The single late 99Tcm granulocyte antibody scan in inflammatory diseases.

Immunoscintigraphy using 555-740 MBq 99Tcm-labelled monoclonal antigranulocyte antibodies (IgG1 against NCA-95) (BW250/183) was performed in 56 patients. In 32 of them inflammatory or infectious lesions were proven or excluded histologically. Gamma camera scans were performed 4 to 6 and 20 h postinjection (p.i.). Eight of 14 infectious or inflammatory lesions could be detected in the early scan (4-6 h p.i.). Sensitivity, specificity and diagnostic accuracy of the early scan were 57, 89 and 75%. Sensitivity, specificity and diagnostic accuracy in 19 patients with bone or prosthetic bone infections (87, 81 and 84%, respectively) were lower than in patients with abdominal or soft tissue infections (100%). The overall sensitivity, specificity and diagnostic accuracy of the 20 h scan was 86, 89 and 88%, respectively. It is concluded that the high diagnostic accuracy of immunoscintigraphy justifies a broader application of the scan in the diagnosis of infectious diseases. It is recommended that only late scans (20 h p.i.) are necessary.

Biokinetics and estimation of dose from 99mTc-labelled polyclonal human immunoglobulin (HIG).

Recently, polyclonal unspecific human immunoglobulin was suggested as a new agent for the localization of inflammatory lesions. Little information about the biodistribution of this radiopharmaceutical was reported so far. To obtain further information, 99mTc-labelled human immunoglobulin (HIG) was administered to a volunteer with presumed normal biokinetics. The absorbed doses to the organs were calculated according to the MIRD concept. The scintigraphic images at 1, 2, 4 and 24 h post injection demonstrated a prolonged activity retention in the blood and high activity in the kidneys, bladder and also in the liver. No significant uptake in the bowels and the marrow could be observed over the whole period of study. 27.4% of the administered activity was excreted in the urine within 24 h. The calculated organ absorbed doses, all in microGy/MBq, were estimated as follows: whole body 2.7, liver 7.3, spleen 12.0, kidneys 15.3, lungs 3.2, marrow 9.6 and gonads 17.0. From these results an effective dose equivalent of 7.9 x 10(-3) mSv/MBq was calculated. The cancer risk estimate of 5 x 10(-5), using 370 MBq 99mTc-HIG, may be considered quite low in comparison to other scintigraphic methods of diagnosing inflammation.

Octreotide scintigraphy localizes somatostatin receptor-positive islet cell carcinomas.

Tyr-3-Octreotide is a synthetic derivative of somatostatin and a somatostatin-receptor analogue. The iodine-123-labelled compound localizes somatostatin-receptor-positive tumours. In this paper two patients are reported in whom somatostatin receptors were demonstrated in vitro. In a 60-year-old female with an islet cell carcinoma of the pancreas, multiple liver metastases and previously unrecognized bone metastases in the right acetabulum could be diagnosed as the reason for a persistent hypoglycaemia. In a 60-year-old male an islet cell carcinoma of the pancreas was localized with 123I-Tyr-3-octreotide. The somatostatin receptors were demonstrated in vitro and the tumour was successfully treated with somatostatin. These studies demonstrate that 123I-Tyr-3-octreotide offers the possibility of localizing somatostatin-receptor-positive tumours and their metastases. Moreover the method makes it possible to determine the receptor status of a tumour in vivo.

99mTc-labelled polyclonal human immunoglobulin for localization of inflammatory sites--early in vitro-results.

99mTc-labelled polyclonal human immunoglobulin (HIG) has been shown to be able to localize inflammatory sites. Hypothetically these immunoglobulins bind directly to bacteria, HIG binds directly to Fc-receptors on the surface membrane of leucocytes or HIG simply passes vessels of increased permeability. To collect further information experiments were carried out in vitro with the blood of human volunteers. 0.5 mg 99mTc-HIG, 2 mg 99mTc-human albumin and 0.5 mg 99mTc-labelled murine monoclonal antigranulocyte antibodies were added to in vitro isolated human "mixed" leucocyte pellets and to 30 ml whole blood of 6 healthy volunteers. The whole blood and the directly labelled leucocyte pellet were layered and separated on a discontinuous Percoll/plasma gradient. The activity distribution was measured within the gradient. The 99mTc-HIG labelled gradients showed a significant uptake of the activity within the monocyte band whereas the 99mTc-albumin gradients showed no specific albumin uptake in any cellular band. The 99mTc-antibody labelled gradients showed a significantly increased uptake on granulocytes. It is concluded that in man a specific monocyte-associated uptake and binding mechanism of 99mTc-HIG plays an important role in the localisation of inflamed sites.