Annual safety training expected or typical ct dose levels. In addition, positron emitting isotopes that are used in medical imaging c11, n, o15, f18, etc. Manual on contrast media reports that studies show the amount of contrast absorbed by the infant. Over the course of a patients radiotherapy treatment, there are often changes of internal anatomy relative to the planning ct scan. Wholebody petct scanning is accompanied by substantial radiation dose and cancer risk. This chapter focuses on the techniques of ct imaging and covers equipment used to acquire an image, how the image is formed and displayed, the factors affecting the quality of the image and how dose is measured.
The aapmrsna physics tutorial for residents radiographics. Ct can also be used to image the head in order to locate injuries, tumors, clots leading to stroke, hemorrhage, and other conditions. The patient rests on the couch or table which is able to raise or lower and travel into and out of the bore during a scan. Only minute amounts of imaging substrate need to be injected tracer principle because of the high sensitivity of pet. Vodcasts, podcasts, ct topics, quiz, discussions, interesting case discussion, ct scan protocols, organ specific lectures, hot topics in ct all sections journal club lectures pearls protocols case studies medical illustrations search.
Ct is fundamentally a method for acquiring and reconstructing an image of a thin cross section of an object, 1, 3. Computed tomography ct is a technique that uses an xray beam to generate images. Xray imaging joint cijai advanced accelerator lecture series. Whiting introduction slightly more than three decades old, computed tomography ct continues to advance rapidly in both imaging performance and widening clinical applications. The table slowly passes through the center of a large xray machine. Lothar schad 1292008 page 1 physics of imaging systems roe, ct, mri. Lothar schad ruprechtkarlsuniversity heidelberg computer assisted clinical medicine prof.
Mayo clinic professor of radiological physics cynthia mccollough calls last falls news from cedarssinai medical center the straw that broke the camels back for the ct scan. Spect joint cijai advanced accelerator lecture series. Ct scans are generally used for studying the chest. Any ctdivol values that are outside these ranges should be evaluated to determine if the exposure to the. With the advent of dual energy ct, spectral imaging came into the focus of. It can image the lungs in order to reveal the presence of tumors. The typical effective dose for a ct head scan is 10 msv. Basic principles of computed tomography physics and technical considerations kyongtae t. These differences can be confusing, and if you are not sure, you should check with a ct technologist, a medical physicist, or the manufacturers representative. Browsing masters theses by department medical physics. In pediatric patients, ct imaging is often used to evaluate.
Basic principles of computed tomography physics and. Medical physics lecturer department of diagnostic radiography university of salford. In the medical community they simply call them ct scans, because axial, as youll find out, is unnecessary in the title. Home all free medical books step by step ct scan pdf. However, the risk of developing cancer from radiation exposure is generally small. Ct imaging information sheet risks associated with diagnostic imaging using computerized tomography ct howard dickson health physics society specialists in radiation safety a ct scan also called computerized tomography or just ct is an xray technique that produces images of your body to visualize internal structures in. Links, medical imaging signals and systems, and lecture notes by prince. They are made of a number of b scans, which build up an image of the sector in the body through a series of dots of varying intensities.
Ct was introduced into clinical practice into 1971 with a scan of a cystic. Computed tomography, more commonly known as a ct or cat scan, is a diagnostic medical imaging test. For the purposes of this fact sheet, the word radiation refers to ionizing radiation. Imaging and detectors for medical physics lecture 6. Welcome to part 2 in my series of the physics of medical imaging. Ct scans performed annually in usa courtesy mike partridge oxford computed tomography ct. The american association of physicists in medicine aapm is a nonprofit. Free radiology books download ebooks online textbooks. Health physics society specialists in radiation safety radiation exposure from medical exams and procedures fact sheet adopted. The ct scan format consists of many cells,each assigned a no. In this paper, we study the scan and reconstruction principles of the multi. An appreciation of the potential of ct and its limitations can be obtained with an understanding of basic. The increased fov is beneficial in many applications. Anderson does more than 500,000 diagnostic imaging procedures per year, said the medical physics community is deeply concerned about overexposures associated with ct scans, a sentiment echoed by mahadevappa mahesh, an associate professor of radiology and medicine at johns hopkins university school of medicine.
Computed tomography national institute of biomedical imaging. The membership includes academic and consulting medical physicists who specialize in ct imaging, representatives of each of the major ct scanner. A ct scan of the heart may be ordered when various types of heart disease or abnormalities are suspected. A ct scan, or computed tomography scan is a medical imaging procedure that uses computerprocessed combinations of many xray measurements taken from. Ct scans provide a better image of the lungs and organs in the chest cavity between the lungs. The ionising radiation medical exposure regulations 2000. It also presents new challenges and new characteristics. Medical imaging including mri, nuclear medicine and ultrasound imaging as well as xray and ct radiation oncology treatment of cancer with various kinds of radiation medical health physics protection of workers and patients from radiation both ionizing radiation, like xrays, and nonionizing radiation, like lasers and magnetic fields typical professional training for medical physics. Aapm ct scan protocols the alliance for quality computed. It uses special xray equipment to make crosssectional pictures of your body. The role of the medical physicist in managing radiation. Computed tomography ct scanning, also known as, especially in the older literature and textbooks, computerized axial tomography cat scanning, is a diagnostic imaging procedure that uses xrays to build crosssectional images slices of the body.
Mathematics of medical imaging 3 essentially, the mathematics of ct scanning involves two problems. Physics of mri yao wang polytechnic university, brooklyn, ny 11201 based on j. The crosssectional images generated during a ct scan can be reformatted in multiple planes. Physics of imaging systems basic principles of magnetic. Your doctor will have weighed up the odds and spoken to you about this. Xray computed tomography ct is a medical imaging technique that. Pdf the american association of physicists in medicine aapm is a nonprofit. This note introduces the physics, instrumentation, and signal processing methods used in xray projection radiography, xray computed tomography, nuclear medicine spectpet, optical imaging, ultrasound imaging, and magnetic resonance imaging. Broken bones and vertebrae are more clearly visible on a ct scan.
However, any risk of having a ct scan is generally heavily outweighed by the advantages of having the scan. The patient transits through the bore during a scan. The integration of ct scanners in multi modality imaging applications, for example by integration of a ct scanner with a pet scanner or a spect scanner. This allows extraction of accurate information from pet images. In the forward problem, we model the data obtained from realworld ct scans using the radon transform. A computerized tomography is an xray imaging procedure in which a narrow beam of xrays is aimed at a patient and quickly rotated around the body. Setup lasers projected from the bore are used to center the patient in the bore prior to a scan.
Yao wang, polytechnic institute of new york university. Lothar schad 3142019 page 2 literature i dance et al diagnostic radiology physics publisher. How ct scans work using only basic high school mathematics. Radiologists and radiation oncologists often use the ct examination to. Medical physicists assist the medical imaging community in providing safe and effective ct examinations. Radiation exposure from medical exams and procedures. A ct scan in a pregnant woman poses no known risks to the baby if the area of. Crosssections are reconstructed from measurements of attenuation coefficients of xray beams in the volume of the object studied. Imaging and detectors for medical physics dr barbara camanzi barbara. The manual labor involved in identifying, recording, and compiling for.
For medical applications, xrays are usually generated in vacuum tubes by bombarding a metal target with highspeed electrons and images produced by passing the resulting radiation through the patients body on to a photographic plate or digital recorder to produce a radiograph, or by rotating both source and detector around the patients body to produce a slice image by computerised tomography ct. Ct scanner uses a motorized xray source that rotates around the circular opening of a donutshaped structure called a gantry. Although ct scans expose the patient to higher doses of ionising radiation the. It differs from conventional projection in two significant ways. Medical imaging is the technique and process of creating visual representations of the interior. Principles and practice of pet ct part 1 a technologists guide publications brochures. Physics of imaging systems basic principles of magnetic resonance imaging ii prof. Imaging and detectors for medical physics lecture 3. Unlike ct, mri does not involve the use of ionizing radiation and is therefore not associated with.
The radon transform allows us to create \ lm images of objects that are very similar to those actually occurring in xrays or ct scans. Their effort to manage dose carefully is consistent with the aapms position statement on radiation risks from medical imaging procedures 5. Typical bore sizes are between 70cm and 85cm in diameter. Specification and acceptance testing of computed tomography scanners published for the i american association of physicists in medicine by the american institute of physics. Computed tomography ct, sometimes called computerized tomography or computed axial tomography cat, is a noninvasive medical examination or procedure that uses specialized x.
Like traditional xrays, it produces multiple images or pictures of the inside of the body. Takes longer to acquire a scan than ct, more susceptible to patient motion ct mri pet. January 2010 ionizing radiation is used daily in hospitals and clinics to perform diagnostic imaging exams and medical interventions. Mpc has developed the following table of expected ctdivol ranges, based on years of testing hundreds of ct scanners. However, the basic parameters are similar, so it is usually possible to make sense of the parameters. Ct imaging information sheet health physics society.
First, ct forms a crosssectional image, eliminating the superimposition of structures that occurs in plane film imaging because of compression of 3d body structures onto the twodimensional. The centre for medical, health and environmental physics, queensland university of. Pregnant women are advised not to have ct scans as there is a risk the ioising radiation may cause some damage to the dna of the unborn child. The quiz below is designed to help you revise what you know about ct physics and instrumentation.