Positron emission tomograph compression by using wavelet transform

The use of digitized information is rapidly gaining acceptance in radiological applications. Image compression plays an important role in the archiving and transmission of different digital diagnostic modalities. Currently block DCT based compression schemes (i.e. JPEG, MPEG) are usually used for telephone conferencing, cable video transmission and other non-medical applications. This scheme is not suitable for medical tomographic imaging (like PET) because of block artifacts resulting from the block based DCT coefficient quantization. For PET data, it is usually stored in two byte integer format per pixel for the precision preservation which makes the DCT based compression coding procedure difficult without specially designed and trained codebooks. A full frame wavelet image coding approach has been investigated in this study. It adopts the zerotree data structure, bit-plane coding and adaptive arithmetic coding to improve the coding efficiency. This lossy image compression increases the data size reduction and keeps the reconstructed images visually indifferent to the original images at compression ratio up to 10:1 in clinical image quality evaluation. Our algorithm not only achieves a higher compression ratio but also maintains high fidelity for the reconstructed image which could be used in the PACS system and telediagnosis environment