Principles of MRI EE225E / BIO265
Total Page:16
File Type:pdf, Size:1020Kb
Today.... • Administration – http://www-inst.eecs.berkeley.edu/~ee225e/sp14/ • Intro to Medical Imaging and MRI Principles of MRI EE225E / BIO265 Instructor: Miki Lustig UC Berkeley, EECS M. Lustig, EECS UC Berkeley 1 2 Medical Imaging (Before 1895) Medical Imaging (Post 1895) • Only way to see is to cut! • Revolutionized diagnostic medicine • See internal anatomy • Visualize function • Many modalities • Many sources of contrast M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 3 4 Basic Concept Medical Imaging System Requirements • Diagnostic contrast • Inexpensive • Sensitivity • Easy to use Energy Energy • Specificity Body Source Detection • Function • Can’t satisfy all • High Spatial-resolution • Many modalities • High Temporal-resolution • Often several used to • Safe make diagnosis Imaging System • Fast (Electronics, control, computing, algorithms, visualization....) e.g., Engineering! M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 5 6 Common Imaging Modalities Medical Imaging is Multi-Disciplinary • Projection X-Ray (Electromagnetic) • Computed Tomography (Electromagnetic) Math Medicine • UltraSound (Sound waves) • Positron Emission Tomography (Nuclear) Engineering • Single-Photon Emission Tomography (Nuclear) Physics • Magnetic Resonance Imaging (magnetic) Biology Chemistry M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 7 8 History: X-Rays History: Computed Tomography Wilhelm Conrad Röntgen The breakthrough: 2 8 November 1895: discovers X-rays. 2 acquiring many projections around the object enables the reconstruction of the 3D 2 22 November 1895: X-rays Mrs. RöntgenCs hand. object (or a cross-sectional 2D slice) 2 1901: receives first Nobel Prize in physics Cartotid Stenosis Virtual Medicine CT reconstruction pioneers: Virtual colonoscopy, endoscopy, arthroscopy An early X-ray imaging system: 2 1917: Johann Radon establishes the mathematical framework for tomography, Virtual therapy and surgery planning now called the Radon transform. 2 1963: Allan Cormack publishes Training platform mathematical analysis of tomographic image reconstruction, unaware of RadonCs work. 2 1972: Godfrey Hounsfield develops first CT system, unaware of either Radon or CormackCs work, develops his own reconstruction method. 2 1979 Hounsfield and Cormack receive the Nobel Prize in Physiology or Medicine. Note: so far all we can see is a projection across the patient: Radon Cormack Hounsfield Computed Tomography: Concept Computed Tomography: Past and Present History: Ultrasound Ultrasound: Present Image from the Siemens Siretom CT scanner, ca. 1975 1942: Dr. Karl Theodore Dussik,2 128x128 matrix. Engineering Advances Engineering Advances 1st x-ray (1895) x-ray today 1978, British Journal of Radiology, 51, 921-922 @ transmission ultrasound investigation of the brain early CT (1975) CT today NOVEMBER 1978 Short communications Human whole body line-scan imaging by NMR 1955: Holmes and Howry By P. Mansfield, I. L. Pykett, and P. G. Morris Department of Physics, University of Nottingham and R. E. Coupland @ SuBject suBmerged in water tank to achieve good acoustic coupling Department of Human Morphology, School of Medicine, University of Nottingham {Received July, 1978) Historically, the first nuclear magnetic resonance (NMR) fast line-scanning adaptation (Mansfield et al., 1976) is the pictures demonstrating live human anatomy were produced basis of the technique reported in this paper. The thickness recently (Mansfield and Maudsley, 1976; 1977) using a line- of the cross-sectional slice examined was set to approxi- scanning technique. The original specimens studied were mately four cm in these first experiments. Selected lines of limited in object size to cross-sectional views through material across the slice are scanned from one edge of the fingers. A number of other approaches to imaging by NMR subject to the other and the subsequent data sets for each are also being developed and are compared, discussed and scanned line are stored in a computer for subsequent display referred to elsewhere (Brunner and Ernst, 1978; Pykett and as a picture (Baines and Mansfield, 1976). Large signals Mansfield, 1978). which produce the bright zones in the images come in Recent development and expansion of our imaging general from high concentrations of mobile protons con- apparatus has now allowed us to examine objects of the tained within or near the various tissues and organs. By image of normal neck dimensions of the whole human body. In this paper we wish mobile protons, we have in mind those associated with the M. Lustig, EECS UC Berkeley to reporM.t th Lustig,e first NMEECSR UCline-sca Berkeleyn medical image of a thin free water, fat or oil containe3Dd in or distributeUltrasoundd throughout cross-sectional slice of a live human body. the various tissues and organs of the body. 9 Our work should be seen in the general context of other The whole body image shown in Fig. 1 is a transvers10e medical imaging schemes (Hounsfield, 1973; Hill, 1976; section through the abdominal region (of PM) at the level of Budinger, 1974), where improvements in techniques and the third and lower part of the second lumbar vertebrae. picture quality have recently achieved very high standards. Figure 2 is a line tracing of Fig. 1 labelling the recognizable NMR imaging, however, is in its infancy, but nevertheless morphological features. The liver is visible as a well-defined has merit as a non-invasive and, we believe, non-hazardous mass mainly on the right of the picture and blends with the technique. There is also the possibility of using NMR imag- abdominal wall at the periphery. The vertebrae are identi- ing in conjunction with other measurable NMR parameters fiable in the mid-line and the kidneys lie in the mid-lateral Engineering Advances for Engineeringnormal and abnormal Advancestissue characterization and for region with the spleen adjacent on the left. The central physiological studies including blood flow measurements. circular images probably correspond to the abdominal aorta, Our NMR imaging technique, based on selective excita- with the pancreas lying anterior, inferior vena cava and duo- tion in switched magnetic field gradients, was first described denum. We believe that the variable dense anterior central early ultrasound (1959) ultrasound today by Garroway et al. (1974). A slightly modified version of the Modern CT image acquired with a Siemens scannerearly MRI (1978) MRI today 1959: Automatic scanner, 2Glasgow512x512 matrix MRI today FIG. 1. FIG. 2. Cross-sectional line-scan NMR image through the abdomen Labelled image of Fig. 1. A = aorta, C = colon, D = duo- at L2-3. Arrow indicates mid-line posterior. Left side lies to denum, G = gall-bladder, I = inferior vena cava, K = the left of the illustration. Bright zones correspond in general kidneys, L = liver, P = pancreas, S = spleen, SI = stomach to high mobile proton content. See Fig. 2 for labelled and intestines, V=vertebra. Abdominal muscles and retro- Intravasulardetails. peritonea ultrasoundl fat (MF) are seen adjacent to the vertebra. M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 921 Doppler ultrasound twin gestation sacs (s) and bladder (B). 11 12 Projection X-Ray Computed Tomography (CT) Pneumonia abdominal CT • Projection Format • Tomographic • Small Dose • Fast • Fast • High-Res • Inexpensive • Moderate dose • ~1M$ Projection Many Projections M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 13 14 Computed Tomography Computed Tomography • Gantry rotation Sinogram cross-section FBP x-ray source M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley http://www.youtube.com/watch?v=4gklQHM19aY&feature=related 15 16 Ultrasound Anatomy vs Function Echo • Real-time • Inexpensive • No-radiation • Many applications • Low contrast and penetration M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 17 18 Nuclear Medicine Magnetic Resonance Imaging (MRI) brain metabolism • Specific metabolic • NMR: Nuclear Magnetic Resonance information (function) • MRI : Magnetic Resonance Imaging • Low-res – please don’t say MRI imaging! • High dose • MRI is VERY VERY VERY different from CT! • 1-2M$ PET • Cost: 1M-3M, mainly because of the Magnet • SPECT: Gamma radiation • PET: Positron-> Gamma M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 19 20 History History • 1975 - Ernst proposed key concepts. • 1946 - Felix Bloch (Stanford) Edward Purcell Nobel prize (Chemistry) 1991. (Harvard) independently discovered NMR. Nobel Prize (Physics) in 1952. • 1970’s - Mansfield contributes key ideas • 1971 - Raymond Damadian showed changes in MR (slice selection) parameters (T1 and T2) in cancer. People • 1982 - Widespread clinical MRI begins. started thinking about medical NMR 2003 - Lauterbur/Mansfield receive Nobel applications. • prize (Medicine) for their contributions. • 1972 - Invention of CT by Hounsfield and Cormack. Nobel Prize (Medicine) in 1979. • 1973 - Lauterbur described MRI in a similar way to CT M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley 21 22 MR Imaging Neuro Examples • Magnetic resonance imaging has revolutionized medicine PD T1 T2 • Directly visualizes soft tissues in 3D • Wide range of contrast mechanisms – Tissue character (solid, soft, liquid, fat, ...) – Diffusion – Temperature – Flow, velocity Many different contrasts available – Oxygen Saturation K. Pauly, G. Gold M. Lustig, EECS UC Berkeley M. Lustig, EECS UC Berkeley Stanford Rad 220 23 24 Clinical Example Body Examples PrecontrastPrecontrastNo Contrast Agent PostcontrastPostcontrastContrast