Washout of 10C and 11C implanted by radioactive beams in brain and thigh muscle of rabbits was studied. The biological washout effect in a living body is important in the range verification system or three-dimensional volume imaging in heavy ion therapy. Positron emitter beams were implanted in the rabbit and the annihilation gamma-rays were measured by an in situ positron camera which consisted of a pair of scintillation cameras set on either side of the target. The ROI (region of interest) was set as a two-dimensional position distribution and the time-activity curve of the ROI was measured. Experiments were done under two conditions: live and dead. By comparing the two sets of measurement data, it was deduced that there are at least three components in the washout process. Time-activity curves of both brain and thigh muscle were clearly explained by the three-component model analysis. The three components ratios (and washout half-lives) were 35% (2.0 s), 30% (140 s) and 35% (10 191 s) for brain and 30% (10 s), 19% (195 s) and 52% (3175 s) for thigh muscle. The washout effect must be taken into account for the verification of treatment plans by means of positron camera measurements.

The isolation and identification of the 87A strain of hepatitis E virus (HEV) by means of cell culture have been described previously. This paper reports the nucleotide sequence of a portion of this HEV strain. The RNA extracted from the supernatants of the different passages of the 87A strain cultured in the A549 cell line was reverse-transcribed (RT) to cDNA, and then the polymerase chain reaction (PCR) amplification was carried out using the primers of HEV ET1.1 region. The PCR products from 1) the supernatant of the infected cells at the fourth passage, 2) the virus concentrated by polyethylene glycol (PEG) precipitation at the tenth passage, and 3) the virus purified by a sucrose gradient at the tenth passage were sequenced. In addition, three other PCR products obtained from sera of acute hepatitis E patients in Beijing (B-9) and Guangzhou (G-9 and G-20) were also sequenced. The nucleotide sequences of the above four strains of HEV (located in the genome from positions 4545-4754) were compared to those of some reported HEV strains. The nucleotide sequences of the B-9 strain and the 87A strain were similar to the Burmese strain and may belong to the same branch of HEV. The nucleotide sequences of the G-9 strain and the G-20 strain were a novel and unique branch. The Chinese HEV strains are multiplex and variable in gene structure.

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