II. Image Acquisition (simulation, portal imaging, onboard image guidance) Flashcards
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Fluoroscopy
Imaging modality that provides a continuous image of the motion of internal structures while the x-ray tube is energized. Real-time imaging.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Fan beam (tomotherapy)
X-ray beam pattern used in computed tomography and DR; projected as a slit.Delivers treatment slice-by-slice using a narrow X-ray beam.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Single/double exposure
Single exposure captures one image; double exposure compares two images for accuracy.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Cone beam (CT)
Produces 3D imaging for accurate tumor and patient positioning.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
kV/kV matching
Uses low-energy X-rays for image alignment during setup.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
MV/MV matching
High-energy X-rays are used for imaging alignment during treatment.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Ultrasound guided
Provides soft tissue imaging to localize tumors.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Cine (e.g., motion management)
Provides continuous imaging for tracking motion, such as breathing.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Digital reconstructed radiograph (DRR)
2D images reconstructed from CT data, aiding in setup and verification.
Image-Guided Radiation Therapy (IGRT) for Verification/Localization
Electronic portal imaging device (EPID)
Captures portal images to verify the accuracy of beam alignment.
Patient Positioning and Dynamic Targeting
Interfraction motion
Changes in patient or tumor position between treatment sessions.
Patient Positioning and Dynamic Targeting
Intrafraction motion
Movement of the patient or tumor during a single treatment session.
Patient Positioning and Dynamic Targeting
Respiratory gating
Synchronizes treatment delivery with the patient’s breathing cycle.
Patient Positioning and Dynamic Targeting
Fiducial markers
Small markers placed in or near the tumor for precise tracking.
Patient Positioning and Dynamic Targeting
Volumetric imaging
3D imaging used to verify tumor position before treatment.
Image Extraction
Rows and columns read line by line
Digital image data is read systematically, line by line, to form the final image.
Image Extraction
Data transferred to external electronics
Captured image data is sent to processing units for further analysis.
Image Extraction
Digitized by analog-to-digital converter (ADC)
Converts the analog signals received by the detector into digital data.
Image Extraction
Histogram created and analyzed by software
Software generates a histogram to analyze the brightness and contrast levels in the image.
Image Extraction
Initial image processing
a. Exposure filed recognition:
Identifies the area exposed to radiation.
Image Extraction
Initial image processing
b. Histogram analysis:
Evaluates the brightness and contrast distribution.
Image Extraction
Initial image processing
c. Automatic rescaling – risk of failure:
Adjusts image brightness to standard levels but may fail if the exposure is incorrect.
*Image Formation *
Image extraction
a. TFT, SMOS, CCD:
Various detector technologies extract image data in digital imaging systems.
*Image Formation *
Image extraction
b. PSP plate scanned by laser:
In computed radiography (CR), PSP plates are scanned using a laser to retrieve image data. Laser stimulates stored energy, converting it into a digital image.
*Image Formation *
Digitized by analog-to-digital converter (ADC)
Converts the analog signal into a digital format for processing.
*Image Formation *
Exposure field recognition
Identifies the radiation-exposed area to optimize image quality.
*Image Formation *
Histogram created and analyzed by software
Assesses brightness, contrast, and exposure levels.
*Image Formation *
Initial image processing
a. Exposure indicator determination:
Measures and assigns values to determine whether exposure levels are within an acceptable range.
*Image Formation *
Initial image processing
b. Automatic rescaling:
Adjusts image brightness and contrast for consistency.
*Image Formation *
Initial image processing
a. Exposure field recognition:
Ensures the detected exposure area matches the intended region of interest.
*Image Formation *
Initial image processing
b. Histogram analysis:
Evaluates and adjusts image contrast settings.
*Image Formation *
Initial image processing
c. Automatic rescaling:
Normalizes image brightness but may cause artifacts if misapplied.
Exposure Indicators
Dose area product (DAP)
Measures the total radiation dose delivered over an area to assess exposure levels.
Exposure Indicators
Vendor-specific values
a. Relationship to patient exposure:
Each manufacturer provides proprietary exposure indicators correlating to patient dose.
Exposure Indicators
Vendor-specific values
b. Optimal value ranges
Defines acceptable exposure ranges to maintain image quality and minimize patient dose.
