电离辐射对细胞中ADPRT的激活与诱导作用

研究了不同剂量γ线照射对小鼠ＳＲ－１细胞中ＡＤＰＲＴ活性的影响。结果表明５０Ｇｙ以上剂量照射对ＡＤＰＲＴ的催化反应有明显的激活作用，并且随照射剂量的增加而提高。此外，细胞受０．０１Ｇｙ低剂量照射之后一定时间，无论是再照射还是不照射５０Ｇｙ大剂量，所测得的ＡＤＰＲＴ活性都明显高于未受低剂量照射的细胞，表明低剂量辐射对细胞中ＡＤＰＲＴ具有诱导作用。     

A cost-effective thoracoscopic treatment strategy for pediatric spontaneous pneumothorax

Background: Recent data suggest that children have a higher incidence of recurrence than adults after nonoperative treatment of primary spontaneous pneumothorax (PSP). Video-assisted thoracoscopic surgery (VATS) allows efficacious therapy with significantly less morbidity. We attempt to define the most cost-effective clinically efficacious strategy using VATS to manage pediatric PSP. Methods: We retrospectively reviewed all admissions to a tertiary care children's hospital for PSP between January 1, 1991 and June 30, 1996. Results: Fifteen children had 29 primary or recurrent PSPs. Mean patient age was 14.8 ± 1.1 years, boy–girl ratio 4:1, median body mass index 18 (normal, 20–25), and 67% of pneumothoraces left sided. All patients were managed initially nonoperatively: 14 with tube thoracostomy drainage and 1 with oxygen alone. Of the children initially managed nonoperatively, 57% had a recurrent pneumothorax, and 50% of these patients eventually developed contralateral pneumothoraces. Nonoperative treatment for recurrence resulted in a 75% second recurrence rate. In contrast, eight children who underwent operative management had a 9% incidence of recurrence. The total for charges accrued in treating 29 pneumothoraces in these 15 patients was approximately $315,000. In the same population, the estimated charges for initial nonoperative therapy followed by bilateral thoracoscopy after a single recurrence would be $230,000. Conclusions: A cost-effective treatment strategy for pediatric primary spontaneous pneumothorax is tube thoracostomy at first presentation, followed by VATS with thoracoscopic bleb resection and pleurodesis for patients who experience recurrent pneumothorax. Received: 15 May 1998/Accepted: 15 January 1999     

Effects of tube potential and scatter rejection on image quality and effective dose in digital chest X-ray examination: An anthropomorphic phantom study

ObjectivesThe purpose of this study was to investigate the effects of tube potential and scatter rejection techniques on image quality of digital posteroanterior (PA) chest radiographs.Methods: An anthropomorphic phantom was imaged using a range of tube potentials (81–125 kV_p) without scatter rejection, with an anti-scatter grid, and using a 10 cm air gap. Images were anonymised and randomised before being evaluated using a visual graded analysis (VGA) method.ResultsThe effects of tube potential on image quality were found to be negligible (p > 0.63) for the flat panel detector (FPD). Decreased image quality (p = 0.031) was noted for 125 kV_p relative to 109 kV_p, though no difference was noted for any of the other potentials (p > 0.398) for computed radiography (CR). Both scatter rejection techniques improved image quality (p < 0.01). For FPD imaging the anti-scatter grid offered slightly improved image quality relative to the air gap (p = 0.038) but this was not seen for CR (p = 0.404).ConclusionsFor FPD chest imaging of the anthropomorphic phantom there was no dependence of image quality on tube potential. Scatter rejection improved image quality, with the anti-scatter grid giving greater improvements than an air-gap, but at the expense of increased effective dose.CR imaging of the chest phantom demonstrated negligible dependence on tube potential except at 125 kV_p. Scatter rejection improved image quality, but with no difference found between techniques. The air-gap resulted in a smaller increase in effective dose than the anti-scatter grid and would be the preferred scatter rejection technique.     

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.     

低剂量辐射适应性反应对辐射诱发小鼠胸腺淋巴瘤的影响

目的 探讨低剂量辐射对致癌剂量辐射诱发小鼠胸腺淋巴瘤的影响及其免疫学机理。方法 采用4次1.75GyX射线全身照射C57BL/6J小鼠诱发胸腺淋巴瘤模型, 观察不同剂量照后6个月小鼠胸腺淋巴瘤发生率, 照后1个月脾脏NK细胞毒活性、IL-2和γIFN分泌活性、腹腔巨噬细胞吞噬功能及其TNFα分泌活性以及胸腺细胞分化的变化。结果 每次1.75Gy照射前6h或12h接受25mGy或75mGy全身照射均可降低胸腺淋巴瘤发生率, 且预先接受75mGy全身照射的作用效果更为明显; 每次1.75Gy照射前12h接受75mGy照射小鼠, 上述免疫指标均比单纯1.75Gy照射组增强, 且多数指标接近假照射组; 其胸腺CD4^-CD8^-和CD4^-CD8⁺细胞较单纯1.75Gy照射组减少、CD4⁺CD8⁺细胞增多。结论 低剂量辐射可诱导辐射诱发胸腺淋巴瘤适应性反应, 对致癌剂量辐射诱发小鼠胸腺淋巴瘤有抑制作用, 其抑制作用的免疫学机理可能与低剂量辐射的免疫增强效应及诱导的免疫学适应性反应, 减轻致癌剂量辐射对机体免疫功能的损伤, 使胸腺淋巴瘤前体细胞在形成胸腺淋巴瘤之前被免疫系统清除有关。     

青海省环境中氡及其子体浓度所致居民内照射剂量

本文对青藏高嫌北部的青海省室内外氡-222及其子体进行了测量。采用闪烁法测氡浓度, 托马斯三段法测氡子体α潜能浓度。测量了162个居室和161个室外的氡及其子体浓度。全省室内外氡的平均浓度分别为：20.94Bq·m^-3和8.01mq·m^-3。     

低剂量辐射诱导细胞遗传学适应性反应的某些规律

10mGyX射线可诱导人外周血淋巴细胞和家兔外周血淋巴细胞产生对相继较大剂量(1.5Gy)X射线诱发染色体畸变的抗性, 称之为适应性反应。在离体和整体条件下, 该反应广泛存在于体细胞和生殖细胞中, 其反应程度与低剂量辐射的剂量呈负相关, 即辑先照射的剂量愈低, 诱导的适应性反应愈明显。同时还发现该反应也受许多因素的影响, 如: 低剂量辐射的剂量、剂量率, 照射时间以及生物个体差异等因素。     

河南省环境氡水平及所致公众剂量

用闪烁室法测量了河南省室内外空气中氡浓度。结果表明, 室内外环境氡浓度量对数正态分布, 95%的居室氡浓度小于55Bq·m^-3。全省室内外平均氡浓度分别为21.5Bq·m^-3和16.4Bq·m^-3。若室内外平衡因子F分别米取0.5和0.6, 则氡子体所致公众年有效剂量为0.97mSv, 年集体有效剂量约为7× 10⁴man·sv。     

64排螺旋CT冠状动脉成像的前瞻性与回顾性心电门控技术的图像质量及辐射剂量的比较研究

目的 研究前瞻性心电门控触发(prospective ECG-triggering)与回顾性心电门控(retrosp-ective ECG gating)两种技术方法行冠状动脉CTA检查时,对冠状动脉图像质量及辐射剂量的比较.方法 33名疑似冠状动脉疾病的患者分两组进行对比研究.前瞻组16例为前瞻性心电门控成像,心率小于65次/min;回顾组17例为回顾性心电门控成像,心率小于75次/min.记录两组的辐射剂量并统计分析,同时进行图像质量评价.结果 两组图像质量比较,差异无统计学意义(P0.05).前瞻性心电门控冠状动脉CTA的平均DLP 234.4 mGy·cm,占回顾性心电门控冠状动脉CTA的平均DLP 974.4 mGy·cm的24.1%.前瞻性心电门控冠状动脉CTA的患者的平均有效剂量为3.2 mSy,回顾心电门控冠状动脉CTA患者的为13.6 mSv,降低76.47%.结论 64排螺旋CT在前瞻性心电门控冠状动脉CTA与回顾性心电门控冠状动脉CTA比较可以获得相似的图像质量,可大幅降低患者的有效剂量对于不能接受高辐射剂量且心率较低的受检人群具有重要的临床价值.     

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.