Alternatives to the discrete cosine transform for irreversible tomographic image compression

Area of Science:

• Medical Imaging
• Image Compression
• Signal Processing

Background:

• Current irreversible medical image compression relies on the discrete cosine transform (DCT).
• The DCT is optimal for video compression but may not be for all medical imaging types.
• Positron emission tomography (PET) and magnetic resonance imaging (MRI) have unique image characteristics.

Purpose of the Study:

• To evaluate the performance of discrete Fourier transform (DFT) and discrete Hartley transform (DHT) against DCT for medical image compression.
• To determine if DFT and DHT offer advantages for PET and MRI image compression.
• To analyze the impact of image characteristics on transform efficiency.

Main Methods:

• Comparative analysis of DCT, DFT, and DHT for irreversible compression.
• Evaluation using medical images from PET and MRI modalities.
• Consideration of image properties, including regions of zero intensity and rectangular grid storage constraints.

Main Results:

• DFT and DHT outperform DCT for compressing PET and MRI images.
• The specific image characteristics of PET and MRI, with bounded non-zero intensity regions, favor DFT and DHT.
• DCT's advantage diminishes due to zero-intensity regions inherent in medical image storage.

Conclusions:

• DFT and DHT are superior to DCT for irreversible compression of PET and MRI medical images.
• The computational efficiency of DFT and DHT is also better than DCT for these applications.
• Alternative transforms like DFT and DHT should be considered for optimizing medical image compression workflows.