Low-Dose Chest CT: Optimizing Radiation Protection for Patients

Zhu, Xiaoyan; Yu, Jianqun; Huang, Zheng

doi:10.2214/ajr.183.3.1830809

Cited by 67 publications

(35 citation statements)

References 24 publications

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“…This was the reason that findings were thought to have been missed in only 4% of scans. This interesting, incidental observation is in keeping with suggestions in the literature that excessive doses of radiation are used routinely in CT scans and are unnecessary for diagnostic images (22)(23)(24).…”

Section: Discussionsupporting

confidence: 86%

Limitations of CT During PET/CT

Gollub¹,

Hong²,

Sarasohn³

et al. 2007

Journal of Nuclear Medicine

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Our aim was to determine the diagnostic limitations of low-dose, unenhanced CT scans performed for anatomic reference and attenuation correction during PET/CT. Methods: The Radiology Information System at our oncologic hospital was queried during the 9-mo period from July 2002 to April 2003 for patients with PET/CT scans and diagnostic enhanced CT within 2 wk of each other. One radiologist interpreted the CT portion of the PET/CT (CT p ) unaware of the PET results and the associated enhanced diagnostic CT (CT d ). A medical student compared this interpretation with the official report of the CT d and listed all discrepancies between reports. A separate radiologist compared CT p and CT d images and classified true discrepant findings as due to lack of intravenous contrast, arm-position artifact, lack of enteric contrast, low milliamperage (mA), and quality of lung images. Results: Among 100 patients, the most common malignancies were lymphoma (n 5 37), cancer of the colorectum (n 5 31), and esophageal cancer (n 5 15). Among 194 true discrepancies in which findings were missed at CT p , causes were as follows: (a) lack of intravenous contrast (128/194, 66%), (b) armdown artifact (17/194, 9%), (c) quality of lung images (26/194, 13%), (d) lack of enteric contrast (15/194, 8%), and (e) low mA (8/194, 4%). Discrepancies were seen most commonly in detecting lymphadenopathy and visceral metastases. Conclusion: Most missed findings on the unenhanced CT portion of the PET/CT scans were due to technical factors that could be altered. Discrepant findings would have led to altered management in only 2 patients, suggesting a role for limited repeat imaging to reduce radiation and use of valuable resources. Di agnostic CT scanning has been the mainstay of oncologic imaging over the past 25 y. By the end of the 1990s, 18 F-FDG PET/CT was developed, offering the first opportunity to combine metabolic and anatomic information leading to a powerful new combined-modality imaging examination.Methodologic and technical differences between the CT performed for anatomic localization and attenuation correction (CT p ) and a typical diagnostic CT scan (CT d ) include arm position (frequently down for CT p ), suspended respiration (vs. quiet breathing for CT p ), use of enteric contrast (variable in CT p ) and intravenous contrast materials (not typically used in CT p ), and levels of microamperageÁseconds (mAÁs) of radiation (much lower in CT p ).The limitations of the CT p are partly intuitive, based on the increased accuracy of CT using oral and intravenous contrast agents noted early on in the development of CT protocols (1). The functional information provided by PETwhen correlated with the CT anatomic information, in some clinical scenarios, served to overcome expected limitations incurred with the absence of intravenous or oral contrast. This has been most obvious in patients with lymphoma, where nodal disease status is not well predicted by size or morphology on CT as much as by metabolic activity on 18 F-FDG PET; thus, diagnosti...

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Section: Discussionsupporting

confidence: 86%

Limitations of CT During PET/CT

Gollub¹,

Hong²,

Sarasohn³

et al. 2007

Journal of Nuclear Medicine

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“…Theoretically, increase in noise and streak artifacts in low dose CT will invariably lead to image degradation to some degree. The least current time product for acceptable images cited in the reports varies form 13–140 mAs [22], [24], [25], [26], [27], probably depending on the criteria of image quality. This study indicates that image quality degradation is evident at current-time product of 50 mAs for readers and also confirmed that the diagnostic accuracy can be preserved even with noticeable image quality degradation.…”

Section: Discussionmentioning

confidence: 99%

Low dose chest CT protocol (50 mAs) as a routine protocol for comprehensive assessment of intrathoracic abnormality

Kubo

Ohno

Nishino

et al. 2016

European Journal of Radiology Open

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HighlightsWe planned to confirm the efficiency of low dose CT protocol at 50 mAs as a routine protocol.We examined the difference in the diagnostic result between the low dose CT images and standard dose CT image protocol.Fundamental chest CT abnormal findings including both lung and soft tissue abnormality were recorded and compared between two protocols.The difference in the diagnostic result of a reader from the other two readers is not greater in low dose CT images.The result of present study supported the use of routine low dose CT protocol.

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“…Multidetector (ie, at least four detectors) scanners were used to ensure that the whole chest could be scanned in a single maximal breath hold and to achieve good spatial resolution. All NLST acquisitions utilized a low radiation exposure protocol consistent with lung cancer screening protocols in use at the time the study began ( 29 ) and defi ned as a protocol to minimize patient radiation exposure while maintaining the performance of CT for the detection of lung nodules ( 37 ). Although the acquisition parameters for low-dose CT are not explicitly defi ned in the imaging community, each of the scanners used in NLST was individually tested by using a CT dose index phantom and patient data to achieve comparable subjective image quality by using tube current-time products of 40 mAs or lower for the average-sized patient.…”

Section: Low-dose Ct Techniques and Proceduresmentioning

confidence: 99%