The Effect of Helical CT on X-Ray Attenuation

Hopper, Kenneth D.; Gouldy, Christine A.; Kasales, Claudia J.; TenHave, Thomas R.; Fisher, Alicia L.

doi:10.1097/00004728-199701000-00029

Cited by 11 publications

(5 citation statements)

References 8 publications

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“…These differences could potentially add to the variability of measurements of contrast enhancement in clinical practice. However, the degree of variability is likely to be small in view of the findings of Hopper et al in which measured attenuation values were not significantly affected by a 20-cm y-direction change in the isocentre of a phantom containing multiple tissue equivalents [21]. Such effects were not evaluated by our study in which the position of the phantom and the height of the table were adjusted to align the central axis of the phantom with the centre-point of the CT gantry on each occasion.…”

Section: Discussionmentioning

confidence: 97%

Quantitative contrast-enhanced computed tomography: is there a need for system calibration?

Miles

Young²,

Chica³

et al. 2006

Eur Radiol

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The purpose of the study was to perform phantom studies to assess the impact of computed tomography (CT) system variability on quantitative measurements of contrast enhancement. A phantom containing tubes of contrast material at dilutions of 120, 1:35, 1:50, 1:100 and 1:200 arranged in air or water was imaged using 11 CT systems at 9 institutions. All systems had undergone routine calibration against air and water in accordance with the manufacturers' recommendations. For a given tube voltage, the relationship between the iodine concentration and CT attenuation value on a single system varied by 17 to 24% over 46-48 weeks. The coefficients of variance for iodine calibration factors across different CT systems were 8.9% in air and 5.1% in water. Calibration of individual CT systems for iodine response is required to allow comparison of quantitative measurements of contrast enhancement across different institutions. Using the iodine calibration factor to express contrast enhancement as iodine concentration would facilitate the universal application of diagnostic enhancement thresholds, especially if the necessary calculations were performed by software installed on the CT console.

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Section: Discussionmentioning

confidence: 97%

Quantitative contrast-enhanced computed tomography: is there a need for system calibration?

Miles

Young²,

Chica³

et al. 2006

Eur Radiol

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“…Differentiation of fat, fibrosis, calcium, and contrast using pixel density permits visualization of plaque composition, intimal hyperplasia, intraplaque hemorrhage, and dissection. 32,33 Ulcerations were seen best on MIP images and were identified in 8 patients by means of CTA. However, 9 ulcerations reported by means of arteriogram were not identified by means of CTA.…”

Section: Discussionmentioning

confidence: 97%

Helical CT angiography in the preoperative evaluation of carotid artery stenosis

Cinat

Lane

Pham

et al. 1998

Journal of Vascular Surgery

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“…First, HU measurements were taken from a single image slice and we did not quantify the variation of HU based on slice thickness within vertebral bodies. Although slice thickness does not appear to significantly affect attenuation measurements in a medullary bone tissue phantom, 26 the effect has not been investigated using human CT data, where trabecular-space heterogeneity could increase attenuation variability due to partial volume effects at larger slice thicknesses. Additionally, craniocaudal zone-dependent changes in trabecular bone density and marrow volume have been described previously by histomorphometry, showing more pronounced trabecular bone loss in the sub-endplate zones relative to the center of vertebrae.…”

Section: Discussionmentioning

confidence: 99%

Future Osteoporotic Fracture Risk Related to Lumbar Vertebral Trabecular Attenuation Measured at Routine Body CT

Lee

Graffy

Zea

et al. 2018

Journal of Bone and Mineral Research

100

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We sought to determine if vertebral trabecular attenuation values measured on routine body computed tomography (CT) scans obtained for a variety of unrelated indications can predict future osteoporotic fractures at multiple skeletal sites. For this Health Insurance Portability and Accountability Act (HIPAA)-compliant and Institutional Review Board (IRB)-approved retrospective cohort study, trabecular attenuation of the first lumbar vertebra was measured in 1966 consecutive older adults who underwent chest and/or abdominal CT at a single institution over the course of 1 year. New pathologic fragility fractures that occurred after a patient's CT study date were identified through an electronic health record database query using International Classification of Diseases (ICD)-9 codes for vertebral, hip, and extremity fractures. Univariate and multivariate Cox proportional hazards regression were performed to determine the effect of L trabecular attenuation on fracture-free survival. Age at CT, sex, and presence of a prior fragility fracture were included as confounders in multivariate survival analysis. Model discriminative capability was assessed through calculation of an optimism-corrected concordance index. A total of 507 patients (mean age 73.4 ± 6.3 years; 277 women, 230 men) were included in the final analysis. The median post-CT follow-up interval was 5.8 years (interquartile range 2.1-11.0 years). Univariate analysis showed that L attenuation values ≤90 Hounsfield units (HU) are significantly associated with decreased fracture-free survival (p < 0.001 by log-rank test). After adjusting for age, sex, prior fracture, glucocorticoid use, bisphosphonate use, chronic kidney disease, tobacco use, ethanol abuse, cancer history, and rheumatoid arthritis history, multivariate analysis demonstrated a persistent modest effect of L attenuation on fracture-free survival (hazard ratio [HR] = 0.63 per 10-unit increase; 95% confidence interval [CI] 0.47-0.85). The model concordance index was 0.700. Ten-year probabilities for major osteoporosis-related fractures straddled the treatment threshold for most subcohorts over the observed L HU range. In conclusion, for patients undergoing body CT scanning for any indication, L vertebral trabecular attenuation is a simple measure that, when ≤90 HU, identifies patients with a significant decrease in fracture-free survival. © 2018 American Society for Bone and Mineral Research.

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The Effect of Helical CT on X-Ray Attenuation

Abstract: The measurement of X-ray attenuation does not vary significantly with the use of the helical technique.

Cited by 11 publications

References 8 publications

Quantitative contrast-enhanced computed tomography: is there a need for system calibration?

Quantitative contrast-enhanced computed tomography: is there a need for system calibration?

Helical CT angiography in the preoperative evaluation of carotid artery stenosis

Future Osteoporotic Fracture Risk Related to Lumbar Vertebral Trabecular Attenuation Measured at Routine Body CT

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