CT Dose Computation Using Patient-Specific Anatomical Models
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Solution Overview
Problem
Current CT dosimetry techniques underestimate radiation doses due to the use of homogeneous PMMA cylinders that do not account for patient shape or density variations, and fail to accurately measure scattered radiation, leading to inadequate risk assessment for patients undergoing CT scans.
Innovation Solution
A method for computing CT dose that involves determining both primary and scattered radiation levels using CT scan image data, incorporating parameters like mA modulation schemes and x-ray source properties to calculate individualized radiation doses, and generating dose distribution maps that account for patient anatomy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If homogeneous PMMA cylinders are used for CT dosimetry, then the dosimetry process is simple and standardized, but the radiation dose calculation underestimates the actual patient dose due to not accounting for patient shape and density variations
Solution Approach 1:
The patent applies local quality by replacing the homogeneous PMMA phantom with a patient-specific computational model that assigns different density values to different tissue types (e.g., bone, soft tissue, air). This allows the dosimetry system to account for local variations in tissue density and patient anatomy, thereby improving dose calculation accuracy without requiring physical phantoms for each patient.
Solution Approach 2:
The patent creates a digital copy of the patient's anatomy from CT scan images and uses this virtual model for dosimetry calculations. Instead of using physical phantoms, the system generates a computational representation that mirrors the patient's unique body shape, tissue distribution, and anatomical features, enabling personalized dose assessment.
2Ease of manufacture
If cylindrical PMMA phantoms are used, then the dosimetry setup is standardized, but scattered radiation measurement is insufficient because the pencil chamber cannot measure scattered radiation at high energies
Solution Approach 1:
The patent replaces the physical pencil chamber measurement system with a computational algorithm that calculates scattered radiation dose based on the patient's CT images and the x-ray beam parameters. This substitution eliminates the limitations of physical measurement devices while maintaining standardized dosimetry protocols.
Solution Approach 2:
The patent introduces a computational intermediary between the x-ray beam and the dose calculation. The system uses the patient's anatomical data and radiation transport algorithms to model and calculate scattered radiation contributions, serving as a virtual mediator that bridges the gap between beam parameters and actual tissue dose.
3Ease of operation
If standard CT dosimetry techniques are used, then the measurement process is straightforward, but the radiation dose is underestimated due to using 32 cm diameter phantoms that do not represent most patients
Solution Approach 1:
The patent implements dynamic adaptation by adjusting the dosimetry calculations to match each patient's specific anatomical characteristics extracted from their CT scans. Instead of using a fixed phantom size, the system dynamically models the patient's unique body shape, tissue distribution, and anatomical features to provide personalized dose assessments.
Solution Approach 2:
The patent changes the fundamental parameters of the dosimetry model from fixed physical phantom dimensions to patient-specific anatomical parameters derived from CT images. The system uses variables such as patient height, weight, body composition, and organ locations to calculate personalized radiation doses, replacing the standardized 32 cm phantom parameters.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides more accurate radiation dose calculations, enabling informed decisions about patient safety and reducing the risk of underestimating radiation exposure during CT procedures.
Implementation Method 1
A CT scanner acquires the raw data necessary for producing the CT images. As shown in FIG. 1, most modern CT scanners 10 have a x-ray tube 12 rotates in unison with the detector arrays 14 around the patient's body 16, emitting x-ray photons which interrogate the patient
Implementation Method 2
the primary radiation dose (the deposition of energy in tissues from x-ray photons which started their trajectory in the x-ray tube focal track)
Implementation Method 3
from scattered radiation (x-rays which have been scattered within the patient, and are redistributed, contributing dose appreciably to tissues away from the original x-ray interaction point in the patient)
Data Source
AI summary
A system and method are disclosed for computing a radiation dose delivered to a patient during a computed tomography (CT) scan of the patient. The CT image dataset generated during the scan of the patient, and one or more parameters relating to a x-ray source are used to calculate the radiation dose delivered to the patient as a function of the CT image data set and the one or more parameters of the x-ray source. The radiation dose is generally found by calculating a primary x-ray dose distribution and scattered x-ray dose distribution from the CT image dataset and taking the sum of the primary x-ray dose distribution and scattered x-ray dose distribution.