A comparison of fixed and variable kVp technique protocols for film-screen mammography

Area of Science:

• Radiology and Medical Imaging
• Diagnostic Imaging Technology
• Radiation Dosimetry

Background:

• Film-screen mammography utilizes fixed kilovoltage peak (kVp) protocols, requiring exposure compensation for varying breast thicknesses.
• Optimizing mammographic technique is crucial for balancing image quality, radiation dose, and diagnostic accuracy.

Purpose of the Study:

• To investigate the impact of a variable tube potential (kVp) technique on mammographic image quality, contrast, and radiation dose.
• To compare the variable kVp protocol against fixed kVp protocols for film-screen mammography.

Main Methods:

• Measurements were conducted on a mammography unit with a molybdenum target and filter.
• Image quality assessed via contrast, detail detection, and minimum detectable dimension of low-contrast objects.
• Variable kVp protocol increased tube potential for larger breast thicknesses, unlike fixed kVp protocols.

Main Results:

• Variable kVp yielded negligible dose impact but significant image quality improvement for breasts < 40 mm.
• For breasts > 60 mm, image quality impact was reduced, but dose reduction was significant (e.g., 35% decrease in mean glandular dose).
• The variable kVp protocol resulted in a median patient mean glandular dose of 2.7 mGy, largely independent of breast thickness.

Conclusions:

• The variable kVp protocol significantly lowers radiation dose for thicker breasts with minimal, often negligible, impact on image quality.
• This protocol enables better differentiation of breast composition changes related to patient age and thickness.
• The study highlights that reference breast tissue composition may not accurately represent patient populations in all centers.