γ射线与噪声对豚鼠听觉损伤的复合效应

研究了γ射线（２０Ｇｙ）与噪声（１０５ｄＢＡ，３０ｍｉｎ）一次联合作用及６次重复联合作用（每次γ射线０．６７Ｇｙ，噪声１００ｄＢＡ，３０ｍｉｎ），对豚鼠听觉损伤的复合效应。结果表明，先γ射线２０Ｇｙ照射后噪声暴露对听觉损伤的复合效应是协同的。６次重复联合作用时，先噪声暴露后照射组的听阈偏移小于先照射后噪声暴露组；前者的复合效应为拮抗，后者为相加。本文对γ射线与噪声对听觉损伤联合作用的机理作了初步探讨。     

实验肿瘤局部照射动物模型的改进

目的对局部照射肿瘤实验动物模型进行改进以提高肿瘤放疗增敏药物增敏实验结果的可靠性。方法分别在小鼠腿上皮下（传统方法）和小鼠脚背皮下（改进方法）接种肝癌H22细胞,使其生长成实体瘤;用5Gyγ射线照射肿瘤后,每隔1d测量肿瘤的长、宽、高并计算肿瘤体积,连续观察24d。结果将肿瘤接种于小鼠腿上皮下时,照射组的肿瘤体积和质量与对照组之间的差异无统计学意义（t=0．55、0．70,P均〉0．05）;而将肿瘤接种于脚背皮下时,照射组的肿瘤体积和质量均明显低于对照组（t=2．25,P〈0．05;t=3．14,P〈0．01）。结论肿瘤接种于小鼠脚背皮下的方法,操作简单、方便、易行且实验结果准确、可靠。     

Radiation-induced optic neuropathy 4 years after radiation: report of a case followed up with MRI

We report a case of radiation-induced optic neuropathy in a 32-year-old man with Cushing's disease and a recurrent tumour of the left cavernous sinus. The patient experienced rapid, painless loss of vision 4 years after treatment without recurrence of tumour or other visual disorder. MRI showed enlargement and contrast enhancement of the optic chiasm. A year later the patient was almost blind and MRI showed atrophy and persistent contrast enhancement of the chiasm. Received: 1 August 1997 Accepted: 15 December 1997     

Radiation Dose Reduction via Sinogram Affirmed Iterative Reconstruction and Automatic Tube Voltage Modulation (CARE kV) in Abdominal CT

Objective

To evaluate the feasibility of sinogram-affirmed iterative reconstruction (SAFIRE) and automated kV modulation (CARE kV) in reducing radiation dose without increasing image noise for abdominal CT examination.

Materials and Methods

This retrospective study included 77 patients who received CT imaging with an application of CARE kV with or without SAFIRE and who had comparable previous CT images obtained without CARE kV or SAFIRE, using the standard dose (i.e., reference mAs of 240) on an identical CT scanner and reconstructed with filtered back projection (FBP) within 1 year. Patients were divided into two groups: group A (33 patients, CT scanned with CARE kV); and group B (44 patients, scanned after reducing the reference mAs from 240 to 170 and applying both CARE kV and SAFIRE). CT number, image noise for four organs and radiation dose were compared among the two groups.

Results

Image noise increased after CARE kV application (p < 0.001) and significantly decreased as SAFIRE strength increased (p < 0.001). Image noise with reduced-mAs scan (170 mAs) in group B became similar to that of standard-dose FBP images after applying CARE kV and SAFIRE strengths of 3 or 4 when measured in the aorta, liver or muscle (p ≥ 0.108). Effective doses decreased by 19.4% and 41.3% for groups A and B, respectively (all, p < 0.001) after application of CARE kV with or without SAFIRE.

Conclusion

Combining CARE kV, reduction of mAs from 240 to 170 mAs and noise reduction by applying SAFIRE strength 3 or 4 reduced the radiation dose by 41.3% without increasing image noise compared with the standard-dose FBP images.     

放疗后脊柱MRI表现

探讨放疗后脊柱骨髓ＭＲＩ的特征。材料与方法；本组５５例脊柱放疗后患者，放疗剂量２１００－７５００ｃＧｙ，各病例开始放疗后ＭＲ检查之间的间隔时间不等，最短的是７周，最长的是２０年。结果：ＭＲＩ表现为：Ｔ１ＷＩ像椎体呈明显高信号改变，且信号均匀，与非照射野的脊柱分界清晰；Ｇ２ＷＩ像呈均匀的稍高信号；ＳＴＩＲ或Ｔ１ＷＩ抑脂成像显示椎体呈明显低信号改变。     

丁胱亚磺酰亚胺对胶质瘤细胞谷光甘肽及放射增敏作用的实验研究

研究巯基修饰剂ＢＳＯ对胶质瘤细胞ＧＳＨ含量的修饰作用和放射增敏作用。方法利用Ｔｉｅｔｚｅ还原酶法观察ＢＳＯ对体外培养的胶质瘤细胞株及裸小鼠移植瘤模型胶质瘤细胞ＧＳＨ的作用。利用ＭＴＴ法观察ＢＳＯ对胶质瘤细胞放射敏感性的影响。结果经ＢＳＯ作用后胶质瘤细胞的ＧＳＨ含量显著下降，放射敏感性增加。结论无论是离体还是整体用药，ＢＳＯ均能降低胶质瘤细胞的ＧＳＨ含量。ＢＳＯ对胶质瘤细胞有放射增敏作用。     

Dose-image optimisation in digital radiology with a direct digital detector: an example applied to pelvic examinations

In diagnostic radiology increasing attention has been focused on dose reduction while maintaining a clinically good image quality. With the use of digital detectors balancing dose vs image quality is done differently than in film-screen radiography, since dose and image brightness are uncoupled in digital imaging. In this study a new direct digital detector (flat-panel detector) was used in a dose-image optimisation of a simulated pelvic examination. X-ray images were taken with a direct digital detector (DDD), of the pelvic of a phantom using varying tube current (varying stochastic noise). The entrance surface dose was measured for each image. These images were scored by two radiologists according to EU guidelines. A dose comparison was made with an older PCR system (storage phosphor plates). With decreasing tube current the noise in the images increased and the image with the lowest dose and still acceptable image quality was identified. The results showed that the entrance surface dose using the DDD decreased from 1.4 mGy (PCR value) to 0.48 mGy (DDD standard settings). Through the optimisation the dose could be further decreased to 0.24 mGy while still maintaining an acceptable image quality. A substantial dose reduction was obtained with this new direct digital detector. This simple but efficient optimisation approach is easily applicable to other examinations and both DDD and storage phosphor plate detectors.     

How good is the ACR accreditation phantom for assessing image quality in digital mammography?

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the American College of Radiology (ACR) accreditation phantom for assessing image quality in digital mammography. MATERIALS AND METHODS: Digital images were obtained of an ACR accreditation phantom at varying mAs (constant kVp) and varying kVp (constant mAs). The average glandular dose for a breast with 50% glandularity was determined for each technique factor. Images were displayed on a 5 mega-pixel monitor, with the window width and level settings individually optimized for viewing the fibers, specks, and masses in the ACR phantom. Digital images of the ACR phantom were presented in a random manner to eight observers, each of whom indicated the number of objects visible in each image. RESULTS: Intraobserver variability was greater than interobserver variability for the detection of fibers and specks, but the reverse was true for the detection of masses. As the mAs increased, the number of fibers visible increased from less than one at 5 mAs to all six being visible at 80 mAs. The corresponding number of visible specks increased from 12 to 24, and the number of visible masses increased from 1.25 to about four. Above 26 kVp, object visibility was constant with increasing x-ray tube voltage. Reducing the x-ray tube voltage to 24 kVp, however, reduced the number of visible fibers from six to five, the number of visible specks from 24 to 21.1, and the number of visible masses from four to 3.1. Observer performance was approximately constant for average glandular doses greater than 1.6 mGy, so that the range of lesion detectability in the ACR phantom occurs at doses lower than those normally encountered in clinical practice. CONCLUSION: The current design of the ACR phantom is unsatisfactory for assessing image quality in digital mammography.     

全身放射损伤影响皮肤创伤愈合的剂量效应研究

目的 探讨全身不同剂量照射对皮肤软组织创伤愈合的剂量效应关系。方法 用^60Coγ射线一次性均匀照射1－8Gy，照后1h内，用特制的圆孔刀致大鼠背部全层皮肤φ22mm创面2个（占体表面积的2．5％）。结果 创伤合并0、1、2、3、4、5、6、7、8Gy全身照射后，随照射剂量增加，创伤愈合速度明显减缓，残留面积明显增大，如伤后7d，单创组有33.5%的创面未愈合，复合伤组分别有35．4％，38．1％，41．6％，48．8％，53．9％，63．7％，69．2％，73．9％的创面未愈合。统计学显示，伤后不同剂量与未愈合创面％（Y^)间有明显的剂量效应关系。据此推导出9个剂量效应公式。这些结果主要为群体判估放创复合伤伤情发展提供了重要基础数据。结论 放创复合伤时创伤愈合延迟有明显的剂量效应关系。     

放射自显影术用于细胞水平微吸收剂量分布研究

目的：研究放射性药物在小鼠肝脏细胞的微吸收剂量分布，试图建立估算的数学模式。方法：采用冰冻切片光阄放射自显影技术，研究99Tc^m－甲氧基异丁基异腈（MIBI）在小鼠肝脏细胞内细胞水平的分布。结果：99Tc^m－MIBI在肝脏细胞水平的分布是不均匀的，肝细胞核微吸收剂量数值与利用医学内照射剂量（MIBI）模式估算的结果差异较大。结论：该方法不仅可弥补MIRD模式的不足，而且可评估临床放射性药物治疗效果及剂量数据。