Patient‐specific radiation dose and cancer risk estimation in CT: Part I. Development and validation of a Monte Carlo program

Li, Xiang; Samei, Ehsan; Segars, W. Paul; Sturgeon, Gregory M.; Colsher, James G.; Toncheva, Greta; Yoshizumi, Terry T.; Frush, Donald P.

doi:10.1118/1.3515839

Cited by 106 publications

(100 citation statements)

References 42 publications

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“…In our previous study (17,22), we reported the development and validation of a Monte Carlo program for simulating dose with a 64-section CT system (LightSpeed VCT; GE Healthcare, Waukesha, Wis). The program was based on a benchmarked Monte Carlo subroutine package for photon, electron, and positron transport (PE-NELOPE, version 2006; Universitat de Barcelona, Barcelona, Spain) (23,24).…”

Section: Ct Examination Simulationsmentioning

confidence: 99%

Pediatric Chest and Abdominopelvic CT: Organ Dose Estimation Based on 42 Patient Models

Tian¹,

Li²,

Segars³

et al. 2013

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Purpose:To estimate organ dose from pediatric chest and abdominopelvic computed tomography (CT) examinations and evaluate the dependency of organ dose coefficients on patient size and CT scanner models. Materials and Methods:The institutional review board approved this HIPAA-compliant study and did not require informed patient consent. A validated Monte Carlo program was used to perform simulations in 42 pediatric patient models (age range, 0-16 years; weight range, 2-80 kg; 24 boys, 18 girls).Multidetector CT scanners were modeled on those from two commercial manufacturers (LightSpeed VCT, GE Healthcare, Waukesha, Wis; SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). Organ doses were estimated for each patient model for routine chest and abdominopelvic examinations and were normalized by volume CT dose index (CTDI vol ). The relationships between CTDI vol -normalized organ dose coefficients and average patient diameters were evaluated across scanner models. Results:For organs within the image coverage, CTDI vol -normalized organ dose coefficients largely showed a strong exponential relationship with the average patient diameter (R 2 . 0.9). The average percentage differences between the two scanner models were generally within 10%. For distributed organs and organs on the periphery of or outside the image coverage, the differences were generally larger (average, 3%-32%) mainly because of the effect of overranging. Conclusion:It is feasible to estimate patient-specific organ dose for a given examination with the knowledge of patient size and the CTDI vol . These CTDI vol -normalized organ dose coefficients enable one to readily estimate patient-specific organ dose for pediatric patients in clinical settings. This dose information, and, as appropriate, attendant risk estimations, can provide more substantive information for the individual patient for both clinical and research applications and can yield more expansive information on dose profiles across patient populations within a practice.q RSNA, 2013

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Section: Ct Examination Simulationsmentioning

confidence: 99%

Pediatric Chest and Abdominopelvic CT: Organ Dose Estimation Based on 42 Patient Models

Tian¹,

Li²,

Segars³

et al. 2013

Self Cite

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“…Christ et al 28 constructed the virtual family models including the 6-yr-old male and 7-yr-old female. Nagaoka et al 29 developed 3-, 5-, and 7-yr-old Japanese children models, whereas Li et al 30 developed two pediatric phantoms based on a 5-week-old girl and a 12-yr-old boy. Nipper et al 31 and Lee et al 32,33 of the University of Florida elaborated a series of pediatric voxel models of various ages.…”

Section: Introductionmentioning

confidence: 99%

Pediatric radiation dosimetry for positron‐emitting radionuclides using anthropomorphic phantoms

et al. 2013

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Purpose: Positron emission tomography (PET) plays an important role in the diagnosis, staging, treatment, and surveillance of clinically localized diseases. Combined PET/CT imaging exhibits significantly higher sensitivity, specificity, and accuracy than conventional imaging when it comes to detecting malignant tumors in children. However, the radiation dose from positron-emitting radionuclide to the pediatric population is a matter of concern since children are at a particularly high risk when exposed to ionizing radiation. Methods: The authors evaluate the absorbed fractions and specific absorbed fractions (SAFs) of monoenergy photons/electrons as well as S-values of 9 positron-emitting radionuclides in 48 source regions for 10 anthropomorphic pediatric hybrid models, including the reference newborn, 1-, 5-, 10-, and 15-yr-old male and female models, using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code. Results: The self-absorbed SAFs and S-values for most organs were inversely related to the age and body weight, whereas the cross-dose terms presented less correlation with body weight. For most source/target organ pairs, Rb-82 and Y-86 produce the highest self-absorbed and cross-absorbed S-values, respectively, while Cu-64 produces the lowest S-values because of the low-energy and highfrequency of electron emissions. Most of the total self-absorbed S-values are contributed from nonpenetrating particles (electrons and positrons), which have a linear relationship with body weight. The dependence of self-absorbed S-values of the two annihilation photons varies to the reciprocal of 0.76 power of the mass, whereas the self-absorbed S-values of positrons vary according to the reciprocal mass. Conclusions: The produced S-values for common positron-emitting radionuclides can be exploited for the assessment of radiation dose delivered to the pediatric population from various PET radiotracers used in clinical and research settings. The mass scaling method for positron-emitters can be used to derive patient-specific S-values from data of reference phantoms.

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“…Dramatic dose variation near the periphery of a scanned volume, which was caused by different tube starting angles alone, has also been reported in the literature. 22,23,43 This characteristic of the helical CT scans created a random factor into our point dose measurements.…”

Section: Resultsmentioning

confidence: 99%

“…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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Patient‐specific radiation dose and cancer risk estimation in CT: Part I. Development and validation of a Monte Carlo program

Cited by 106 publications

References 42 publications

Pediatric Chest and Abdominopelvic CT: Organ Dose Estimation Based on 42 Patient Models

Pediatric Chest and Abdominopelvic CT: Organ Dose Estimation Based on 42 Patient Models

Pediatric radiation dosimetry for positron‐emitting radionuclides using anthropomorphic phantoms

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

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