Objective To study the method of using phantom test for daily quality assurance of on board image(OBI) system. Methods The routine procedures of radiotherapy, including CT simulation, planning,setup,cone beam CT(CBCT) scan and kilovolt X-ray orthogonal film were carried out on a head phantom. The procedures repeated once a day in the following 10 days. The geometric errors of the phantom were recorded. Results The geometric errors of the phantom by CBCT were [0.06±0.11] cm, [0.03±0.05] cm, [0.07±0.07] cm and [0.03±0.10] cm in longitudinal, vertical, lateral and rotation directions, respectively. The geometric errors of the phantom by kilovolt X-ray orthogonal film were [ 0.04±0.10] cm, [0.03±0.05] cm, [0.08±0.06] cm and [0.05±0.05] cm, respectively. The differences of geometric errors of the phantom by CBCT and kilovolt X-ray orthogonal film were not significant(t = 0.44,P=0.667 in longitudinal direction ; t=0.00, P=1.060 in vertical direction ; t=0.34, P=0.735 in lateral direction; t=0.58,P=0.568 in rotation direction). Conclusions The OBI system of our accelerator is reliable and at excellent performance status. The method by using phantom test for the daily quality assurance of OBI system is easy and reliable.

BACKGROUND: As a kind of semitransparent membrane, human amniotic membrance contains many kinds of nutrients, which is a good biological material loaded with keratinocytes.OBJECTIVE: To construct epidermal substitute of the skin from human amniotic membrane loaded with porcine keratinocytes and examine the morphological characteristics of the growth and proliferation of keratinocytes seeded on human amniotic membrane.DESIGN: Single sample study and repetitive measured observation based on the cells.SETTING: Institute of Combined Injuries of Chinese PLA, Academy of Preventive Medicine, Third Military Medical University of Chinese PLA.MATERIALS: The experiment was completed in the State Key Laboratory of Trauma, Burn and Combined Injury and Institute of Combined Injuries of Chinese PLA, Academy of Preventive Medicine, Third Military Medical University of Chinese PLA from January to November 2001. Porcine keratinocytes was collected from Guizhou minipigs aged 3 weeks.METHODS: The primarily cultured keratinocytes of Guizhou minipigs were subcuhured, expanded and bred on the stroma surface of human amniotic membrance at the density of 1.63 × 105/cm2. The growth and proliferation of keratinocytes were observed under inverted microscope every day. From the 3rd day and the 15th day after being cultured, the growth of keratinocytes on human amniotic membrane was examined under light microscope and electron microscope.MAIN OUTCOME MEASURES: The growth of keratinocytes on human amniotic membrane was examined RESULTS: Keratinocytes evidently adhered to the stroma surface of human amniotic membrane about 30 minutes after being cultured, which was observed under inverted microscope. Most keratinocytes grew and adhered to the stroma surface of human amniotic membrane within 24 hours. Monolayer of keratinocytes formed and completely covered human amniotic membrane within 3 days. It was observed under the light microscope that the monolayer of keratinocytes adhered to human amniotic membrane and arrayed tightly. The keratinocytes presented in the shape of polygon, and plasmalemmas of keratinocytes formed many pseudopods under the observation with scanning electron microscope. Keratinocytes adhered to human amniotic membrane well and with many keratinofilaments in them under the observation with transmission electron microscope. Keratinocytes arrayed on human amniotic membrane densely with many cellular debris and some keratinocytes formed cavitations in them due to aging after growth for 15 days under the observation with inverted microscope.CONCLUSION: Human amitotic membrane is a good carrier of keratinocytes cultured on it in vitro, and is able to promote the proliferation of keratinocytes significantly. However, when keratinocytes were loaded on the human amniotic membrane for 15 days, some keratinocytes formed cavitations in them due to aging.