CT-ED conversion on a GE Lightspeed-RT scanner: influence of scanner settings

Area of Science:

• Medical Physics
• Radiological Imaging
• Diagnostic Imaging Technology

Background:

• Accurate CT number-electron density (CT-ED) relationships are crucial for quantitative imaging and dose calculations.
• Understanding the impact of scanner parameters on CT-ED is essential for reliable diagnostic and therapeutic applications.
• High-density materials present unique challenges in CT imaging due to their attenuation properties.

Purpose of the Study:

• To investigate the influence of tube voltage (kV) and tube current (mA) on the CT-ED relationship in a wide-bore GE scanner.
• To evaluate the effect of automatic tube current modulation (ATCM) on CT numbers.
• To determine the impact of phantom geometry on CT number measurements.

Main Methods:

• Utilized an electron density phantom with titanium and stainless steel inserts.
• Examined CT-ED relationships across varying kV and mA settings.
• Assessed the impact of ATCM and phantom dimensions on CT numbers for different materials.
• Employed a 16-bit image reconstruction algorithm for high-density material analysis.

Main Results:

• kV variations significantly altered CT numbers for high-density materials, impacting the CT-ED relationship.
• mA variations and ATCM showed minimal influence on CT numbers.
• Phantom dimensions affected CT numbers, even with fixed or modulated tube currents.

Conclusions:

• Scanner settings, particularly tube voltage, critically influence CT-ED relationships, especially with high-density materials.
• Consideration of specific CT-ED look-up tables tailored to scanner settings is recommended for accurate dose calculations.
• The findings highlight the importance of optimizing scan parameters for quantitative CT applications.