Patient Size and X-Ray Transmission in Body Ct

Ogden, Kent M.; Huda, Walter; Scalzetti, Ernest M.; Roskopf, M

doi:10.1097/00004032-200404000-00009

Cited by 42 publications

(21 citation statements)

References 12 publications

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“…Many metrics of patient size, including weight (15,31), body mass index (32), cross-sectional diameter (33), and perimeter (13), have been used previously for CT dosimetry calculations. The D eff , as selected by the AAPM, is a reasonable choice for manual measure, but it has limitations in regions of irregular body contours that used by each manufacturer (27,29).…”

Section: Medical Physics: Estimating Patient Dose From X-ray Tube Outmentioning

confidence: 99%

Estimating Patient Dose from X-ray Tube Output Metrics: Automated Measurement of Patient Size from CT Images Enables Large-scale Size-specific Dose Estimates

Ikuta¹,

Warden²,

Andriole³

et al. 2013

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Purpose:To test the hypothesis that patient size can be accurately calculated from axial computed tomographic (CT) images, including correction for the effects of anatomy truncation that occur in routine clinical CT image reconstruction. Materials and Methods:Institutional review board approval was obtained for this HIPAA-compliant study, with waiver of informed consent. Water-equivalent diameter (D W ) was computed from the attenuation-area product of each image within 50 adult CT scans of the thorax and of the abdomen and pelvis and was also measured for maximal field of view (FOV Results:In the thorax, D W versus D eff had an R 2 of 0.51 (n = 200, 50 patients at four anatomic locations); in the abdomen and pelvis, R 2 was 0.90 (n = 150, 50 patients at three anatomic locations). By correcting for image truncation, the proportion of clinically reconstructed images with an extracted D W within 65% of the maximal FOV D W increased from 54% to 90% in the thorax (3602 images) and from 95% to 100% in the abdomen and pelvis (6181 images). Conclusion:The D W extracted from axial CT images is a reliable measure of patient size, and varying degrees of clinical image truncation can be readily corrected. Automated measurement of patient size combined with CT radiation exposure metrics may enable patient-specific dose estimation on a large scale.q RSNA, 2013

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Section: Medical Physics: Estimating Patient Dose From X-ray Tube Outmentioning

confidence: 99%

Estimating Patient Dose from X-ray Tube Output Metrics: Automated Measurement of Patient Size from CT Images Enables Large-scale Size-specific Dose Estimates

Ikuta¹,

Warden²,

Andriole³

et al. 2013

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“…17,18 For larger patients typically encountered in chest CT, however, the x-ray tube voltage may need to be increased to ensure that there is adequate patient penetration by the x-ray beam. 19 Accordingly, it is important that methods for dosimetry in CT imaging are equipped to deal with the complete range of x-ray tube voltages ͑i.e., 80 to 140 kV͒ that current scanners offer.…”

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confidence: 99%

Organ doses to adult patients for chest CT

et al. 2010

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Purpose: The goal of this study was to estimate organ doses for chest CT examinations using volume computed tomography dose index ͑CTDI vol ͒ data as well as accounting for patient weight. Methods: A CT dosimetry spreadsheet ͑ImPACT CT patient dosimetry calculator͒ was used to compute organ doses for a 70 kg patient undergoing chest CT examinations, as well as volume computed tomography dose index ͑CTDI vol ͒ in a body CT dosimetry phantom at the same CT technique factors. Ratios of organ dose to CTDI vol ͑f organ ͒ were generated as a function of anatomical location in the chest for the breasts, lungs, stomach, red bone marrow, liver, thyroid, liver, and thymus. Values of f organ were obtained for x-ray tube voltages ranging from 80 to 140 kV for 1, 4, 16, and 64 slice CT scanners from two vendors. For constant CT techniques, we computed ratios of dose in water phantoms of differing diameter. By modeling patients of different weights as equivalent water cylinders of different diameters, we generated factors that permit the estimation of the organ doses in patients weighing between 50 and 100 kg who undergo chest CT examinations relative to the corresponding organ doses received by a 70 kg adult. Results: For a 32 cm long CT scan encompassing the complete lungs, values of f organ ranged from 1.7 ͑thymus͒ to 0.3 ͑stomach͒. Organs that are directly in the x-ray beam, and are completely irradiated, generally had f organ values well above 1 ͑i.e., breast, lung, heart, and thymus͒. Organs that are not completely irradiated in a total chest CT scan generally had f organ values that are less than 1 ͑e.g., red bone marrow, liver, and stomach͒. Increasing the x-ray tube voltage from 80 to 140 kV resulted in modest increases in f organ for the heart ͑9%͒ and thymus ͑8%͒, but resulted in larger increases for the breast ͑19%͒ and red bone marrow ͑21%͒. Adult patient chests have been modeled by water cylinders with diameters between ϳ20 cm for a 50 kg patient and ϳ28 cm for a 100 kg patient. At constant x-ray techniques, a 50 kg patient is expected to have doses that are ϳ18% higher than those in a 70 kg adult, whereas a 100 kg patient will have doses that are ϳ18% lower. Conclusions:We describe a practical method to use CTDI data provided by commercial CT scanners to obtain patient and examination specific estimates of organ dose for chest CT examinations.

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“…It was shown that, although it is common practice to adapt tube load to patient age and size, [9][10][11][26][27][28][29][30][31] …”

Section: Discussionmentioning

confidence: 99%

Energy imparted‐based estimates of the effect of overscanning on adult and pediatric patient effective doses from multi‐slice computed tomography

et al. 2007

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In the present study effective dose values normalized to computed tomography dose index measured free in air were calculated for adult, newborn, 1, 5, 10 and 15 year old patients regarding scans of the head, chest, abdomen, pelvis, abdomen and pelvis, and trunk, using the energy imparted method. The effect of z overscanning on patient doses was accounted for, and normalized doses are provided for varying beam collimation, pitch and reconstruction slice width values. The contribution of overscanning depends on patient age, anatomic region imaged, acquisition and reconstruction settings. For a head scan it constitutes 15% of the adult effective dose and 24% of the effective dose to a newborn but for an abdomen scan it may be as high as 58% for a newborn and 31% for an adult. The ratios of normalized pediatric doses relative to that for adults for helical scans depend not only on age but also on acquisition and reconstruction parameters, because of variations in the relative distance between the primary beam and the radiosensitive tissues/organs of the body. Regarding scans of the trunk, pediatric doses are up to a factor of 2.5 times higher compared to adult doses (abdominal scans), whereas for scans of the head up to a factor of 1.5. Increasing the pitch value of helical scans while maintaining the same effective mAs setting, and hence noise levels, leads to an increase in patient doses which depends on age, body region, scan and reconstruction parameters. The % difference between doses at pitch 1.5 and pitch 1 is more pronounced in the abdominal region (14% increase for adults) and in young patients (31% in a newborn and 18% in a 10 year old patient) and it is minimal in head scans (4% increase in newborns and 1% in adults). If multiple body regions are to be imaged, doses to adults can be reduced by up to 15% and 36% to children by performing single long-range scans. Scanning adult patients at 100 kVp instead of 120 kVp, results in a 32% reduction in effective dose from head scans and 38% for scans of the torso. The corresponding reduction for a 5 year old patient is 31% for the head and 37% for the trunk. Due to the combined overbeaming and overscanning effect the 24 mm collimation is more dose effective in the head mode and the 12 mm collimation in the body mode. Provided data enable informed design of examination protocols, calculation of effective dose values and familiarization with the technical features of multi-detector technology.

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Patient Size and X-Ray Transmission in Body Ct

Cited by 42 publications

References 12 publications

Estimating Patient Dose from X-ray Tube Output Metrics: Automated Measurement of Patient Size from CT Images Enables Large-scale Size-specific Dose Estimates

Estimating Patient Dose from X-ray Tube Output Metrics: Automated Measurement of Patient Size from CT Images Enables Large-scale Size-specific Dose Estimates

Organ doses to adult patients for chest CT

Energy imparted‐based estimates of the effect of overscanning on adult and pediatric patient effective doses from multi‐slice computed tomography

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