The accuracy of the CyberKnife Synchrony Respiratory Tracking System (SRTS) is considered to be patient‐dependent because the SRTS relies on an individual correlation between the internal tumor position (ITP) and the external marker position (EMP), as well as a prediction method to compensate for the delay incurred to adjust the position of the linear accelerator (linac). We aimed to develop a system for obtaining pretreatment statistical measurements of the SRTS tracking error by using beam's eye view (BEV) images, to enable the prediction of the patient‐specific accuracy. The respiratory motion data for the ITP and the EMP were derived from cine MR images obtained from 23 patients. The dynamic motion phantom was used to reproduce both the ITP and EMP motions. The CyberKnife was subsequently operated with the SRTS, with a CCD camera mounted on the head of the linac. BEV images from the CCD camera were recorded during the tracking of a ball target by the linac. The tracking error was measured at 15 Hz using in‐house software. To assess the precision of the position detection using an MR image, the positions of test tubes (determined from MR images) were compared with their actual positions. To assess the precision of the position detection of the ball, ball positions measured from BEV images were compared with values measured using a Vernier caliper. The SRTS accuracy was evaluated by determining the tracking error that could be identified with a probability of more than 95% (Ep95). The detection precision of the tumor position (determined from cine MR images) was <0.2 mm. The detection precision of the tracking error when using the BEV images was <0.2 mm. These two detection precisions were derived from our measurement system and were not obtained from the SRTS. The median of Ep95 was found to be 1.5 (range, 1.0–3.5) mm. The difference between the minimum and maximum Ep95 was 2.5 mm, indicating that this provides a better means of evaluating patient‐specific SRTS accuracy. A suitable margin, based on the predicted patient‐specific SRTS accuracy, can be added to the clinical target volume.PACS number: 87.53.Ly

Lithium l-aziridine-2-carboxylate was synthesized from N-trityl-l-aziridine-carboxylic acid benzyl ester by the treatment with trifluoroacetic acid followed by the saponification with lithium hydroxide. Several N-acylaziridine-2-carboxylic acid esters were synthesized in good yield.

Thirty patients with ulcerative colitis who had been followed clinically for more than 5 years were studied. Patients with total or left-sided colitis were investigated to evaluate the significance of rectal sparing in the prognosis of the disease. Patients were divided into two groups, one with complete or relative sparing of the rectum and the other with homogeneous lesions ranging from the rectum to the proximal colon based on endoscopic findings. The administration of topical corticosteroids seemed to have little effect on rectal sparing. However, the relapse index was significantly higher in patients with rectal sparing. The intractability index, representing the ratio of the duration of the active stage to the investigation period, was also higher, though not significantly so, in this group. The results suggest that rectal sparing may give information about intractability or a tendency to relapse.

SynopsisThe reaction of 2-aziridinecarboxylic acid derivatives with several protic reagents was used to synthesize depsipeptides, dehydroamino acid derivatives, diaminopropionic acid derivatives, and phospho peptide derivatives. The reaction of N-aminoacyl-2-aziridinecarboxylic acid benzyl ester with amino acid ester induced stereoselective transacylation.

A new method is described for the synthesis of threonine from acetaldehyde and copper glycinate. This method gives a mixture of allo-threonine and threonine in a high yield (64%).