CT organ dose calculator size adaptive for pediatric and adult patients

Abstract

Background: Although computed tomography (CT) has played a critical role in medical care since its introduction in the 1970s, its potential long-term risk of adverse health effects has been of concern. It is crucial to accurately estimate the radiation dose delivered to the patient’s critical organs to ensure the dose is As Low As Reasonably Achievable. However, organ-level dose calculation tools for pediatric and adult patients with various body sizes are rare. We extended the existing CT organ dose calculator, NCICT 1.0, which is based on reference-size phantoms, to include body size-specific pediatric and adult phantoms. Methods: We calculated body size-specific organ doses normalized to CTDIvol by using a library of 158 pediatric and 193 adult computational human phantoms with various body sizes combined with a Monte Carlo radiation transport code, MCNP6. We also created a library of generic tube current modulation (TCM) profiles for the phantom library using a ray-tracing algorithm and implemented them into organ dose calculations. We validated organ doses for the body size-specific phantoms using those calculated from ten abdominal CT patients. We also evaluated potential dosimetric errors caused by only using reference phantoms for patients with different body sizes. Results: Organ dose coefficients and TCM profiles for 351 pediatric and adult body size-specific phantoms were implemented into NCICT 2.0. The dose coefficients from the ten abdominal CT patients agreed with those from the program within 13%. The organ doses for the overweight phantoms were overestimated by over 80% when only reference size phantoms were used. Conclusion: We confirmed that the upgraded dose calculator NCICT 2.0 could substantially reduce potential dosimetric errors caused by using only reference size phantoms. The program should be useful for the radiology community to accurately monitor organ doses for pediatric and adult CT patients with various body sizes.

Ionising radiation and cardiovascular disease: systematic review and meta-analysis

“…However, such risks are to some extent an inevitable consequence of life saving treatment, and the benefits of such therapy in general will outweigh cardiovascular disease risks. Doses from most diagnostic procedures are considerably lower, so that, for example, a typical computed tomography scan might deliver a dose of between 0.0005 and 0.015 Gy to the heart 7879. This dosage together with the risks in table 6 suggests that a group of 10 000 people in the UK each exposed to 10 procedures of this sort might expect between 0.2-13.0 excess ischaemic heart disease deaths over a lifetime.…”

Digital phantom versus patient‐specific radiation dosimetry in adult routine thorax CT examinations

“…Specifically, estimated $$nOD_{T,{\mathrm Im} pactMC}$$ for lungs and breast were 0.85 ± 0.19 and 1.08 ± 0.22 mGy/mGy, respectively, for female in Figure 2a versus 1.13 ± 0.18 and 1.26 ± 0.21 mGy/mGy, respectively, for female in Figure 2b. The digital phantoms employed by NCICT, on the contrary, utilize a series of phantoms that describe the human anatomy by combining mathematical equations along with non‐uniform rational basis‐spline and polygon mesh surfaces 10,11,29,30 . To model patients at various body sizes and take into account changes regarding the size of each organ, the phantoms are uniformly scaled.…”

“…The digital phantoms employed by NCICT, on the contrary, utilize a series of phantoms that describe the human anatomy by combining mathematical equations along with non-uniform rational basis-spline and polygon mesh surfaces. 10,11,29,30 To model patients at various body sizes and take into account changes regarding the size of each organ, the phantoms are uniformly scaled. This process is limited in that it does not allow for changes in relative organ position, shape, or body anatomy that may be present in real patients, who commonly suffer changes in tissue characteristics owing to the presence of a pathology.…”

“…This tool provides absorbed doses to radiosensitive organs and tissues based on a pre-calculated dose database and a library of reference voxel models that represent patients at various heights and weights at both sexes (Figure 1). [9][10][11] The dosimetric results contained in the database have been validated through experimental measurements conducted using physical anthropomorphic phantoms combined with dosimeter detectors. [12][13][14][15] This tool constitutes a standalone software that runs on a personal computer and is provided at no charge by the National Cancer Institute, when used for academic non-commercial research purposes.…”

A Review of Organ Dose Calculation Methods and Tools for Patients Undergoing Diagnostic Nuclear Medicine Procedures

“…Subcutaneous fat may not impact internal dosimetry, but visceral fat may increase the interorgan distances so decrease crossfire energy transfer. The dosimetric impact of body size has been actively investigated in other medical radiation procedures such as computed tomography [90][91][92] and fluoroscopy [93,94]. However, little is known about the impact of body size on internal dosimetry to date.…”