Measurement of computed tomography modulation transfer function with a novel polymethyl methacrylate phantom

Area of Science:

• Medical Imaging Physics
• Radiological Technology
• Quality Assurance in Medical Imaging

Background:

• Accurate measurement of the modulation transfer function (MTF) is crucial for assessing computed tomography (CT) scanner performance.
• Existing methods for MTF measurement can be complex or costly, limiting routine quality control (QC).

Purpose of the Study:

• To investigate a novel, cost-effective phantom for measuring the 10% and 50% MTF values of CT scanners.
• To evaluate the accuracy, reproducibility, and applicability of the novel phantom for routine CT QC.

Main Methods:

• A novel phantom was constructed using polymethyl methacrylate (PMMA) with drilled rows of holes of varying sizes and frequencies.
• MTF was determined by analyzing Hounsfield unit ranges within the holes relative to air and PMMA.
• Results were compared against a conventional thin-wire method using identical acquisition and reconstruction parameters.

Main Results:

• The drilled hole phantom demonstrated reasonable accuracy for 50% MTF measurements.
• The phantom underestimated the 10% MTF by an average of 8.2% compared to the conventional method.
• Measurements were reproducible across repeated acquisitions and different users, and accurately reflected changes with different reconstruction kernels.

Conclusions:

• The novel drilled hole phantom is a viable, inexpensive, and user-friendly tool for routine CT scanner QC testing.
• While accurate for 50% MTF, further refinement may be needed for precise 10% MTF measurements.
• The phantom's reproducibility and sensitivity to reconstruction kernels support its application in clinical settings.