The low-dose chest CT scans used in lung cancer screening do not appear to damage human DNA, according to a study appearing in the journal Radiology. The results could help allay fears that such screenings will lead to an increase in radiation-induced cancer. Low-dose CT screening for lung cancer in high-risk patients such as longtime smokers gained favor after the National Lung Screening Trial. The trial reported that use of low-dose chest CT scans could significantly reduce deaths from lung cancer compared to screening with chest X-rays. CT was able to identify cancers at an earlier, more treatable stage. Along with the promise of CT screening came worries over the effects of radiation exposure on patients, as even the low-dose exam delivers more radiation than an X-ray—radiation that could affect DNA and potentially lead to cancer. Studies of these potential effects that rely on epidemiology, or the analysis of diseases in the population at large, have limitations, according to study senior author Satoshi Tashiro, M.D., Ph.D., director of the Research Institute for Radiation Biology and Medicine at Hiroshima University in Hiroshima, Japan. A biological approach that looks at the effects of exposure on DNA has more power, he said. “The National Lung Screening Trial suggested the value of low-dose CT screening in high-risk population for developing lung cancer,” he said. “There were, however, no studies investigating the biological effect of low-dose CT scans on large numbers of patients. These findings led us to investigate these effects.” Dr. Tashiro and colleagues developed a system to look for damage and abnormalities in chromosomes, strands of DNA wound into a double helix structure inside the cell. In a previous study, the technology showed increases in chromosomal aberrations after standard CT scans. For the new study, the researchers compared the DNA in 107 patients who underwent low-dose chest CT with that of 102 who had standard-dose chest CT. They obtained blood samples before and 15 minutes after CT. The median effective radiation dose of low-dose CT was 1.5 millisieverts (mSv). The standard CT dose was 5.0 mSv. Analysis of the DNA found significant differences between the group that had a standard-dose chest CT scan and those who had a low-dose chest CT. “We could clearly detect the increase of DNA damage and chromosome aberrations after standard chest CT,” Dr. Tashiro said. “In contrast, no significant differences were observed in these biological effects before and after low-dose CT.” Although low-dose CT is now commonly used for screening exams, standard CT is an effective diagnostic tool that is appropriate when the benefits outweigh any potential risk. While the study did not endorse lung cancer screening with low-dose CT, its results appear to ease concerns over a potential increase in radiation-related cancer risk related to screening programs. “Even using these sensitive analyses, we could not detect the biological effects of low-dose CT scans,” Dr. Tashiro said. “This suggests that application of low-dose CT for lung cancer screening is justified from a biological point of view.” Beyond lung cancer screening, Dr. Tashiro said the DNA analysis could be used to study the biological effects of other types of imaging. “We are interested in the biological effects of various types of radiological diagnosis, including PET/CT, to establish a better system for the management of medical radiation exposure,” he said. The study is called: “Biological Effects of Low-Dose Chest CT on Chromosomal DNA.” Collaborating with Dr. Tashiro were Hiroaki Sakane, M.D., Mari Ishida, M.D., Ph.D., Lin Shi, Ph.D., Wataru Fukumoto, M.D., Ph.D., Chiemi Sakai, Ph.D., Yoshihiro Miyata, M.D., Ph.D., Takafumi Ishida, M.D., Ph.D., Tomoyuki Akita, Ph.D., Morihito Okada, M.D., Ph.D., and Kazuo Awai, M.D., Ph.D.
CT technology The dose associated with LDCT screening test intrinsically reflects the CT scanner technology. In ITALUNG single detector spiral CT scanner delivered an almost double dose (1.1 mSv for whole lung 3 mm thick sections) than multiple (4) rows of detectors spiral CT scanner (0.59 mSv for whole lung 1 mm sections) (9). With multiple rows of detector scanner technology available today, doses below 1 mSv are delivered for LDCT screening test with whole lung 1 mm or thinner sections. Ultra-low-dose CT (ULCT) enabling reduction of the radiation dose to 1/10 of that of LDCT has been developed by applying new iterative reconstruction algorithms. ULCT was recently applied to lung cancer screening (23).这是对新冠test假阴性的讨论，https://forums.huaren.us/showtopic.aspx?topicid=2536261&&page=1
Efficacy and Radiation Exposure of Ultra-Low-Dose Chest CT at 100 kVp with Tin Filtration in CT-Guided Percutaneous Core Needle Biopsy for Small Pulmonary Lesions Using a Third-Generation Dual-Source CT Scanner
https://doi.org/10.1016/j.jvir.2018.06.013 Get rights and content Abstract Purpose To prospectively investigate efficacy and radiation dose of ultra-low-dose CT–guided percutaneous core needle biopsy (PCNB) at 100 kVp with tin filtration (100Sn kVp) for small pulmonary lesions. Materials and Methods Study enrolled and randomly assigned 210 patients to standard-dose CT (n = 70) or ultra-low-dose CT (n = 140; 1:2 randomization scheme) protocol. Standard-dose CT settings were reference 110 kVp and 50 mAs, and ultra-low-dose CT settings were fixed at 100Sn kVp and 70 mAs. All PCNBs in patients with small pulmonary lesions (< 3 cm) were performed on a third-generation dual-source CT scanner. Diagnostic performance, complication rate, image quality, and radiation dose were compared. Results Sensitivity, specificity, and accuracy for diagnosis of malignancy were 95.7%, 100%, and 96.9% with standard-dose CT and 93.8%, 100%, and 95.4% with ultra-low-dose CT (P > .05). Complication rate showed no significant differences between protocols (P > .05). Mean volume CT dose index) and total dose-length product were significantly lower in ultra-low-dose CT compared with standard-dose CT (0.24 mGy vs 3.3 mGy ± 1.1 and 9.84 mGy-cm ± 0.70 vs 110.5 mGy-cm ± 45.1; P < .001). Effective dose for ultra-low-dose CT was significantly lower than that for standard-dose CT (0.14 mSv ± 0.02 vs 1.78 mSv ± 0.76; −92.1%; P < .001). Image quality of ultra-low-dose CT met the requirements of PCNB. Conclusions Ultra-low-dose CT-guided PCNB at 100Sn kVp spectral shaping significantly reduced radiation dose on a third-generation dual-source CT, while maintaining high diagnostic accuracy and safety for small pulmonary lesions.
Low-Dose Computed Tomography Reduces Radiation Exposure by 90% Compared With Traditional Computed Tomography Among Patients Undergoing Hip-Preservation Surgery
Purpose To compare the delivered radiation dose between a low-dose hip computed tomography (CT) scan protocol and traditional hip CT scan protocols (i.e., “traditional CT”). Methods This was a retrospective comparative cohort study. Patients who underwent hip-preservation surgery (including arthroscopy, surgical hip dislocation, or periacetabular osteotomy procedures) at our institution between 2016 and 2017 were identified. Patients were excluded if they had a body mass index (BMI) greater than 35, they underwent previous surgery, or a radiation dose report was absent. The low-dose group included patients who underwent hip CT at our institution using a standardized protocol of 100 kV (peak), 100 milliampere-seconds (mAs), and a limited scanning field. The traditional CT group included patients who had hip CT scans performed at outside institutions. The total effective dose (Ehip), effective dose per millimeter of body length scanned, patients' age, and patients' BMI were compared by univariate analysis. The correlation of Ehip to BMI was assessed. Results The study included 41 consecutive patients in the low-dose group and 18 consecutive patients in the traditional CT group. Low-dose CT resulted in a 90% reduction in radiation exposure compared with traditional CT (Ehip, 0.97 ± 0.28 mSv vs 9.68 ± 6.67 mSv; P < .0001). Age (28 ± 11 years vs 26 ± 10 years, P = .42), sex (83% female patients vs 76% female patients, P = .74), and BMI (24 ± 3 vs 24 ± 3, P = .75) were not different between the 2 groups. Ehip had a poor but significant correlation to BMI in the low-dose CT group (R2 = 0.14, slope = 0.03, P = .02) and did not correlate to BMI in the traditional CT group (R2 = 0.13, P = .14). Conclusions A low-dose hip CT protocol for the purpose of hip-preservation surgical planning resulted in a 90% reduction in radiation exposure compared with traditional CT. Level of Evidence
我引用实用性科普文章 （专业文章，可以看下面）。
"低剂量CT和普通CT，用的都是同样的设备，同一台设备不同在哪呢？低剂量CT顾名思义，它的扫描病人受到的这个辐射的剂量是非常低的。比方说普通的胸部CT，那么它的辐射剂量，大约可能达到7个 8个mSv，而低剂量CT就能达到，可以做到1个mSv。我们这个在扫描的时候，有两个重要的参数CT，一个是电压，第二个是电流，也就是毫安秒，我们可以通过把这个毫安秒，降下来的方式让这个剂量变低，就变成了低剂量CT。那么低剂量CT的缺点当然也是有的，它最大的缺点就是要比这个普通CT要图像质量要差一些，所以它的使用有严格的适应症，那么现在最典型的例子，就是做肺癌，新冠的这个筛查，要用低剂量CT。"
隔壁lz 的家人是乳腺癌，为了入院化疗，总共得做17次CT, 看起来次数很多，但相当于大约3次普通CT的计量. （ 根据CT 机器类型不同，low dose 降低辐射5-9 倍不等，超低计量可以达到1/10。 但对身体的伤害来讲，17次 低计量ct 要远远小于 3 次普通ct。 就像用手轻轻拍17下没问题，但用同等力的总和猛打2-3次是不一样的。（我尽量说的通俗易懂些）
好处： 及时 查新冠
早期发现乳癌肺转移
坏处： 跟原来比较， 辐射增加 ,费用增加. （low dose ct 单次价格比普通ct便宜，每次240-350 人民币， 合40-50 美元）。
下面来说作为病人家属能做的是: 每次跟开申请单的医生讲，一定要开低剂量CT。 同时到CT室的时候，一定和当班技师讲我们要做的是低剂量。医生和技师是知道的， 只是国内医院病人多，难免疏忽。特殊时期，自己家人多上点心。因为和普通ct 是用同一台ct，是技术员选择不同的参数。
大家都知道化疗直接降低免疫力，如果隔壁lz 家人同一个病房的病人是 新冠假阴性，那对lz 家人，以至整个化疗病区都是致命性的灾难. 即便单人病房，医护，打扫房间的，都会把病毒传播的。多次的化疗吃的苦就都可能全白费了。 加上CT 筛查明显多一道防线。 现阶段如果每个入院化疗病人都筛查ct 的医院，从某种角度将是安全的化疗医院。
covied 的防治就是这样，没有完美的答案。就像戴口罩，隔离，家里蹲，是牺牲所有人的利益来保证所有人的利益。
如果大家都做的模棱两可，所有人的利益都不能保证。
希望有好方法， 检测100%准确/及时是将来的方向。也希望随疫情的好转，CT 筛查短期可以结束 ( 疫情下的无奈，是不符合x-ray 应用的 ALARA ( as low as reasonably achievable ) 原则的。如果病人实在接受不了ct, 看看能否有在家化疗的可能行，看有些医院有没有门诊输液的服务。
另找了一篇论文，虽然还是有争议的，但就当下这种情况，只能权重了。
Study: Low-dose Chest CT Does Not Damage DNA
https://appliedradiology.com/communities/CT-Imaging/study-low-dose-chest-ct-does-not-damage-dna
Article - Study: Low-dose Chest CT Does Not Damage DNA
CT technology The dose associated with LDCT screening test intrinsically reflects the CT scanner technology. In ITALUNG single detector spiral CT scanner delivered an almost double dose (1.1 mSv for whole lung 3 mm thick sections) than multiple (4) rows of detectors spiral CT scanner (0.59 mSv for whole lung 1 mm sections) (9). With multiple rows of detector scanner technology available today, doses below 1 mSv are delivered for LDCT screening test with whole lung 1 mm or thinner sections.
Ultra-low-dose CT (ULCT) enabling reduction of the radiation dose to 1/10 of that of LDCT has been developed by applying new iterative reconstruction algorithms. ULCT was recently applied to lung cancer screening (23). 这是对新冠test假阴性的讨论， https://forums.huaren.us/showtopic.aspx?topicid=2536261&&page=1
大家如果有兴趣，可以读一下下面的专业论文： 我在美国读书的一个小项目写美国如何用low dose ct 从90 年代开始筛查lung cancer. 当时查了很多文献。对现在的病人讲，大家关心的是计量。我就放一篇关于计量的。大家也可以用google : low dose ct lung cancer screen.
https://www.sciencedirect.com/science/article/pii/S1051044318312879
Efficacy and Radiation Exposure of Ultra-Low-Dose Chest CT at 100 kVp with Tin Filtration in CT-Guided Percutaneous Core Needle Biopsy for Small Pulmonary Lesions Using a Third-Generation Dual-Source CT Scanner
ChunhaiLiMDBoLiuMD, PhDHongMengMDWeiweiLvMDHaipengJiaMD, PhD
https://doi.org/10.1016/j.jvir.2018.06.013
Get rights and content
Abstract
Purpose To prospectively investigate efficacy and radiation dose of ultra-low-dose CT–guided percutaneous core needle biopsy (PCNB) at 100 kVp with tin filtration (100Sn kVp) for small pulmonary lesions.
Materials and Methods Study enrolled and randomly assigned 210 patients to standard-dose CT (n = 70) or ultra-low-dose CT (n = 140; 1:2 randomization scheme) protocol. Standard-dose CT settings were reference 110 kVp and 50 mAs, and ultra-low-dose CT settings were fixed at 100Sn kVp and 70 mAs. All PCNBs in patients with small pulmonary lesions (< 3 cm) were performed on a third-generation dual-source CT scanner. Diagnostic performance, complication rate, image quality, and radiation dose were compared.
Results Sensitivity, specificity, and accuracy for diagnosis of malignancy were 95.7%, 100%, and 96.9% with standard-dose CT and 93.8%, 100%, and 95.4% with ultra-low-dose CT (P > .05). Complication rate showed no significant differences between protocols (P > .05). Mean volume CT dose index) and total dose-length product were significantly lower in ultra-low-dose CT compared with standard-dose CT (0.24 mGy vs 3.3 mGy ± 1.1 and 9.84 mGy-cm ± 0.70 vs 110.5 mGy-cm ± 45.1; P < .001). Effective dose for ultra-low-dose CT was significantly lower than that for standard-dose CT (0.14 mSv ± 0.02 vs 1.78 mSv ± 0.76; −92.1%; P < .001). Image quality of ultra-low-dose CT met the requirements of PCNB.
Conclusions Ultra-low-dose CT-guided PCNB at 100Sn kVp spectral shaping significantly reduced radiation dose on a third-generation dual-source CT, while maintaining high diagnostic accuracy and safety for small pulmonary lesions.
另一篇是low dose ct 用于hip 影像，也是减少了90%的计量。 其实胸部可以用更低计量，因为lung 本身对比度就很好。
Low-Dose Computed Tomography Reduces Radiation Exposure by 90% Compared With Traditional Computed Tomography Among Patients Undergoing Hip-Preservation Surgery
Alvin W.SuM.D., Ph.D.aTravis J.HillenM.D.bEric P.EutslerM.D.bAsheeshBediM.D.cJames R.RossM.D.dChristopher M.LarsonM.D.eJohn C.ClohisyM.D.aJeffrey J.NeppleM.D.a
https://doi.org/10.1016/j.arthro.2018.11.013
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Referred to byNiraj V. Kalore
Editorial Commentary: Low-Dose Hip Computed Tomography Sharpens the Saw for Hip Preservation: Can It Cut the Tree?Arthroscopy: The Journal of Arthroscopic & Related Surgery, Volume 35, Issue 5, May 2019, Pages 1393-1395
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Purpose To compare the delivered radiation dose between a low-dose hip computed tomography (CT) scan protocol and traditional hip CT scan protocols (i.e., “traditional CT”).
Methods This was a retrospective comparative cohort study. Patients who underwent hip-preservation surgery (including arthroscopy, surgical hip dislocation, or periacetabular osteotomy procedures) at our institution between 2016 and 2017 were identified. Patients were excluded if they had a body mass index (BMI) greater than 35, they underwent previous surgery, or a radiation dose report was absent. The low-dose group included patients who underwent hip CT at our institution using a standardized protocol of 100 kV (peak), 100 milliampere-seconds (mAs), and a limited scanning field. The traditional CT group included patients who had hip CT scans performed at outside institutions. The total effective dose (Ehip), effective dose per millimeter of body length scanned, patients' age, and patients' BMI were compared by univariate analysis. The correlation of Ehip to BMI was assessed.
Results The study included 41 consecutive patients in the low-dose group and 18 consecutive patients in the traditional CT group. Low-dose CT resulted in a 90% reduction in radiation exposure compared with traditional CT (Ehip, 0.97 ± 0.28 mSv vs 9.68 ± 6.67 mSv; P < .0001). Age (28 ± 11 years vs 26 ± 10 years, P = .42), sex (83% female patients vs 76% female patients, P = .74), and BMI (24 ± 3 vs 24 ± 3, P = .75) were not different between the 2 groups. Ehip had a poor but significant correlation to BMI in the low-dose CT group (R2 = 0.14, slope = 0.03, P = .02) and did not correlate to BMI in the traditional CT group (R2 = 0.13, P = .14).
Conclusions A low-dose hip CT protocol for the purpose of hip-preservation surgical planning resulted in a 90% reduction in radiation exposure compared with traditional CT.
Level of Evidence
大家最好用google scholar 查，文章相对多些。
大家都知道计算机技术突飞猛进，影像医学是最大的受益者。在大幅度降低辐射的同时，图像质量得到了保证。但如果你是发现了局灶性结节，就得用高分辨ct 来观察细节了。
lz来科普，这有什么好砸的？
谢谢lz科普！
你这个对比有点抬杠了。牙医X-ray查牙就行了，把其他部位遮上避免不必要的辐射是risk control。对于那些吸烟和有烟史的人，做低剂量的肺部CT筛查，是利大于弊的，低剂量辐射很小，对人体伤害不大，照出来没事，一年或者几年做一次即可。美国的医生都是强烈recommend有烟史的人做这个筛查的。
你说的筛查是针对有肺癌风险的人，隔壁那个筛查是为了不把新冠带进医院，不是为了病人本身吧？病人已经在接受癌症治疗，这个额外的辐射，影响可跟一般人不一样。就没有对病人本身更安全的筛检方式？
不把新冠带进医院，开始是保护医院里已有的病人。但等筛查后的新病人入院以后，他也会被保护，减少了被后来进院的病人传染的机会。我家里老人也是肺癌晚期，症状还没有特别厉害。因为在国内的重灾区，找的熟人医生都劝我们先不要开始化疗，怕在医院里被传染上。
要不然就干脆分批群体免疫，
这边处理流感差不多就是这样。
我现在在的美国医院每个疑似都做。就是症状很像，等核酸结果，或核酸阴性。
但我们这里发病率很低。不是灾区。
看来要给huaren 科普 还的从头说起
第一： 身体长了恶性肿瘤，比方乳腺癌，局部肿瘤切除了为什么还要化疗？
因为好多恶性肿瘤细胞已经不再局部了，他们已经跑到你的血液中，随循环可以种植到全身各处，一旦遇到合适的土壤就要在那里繁殖了。（转移灶）
第二： 化疗药的作用机理是：干扰细胞代谢的（抗DNA, RNA, 蛋白质），抗细胞分裂，比如； azathioprine, 5- fluorouracil , methotrexate.
抗肿瘤性抗生素 ：bleomycin doxorubicin . 烷化剂， 如 cyclophosphamide （ 切断 细胞 cross-links DNA). 还有阻止细胞 微管代谢的。 靶向药也是阻断细胞各种受体，信号。
重点： 化疗药不仅仅杀死肿瘤细胞，对正常的人体细胞也有很强的干扰和抑制。 病人的肝功能，肾功能，骨髓造血功能，心脏，消化道，内分泌甚至视觉，头发等等都会遭到重创，病人会掉头发，上吐下泻，少尿，出血等等： 这就是化疗的毒副作用。 医生，病人要作出权衡。你在对抗肿瘤的道路上你要作出选择。你要牺牲你的正常组织，来换取对肿瘤细胞打击的胜利。 大家对化疗普遍能接受，是因为多年的医学发展和知识的普及。 低计量ct 的损伤比起化疗是微不足道的。
病人要经十几次的化疗，漫长而且痛苦，免疫力低下，一个轻微的感染：吃的不干净拉肚子，感冒, 都可能是致命性的，因为他们的抵抗感染的白细胞，抗体都被抑制了。如果真的是中了新冠，生的希望是很渺茫的。因此现阶段预防新冠对这些病人非常，非常重要。如果是你见证了亲人历经的十几次化疗，曙光在前方，却被感染去世了，真不敢想像。
现阶段，如果是我自己的亲人，我会选择一个相对安全的医院去做化疗，那如何保证病房内每个病人都不是新冠呢。除了test, test, 低计量ct 筛查所有入院病人就是一个选择, 。大家要搞清楚的是为什么要筛查ct. 目的就是不让一个新冠病人混在其他住院化疗患者当中，要知道一个新冠病可以人传80个病人和医护，而且肺内有病变的传染性可能还强。低计量ct 的-x-ray 计量只有普通ct的 6-9 分之一。只是查住院患者，如果你在门诊输液，你在家观察是没必要的做的。
就像连小学生上学也得戴口罩一样，本来是大口呼吸新鲜空气，自由的在操场奔跑的年龄。我相信即使是很憋气，少吸氧，你也绝对得让你的孩子戴口罩出门的。 我们必须作出选择，二害相权取其轻。希望这只是暂时的。