Attenuation physics rule DE imaging

Article

X-ray matter interactions in the diagnostic imaging energy range are dominated by photoelectric and Compton effects. Both interactions increase in proportion to electron density, which is proportional to physical density. In conventional CT imaging at 120 kVp to 140 kVp, the Compton effect predominates, and hence image quality is primarily governed by physical density.

X-ray matter interactions in the diagnostic imaging energy range are dominated by photoelectric and Compton effects. Both interactions increase in proportion to electron density, which is proportional to physical density. In conventional CT imaging at 120 kVp to 140 kVp, the Compton effect predominates, and hence image quality is primarily governed by physical density.

At lower kilovoltages, the frequency of Compton interactions remains relatively constant, whereas the frequency of photoelectric interactions increases exponentially. While the frequency of photoelectric interactions is strongly dependent on the atomic number Z (approximately proportional to Z3) the Compton effect is independent of the atomic number. For certain substances, the presence of elemental k-edges will further increase the frequency of photoelectric interactions at energies at, or just above, the k-edge (e.g., Iodine at 33keV).

Ultimately, attenuation displayed within a CT voxel is determined by the sum of different x-ray matter interactions, dominated by photoelectric and Compton interactions. Therefore, different substances will demonstrate different CT Hounsfield unit values at different energies. If the substances imaged have sufficiently distinct atomic numbers, it should, in principle, be possible to differentiate these substances based on their known attenuation properties at two different energies.

Newsletter

Stay at the forefront of radiology with the Diagnostic Imaging newsletter, delivering the latest news, clinical insights, and imaging advancements for today’s radiologists.

Recent Videos
SNMMI: Emerging PET Insights on Neuroinflammation with Progressive Apraxia of Speech (PAOS) and Parkinson-Plus Syndrome
Improving Access to Nuclear Imaging: An Interview with SNMMI President Jean-Luc C. Urbain, MD, PhD
SNMMI: 18F-Piflufolastat PSMA PET/CT Offers High PPV for Local PCa Recurrence Regardless of PSA Level
SNMMI: NIH Researcher Discusses Potential of 18F-Fluciclovine for Multiple Myeloma Detection
SNMMI: What Tau PET Findings May Reveal About Modifiable Factors for Alzheimer’s Disease
Emerging Insights on the Use of FES PET for Women with Lobular Breast Cancer
Can Generative AI Reinvent Radiology Reporting?: An Interview with Samir Abboud, MD
Mammography Study Reveals Over Sixfold Higher Risk of Advanced Cancer Presentation with Symptom-Detected Cancers
Combining Advances in Computed Tomography Angiography with AI to Enhance Preventive Care
Study: MRI-Based AI Enhances Detection of Seminal Vesicle Invasion in Prostate Cancer
Related Content
© 2025 MJH Life Sciences

All rights reserved.