BACKGROUND: The human homograft valve has been widely used in the operation of the valve replacement and congenital heart disease. However, reports concerning pulmonary valve biomechanical suitability as a long-term substitute for aortic valve are limited.OBJECTIVE: To compare the biomechanical properties between human aortic and pulmonary valves conserved with ultra low temperature in liquid nitrogen.METHODS: A contrast observation trial was conducted in the laboratory of Congenital Heart Disease of Fuwai Hospital from March to July in 2004. Six samples of heart aorta valves and pulmonary valves were collected from the cadaveric heart within 6 hours, and the experimental procedure was disposed according to ethical criteria. The biomechanical properties of the circumferential direction of the valve were investigated using uniaxial tensile tests. The thickness of the valve was measured by HD-10 thickness instruments.RESULTS AND CONCLUSIONS: Compared to human aortic valves, the thickness of the human pulmonary valves was thinner significantly, but the stress-strain, tensile strength and the maximum tangent modulus E (the slope of linear segment) in the curve had no significant difference (P> 0.05). Biomechanical differences between the aortic and pulmonary valve are minimal, in respect, pulmonary valve can be considered biomechanically suitable for aortic valve replacement.

OBJECTIVETo verify the feasibility of setup error verification by observing patents' source-skin distance (SSD) for patients of head tumor.

METHODSFilms for 21 patients with head tumor were recorded using simulator (Varian Acuity 8.6), and comparison with reference digitally reconstructed radiograph (DRR) from Treatment plan system (TPS). The deviation of setup for 21 patients in the left-right, anterior-posterior and superior-inferior directions were measured by using 2D match, and SSD error was recorded when gantry angle was 0 degrees, 45 degrees, 315 degrees. Then setup error and corresponding SSD error were analyzed.

RESULTSThe systematic errors and random errors of 21 patients in the left-right, anterior-posterior and superior-inferior directions were (1.1 +/- 11.6) mm, (0.7 +/- 1.2) mm, (0.9 +/- 1.5) mm, and (1.51 +/- 3.1) mm, (1.05 +/- 3.3) mm, (1.60 +/- 2.3) mm. The systematic SSD errors and random SSD errors were (1.25 +/- 1.3) mm, (1.04 +/- 1.3) mm. (1.10 +/- 2.3) mm, and (2.03 +/- 1.7) mm, (2.81 +/- 2.3) mm, (2.33 +/- 3.0) mm for gantry angle was 0 degrees, 45 degrees, 315 degrees, respectively.

CONCLUSIONSIt is simple and feasible for setup error verification by observing patients' SSD and can be auxiliary to other verification means.

Algorithms ; Brachytherapy ; methods ; Feasibility Studies ; Head and Neck Neoplasms ; radiotherapy ; Humans ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted