Photon-counting CT for bullet material differentiation: applications in forensic radiology

Area of Science:

• Medical Imaging
• Forensic Science
• Radiology

Background:

• Gunshot fatalities pose a significant public health challenge.
• Noninvasive bullet characterization is crucial for patient care and forensic investigations.
• Distinguishing between bullet materials like lead and brass is important for identification.

Purpose of the Study:

• To investigate the potential of photon-counting CT (PCCT) for differentiating between lead and brass bullets.
• To assess if PCCT can provide noninvasive bullet material characterization.

Main Methods:

• Nine bullets (6 lead, 3 brass) were scanned using a research-mode PCCT.
• Images were reconstructed at four energy thresholds (20, 55, 72, 90 keV).
• Dual-energy indices (DEI) were calculated using mean and max Hounsfield Unit (HU) values at different energy thresholds.

Main Results:

• Significant differences in DEIs were observed between lead and brass bullets at the 20/90 keV threshold (p < 0.001).
• Differences were also statistically significant for 55/90 keV and 72/90 keV DEIs, though less pronounced.
• These findings indicate material-specific signal variations detectable by PCCT.

Conclusions:

• PCCT demonstrates significant differences in energy threshold images between lead and brass bullets.
• This technology shows promise for noninvasive bullet identification in clinical and forensic radiology.
• Quantifiable differences in bullet characteristics can be obtained using PCCT.