The cerebral blood flow agent, 99mTc-HMPAO ('CeretecTM') has been investigated to see if it can be used to estimate tumour blood flow. Its distribution in Balb/c mice bearing either a subcutaneously implanted sarcoma or a plasmacytoma has been shown to be similar to that of 86RbCl. The changes in peripheral blood flow caused by the beta-blocker, propranolol, and by Nembutal anaesthesia, are manifested equally by 99mTc-HMPAO and 86Rb. We conclude, therefore, that HMPAO may be useful in estimating tumour perfusion.

Reactions of excess of thiol R'SH (R' = Me, Et, or Pr') with titanium dialkylamides Ti(NR2)a (R = Me or Et) gave insoluble non-volatile red titanium tetramercaptides containing strongly addended thiol and amine, viz., Ti(SR'),,( R' SH),(R,NH),.It is suggested that these compounds are polymeric owing to mercaptide bridges and that octaco-ordinated titanium may be involved. Controlled addition of ethanethiol or 1 -methylethanethi01 to Ti (N R J 4 gave soluble compounds : Ti (N Me,),SEt, Ti (NMe,),( SEt),, Ti ( NMe,),SPri.and Ti( N Me,),( SPr') which were shown by cryoscopic measurements to be polymeric. Infrared and n.m.r. spectra were also obtained. Reactions with other thiols gave products which could not be characterised.

Mixed leucocytes have been labelled in small volumes of plasma using small aliquots of hexamethylpropylene amine oxime (HMPAO) from vials of Ceretec, which were fractionated after reconstitution and stored frozen under nitrogen. Labelling efficiency was found to be independent of HMPAO concentration >8.8 microg.ml-1 and independent of cell concentration at >8x10(7) ml-1. Results are presented from 145 patients referred for white cell scintigraphy. Labelling efficiency was 78.9+/-9.8%. The labelled mixed leucocytes were separated on a 3-step density gradient of Percoll/plasma which showed that (99)Tc(m)-HMPAO gave a granulocyte/lymphocyte specific activity ratio of 1.67; the ratio for (111)In-tropolone or oxine was 1.0, with no preference for granulocytes. It was noted that the labelling efficiency was reduced when there was a high proportion of lymphocytes present, and also that in one patient with non-Hodgkin's lymphoma the lymphocytes labelled as equally well as the granulocytes. The stability of the label was studied by fractionating the mixed cells after in vitro incubation and after 1 h in vivo; very little loss of label occurred.

Summary: We describe a method for n.c.a. radioiodination of pyrrolidino tamoxifen (Idoxifene) based on the electrophilic destannylation of tributylstannyl pyrrolidino tamoxifen. The methods of separation using preparative tlc and HPLC give >95% radiochemical purity and > 7 0 % recovery.