Kristina Norrgren

A 14-year prospective study of autonomic nerve function in Type 1 diabetic patients: association with nephropathy

Aims  Prospective studies of autonomic nerve function are rare. We have followed the progression of autonomic dysfunction in relation to nephropathy over 14 years in Type 1 diabetic patients.

Accuracy of the quantification of organ activity from planar gamma camera images

The accuracy in determination of organ activity of (99m)Tc was investigated, with activity estimated from gamma camera images of phantoms, using the conjugate view method. The accuracy depends on several parameters such as the choice of background correction method, the accuracy in determination of the effective attenuation coefficient and the thickness of the body and organs and on the determination of the gamma camera sensitivity. The background correction method has a major influence on the quantification of the activity. Methods which take the volume of the source organ into consideration are recommended. The discrepancy in the determined organ activity varied between an underestimation of 26% and an overestimation of 16% in the MIRD phantom, depending on which organ was studied and on the correction method used. To correct for absorption and scattering, an effective attenuation coefficient was used. A theoretical analysis showed that a change in the effective attenuation coefficient of 0.01 cm(-1) resulted in a 15% change in the calculated activity. Also the thickness of the body and the organ of interest influences the calculated activity. A 2 cm deviation in the body thickness causes a deviation of approximately 10% in the calculated activity. The quantification is improved if the attenuation coefficient is determined by transmission measurements.

Gamma camera imaging of platinum in tumours and tissues of patients after administration of 191Pt-cisplatin.

The aim of this study was to visualize non-invasively the uptake of platinum in tumours and tissues after treatment with cisplatin. 191Pt-cisplatin was synthesized from 191PtCl4 with rigorous pharmaceutical quality control. The uptake of platinum by both tumorous and healthy tissues was studied by gamma camera imaging in 14 patients, 5 of whom showed a clear uptake of platinum in regions corresponding to known tumour sites. Maximum concentrations of platinum in the tumours were on average 4.9+/-1.0 microg/g, when normalized to an administered amount of 180 mg cisplatin. In all the patients, the liver was the organ that showed the highest uptake. Platinum uptake was also seen in the spleen, gall bladder, gastrointestinal tract, bladder, kidneys, ureter, neck and mediastinum and urogenital region. By using in-house production of 191Pt-cisplatin, it was possible to monitor the uptake of platinum in tumorous tissues and healthy organs.

Planar gamma scintigraphy—points to consider when quantifying pulmonary dry powder aerosol deposition

Methodological aspects of planar gamma scintigraphy used to quantify pulmonary aerosol deposition were investigated using an experimental dry powder formulation. Particles of micronized salbutamol sulphate were labelled with technetium-99m and admixed to an ordered mixture of unlabelled micronized salbutamol sulphate and larger carrier particles of lactose. The radioaerosol was administered to 24 healthy subjects, 12 in each of two consecutive, similarly designed studies. Pulmonary deposition was determined using two methods: repeated planar imaging, and pharmacokinetic assessments following charcoal co-administration to prevent gastrointestinal salbutamol absorption. After due consideration had been taken to ensure appropriate radiolabelling, image acquisition and processing procedures, a scintigraphic estimate of 26.2% (with 95% confidence interval of 24.2-28.4%) was obtained, which did not significantly differ from the pharmacokinetic estimate of 26.4% (24.4-28.7%). In summary, pre-study validation of the radiolabelling technique, quality control of radioaerosols produced during the study, correction for re-distribution of radiolabel from the lungs, selection of regions of interest, assessment of lung contours, correction for tissue attenuation of gamma rays and establishment of the actual recovery of radioactivity in the scintigraphic measurements could potentially affect the accuracy of the scintigraphic estimate of pulmonary deposition and, thus, should be carefully considered in the design or evaluation of any such study.

Improving radioimmonotargeting of tumors. Variation in the amount of L6 MAb administered, combined with an immunoadsorption system (ECIA).

Extracorporeal immunoadsorption (ECIA) is a new method for the selective removal of circulating radiolabeled monoclonal antibodies (MAb) from plasma to increase the uptake in tumor versus normal tissues (T/N-ratio). To ascertain whether the amount of MAb affects T/N ratios immediately and 24 h after ECIA, we used a rat model with two tumor sites--one intramuscular (im) and one below the subrenal capsule (SR). Extracorporeal immunoadsorption was done with an avidin-agarose column after injection of 125I-labeled biotinylated L6 MAb. The animals received 10, 50 or 250 micrograms of L6 only (controls), or followed by ECIA. The efficacy of the procedure in removing plasma activity was 80-95%. For both tumor sites, the highest T/N-ratios were obtained with 10 micrograms L6. All T/N-ratios significantly improved for SR tumors by a factor ranging from 3.2 (lung) to 12.6 (bone marrow). The T/N-ratios were still elevated 24 h after ECIA. Injection of larger amounts of MAb, probably causing a higher degree of tumor saturation, will not necessarily improve the T/N ratio after ECIA.

Radio-immunotherapy dosimetry with special emphasis on SPECT quantification and extracorporeal immuno-adsorption

Results from therapeutic trials with radiolabelled monoclonal antibodies are difficult to compare, because of lack of accurate macroscopic and microscopic dosimetry for both tumours and normal tissues. Requirements for such a dosimetry are covered in the paper. Accurate in vivo dosimetric measurement techniques for verification of calculated absorbed doses are also needed to verify treatment planning. In the review, important topics related to dosimetry in therapeutic trials in RIT are covered, such as, absorbed-dose calculations and activity-quantification techniques for planar imaging and SPECT. The latter is particularly discussed, including a summary of different correction techniques. Absorbed-dose calculations and treatment-planning techniques are also discussed. Possible ways of enhancing the therapeutic ratio are reviewed, especially the novel technique with extracrooreal immuno-adsorption. The review could form the basis of the development of future treatment-planning protocols and for dosimetry calculations in radio-immunotherapy, considering some of the most important parameters for approaching an accurate in vivo dosimetry.

A general extracorporeal immunoadsorption method to increase tumor-to-tissue ratio

The idea of applying extracorporeal immunoadsorption (ECIA) in radioimmunodiagnosis and radioimmuno‐therapy has been proposed previously. The authors here report on the development of new concept using a general method for ECIA based on biotinylated MoAb adsorbed on an avidin column.

Radio-iodinated and internally labelled (35S) IgM monoclonal antibodies in a syngenic rat model

To simulate the human situation concerning human monoclonal antibodies (MAbs), we have introduced a new syngenic rat model with an implanted rat colon carcinoma. Rat IgM MAbs (10B12), labelled by the chloramine-T method with 125I or internally with 35S, were injected intravenously into the rats and the biodistribution was studied for 8 days. The radioactivity uptake in the tumours of the 35S label was higher than that of the 125I label and the retention of 35S in the tumours gave tumour/blood ratios 8 times higher than those of 125I at 48 and 96 h after injection. In this model we have shown that dehalogenation of iodinated IgM MAbs is a serious problem. We therefore suggest that internally labelled MAbs should be used and that further investigations should be carried out in a syngenic rat model, since this probably reflects the clinical situation better than the nude mouse model.

Tumour Uptake of Monoclonal Antibody After Regional Intraarterial Injection: Biokinetics in the Nude Rat Heterotransplanted with Malignant Melanoma

Nude rats were heterotransplanted with human melanoma metastases on both thighs. Ten days later a bolus of 125I-labelled monoclonal antibody (MAb) 96.5 was injected through a catheter in the common femoral artery. The femoral vein was clamped for 15 min to obstruct the venous outflow from the injected leg. The specific tissue uptake (%/g) in the tumour on the injected side compared to the non-injected side showed initially higher uptake (ratio 7.2 at 3 h). After 24 h there were no side differences. The tumour to muscle ratio was 2.8 at 3 h when injected and control sides were compared. Intravenous or subcutaneous injection gave similar specific tissue uptake as regional arterial injection after 24 h. Tissue to plasma ratios were similar after intravenous and subcutaneous injection of monoclonal antibodies. Intraarterial injection of a bolus of labelled monoclonal antibodies and obstructing the venous outflow thus increased the tumour uptake during a short period of time during which the contrast enhancement was three-fold.

Subcutaneous Injection of Monoclonal Antibody 96.5 Biokinetics in the nude rat heterotransplanted with malignant melanoma

Nude rats heterotransplanted with human melanoma metastasis were injected subcutaneously on the hind paw with 125I-labelled monoclonal antibody 96.5 and with control antibody 131I-OKT3. The elimination from the injection site followed a biexponential function. The uptake in the inguinal lymph nodes on the side of the injection was initially high, but after 90 h it equalled the control side. The uptake in the tumour was slower than after i.v. injection but higher than in other tissues except blood. More than 80% of the activity in the dissected liver represented circulating blood. The uptake ratio of 96.5/OKT3 was c.3 in the tumours but c. 1 in all other tissues including blood. The capillary filtration coefficient was proportional to the uptake in organs like liver, lungs and muscle. It is concluded that subcutaneously injected radiolabelled monoclonal antibodies are initially transported via the lymph but then mainly distributed via the blood reaching the different tissues including tumours.