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     

Radionuclide diagnosis of vertebral osteomyelitis: indium-111-leukocyte and technetium-99m-methylene diphosphonate bone scintigraphy

Seventy-six 111In-labeled leukocyte images performed on 71 patients with possible vertebral osteomyelitis were reviewed. Twenty-eight cases of vertebral osteomyelitis were diagnosed. Vertebral labeled leukocyte activity was normal in 2, increased in 11, and decreased in 15 cases of osteomyelitis. The median duration of symptoms was significantly longer in patients with osteomyelitis and decreased vertebral activity than in patients with osteomyelitis and increased activity (3 mo versus 2 wk; p = 0.019). No significant relationship between the duration of antibiotic therapy and the appearance of vertebral osteomyelitis on leukocyte images was identified (p = 0.62). Increased vertebral activity was highly specific (98%) for osteomyelitis but relatively insensitive (39%). Decreased activity was neither sensitive (54%) nor specific (52%). Seven patients with clinically resolved infection underwent follow-up imaging. Of four patients who initially presented with increased activity, one had normal and three had decreased vertebral activity on follow up studies. All three patients with decreased activity initially had decreased activity on follow-up. Using increased or decreased activity as criteria for infection, the accuracy of leukocyte imaging for diagnosing vertebral osteomyelitis was 66%, similar to that of 99mTc bone imaging (63%) in our population. Leukocyte imaging did however provide important information about extraosseous infection in 12 of the patients studied.     

Total-hip arthroplasty: periprosthetic indium-111-labeled leukocyte activity and complementary technetium-99m-sulfur colloid imaging in suspected infection

Indium-111-labeled leukocyte images of 92 cemented total-hip arthroplasties were correlated with final diagnoses. Prostheses were divided into four zones: head (including acetabulum), trochanter, shaft, and tip. The presence (or absence) and intensity of activity in each zone was noted, and compared to the corresponding contralateral zone. Though present in all 23 infected arthroplasties, periprosthetic activity was also present in 77% of uninfected arthroplasties, and was greater than the contralateral zone 51% of the time. When analyzed by zone, head zone activity was the best criterion for infection (87% sensitivity, 94% specificity, 92% accuracy). Fifty of the arthroplasties were studied with combined labeled leukocyte/sulfur colloid imaging. Using incongruence of images as the criterion for infection, the sensitivity, specificity, and accuracy of the study were 100%, 97%, and 98%, respectively. While variable periprosthetic activity makes labeled leukocyte imaging alone unreliable for diagnosing hip arthroplasty infection, the addition of sulfur colloid imaging results in a highly accurate diagnostic procedure.     

Breast cancer staging using technetium-99m sestamibi and indium-111 pentetreotide single-photon emission tomography

We evaluated the clinical usefulness of single-photon emission tomography (SPET) with technetium-99m sestamibi and indium-111 pentetreotide in breast cancer staging. Fifteen patients with clinical and/or mammographic findings suggesting T1-2N0-1 breast cancer were studied. SPET images were acquired 20 min after^99mTc-sestamibi injection and 4 and 24 h after¹¹¹In-pentetreotide injection. Patients underwent surgery the day after the later¹¹¹In-pentetreotide acquisition. Pathological examination showed 16 tumours in the 15 patients, with one bilateral carcinoma. The mean tumour diameter was 18.7 mm. Metastatic axillary involvement was found in 6/16 tumours, with a mean of five metastatic nodes per axilla. Both tracers correctly identified 15/16 primary tumours and five of the six cases of metastatic axillary node involvement. No difference between the tracers was observed in breast cancer staging.^99mTc-sestamibi seems to be the better tracer in terms of physical characteristics, execution time and cost-effectiveness. Our data suggest the future possibility of using nuclear medicine imaging to avoid axillary dissection in patients with T1 breast cancer.     

Tc-99m MDP and indium-111 chloride scintigraphy in skeletal tuberculosis

A case of diffuse osseous tuberculosis with changes on skeletal Tc-99m methylene diphosphonate (MDP) and indium-111 chloride scintigraphy is presented. Only two other cases of bone scan findings in osseous tuberculosis (TB) were reported in the literature and both show patterns similar to diffuse metastatic disease. In addition, the demonstration of corresponding areas of decreased tracer activity on indium-111 bone marrow scintigraphy is a finding that has not been previously reported for skeletal tuberculosis.     

Myocardial damage delineated by indium-111 antimyosin Fab and technetium-99m pyrophosphate

Technetium-99m-labeled pyrophosphate and radiolabeled antimyosin antibodies are two infarct localizing agents with apparently different kinetics of localization. To determine whether these agents localize in a similar fashion in early acute myocardial necrosis, we studied the simultaneous distribution of 111In-labeled antimyosin and 99mTc-labeled pyrophosphate in dogs after intracoronary (i.c.) (n = 9) or intravenous (i.v.) (n = 9) administration of a mixture of these two agents in a reperfused infarct model. The mean infarct size (+/- s.d.) delineated by pyrophosphate [20.2 +/- 14.1 (i.v.), 29.8 +/- 12.3 (i.c.)] was larger than that by antimyosin [14.2 +/- 11.3 (i.v.) (p = 0.05), 20.0 +/- 11.8 (i.c.) (p = 0.05)] which was larger than that by triphenyl tetrazolium chloride [13.9 +/- 8.0 (i.v.) (p = 0.05), 15.3 +/- 6.5 (i.c.) (p = 0.05)]. This overestimation persisted whether the radiopharmaceuticals were administered by intracoronary or intravenous injections, although the latter with antimyosin was only slightly larger (TTC:AM = 13.9:14.2) (p = n.s.). There was a good correlation, however, between antimyosin and pyrophosphate delineated infarct sizes in dogs with intracoronary injection (y = 0.82x + 13.33, r = 0.79) or i.v. injection (y = 1.208x + 3.01, r = 0.97) of the mixture of the two agents. Since the images of the 111In and 99mTc activities were obtained consecutively by identical methods, the overestimation of infarct size by pyrophosphate cannot be due to differences in spatial resolution of the techniques used. The differences in the areas of myocardial damage delineated by pyrophosphate and antimyosin in our study most probably denote the area of viable but compromised myocardium.     

Sequential technetium-99m sulfur colloid/indium-111 white blood cell imaging in macroglobulinemia of Waldenstrom

Technetium-99m sulfur colloid (SC) and indium-111 labeled leukocyte (In-111 WBC) scintigraphy was performed on a 77-year-old female patient to rule out a left periprosthetic infection. Anterior Tc-99m SC and In-111 WBC images of the pelvis and femurs revealed no abnormal deposition of radiotracer about the Austin-Moore prosthesis. Absent radiotracer uptake, however, was demonstrated within the left hemipelvis. A left iliac bone marrow aspirate and biopsy revealed a lymphoplasmacytic infiltrate consistent with Waldenstrom's macroglobulinemia.     

Visualization of metastatic liver disease on technetium-99m bone scintigraphy

To determine the frequency with which liver metastases are visualized on bone scintigraphy, 425 pairs of liver and bone scans, performed within one month of each other, were reviewed. Sixty-three of the 425 liver scans showed metastases. Of these 63, five cases of carcinoma of the colon and six cases of carcinoma of the lung also visualized by Tc-99m MDP scintigraphy. This represented 46% of colon metastases and 15% of lung metastases detected on liver scan. Liver metastases from other primary tumors were not detected on bone scan, but the numbers for these tumors were small. The liver metastases which were detected on bone scan were significantly larger than those which were not. The literature was reviewed and the primary and secondary tumors of liver with uptake of Tc-99m phosphate compounds listed.     

Parathyroid scintigraphy: comparison of technetium-99m methoxyisobutylisonitrile and technetium-99m tetrofosmin studies

We report the preliminary results of a prospective study demonstrating tetrofosmin uptake in surgically and histologically proven parathyroid adenomas. In ten patients with primary chronic hyperparathyroidism, parathyroid imaging was performed using (1) technetium-99m methoxyisobutylisonitrile (MIBI) and (2)^99mTc-1,2-bis(bis(2-ethoxyethyl)phosphino)ethane (tetrofosmin) within a time interval of 3–5 days. Both tracers correctly identified the parathyroid adenomas by focal prolonged tracer retention. On visual inspection image contrast was generally higher with MIBI than with tetrofosmin in all the patients studied. Tetrofosmin showed a slower elimination from the parathyroid adenomas than MIBI in six of the ten cases. Our preliminary results show that tetrofosmin, like MIBI, as a feasible, sensitive tracer for parathyroid scintigraphy. For routine use, the rapid kit preparation without heating and the lower radiation dose to the patient make tetrofosmin an alternative tracer for parathyroid scintigraphy. Further evaluation is needed to determine which of the two tracers is the more sensitive for the detection of parathyroid adenomas, and which tracer properties better reflect the degree of endocrine activity.[/p]     

Detection of radiation-induced myocardial damage by technetium-99m sestamibi scintigraphy

A prospective study was initiated to assess the side-effects of postoperative adjuvant radiotherapy in patients with left-sided early breast cancer. Twelve patients with early breast cancer were examined before and a year after radiotherapy. Echocardiography, ECG and bicycle ergometry stress test with technetium-99m sestamibi myocardial perfusion scintigraphic were carried out to assess changes in regional myocardial blood flow. Six of the 12 patients had new fixed scintigraphic defects after radiotherapy (as compared with the preradiation examination). The localization of the defects corresponded well with the irradiated volume of the left ventricle. These defects were probably due to microvascular damage to the myocardium. Neither ECG changes nor left ventricular segmental wall motion abnormalities could be detected by echocardiography. To our knowledge this study is the first to show that radiation-induced microvascular damage to the myocardium may be detected by perfusion scintigraphy. This may limit the use of scintigraphy in diagnosing coronary artery disease in patients treated with thoracic radiotherapy. Long-term follow-up is necessary to assess whether the presence of microvascular damage is a prognostic sign for the development of radiation-induced coronary artery disease.     

Detection of hemangiomas using whole-body imaging with technetium-99m labeled RBCs

Hemangiomas are easily, quickly and relatively noninvasively detected using whole-body imaging with Tc-99m labeled RBCs. A case in which this method was used to confirm known lesions and detect additional unsuspected lesions is described. This method can also be useful in the detection and evaluation of other types of vascular malformations, such as arteriovenous communications. The lesions must be of sufficient size and flow to be seen. Applications include the examination of patients known to have one vascular malformation in a search for additional lesions and the screening of relatives of patients with familial conditions that include hemangiomas.     

Subacute splenic abscess. Appearance on indium-111 leukocyte, gallium-67, and technetium-99m sulfur colloid imaging

A case of a 23-year-old man with an encapsulated, anaerobic splenic abscess is reported. Both the In-111 leukocyte and Tc-99m sulfur colloid scans demonstrated an intrasplenic defect. The Ga-67 citrate scan revealed uptake in the rim of the abscess only where the abscess cavity was relatively photon-deficient. The combined Tc-99m sulfur colloid/In-111 leukocyte/Ga-67 scan appearance of a subacute splenic abscess has not been described previously. In cases suspected to be splenic abscesses the combined In-111 leukocyte/Tc-99m sulfur colloid imaging is the most useful.     

In vivo kinetics of canine leukocytes labeled with technetium-99m HM-PAO and indium-111 tropolonate

Two weeks after the introduction of osteomyelitis in three dogs, autologous leukocytes were dual-labeled with both [99mTc]HM-PAO and [111In]tropolonate, and reinjected. Blood sampling and imaging were then performed. Two weeks later, the same dogs received simultaneous injections of singly-labeled [99mTc]WBC and [111In]WBC for comparison. For both studies, blood samples were drawn over 6 hr to determine the respective blood clearance half-time (TB) and % recovery (%R0) of cell-bound radioactivity. There were no significant differences in the average TB results of the 99mTc and 111In groups, either within or between the dual- and singly-labeled studies. The %R0 of singly-labeled [99mTc]WBC was about half that of the other groups (p less than 0.01); however, this difference was attributed to the dissimilar radiochemical purity of the [99mTc]HM-PAO reagents. Region of interest analysis of the 6 and 24 hr images revealed no significant differences between either cell label in the relative or absolute in vivo uptake at known sites of osteomyelitis, noninfected surgery, and normal bone marrow.     

Gastrointestinal activity following bone marrow scintigraphy with technetium-99m nanocolloid in patients with multiple myeloma

Unexpected abdominal activity was registered later than 1 h post injection in technetium-99m bone marrow scintigrams of 13 multiple myeloma patients and of five controls. The activity was considered to be localised in the gastro-intestinal tract. It is attributed to accumulation of degradation products of the used nanocolloid tracer. Corresponding results are known in patients with inflammatory bowel disease when scintigraphy is performed with other radiopharmaceuticals.     

Optimal collimator choice for sequential iodine-123 and technetium-99m imaging

Dual-isotope studies with technetium-99m and iodine-123 may be useful for various organs, including brain and myocardium. For the images obtained with each of the tracers to be comparable, it is important that activity ratios (activity in one part of the image/reference activity in the image) are preserved by the imaging method. We have used a Rollo phantom to study how collimator response affects such ratios. All investigations were performed with¹²³I(p,5n) and on a Siemens Orbiter 3700 camera fitted with either a low-energy high-resolution (LEHR) or a medium-energy (ME) collimator. Images were made of a Rollo phantom filled with an aqueous solution of either⁹⁹Tc or¹²³I, and placed on the collimator surface with 8 cm of methyl-methacrylate interposed. Count densities were measured in ROIs drawn in each cell of the phantom, and normalised to the maximal ROI value in the image. The mean square error (MSE) was used to assess how well the ratios of count densities approximated the known activity ratios based on the dimensions of the cells of the phantom. For^99mTc, regardless of the collimator used, the count density ratios approximated the activity ratios fairly well (LEHR: MSE=0.008; ME: MSE=0.020). For¹²³I, count density ratios obtained with the LEHR were consistently higher than activity ratios (MSE=0.235), whereas the differences between the measured and the theoretical values were less with the ME collimator (MSE=0.013). Contrast fidelity of the¹²³I images obtained with the LEHR collimator could be improved with Jaszczak scatter correction withk=1, but this led to unfavourable signal-to-noise ratios. For sequential^99mTc/¹²³I studies with extended sources, ME is to be preferred because of its higher contrast accuracy. Spatial resolution is less for the ME than for the LEHR collimator (FWHM with scatter: LEHR/^99mTc=6.9 mm, LEHR/¹²³I=7.4 mm, ME/^99mTc=10.1 mm, ME/¹²³I=11.1 mm), but remains similar for both tracers when the ME is used.