Design and clinical application evaluation of multi-leaf collimators / 中国辐射卫生

@#Multi-leaf collimators are devices to block rays from medical linear accelerators, which directly affect doses to targets and organs at risk by adjusting field shape and dose distribution in radiation therapy. As multi-leaf collimators are diversified in structure, there has been growing research on dosimetric comparison of various multi-leaf collimators. In this paper, we introduced the classifications of multi-leaf collimators according to their basic components, as well as the hardware structure and design features of the products of main accelerator manufacturers, including Varian’s Millennium MLC, HD120 MLC, and Halcyon, Elekta’s MLCi/i2 and Agility, and Accuray’s InCise 2 MLC and TomoTherapy. In terms of clinical application evaluation, focusing on radiotherapy plans for nasopharyngeal carcinoma, we reviewed comparative studies on the dosimetry performance of multi-leaf collimators and the effects of relevant parameters on dose distribution. We hope this review on the design and application evaluation of multi-leaf collimators can provide a reference for more innovative design and accelerator selection and parameter setting in clinical individualized treatment.

The Development of RAGE Pulse Sequence with Clinical MRI Scanner / 中国医学物理学杂志

Objective:To implement rapid acquisition gradient echo(RAGE)pulse sequence in clinical MRI scaner.Methods:Pascal language is engaged to edit source code.Number of slice excited,order of phase encoded,phase recycle of RF pulse,NEX,on/off of the gradients,and so on are all controlled by sequence parameters.SI×N_(phase)×N_(slice) data of 32 bctys were allocated to restore the k space.Source code of sequence was compiled with executable file and is loaded to RINMR software.Image of human brain are acquired.The experiment has been conducted on 0.36T permanent MRI system.Resuits:In the case of 256×256 matrix acquisition,time of single slice is 4 seconds.The resolution and SNR of the image are all adquately satisfy the clinical application.

The improved design of table operating box of digital subtraction angiography device / 生物医学工程学杂志

In this paper are analyzed the disadvantages of CGO-3000 digital subtraction angiography table Operating Box. The authors put forward a communication control scheme between single-chip microcomputer(SCM) and programmable logic controller(PLC). The details of hardware and software of communication are given.

The study of tube voltage selection influencing image quality in digital chest radiography / 中华放射学杂志

Objective To study the relationship between the selection of tube tension in digitalchest radiograph and image quality.Methods When tube current was fixed at 4 mAs, the choice of X-ray tube voltage changed from 60 to 120 kV.CDRAD2.0 contrast details phantom and normal human chest were exposed by X-ray system with 7 kinds of tube voltage (the difference between tube voltage was 10 kV) ,and the X-ray incidental dose of phantom surface was measured.Five radiologists with 3 years working experience evaluated the image quality on monitor and calculated the image quality factor (IQF) and image reading score.Statistics analysis was then performed by using ANOVA test and t test.According to the results, the optimum tube voltage range was determined.Results (1) The incidental dose of phantom surface increased with the higher tube voltage.(2)When the tube voltage was changed from 60 kV to 120 kV, the IQF value observed in CDRAD2.0 phantom image on monitor was 75.0±10.4,57.1±6.4,52.7±2.5,47.9±4.5, 46.0±3.8,46.0±2.8,45.2±3.5 ,there was significant statistical differences between groups(F=19.10, P<0.01).(3)The integrated score of the chest image quality in the tube voltage 90 kV and 120 kV were 12.4±0.9 and 13.0±0.7, respectively, and there was no statistical difference between two groups(t= 1.500,P>0.05).Conclusions (1)With the increase of tube tension,the display capacity of display device gradually strengthened.When the tube tension exceeded 90 kV, the increase of image quality on monitor was not evident.(2) With proper radiation dose, the value of tube tension in digital X-ray chest photograph was about 90 kV.

The effect of X-ray radiography exposure intensity on image quality of the monitor / 中华放射学杂志

Objective To explore the relationship between image quality and different exposure intensity of digital radiography(DR).Methods Using a contrast-detail phantom Cdrad 2.0,observers evaluated images on the monitots when exposure parameters were 90 kV and mAs ranged from 0.5 to 16.0 mAs.Then calculate image quality figure(IQF),and ANOVA was used to analyze the difference of IQF under different radiation dose in 8 subjects.Results (1)When exposure parameters were 90 kV and mAs altered from 0.5 to 8.0 mAs.the IQF observed on the monitor was reduced,and the minimal value was 38.54±2.82.When mAs changing from 8.0 to 16.0 mAs.IQF observed on the monitor was increased,and the maximum was 44.33±2.35.(2)Under the different exposure condition,the difference of IQF values were statistically significant(F=60.35,P＜0.01).Conclusions With the increased exposure intensity,the image quality on monitor increased.When mAs was 8.0 mAs,image quality was the optimum When mAs was more than 8.0 mAs,the image quality on monitor reduced.

Design and manufacture of digital stopwatch for experiment / 医疗卫生装备

This paper introduces the digital stopwatch designed by our lab for teaching and experiment of medical imaging specialty.Its design idea,principle and configuration are discussed in detail.

Improvement of main thyristor's protection circuit of XHD150B-1O 800mA X-ray machine / 医疗卫生装备

Although the type of XHD150B-IO 800mA X-ray machine possesses a damage protection electric circuit for the main thyristors, with the first switch of photographic hand valve pressed, abnormal instant exposure still appears when double (in different phase) or more than three main thyristors are broken through, short-circuited or mis-energized, and consequently the high voltage element or X-ray machine will break down. Therefore the original electric circuit must be improved. Material: A few of leads. Method: We exchange the conjunction sequence of three NO (normal open) contacting points of radiograph high voltage preparing work relay--MAG SW- R with three reverse parallel connection of main thyristors. Conclusion: The normal procedure of radiographic exposure won't be disturbed after the improvement. When whichever one or more than two main thyristors is broken through, short-circuited or mis-energized, the spoilage can be detected instantly and the protection circuit works correspondingly, which guarantees the safety of X-ray machine.