The feasibility of a scanner-independent technique to estimate organ dose from MDCT scans: Using CTDIvol to account for differences between scanners

Turner, Adam C.; Zankl, M.; DeMarco, John J.; Cagnon, Chris H.; Zhang, Di; Angel, Erin; Cody, Dianna D.; Stevens, David B.; McCollough, Cynthia H.; McNitt‐Gray, Michael F.

doi:10.1118/1.3368596

Cited by 137 publications

(151 citation statements)

References 25 publications

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“…This is consistent with previous work which studied the doses to different organs in abdominal region and also showed large dose differences. 24 This is primarily because of differences in filtration (including bowtie composition, thickness, and shape) among various CT scanners. However, one cannot assert the superiority of one scanner over another solely based on dose information as image quality across scanners can also differ, requiring different scan protocols.…”

Section: Discussionmentioning

confidence: 99%

“…24 For example, for Donna at 120 kV, the peak skin dose from the Toshiba Aquilion64 was 14.2 mGy/100 mAs, while it was 7.3 mGy/100 mAs from the Philips Brilliance 64. This shows that a factor of two difference can exist between two different scanners, even using the same tube potential and mAs settings.…”

Section: A Peak Radiation Dose To Skin and Eye Lens For Different mentioning

confidence: 99%

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Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDI_vol, AAPM Report No. 111, and ImPACT dosimetry tool values

Zhang

Cagnon²,

Villablanca³

et al. 2013

Medical Physics

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Purpose: CT neuroperfusion examinations are capable of delivering high radiation dose to the skin or lens of the eyes of a patient and can possibly cause deterministic radiation injury. The purpose of this study is to: (a) estimate peak skin dose and eye lens dose from CT neuroperfusion examinations based on several voxelized adult patient models of different head size and (b) investigate how well those doses can be approximated by some commonly used CT dose metrics or tools, such as CTDI vol , American Association of Physicists in Medicine (AAPM) Report No. 111 style peak dose measurements, and the ImPACT organ dose calculator spreadsheet. Methods: Monte Carlo simulation methods were used to estimate peak skin and eye lens dose on voxelized patient models, including GSF's Irene, Frank, Donna, and Golem, on four scanners from the major manufacturers at the widest collimation under all available tube potentials. Doses were reported on a per 100 mAs basis. CTDI vol measurements for a 16 cm CTDI phantom, AAPM Report No. 111 style peak dose measurements, and ImPACT calculations were performed for available scanners at all tube potentials. These were then compared with results from Monte Carlo simulations. Results: The dose variations across the different voxelized patient models were small. Dependent on the tube potential and scanner and patient model, CTDI vol values overestimated peak skin dose by 26%-65%, and overestimated eye lens dose by 33%-106%, when compared to Monte Carlo simulations. AAPM Report No. 111 style measurements were much closer to peak skin estimates ranging from a 14% underestimate to a 33% overestimate, and with eye lens dose estimates ranging from a 9% underestimate to a 66% overestimate. The ImPACT spreadsheet overestimated eye lens dose by 2%-82% relative to voxelized model simulations. Conclusions: CTDI vol consistently overestimates dose to eye lens and skin. The ImPACT tool also overestimated dose to eye lenses. As such they are still useful as a conservative predictor of dose for CT neuroperfusion studies. AAPM Report No. 111 style measurements are a better predictor of both peak skin and eye lens dose than CTDI vol and ImPACT for the patient models used in this study. It should be remembered that both the AAPM Report No. 111 peak dose metric and CTDI vol dose metric are dose indices and were not intended to represent actual organ doses.

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Section: Discussionmentioning

confidence: 99%

Section: A Peak Radiation Dose To Skin and Eye Lens For Different mentioning

confidence: 99%

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDI_vol, AAPM Report No. 111, and ImPACT dosimetry tool values

Zhang

Cagnon²,

Villablanca³

et al. 2013

Medical Physics

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“…9,10 The mean dose and the dose distribution over the central phantom plane (i.e., z = 0, dose maximum image) are valuable in that they enable cross-CT scanner or cross-acquisition protocol comparisons of radiation dose levels. Previous studies [12][13][14] have explored estimation approaches for systemindependent organ doses utilizing the CTDI-based mean dose such as weighted CTDI (CTDI w ). Although the mean dose is valuable, no analytic expression is available for the mean dose and the dose distribution in the PMMA phantom.…”

Section: Introductionmentioning

confidence: 99%

Practical dose point‐based methods to characterize dose distribution in a stationary elliptical body phantom for a cone‐beam C‐arm CT system

et al. 2015

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Purpose: To propose new dose point measurement-based metrics to characterize the dose distributions and the mean dose from a single partial rotation of an automatic exposure control-enabled, C-armbased, wide cone angle computed tomography system over a stationary, large, body-shaped phantom. Methods: A small 0.6 cm 3 ion chamber (IC) was used to measure the radiation dose in an elliptical body-shaped phantom made of tissue-equivalent material. The IC was placed at 23 well-distributed holes in the central and peripheral regions of the phantom and dose was recorded for six acquisition protocols with different combinations of minimum kVp (109 and 125 kVp) and z-collimator aperture (full: 22.2 cm; medium: 14.0 cm; small: 8.4 cm). Monte Carlo (MC) simulations were carried out to generate complete 2D dose distributions in the central plane (z = 0). The MC model was validated at the 23 dose points against IC experimental data. The planar dose distributions were then estimated using subsets of the point dose measurements using two proposed methods: (1) the proximity-based weighting method (method 1) and (2) the dose point surface fitting method (method 2). Twenty-eight different dose point distributions with six different point number cases (4,5,6,7,14, and 23 dose points) were evaluated to determine the optimal number of dose points and their placement in the phantom. The performances of the methods were determined by comparing their results with those of the validated MC simulations. The performances of the methods in the presence of measurement uncertainties were evaluated. Results: The 5-, 6-, and 7-point cases had differences below 2%, ranging from 1.0% to 1.7% for both methods, which is a performance comparable to that of the methods with a relatively large number of points, i.e., the 14-and 23-point cases. However, with the 4-point case, the performances of the two methods decreased sharply. Among the 4-, 5-, 6-, and 7-point cases, the 7-point case (1.0% [±0.6%] difference) and the 6-point case (0.7% [±0.6%] difference) performed best for method 1 and method 2, respectively. Moreover, method 2 demonstrated high-fidelity surface reconstruction with as few as 5 points, showing pixelwise absolute differences of 3.80 mGy (±0.32 mGy). Although the performance was shown to be sensitive to the phantom displacement from the isocenter, the performance changed by less than 2% for shifts up to 2 cm in the x-and y-axes in the central phantom plane. Conclusions: With as few as five points, method 1 and method 2 were able to compute the mean dose with reasonable accuracy, demonstrating differences of 1.7% (±1.2%) and 1.3% (±1.0%), respectively. A larger number of points do not necessarily guarantee better performance of the methods; optimal choice of point placement is necessary. The performance of the methods is sensitive to the alignment of the center of the body phantom relative to the isocenter. In body applications where dose distributions are important, method 2 is a better choice than method 1, as it reconstructs the do...

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“…With the advances in both computational phantoms and modeling of CT systems, several research groups have worked on more patientspecific CT dose estimation methods. [20][21][22][23][24][25][26] One such software is the VirtualDose (www.virtual-dose.com) that employs a library of adult and pediatric patient phantoms for organ dose reporting.…”

Section: Introductionmentioning

confidence: 99%

In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans

Zhang

Padole

et al. 2014

Medical Physics

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Purpose: To present a study of radiation dose measurements with a human cadaver scanned on a clinical CT scanner. Methods: Multiple point dose measurements were obtained with high-accuracy Thimble ionization chambers placed inside the stomach, liver, paravertebral gutter, ascending colon, left kidney, and urinary bladder of a human cadaver (183 cm in height and 67.5 kg in weight) whose abdomen/pelvis region was scanned repeatedly with a multidetector row CT. The flat energy response and precision of the dosimeters were verified, and the slight differences in each dosimeter's response were evaluated and corrected to attain high accuracy. In addition, skin doses were measured for radiosensitive organs outside the scanned region with OSL dosimeters: the right eye, thyroid, both nipples, and the right testicle. Three scan protocols were used, which shared most scan parameters but had different kVp and mA settings: 120-kVp automA, 120-kVp 300 mA, and 100-kVp 300 mA. For each protocol three repeated scans were performed. Results: The tube starting angle (TSA) was found to randomly vary around two major conditions, which caused large fluctuations in the repeated point dose measurements: for the 120-kVp 300 mA protocol this angle changed from approximately 110• to 290• , and caused 8% − 25% difference in the point dose measured at the stomach, liver, colon, and urinary bladder. When the fluctuations of the TSA were small (within 5• ), the maximum coefficient of variance was approximately 3.3%. The soft tissue absorbed doses averaged from four locations near the center of the scanned region were 27.2 ± 3.3 and 16.5 ± 2.7 mGy for the 120 and 100-kVp fixed-mA scans, respectively. These values were consistent with the corresponding size specific dose estimates within 4%. The comparison of the per-100-mAs tissue doses from the three protocols revealed that: (1) dose levels at nonsuperficial locations in the TCM scans could not be accurately deduced by simply scaling the fix-mA doses with local mA values; (2) the general power law relationship between dose and kVp varied from location to location, with the power index ranged between 2.7 and 3.5. The averaged dose measurements at both nipples, which were about 0.6 cm outside the prescribed scan region, ranged from 23 to 27 mGy at the left nipple, and varied from 3 to 20 mGy at the right nipple over the three scan protocols. Large fluctuations over repeated scans were also observed, as a combined result of helical scans of large pitch (1.375) and small active areas of the skin dosimeters. In addition, the averaged skin dose fell off drastically with the distance to the nearest boundary of the scanned region. Conclusions: This study revealed the complexity of CT dose fluctuation and variation with a human cadaver.

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The feasibility of a scanner-independent technique to estimate organ dose from MDCT scans: Using CTDIvol to account for differences between scanners

Cited by 137 publications

References 25 publications

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDI_vol, AAPM Report No. 111, and ImPACT dosimetry tool values

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDI_vol, AAPM Report No. 111, and ImPACT dosimetry tool values

Practical dose point‐based methods to characterize dose distribution in a stationary elliptical body phantom for a cone‐beam C‐arm CT system

In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans

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The feasibility of a scanner-independent technique to estimate organ dose from MDCT scans: Using CTDIvol to account for differences between scanners

Cited by 137 publications

References 25 publications

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDIvol, AAPM Report No. 111, and ImPACT dosimetry tool values

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDIvol, AAPM Report No. 111, and ImPACT dosimetry tool values

Practical dose point‐based methods to characterize dose distribution in a stationary elliptical body phantom for a cone‐beam C‐arm CT system

In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans

Contact Info

Product

Resources

About

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDI_vol, AAPM Report No. 111, and ImPACT dosimetry tool values

Estimating peak skin and eye lens dose from neuroperfusion examinations: Use of Monte Carlo based simulations and comparisons to CTDI_vol, AAPM Report No. 111, and ImPACT dosimetry tool values