TAILIEUCHUNG - Ebook Asterion the practical handbook of anatomy (2nd edition): Part 2

(BQ) Part 1 book "Asterion the practical handbook of anatomy" presents the following contents: Radiology, osteology, surface marking, spotters and discussion topics, red alert. Invite you to consult. | Radiology CHAPTER 3 Basics IMAGING MODALITIES The principal imaging modalities used today are 1. Using ionizing radiations like X-rays gamma rays a. Plane radiographs b. Contrast radiographs c. Computated tomography CT PET 2. Using non ionizing radiations a. Ultrasonography Doppler etc b. Magnetic resonance imaging MRI RADIO-OPACITIES The fundamental principle of all radiographic tests that employ X-rays is that different body tissues have a different capacity to block or absorb X-rays. The tissue densities in order of increasing radio-opacity . whiteness on conventional radiographic film or computerized tomograms which are usually seen on a radiograph are 1. Air as found for example in the trachea and lungs the stomach and intestine and the paranasal sinuses. 2. Fat. 3. Soft tissues . heart kidney muscles these are all approximately the density of water . 4. Calcific due to the presence of calcium and phosphorus for example in the skeleton. Radiology 153 5. Enamel of the teeth. 6. Dense foreign bodies for example metallic fillings in the teeth. Also radio-opaque contrast media such as a barium meal in the stomach or intravascular contrast. PLANE RADIOGRAPHS Here no contrast media is used. Produced by passage of X-rays through subject and exposing a radiographic film. Here bone absorbs most radiation causing least film exposure thus developed film appears white at such regions. On the other hand air absorbs least radiation causing maximum exposure so film appears black on such areas. Between these extremes large differential tissues absorb radiation producing grey scale image. Types of Views Posteroanterior view PA view - Here the beam of rays enters from back to front of the subj ect. - Here the structures visible are mostly the anterior most structures. Anteroposterior view AP view - Here the beam enters from front to the back of the subject. - Here the structures visible are mostly the posterior most structures. Lateral view - Here the beam passes through

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