[Statistical Process Control (SPC) can help prevent treatment errors without increasing costs in radiotherapy]. / El control estadístico de proceso puede ayudar a prevenir los errores de tratamiento sin aumentar los costes en radioterapia.

PURPOSE: Statistical Process Control (SPC) was applied to monitor patient set-up in radiotherapy and, when the measured set-up error values indicated a loss of process stability, its root cause was identified and eliminated to prevent set-up errors. MATERIALS AND METHODS: Set up errors were measured for medial-lateral (ml), cranial-caudal (cc) and anterior-posterior (ap) dimensions and then the upper control limits were calculated. Once the control limits were known and the range variability was acceptable, treatment set-up errors were monitored using sub-groups of 3 patients, three times each shift. These values were plotted on a control chart in real time. RESULTS: Control limit values showed that the existing variation was acceptable. Set-up errors, measured and plotted on a X chart, helped monitor the set-up process stability and, if and when the stability was lost, treatment was interrupted, the particular cause responsible for the non-random pattern was identified and corrective action was taken before proceeding with the treatment. CONCLUSION: SPC protocol focuses on controlling the variability due to assignable cause instead of focusing on patient-to-patient variability which normally does not exist. Compared to weekly sampling of set-up error in each and every patient, which may only ensure that just those sampled sessions were set-up correctly, the SPC method enables set-up error prevention in all treatment sessions for all patients and, at the same time, reduces the control costs.

Structure-specific binding recognition of a methanogen chromosomal protein.

The archaeon Methanosarcina thermophila expresses large amounts of a small basic protein, called MC1 (methanogen chromosomal protein), which was previously identified as a DNA-binding protein possibly involved in DNA compaction in some methanogenic species. We have investigated the binding of MC1 to various kinds of branched DNA molecules whose double helix axis is severely kinked. We show that MC1 is able to distinguish and to bind preferentially to four-way junctions. This preferential binding is observed in the absence and presence of divalent cations. However, we find that MC1 has a low affinity for bulged DNA structures. These results show how MC1 is able to discriminate between different deformations of the DNA double helix.

Metabolic changes induced by human growth hormone.

In man purified human growth hormone shows anti-lipolytic effect and glycolysis is inhibited. The activity of lecithin-cholesterol-acyl-transferase is stimulated. The blood level of certain aminoacids fall.

Study of the effect of ACTH and cortisol on the plasms lipids in man using thin-layer chromatography.

This is a study of the action of ACTH and cortisol on plasma lipids using thin-layer chromatography and evaluation by densitometry. We have studied the action of 50 I.U. of ACTH in eight healthy individuals. We found an increase of free fatty acids after four hours and of triglycerides and esterified cholesterol after six hours. Free cholesterol levels declined after another six hours, the decrease becoming more intense after twenty-four hours. After twenty-four hours lecithin underwent a decline which is accompanied by an increase of lisolecithin. There was a decrease in the total amount of phospholipids. Seven patients received 100 mg. of cortisol intravenously over a period of ten minutes. We obtained an increase in free fatty acids after four hours and an increase of cholesterol after half and hour. We concluded that ACTH activates peripheral lipolysis thereby facilitating the hepatic synthesis of triglycerides and that it exerts a stimulating action on the lecithin-cholesterol-acyl-transferase system. Cortisol acts by facilitating the synthesis of triglycerides in the liver and increasing the hydrolysis of triglycerides in the plasma.