M EDICAL I MAGING By Anuja Kulkarni

LIST OF ACRONYMS CAT - Computed Axial Tomography CT - Computed Tomography DICOM - Digital Imaging and Communications in Medicine EEG - Electroencephalography EKG - Electrocardiography fMRI- Functional Magnetic Resonance Imaging JFIF- JPEG File Interchange Format JPEG- Joint Photographic Experts Group JPIP- JPEG 2000 Interactive Protocol MEG - Magnetoencephalography MRI - Magnetic Resonance Imaging NMR- Nuclear Magnetic Resonance PET- Positron Emission Tomography PNG- Portable Network Graphics PSNR- Peak Signal to Noise Ratio RF- Radio Frequency SSIM- Structural Similarity

I NTRODUCTION Medical imaging as the name suggests is the technique and process used to create images of parts and functions of human body for clinical purposes. It is a medical procedure seeking to reveal, diagnose or examine disease. [1] There are two types of medical imaging, they are- Invisible light medical imaging- radiology /clinical imaging Visible light medical imaging- involves digital video or still pictures that can be seen without special equipment.

I MAGING T ECHNOLOGIES Radiology: [2] Two forms of radiographic images are in use in medical imaging; projection radiography and fluoroscopy. Figure 1: Digital Radiography

M AGNETIC R ESONANCE IMAGING AND FIDUCIARY MARKER A magnetic resonance imaging instrument, uses powerful magnets to polarise and excite hydrogen nuclei in water molecules in human tissue, producing a detectable signal which is spatially encoded, resulting in images of the body. [3] Fiduciary markers are used in a wide range of medical imaging applications. Images of the same subject produced with two different imaging systems may be correlated by placing a fiduciary marker in the area imaged by both systems. [4] Figure 2: fMRI scan Figure 3: Fiducial Marker Example

TOMOGRAPHY Tomography is the method of imaging a single plane, or slice, of an object resulting in a tomogram. [5] Figure 4: Computed tomography of brain

D IGITAL PATHOLOGY Digital Pathology is an image-based information environment enabled by computer technology that allows for the management of information generated from a digital slide. [6] Digital pathology involves the practice of converting glass slides into digital slides that can be viewed, managed, and analyzed. Digital Pathology Environment  Scan  View  Manage  Analyze  Integrate  Sharing

P HILIPS D IGITAL PATHOLOGY SCANNER Figure 5: A prototype of a digital pathology scanner by Philips [8]

C REATION OF THREE - DIMENSIONAL IMAGES Recently, techniques have been developed to enable CT, MRI and ultrasound scanning software to produce 3D images for the physician. [9] To produce 3D images, many scans are made, then combined by computers to produce a 3D model, which can then be manipulated by the physician.

C OMPRESSION OF MEDICAL IMAGES Image compression may be lossy or lossless. For medical imaging, lossless compression is preferred for archival purposes. [10] JPEG and JPEG2000 are the compression techniques used for medical imaging. The JPEG 2000 family offers many extended functionalities, some of which grow out of the options of scalability offered by the various encodings, and which extend to the interactivity provided by JPIP, Part 9 of the JPEG 2000 standard. [10]

BLOCK DIAGRAM OF JPEG 2000 Figure 6: Block diagram of JPEG Encoder/decoder [11]

W HY JPEG 2000? JPEG 2000 is the state-of-the-art image compression DICOM standard for storage and transmission of medical images. [12] JPEG 2000 has many characteristics which are useful to medical imaging. Images can be communicated losslessly, without any distortions introduced by a compression process that may lead to mis-diagnosis. This often results in huge files, which can be difficult to store, handle, and communicate. JPEG 2000 can be used to encode files completely losslessly, and provides good compression performance.

C RITERIA TO EVALUATE A COMPRESSED IMAGE Compression ratio Bit rate PSNR – Peak signal to noise ratio SSIM – Structural Similarity

C OMPARISON OF COMPRESSION TECHNIQUES Figure 7: Comparison of compression techniques [13]

C OMPRESSION OF MEDICAL IMAGES JPIP (JPEG 2000 Interactive Protocol) is a compression streamlining protocol that works with JPEG 2000 to produce an image using the least bandwidth required. [14] JPIP has the capacity to download only the requested part of a picture, saving bandwidth, computer processing on both ends, and time.

N ON - DIAGNOSTIC IMAGING (N EUROIMAGING ) Neuroimaging has also been used in experimental circumstances to allow people to control outside devices, acting as a brain computer interface. [15] Neuroimaging falls into two broad categories: Structural imaging Functional imaging which is used to diagnose metabolic diseases and lesions on a finer scale (such as Alzheimer's disease) Figure 8: 3D MRI section of the head [16]

RESULTS Figure 9: At bits per pixel 0.25 (a) Original image (b) JPEG (c) JPEG 2000

RESULTS Figure 10: At bits per pixel 0.25 (a) Original image (b) JPEG (c) JPEG 2000

R EFERENCES 1. L.F.Squire and R.A.Novelline Squire's fundamentals of radiology (5 th ed.). Harvard University Press. ISBN ; M. Xu and L.H. Wang ; "Photoacoustic imaging in biomedicine". Review of Scientific Instruments 77 (4): doi: / ; G.T.Herman, “Fundamentals of computerized tomography: Image reconstruction from projection”, 2nd edition, Springer, S.Richard., and C. Cobbold, Foundations of Biomedical Ultrasound, Oxford University press pp. 422– A.Khademi and S.Krishnan ; Comparison of JPEG 2000 and other lossless compression schemes; Paper in Engineering in medicine and biology society (IEEE EMBS); A. Yamani; A novel pulse-echo technique for medical three dimensional imaging; IEEE trans med imaging; Volume 16 Issue 6 Pages ; Dec 1997

R EFERENCES 10. D. S. Taubman and M. W. Marcellin, "JPEG2000 – Image compression fundamentals, standards, and practice," Kluwer, eeweb.poly.edu/~yao/EE3414/JPEG.pdf 12. C. Christopoulos, A. Skodras and T.Ebrahimi, “ The JPEG2000 still image coding system: an overview ”, IEEE Trans. on Consumer Electronics, vol.46, pp , Nov Z. Wang, A. C. Bovik, H. R. Sheikh and E. P. Simoncelli, “Image quality assessment: From error visibility to structural similarity,” IEEE Trans. on Image Processing, vol. 13, no. 4, pp , Apr Microsoft and NASA Bring Mars Down to Earth Through the WorldWide Telescope ( ) – NASA 15. A.G.Filler, “The history, development, and impact of computed imaging in neurological diagnosis and neurosurgery: CT, MRI, DTI: Nature Proceeding DOI: /npre Neurosurgical Focus (in press); (Figure7)/ Picture reference: sbharris on wikipedia S. Shrestha and K.A. Wahid, A Sub-sample Based Hybrid DWT-DCTAlgorithm for Medical Imaging Applications, Cyber Journals: Multidisciplinary Journals in Science and Technology, Journal of Selected Areas in Bioengineering (JSAB), November Edition, pp. 1-11, Nov 2010