucocyte scintigraphy in patients with fever of unknown origin in an era of changing disease spectrum and investigational techniques

BACKGROUND: (111)In-labelled leucocyte, imaging is often used to investigate patients with fever of unknown origin (FUO). Its diagnostic performance, however, has been variable and a broad range of sensitivities and specificities have been reported. The purpose of this investigation was to evaluate the usefulness of (111)In-labelled leucocytes scintigraphy in the detection of a cause of FUO in the light of a changing spectrum of diseases causing it and advances in investigational techniques. MATERIALS AND METHODS: Sixty-one patients with a clinical diagnosis of FUO underwent whole-body (111)In-troponolate-labelled leucocyte scintigraphy in our department over a 2-year period between February 2004 and February 2006. Of these, 54 patients were retrospectively reviewed to identify a cause of FUO. Other parameters such as C-reactive protein (CRP), leucocyte count and radiological findings were also evaluated. RESULTS: Leucocyte scintigraphy was found to be true positive in 12 patients, true negative in 24 patients, false positive in 10 patients and false negative in eight patients. The overall sensitivity of scintigraphy was 60%, specificity 71%, positive predictive value 55%, and negative predictive value 75%. There was no difference in the scintigraphic sensitivity between patients with spontaneous FUO and those with post-operative FUO although the latter showed a higher specificity and PPV. CRP and leucocyte count did not differ significantly between patients with true positive and true negative scintigrams. Overall, 83% of patients with abnormal radiological examinations had positive findings on scintigraphy and 87% of patients with negative findings on radiology had normal scintigraphy. CONCLUSION: Despite changes in disease spectrum and advances in investigational techniques, our results suggest that (111)In-leucocyte scintigraphy is still a useful technique in establishing the cause of FUO. A higher PPV of this test in post-operative situations makes it especially applicable in this category of patients. Equally, the higher NPV in patients with spontaneous FUO virtually excludes infection/inflammation. Finally, a higher pre-test probability based on the radiological tests seems to be important in the optimal use of leucocyte imaging.     

Acquired immunodeficiency syndrome: Ga-67 citrate imaging

All gallium-67 citrate scans obtained in patients with acquired immunodeficiency syndrome (AIDS) at the Clinical Center, National Institutes of Health (Bethesda, Md.) were retrospectively analyzed and correlated with the results of bronchoscopy, chest radiography, and endoscopy. There were 164 scans of 95 patients. Twenty scans were from patients with Pneumocystis carinii pneumonia; 19 were abnormal, for a sensitivity of 95%. Ga-67 uptake tended to be less in patients receiving therapy for P. carinii pneumonia. Chest radiographs were normal at least initially in three patients with abnormal scans and P. carinii pneumonia. Unusually prominent colonic activity was associated with infection in some patients. No lesions of Kaposi sarcoma showed tracer uptake. Gallium scanning is useful for detecting P. carinii pneumonia and other opportunistic infections in patients with AIDS, but it is not useful for localizing Kaposi sarcoma.     

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.     

99mTc-human immunoglobulin (HIG) — first results of a new agent for the localization of infection and inflammation

Technetium (^99mTc) labelled, polyclonal human immunoglobulin (HIG) is a new agent that detects focal infection and inflammation. This new agent was compared in 40 patients with the accepted standard, namely¹¹¹In-oxine-labelled leucocytes. This comparison resulted in a sensitivity of 94% and a specificity of 96% for^99mTc-HIG when¹¹¹In-oxine leucocytes were defined as giving the true result. The new agent was shown to localize both sepsis and active inflammatory bowel disease (IBD). There was 100% concordance in the 16 patients with IBD who were imaged with both^99mTc-HIG and¹¹¹In-oxine leucocytes. Discordant results were obtained in one case of suspected osteomyelitis, which was false-positive on the^99mTc-HIG scan, and one case of pyrexia of unkown origin when the^99mTc-HIG was false-negative and the¹¹¹In-oxine leucocyte scan demonstrated accumulation of tracer in the caecum at 24 h post-injection. Normal distribution for^99mTc-HIG demonstrated activity in the kidneys and bladder and that 50% of the tracer is cleared through the kidneys during the first 24 h post-injection. There were no major or minor side-effects.     

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.     

The 111In-granulocyte scan in prosthetic vascular graft infections: imaging technique and results

Fourteen patients were examined between 3 weeks and 11 years after implantation of an aortobifemoral vascular graft with 111In labelled leukocytes isolated with discontinuous gradient centrifugation. The camera acquisition was performed with a three phase technique (acquisitions at 30 min, 4 h and 24 h p.i.). The presence and extent of a graft or perigraft infection including complicating fistulas could be correctly diagnosed in six of eight patients with surgically proven infections. Leukocyte uptake index was calculated as 1.77 +/- 0.4 (30 min p.i.) and 2.4 +/- 0.7 (24 h p.i.). All infections could be diagnosed by 30 min p.i., fistulas only could be seen 24 h p.i. In two of eight patients, false positive results were observed. These patients suffered from suspected perigraft hematomas and noninfected aortic graft aneurysms. Both had a negative 30 min scan and a slight uptake in the late scans comparable to bone marrow activity. Six patients with fever of unknown origin showed true negative scans. There were no false negative scans. We conclude that only the leukocyte scan can diagnose the presence and the extent, including fistulas, of vascular graft infections. The three phase technique is recommended to localize the blood pool in the 30 min scan and to diagnose complications 24 h p.i. In cases of a negative 30 min scan and positive 4 h and 24 h scans, false positive results should be suspected. All infections have a leukocyte uptake index higher than 1.2.