Single Photon Emission Computed Tomography (SPECT) :Single Photon Emission Computed Tomography (SPECT) Tom Walsh Dylan Schoo Sean Wilson Annie Moranski


History of Nuclear Medicine :History of Nuclear Medicine Has it origins in a great many scientific discoveries dating back to the invention of the X-ray. In 1946, radioactive iodine was used to treat a patient’s thyroid cancer. By the 1950’s, radioactive nucleotides were being used to treat hyperthyroidism. Soon after, it was possible to record snapshot images of form and structure or organs (liver, spleen, brain, gastrointestinal track, ect.).


History of Nuclear Medicine Cont. :History of Nuclear Medicine Cont. By the 1980’s, nuclear medicine cameras and imaging computers allowed for the instillation of over 100 different procedures. Nuclear medicine became an integral part of patient care, and an important diagnostic and therapeutic specialty.


History of SPECT :History of SPECT Edwards and Kuhl developed the MARK VI, the first Emission Computed Tomography (ECT) device. MARK VI consisted of several sodium iodide photon detectors arranged in the rectangular shape around the head of the patient. Tomomatic-32, first SPECT imaging device, was similar to the MARK VI but had 32 photon detectors.


History of SPECT Cont. :History of SPECT Cont. ECT was discredited due to unusable images. Gained acceptance once X-ray CT image reconstruction algorithms were applied to ECT to take into account for attenuation for scatter in the body.


SPECT vs. PET :SPECT vs. PET PET uses beta-plus-emitting radionuclides such as C-11, N-13, O-15, and F-18 which annihilate into two 511-keV photons that travel in opposite directions. SPECT involves detection of gamma rays emitted singly from radionuclides such as Tc-99m, I-123, and In-111.


Pros of SPECT :Pros of SPECT Unlike MRI and X-ray, ECT produces 3-D images that relate an organ’s function. This allows for better relay of extent of disease and reveals the course of the disease earlier. Large amount of data on brain function already comes from SPECT scans. Simple process with immediate results. Much less expensive than MRI or PET ($1000 per scan) Covered by insurance when brain injury is present.


Cons of SPECT :Cons of SPECT Unlike MRI and X-ray, there is an injection. Claustrophobia is a cause for concern. Quality of image can be lessened by patient movement.


Instrumentation :Instrumentation Radionuclides Gamma emitting 99mTc, 123I, 67Ga, 111In Targeted for different tissues attentuation Collimator Detector (scintillation) Photomultiplier tubes Circuitry Preamplifier Amplifier Image Reconstruction


Gamma Cameras :Gamma Cameras Scintillation type Gamma Cameras Collimators Lead (tungsten or platinum) Excludes erroneous gamma rays (focus camera) Spatial Resolution to Detection efficiency ratio


Gamma Cameras :Gamma Cameras NaI(Tl) crystals Produce lower frequency photons Photomultiplier tubes Transform photons to electrical signals Using photocathode


Gamma Cameras :Gamma Cameras Multiple Camera Systems Reduce acquisition time Rotating camera vs. full ring camera


Image Reconstruction :Image Reconstruction Gamma rays counted into matrix Filtering Convolution Method (9 point smoothing) Fourier Method Digital vs. Annalog Too few pixels Too few bytes per pixel


Technological Advances :Technological Advances Problems with SPECT: Long scan times Low resolution Attenuation Solutions: Triple headed cameras drastically reduce scan times Improved cameras and computers enhance resolution Visual Tracking Systems to monitor patient movement and correct images accordingly Attenuation Correction software


Clinical Applications :Clinical Applications In the 70’s & 80’s, SPECT was largely replaced by CAT and MRI scans because they provided superior resolution. Recently, SPECT has returned to prominent use, especially in diagnosing cardiac and neurological abnormalities. While CAT and MRI scans only provide images of static brain anatomy, SPECT offers clues to brain function by tracing blood allocation.


Diagnosis of Neurological and Psychiatric Disorders with SPECT :Diagnosis of Neurological and Psychiatric Disorders with SPECT Doctors study two kinds of brain SPECT images: Surface Image: Active Image: Full symmetrical activity across cortical surface High activity in cerebellum and visual or occipital cortex Doctors look for too much/little activity in a certain area, or asymmetry in areas that should be symmetrical.


SPECT Images of Common Neurological and Psychiatric Disorders :SPECT Images of Common Neurological and Psychiatric Disorders Right Sided Stroke Alzheimer’s Disease pervasive hypoperfusion Head Trauma to left PFC - severe aggression problems/violence Depression increased limbic activity (left) and decreased prefrontal and temporal lobe activity


SPECT Images of Common Neurological and Psychiatric Disorders :SPECT Images of Common Neurological and Psychiatric Disorders Schizophrenia Before (left) and after (right) medication ADHD Normally (left) and while performing a concentration task (right) Alcohol Marijuana Cocaine Heroin


Cardiac SPECT Images :Cardiac SPECT Images Normal Myocardial Perfusion at stress and rest Single Vessel Coronary Artery Disease at stress and rest SPECT image exhibits full perfusion (bright, donut shape) both at rest and under stress SPECT image shows limited perfusion (horseshoe shape rather than donut) especially under stress.


Slide 20:Alcohol induced brain activity ADHD SPECT and aggressiveness ADD Current studies using SPECT


CT and SPECT :CT and SPECT SPECT provides functional information, but it has relatively poor spatial resolution and can lack the anatomical information needed to localize or stage disease. CT offers excellent spatial resolution and rich anatomical detail.


Developments in Instrumentation :Developments in Instrumentation