Radiology and ultrasound are the primary diagnostic imaging techniques available to the veterinarian. The responsibility to provide useful diagnostic images usually falls on the shoulders of the veterinary radiologist/radiographer. The book has twenty four s prepared as per the syllabus framed by Veterinary Council of India (VCI) will assist veterinary students in their understanding the radiology and other diagnostic imaging technology in veterinary discipline and act as an excellent complement to the students both at undergraduate and postgraduate level, interns, veterinarian who are called upon to diagnose an unfamiliar species. Present book is aimed to provide a s: review questions, contains more than two hundred solved objective types questions for various entrance tests viz: Pre- P.G, ICAR-JRF, ICAR-SRF, ARS, Pre-IAS, State PSC, State civil services examination and interviews. At the end, available glossary literature on imaging related terms has been incorporated for the benefit of ready and quick revision. The subject matter in the book is so graded that undergraduate and post-graduate students, veterinary surgeons working in the field, teachers and as well as research scholar in veterinary surgery and those interested in the welfare of the farmers could benefit from the book.
Preface Radiology and ultrasound are the primary diagnostic imaging technique available to the veterinarian. The responsibility to provide useful diagnostic images usually falls on the shoulders of the veterinary radiologist/radiographer. The book in the concise form is a first publication on ‘‘diagnostic imaging’’comprises of approximately 250 pages and runs in twenty four chapters prepared following the syllabus framed by Veterinary Council of India (VCI) will assist veterinary students in their understanding the radiology and other diagnostic imaging technology in veterinary discipline. It can act as an excellent complement to the students both at undergraduate and postgraduate level, interns, veterinarian who are called upon to diagnose an unfamiliar species. Present book is aimed to provide a exercises: review questions, contains more than two hundred solved objective types questions, help reinforce key information for various entrance tests viz: Pre- P.G, ICAR-JRF, ICAR-SRF, NET, ARS, Pre-IAS, State PSC, State civil services examination and interviews. At the end, available glossary literature on imaging related terms has been incorporated for the benefit of ready and quick revision. The subject matter in the book is so graded that undergraduate and post-graduate students, veterinary surgeons working in the field, teachers and as well as research scholar in veterinary surgery and those interested in the welfare of the farmers could benefit from the book. Readers may find it helpful to refer back to those chapters if they wish to develop deeper into subject matter or reference not included in this Essentials book. At the end of the book detailed references are included for ready reference.
· Radiology (Roentgenology): the science, which deals with diagnostic (radio-diagnosis) and therapeutic applications (radiotherapy) of radiant energy particularly of X-rays. · Veterinary radiology: the science, which deals with the uses of radiant energy for diagnostic (radio-diagnosis) and therapeutic applications (radiotherapy) in domestic, zoo, laboratory, exotic animals and birds. · Veterinary radiologist: a qualified person in radio-diagnosis and radiotherapy. · Radiography: is the making of film records (radiographs) of internal structures of the body by passing X-rays through the body to act on specially sensitized film.
Within a few weeks after November 8, 1895, Wilhelm Conrad Roentgen made the discovery of X-rays, they were being used in medicine and many sophisticated medical applications. This single discovery of X-rays revolutionized the entire medical field and developed into a separate discipline in the diagnostic and therapeutic applications in human beings and animals. On 10 December, 1901, Roentgen received the first Nobel Prize for Physics in recognition for discovery of X-rays. Radiography in veterinary practice may not always be used to arrive at a final diagnosis of the disorders. In the last few years, various types of X-ray scanners have been developed that allow highly detailed views of a particular section of the body. One type, known as a computerized tomography (CT) scanner, sends narrow beams of X- rays at various angles through a patient’s body. The information obtained from the X-rays is processed by a computer to produce an image of a cross-section of the body. The image shows much more detail than an ordinary X-ray picture. A section of the body can be studied in three dimensions by producing a series of adjacent cross-sectional images. Nevertheless, radiography remains a valuable modality in diagnostic purposes and has significantly extended the usefulness in medicine and research.
Radiographic positioning refers to placement of the body in respect to linear alignment of X-ray tube and film. Correct positioning is a most important prerequisite to obtain a diagnostic radiograph. Misinterpretations can result from inaccurate positioning. Label the film before exposure with anatomical lead markers/ X-rite tape. The anatomical markers should be placed in close proximity to the area of interest without overlying important structures. At least two exposures of the part at 900 to each other should be taken to get complete anatomical information of the part.
Structure of matter: every structure is made up of elements. Elements can join together to make compounds. The smallest particle of a compound is a molecule. The periodic table gives details of all elements. Nucleus: the center of atom containing protons and neutrons and hence almost whole mass of the atom. Atom: the smallest units of matter composed of electrons are negatively charged, protons have a positive charged and neutrons are neutral. If there are more electrons atom will be negatively charged, if there are more protons it will be positively charged. The total charge of electrons is equal to protons and hence the atom is electrically neutral.
To understand how radiographs are produced by using X-rays, an understanding of how photons of diagnostic range can interact with matter is necessary in five possible mechanism of interaction: · Coherent scattering. · Photoelectric absorption. · Compton scattering. · Pair production. · Photodisintegration.
· An X-ray tube is an energy converter. It receives electrical energy and converts it into two other forms: X-radiation and heat. · It is a source of X-rays used in diagnostic radiology. · Designed and constructed to maximize X-ray production and to dissipate heat as rapidly as possible. · It is a thermo ionic diode type electronic vacuum tube where X-rays are produced. · A basic element of an X-ray tube (Figure) consists of the cathode, anode, glass tube and tube housing.
A tube rating chart is a guide regarding operational limits of the X-ray tube for single and multiple exposures and permissible heat load of the anode and the tube housing. It is an essential component for obtaining diagnostic X-ray examinations is a consistent way. The tube rating chart provides important information on the maximum safe exposure time that can be used with specific mA and kV setting. If lower than designated exposure times are used, tube damage may occur. The size of the anode focal spot determines the rating of the tube because size controls the amount of energy it can absorbs and convert into X-rays and heat. Therefore, one should never use an X-ray chart formulated for another X-ray machine (even those made by the same manufacture) without making appropriate changes. Knowledge of three charts is important to extend tube life and includes tube rating chart, anode heat cooling chart and housing cooling chart.
X-ray photons are produced as a result of electrons hitting metal while extremely rapidly moving at high speed. This is achieved through the application of an electric current to a cathode (negative electrode) via a high voltage power source (electricity) which enables electrons to be released from the cathode into the X-ray tube. These electrons, being negatively charged, are attracted to the anode (positive electrode or target). When the electrons strike the metallic target (anode) in the tube, X-rays and heat are produced. Basically the process of producing an X-ray involves a source that produces X-rays and radiating them through a body or object, where they are absorbed at different rates until they are detected by a sensitive film or cassette. It should be mentioned at this point that most of the energy of the electrons is not converted into X-rays but is dissipated as heat. In fact 99% of the energy dissipated in the target is lost as heat, and only 1% is converted to X-ray energy.
X-ray Machines There are many factors to consider when choosing X-ray equipment. The need of an individual practice varies depending on the species majority and case work load. Types of X-ray machines: X-ray machines can be grouped into 3 categories: I. Portable X-ray Machine · Is one that can be carried to the animal. · Portable X-ray machines are widely used in veterinary practice. · The maximum output is 15 to 35 mAs and kV ranges from 70-110 kVp. · Cost is less and easy to move around and transport. · Suitable for X-raying of thin and small parts (limbs below stifle and elbow of large animals and can be used taking X-rays of abdomen an skeletal systems of small animals).
1. X-ray beam collimators: Comprised of 2 independently-acting sets of adjustable lead shutters. These are the devices made of lead and are used to restrict X-ray beam up to a desire area. In diagnostic radiology they are essential for safety of the patients, and persons and also to prevent fogging of films due to unnecessary radiations. The collimator is the most effective of beam limiting devices.
To set up of an X–ray (radiology) section following points should be considered while planning: 1. Anticipated present work load (number of cases and species of animals to be X-rayed) and future requirement in the next 10-15 years. 2. Financial resources available. 3. Type of equipment to be installed for radiographic work. 4. Requirement of radiation safety enforcing agencies e.g. of Bhaba Atomic Research Centre, Mumbai. The overall set up of radiology section should consider the following requirements:
Handling X-ray film is delicate and should not be handled carelessly or roughly. Avoid touching its surfaces, holding it as near the edges as possible with clean, dry hands. It is sensitive to maltreatment of any kind; heat and light adversely affect the emulsion. It can be handled safely and rapidly for all radiographic purposes as long as the X-ray specialist uses precaution to avoid the production of foreign marks (artifacts) on the film.
The radiographic appearance of various tissues is influenced by a number of factors which determine the character of X-rays. Various exposure factors control the radiographic dentsity, detail and contrast: milliamperage (mA), time (sec), kilovoltage (kV), focal spot/film distance (FFD) and object-film distance (OFD), thickness and nature of the part radiogaphed, speed and type of film and intensifying screens, temperature and time of developing, grid type, incoming line voltage, make and type of X-ray machine. Of these, first five exposure factors (milliamperage (mA), time (sec), kilovoltage (kV), focal spot/film distance (FFD) and object-film distance (OFD) are very important as radiographic technique chart may be worked out by varying one or more of the five factors. These exposure factors are integral to image quality and should, therefore, to be adjusted appropriately in order to achieve a diagnostic radiograph of optimal quality (image contrast, brightness and clarity).
A diagnostic radiograph is defined as one showing the tissues adequately penetrated, sharply outlined, and the variations in tissue opacity sufficiently demonstrated. An ideal diagnostic radiograph should have excellent detail, correct density and proper scale of contrast. The sharpness of the image determines the detail or definition of an image. There are two factors in radiographic quality control, viz: photographic and the geometric effect. Density, contrast and detail are photographic aspects of radiographic quality. Detail and distortion are geometric aspects of radiographic quality. Because a radiograph is a two-dimensional (2-D) image of a three-dimensional (3-D) object, the appearance of a radiographic image varies with the patient’s orientation in relation to the primary X-ray beam.
One of the most important pieces of information in the field of X-rays is a radiographic technique chart. If one select exposure factors from a good rating chart, consistent radiographic examinations of diagnostic quality will be obtained. In addition, there will be a saving of X-ray films because waste from repeated exposures will be avoided. There are several types of techniques chart that can be formulated, each type must be formulated with the goat of maximum potential of a particular X-ray machine. Perhaps the most popular type of technique chart used by veterinarians is a variable kilovoltage technique chart. A variable mA second chart is probably more appropriate for the most powerful X-ray machine. However, combination of variable kilovoltage and mAs technique chart is best. Such charts take into consideration the need to adopt a technique chart for different body systems, such as a thoracic and abdominal study, as well as examination involving the musculoskeletal system. The principle of how to prepare a variable kilovoltage technique chart along with an example of such a chart is given.
The X-ray film is the major element that record the image of part exposed with X-rays. Although the situation is changing with the introduction of new technologies in recent years. The film can be exposed by the direct action of X-rays, but more commonly the X-ray energy is converted into light by intensifying screens and this light is used to expose the film. The X-ray film is somewhat similar to photographic film in its basic composition. However unlike photographic film, the light (or radiation) sensitive emulsion is usually coated on both sides of the base of X- ray film so that it can be used with intensifying screens. Because of its importance to medicine, X-ray film is manufactured with consistent uniformity and quality, which facilitates standardization of exposure and processing.
After the patient has been radiographed, the exposed X-ray film is processed to produce the consistent quality radiographs. Film processing can be manually, or use an automatic film processor. Manual film processing is a multi-stage process involving five basic steps in processing X-ray film: i) Developing ii) Rinsing iii) Fixing iv) Washing v) Drying.
Artifacts are any unwanted radiographic densities in the form of blemishes arising from improper handling x-ray film, exposure, processing, housekeeping or setting up a technique for an examination. Artifacts will reduce the overall quality of the radiograph and in certain cases may nullify its diagnostic outcome. An idea about the possible errors is desirable in order to adopt corrective measures.
Orthopaedic Radiography Radiography as an aid to diagnosis the orthopaedic cases has become an integral part of every modern hospital. This technique may also be helpful in detecting some previously unrecognized lesions in the area radiographed. The radiologist must be aware of the radiological anatomy of part being examined, and of its normal variation with age, species and breed. The anatomical features which can be appreciated in a radiograph are:
Contrast radiography: The radiographic technique which employ the use of contrast media to identify a soft tissue structure or an organ and pathological findings which may be difficult or even impossible to visualize clearly in plain films due to lack of contrast with surrounding tissue is known as contrast radiography. This is a special radiographic techniques/procedures may be required to supplement or confirm the information obtained from plain or survey radiography. The substances used for this purpose is called contrast agents/medium/materials.
Radiology has been an important diagnostic modality in exotic animals and birds (includes rodents, reptiles and fish). The radiographic equipment needed for radiography of exotic animals and birds is basically the same to that used for domestic animals. A high-milliamperage (mA) X-ray machine, having 200- or 300 mA unit is recommended to allow the use of a short exposure time (1/40 seconds) or less are preferred. Maximum kilovoltage (kVp, 40-75) is less important for avian and exotic radiography than for domestic animal radiography. As with other species, at least two radiographic views at 900 angles to each other are recommended. However, restraining and knowledge of radiographic anatomy of different species of exotic animals and birds are the prerequisite for the modality. Restrain and immobilization:
Diagnostic imaging refers to technologies that doctors use to look inside the body of the patient for clues about any disease condition. A variety of machine and techniques can create pictures of the structures and activities inside the patient body. In India, some of these modalities like digital radiography and ultrasonography are being used at some of the veterinary colleges and reaseach institutes while at some places some of the veterinarians have access to the techniques like computed tomography (CT) and magnetic resoncace imaging (MRI) of the human hospitals. So this is the responsibility of the scientists and researchers engaged in the advancement of the diagnostic imaging and the manufacturing companies to make these facilities cot effective so that an animal of a common man can be benefited with these facilities.
Radiation therapy is the delivery of ionizing radiation to a specific body areas with the goal of obtaining maximum lesion control with minimal complication. Radiation therapy is based on the fact that ionizing radiation is lethal to the cells, particularly rapidly dividing ones. Normal cells in the irradiated area may be as sensitive to ionizing radiation as tumor cells. Therefore, the normal tissue response limits the amount of ionizing radiation that can be tolerated by the patient. Effective use of radiation therapy requires an understanding of the physics of the radiation used and normal cellular and tumor biology as it relates to radiation therapy as well as an appreciation of the clinical application of veterinary radiation therapy.
It has been well established that the risk of health problems rises as the amount of radiation exposure increases. All types of radiation produce changes in the living tissues. The resultant cellular injury causes physiological and pathological changes leading to “Radiation sickness”. The radiation effects may be somatic or genetic. Somatic effects are harmful to a person in his lifetime whereas genetic effects affect generations. Radiation may cause changes in complex molecular systems of living cells, primarily in following two ways :-
Glossary A, an: Prefixes signifying without, lack of, e.g. atypical is not characteristic of type. ab, abs: Prefixes signifying away from, departure, eg abduct is to draw away from median plane or axis. Absorb : To suck in, as in a sponge; to assimilate fluids or other substances from skin. Absorbed dose: The amount of energy deposited by ionizing radiationin a unit mass of tissue. It is expressed in units of joule per kilogram (J/kg), and called “Gray” (Gy). Absorption unsharpness: The unsharpness in the image due to variations in absorption throughout a three-dimensional structure, caused by the particular shape of that structure. For example, a spherical object projects “unsharp” edges onto film. Absorption: As applied to radiography, the act of attenuating an X-ray beam. Tissues of different densities have differing numbers of X-ray photons and therefore appear relatively “blacker” (less dense) or “white” (denser) on an X-ray film. Lead, which is denser than most materials, is one of the best absorber of X-rays. Activator: Chemical, usually acetic acid in the fixer and sodium carbonate in the developer, used to neutralise the developer and swell the gelatin.
Exercise: Review Questions The following exercises are to be answered by marking the lettered responses that best answers of the question or best completes the statement or by writing the answer. After you have completed all the exercises, turn to “ Check Your Answers” at the end of the lesson. Answers are given to most of them in “Check Your Answers” except for the long types.
Check Your Answers 1. Photons. 2. Wilhelm Conrad Roentgen 3. Wilhelm Conrad Roentgen, Bavarian physicist discovered the X-ray on November 8, 1895. 4. Wilhelm Conrad Roentgen 5. Richard Eberlein 6. Charles Dotter 7. more energy 8. short, high 9. penetrate 10. protons and neutrons 11. Air
References/Selected Readings Ansari, M.M. 2011. Advances and application of diagnostic ultrasonography in Veterinary practice-a review. Livestock Line. 5 (3): 11-14. Ansari, M.M. 2013. Myelography in Veterinary Practice. Handbook on short course on diagnostic imaging, SKUAST-K, Srinagar, pp 28-34. Ansari, M.M. 2013. Contrast enhanced unltrasonography. Handbook on short course on diagnostic imaging, SKUAST, Srinagar, pp 64-73. Becher, H and Burns, P.N. 2000. Handbook of Contrast Echocardiography. Berlin: Springer Verlag. Bojrab, M. J., Ellison, G.W. and Barclay, S. 1998. Current techniques in small animal surgery. 4th edition, William and Wilkins, A Waverly Company, London. Bowden, C. and Masters, J. 2002. Quick reference guide to veterinary radiography kits. Butterworth Heinemann Publisher, New York. Bushberg, J.T., Seibert, J.A., Leidholdt, E.M and Boone.J.M .2002. The essential physics of medical imaging, Second edition, Lippincott Williams and Wilkins, pp 1-15. Connor, J.J.O.2005. Veterinary Surgery. 4th edition, CBS Publishers and Distributors, Delhi-110032. Denny, P. P. and Heaton, B. 1999. Physics for Diagnostic Radiology. USA: CRC Press. DileepKumar, K.M. and Ansari, M.M. 2011. Computed tomography (CT) in Veterinary practice –a review. Livestock Line. 5 (7): 9-14. Douglas, S.W., Herrtage, M.E. and Williamson, H.D. 1987. Priniciple of veterinary radiography, 4th edn, Bariiere Tindal, London. Easton, S. 2006. Veterinay radiography a workbook for students. Elsvier Butterworth Heinemann Publisher, New York. Frank, E.R. 2002. Veterinary Surgery. 7th edition, CBS Publishers and Distributors, Delhi-110032.
