Diagnostic Imaging Introduction

1. Diagnostic ImagingIntroduction Chatham University January 14, 2014 Rajiv Sawhney, PT, MS, DPT, OCS

2. Diagnostic Imaging • What is it? • Branch of medicine that is concerned with imaging techniques to diagnose, prevent, and treat a disease. • Includes ionizing and non-ionizing radiation • List some?

3. Diagnostic Imaging • Why do we need to study this area of medicine? • Primary care responsibilities • Direct access • Being accepted by the medical community as a professional • Cost saving • Vision 2020

4. Vision 2020 • “By 2020, physical therapy will be provided by physical therapists who are doctors of physical therapy, recognized by consumers and other health care professionals as the practitioners of choice to whom consumers have direct access for the diagnosis of, interventions for, and prevention of impairments, functional limitations, and disabilities related to movement, function, and health.” • APTA House of Delegates

5. Vision 2020 • APTA’s BOD suggests focus effort on 5 areas: • Professionalism • Direct access • The doctor of physical therapy • Evidence-based practice • Practitioner of choice

6. Diagnostic Imaging • Imaging techniques • Plain film radiography • Computed Tomography • Nuclear Imaging • Magnetic Resonance Imaging • Fluoroscopy • Sonography • Arteriography and Venography

7. Diagnostic Imaging • Imaging techniques • Plain film radiography • Computed Tomography • Nuclear Imaging • Magnetic Resonance Imaging • Fluoroscopy • Sonography • Arteriography and Venography

8. Plain Film • Characteristics: • Inexpensive • Very sharp detail of bony structures • Poor detail of soft tissues • Two dimensional summation image • Difficulty detecting subtle changes in bone structure • Easily obtained • Can be portable • Rapid

9. Plain Film • ABC’s of plain film radiography • Alignment • Bony mineralization • Cartilage space • Soft tissues

10. X-Radiation • Electromagnetic vibration (short wave length) • 1/10,000 the wave length of visible light rays • X-rays can penetrate dense substances and ionize matter • Ionization of silver atoms on film produces the gray images • Various densities inherent to the body and attenuation of x-rays

11. X-Radiation • X-rays and gamma rays are able to ionize atoms • Ionization- neutral atom loses or gains an electron • Leads to net charge • Can disrupt the make up of matter and alter life processes • Natural or background and artificial

12. Radiation Exposure • Measuring radiation dosage • Scientific unit of measurement for radiation dose, commonly referred to as effective dose • Millisievert (mSv) • Other measures include rad, rem, roentgen, and sievert • Different tissues and organs have varying sensitivities to radiation exposure, actual dose varies (effective dose is an ave. over the entire body)

13. Radiation Exposure • We are exposed to radiation from natural or back ground sources • Ave person in U.S. 3 mSv per year, 1.5 more in higher elevation than sea level

14. Radiation Exposure

19. Positioning for Radiographs • Chest films are the most common • PA position, patient stands against the film cassette • X-ray tube behind • Lungs more anterior • Structures closer to x-ray cassette are more sharply defined • The farther away the structure the greater the distortion • Distortion is obtained when the structure is outside the central focal ray

21. Identifying right and left • Films are labeled with a registration plate (patient name, case #, date, and facility) • Labeled with right or left (R or L) • Don’t orient film to right or left • When reading position as if you are facing the patient

22. Radiographic Detail • Radiographic density: • Radiolucent – transparency of an object to x-radiation • Radiopaque – lack of transparency to x-radiation • Greater the difference in densities the higher the contrast and easier the identification process • Objects are described as more or less radiodense

23. Radiographic Detail • Radiographic density: • Human body – (4) • Air- • Fat- • Water- • Bone- • (air-fat-water-bone-contrast media-heavy metals)

24. Radiographic density: • Radiographic density: ?? ?? ?? ??

25. Radiographic Detail • Radiographic density: • Human body – (4) • Air- lungs, stomach, intestines • Fat- subcutaneous, around organs, along muscle sheaths • Water- muscle, bl. Vessels, cartilage, tendon, ligament, nerve, and skin • Bone • (air-fat-water-bone-contrast media-heavy metals)

26. Computed Tomography • Computerized enhancement of a series of radiographs at consecutive planes thru a body part. • Three dimensional, can get sections • Good spatial resolution • Good contrast resolution • Best for identifying foreign bodies • Usually requires contrast agents • Not portable • Moderately expensive

27. Computed Tomography • CT is the preferred method for assessment of osseous based abnormalities • Trauma • Acetabular fractures • Congenital disorders (dysplasia)

28. Computer Axial Tomography • Tissue contrast • Function of tissue composition • Similar to radiodensity brightness scale for plain film radiographs • Brightness scale • Brightest to darkest • Lead, bone, muscle, blood, liver, fat, and air

35. Nuclear Imaging (Bone Scan) • Technique where the emission of a injected radioactive tracer is used to construct an image of the patient • Poor spatial resolution • Nonspecific alone • Small radiation dose • Sensitive to early physiologic bone changes • Relatively expensive

36. Bone Scan • Indicates areas of increased metabolic activity (hot spots) • Increase uptake of radioactive tracer • Useful in detection of bony metastatic disease, AVN, arthritis, Paget disease • Should be used in conjunction with plain films, CT, or MRI to detect the type of lesion (not very specific)

39. MRI • Method of imaging based on the interactions of atomic nuclei with a magnetic field • Three dimensional sectional images in any plane • No radiation • Good spatial resolution • No real time imaging (coming soon) • Allow image processing • Lengthy time test • Not portable • Expensive • Requires gaiting for cardiac and abdominal applications

40. MRI • Two main pulse sequences (T1 and T2) • Have dramatic effect on the appearance of the image • Pulse sequence weightings relate to the type of spinning the protons can do and the type of environment of the protons • A third pulse sequence (proton density) can also be used as well as a fat suppression mode (better delineation of certain features)

41. MRI • Interpretation • T1 weighted images (fat is bright and fluid is light), Low signal (dark) to High signal (bright) bone, ligaments, tendons, gas, muscle, fluid, organs, bone marrow, fat (anatomy) • T2 weighted images (fat is light and fluid is bright), Low signal (dark) to High signal (bright) bone, ligament, tendons, gas, muscle, fat, organs, water and tissues with high water content ie., edema (pathology)

42. MRI • Procedure: • Patient lies with in a large bore (powerful magnet)- 0.5 to 2 T • T = Tesla (magnet rating unit) • Gauss is also used to measure magnet strength • 1 T = 10,000 gauss • .5 to 2 T approved for medical imaging • Most powerful magnets up to 60 T • Earth’s magnetic field = .5 gauss

48. Fluoroscopy • Uses radiography in real-time • Allows direct visualization of needle placement • Moderately expensive • Same as radiography • Very useful in case of dislocations esp the hip, also in cases where pins placement is necessary for femoral neck fxs