Lecture 1: Medical Physics PDF

Terminology, Modeling, And Measurements Dr. Ahmed Jassim Allami [email protected]  Goals for lecture 1 Examine what we mean by medical physics and describe some related and overlapping disciplines. Discuss modeling, an essential concept in science, engineering, and medic...

Terminology, Modeling, And Measurements Dr. Ahmed Jassim Allami [email protected]  Goals for lecture 1 Examine what we mean by medical physics and describe some related and overlapping disciplines. Discuss modeling, an essential concept in science, engineering, and medicine. Understand measurement and list types of measurements. Define the accuracy and precision Structure of the lecture Medical Physics 01 Defension of Medical Physucs Imaging Methods 02 Types of Imaging techniques Measurement 03 Importance of measurments in medicine Units 04 Understand units in Medicine  Definition Medical physics is the application of physics in Medicine. All the disciplines in physics can have a direct relationship with Medicine: Such as: Mechanics, electromagnetics, etc… The main two advantages of medical physics is used for diagnosis and treatment.  PHYSICS AND MEDICINE The two types of medical procedures that are based on physics are diagnosis and therapy(treatment). what are the types of medical procedurs ? what are they based on ?  THE DIAGNOSTIC PROCESS Diagnosis of diseases or injuries is usually a two-step process: 1. The first step is obtaining information from the human body in the form of images that are produced by physical interactions within the body. 2. The second step is the ‘reading of the image’ and interpreting or translating that information into a medical diagnosis. This last step is usually performed by qualified medical doctors, generally radiologists.  THE THERAPEUTIC PROCESS There are several forms of therapy based on the application of various forms of physical energy to the body to treat and hopefully cure various diseases, injuries or other abnormal conditions. The use of ionizing radiation is the medical specialty of radiation oncology or radiotherapy and is done by or under the direction of qualified medical professionals, generally physicians certified in that field. Thank you!  Imaging Methods or Modalities Radiography: The formation of an image by passing an x-ray beam through the body and recording the image on film or digital media.  Imaging Methods or Modalities Mammography: A specific type of radiography developed for breast imaging. It provides for visualization of signs of breast cancer and other conditions not visible with conventional radiography  Imaging Methods or Modalities Fluoroscopy: In fluoroscopy, the same principle as in radiography is applied to obtain real-time and continuous images especially useful for observing motion.  Imaging Methods or Modalities Computed tomography (CT): CT is an x-ray imaging method that has two major advantages over radiography. Tomography is the process of ‘slicing’ and producing images of individual slices of the body so they can be viewed directly.  Imaging Methods or Modalities Magnetic resonance imaging (MRI): This technique produces images that often look like CT images but is based on different tissue characteristics. Images are produced by placing the body in a strong magnetic field which produces the condition of RF resonance in the tissues  Imaging Methods or Modalities Ultrasound imaging: High-frequency sound, or ultrasound, is used for medical imaging in two ways: 1. First, pulses of ultrasound are transmitted into the body, resulting in reflections or echoes which display the tissue structure characteristics. 2. The Second is using the Doppler physics principle to produce images of flowing blood  Imaging Methods or Modalities Nuclear medicine or radionuclide imaging: uses radioactive material inside the body to see how organs or tissue are functioning (for diagnosis) or to target and destroy damaged or diseased organs or tissue (for treatment).for example (PET scan) Thank you! Measurement One of the main characteristics of science is its ability to reproducibly measure quantities of interest. The growth of science is closely related to the growth of the ability to measure. 1-Quantitative measurement 1. Thermometer: which measure the temperature. 2. A weighing machine to measure the weight. 3. Sphygmomanometer to measure blood pressure. 4.Syringes of different sizes for injection and aspiration of blood and fluid from the body 2- Qualitative measurement gives information about the inside of the body ,such as x-ray image , computed tomography ( CT scan ) , ultrasound (US ) image , magnetic resonance image ( MRI ) Measurement There are many other physical measurements involving the body and time. We can divide them into two groups:- 1. Measurements of repetitive processes, such as pulse. 2. Measurements of nonrepetitive processes, such as how long it takes the kidneys to remove a foreign substance from the blood. Measurements of the repetitive processes usually involve the number of repetitions per second, minute, hour, and so forth. For Example: - The pulse rate is about 70/min. The breathing rate is about 15/min. Measurement When a physician must decide if the patient is ill or not, and what the illness is? After a physician has reviewed a patient’s:- 1. Medical history. 2. The findings of the physical examination. 3. The results of the clinical laboratory measurements The decisions are two types: - 1. Right decisions. 2. Wrong decisions. Measurement It is not surprising that sometimes wrong decisions are made. These wrong decisions are of two types:- 1. False Positives. 2. False Negatives A false positive error occurs when a patient is diagnosed to have a particular disease when he or she does not have it. A false negative error occurs when a patient is diagnosed to be free of a particular disease when he or she does have it. Note: -In some situations a diagnostic error can have a great impact on a patient's life. Measurement For Example: - A young woman was thought to have a rheumatic heart condition and spent several years in complete bed rest before it was discovered that a false positive diagnosis had been made-she really had arthritis, a disease in which activity should be maintained to avoid joint stiffening. In the early stages of many types of cancer it is easy to make a false negative diagnostic error because the tumor is small. Since the probability of cure depends on early detection of the cancer, a false negative diagnosis can greatly reduce the patient's chance of survival. Measurement Diagnostic errors (false positives and false negatives) can be reduced by: - 1. Research into the causes of misleading laboratory test values. 2. Development of new clinical tests and better instrumentation. Errors or uncertainties from measurements can be reduced by: - 1. Using care in taking the measurement. 2. Repeating measurements. 3. Using reliable instruments. 4. Properly calibrating the instruments. Accuracy and precision Accuracy: Accuracy is how close a measured value is to the actual (true) value. Precision: Precision is how close the measured values are to each other. Difference between Accuracy and precision Both accuracy and precision reflect how close a measurement is to an actual value, but they are not the same. Accuracy reflects how close a measurement is to a known or accepted value, while precision reflects how reproducible measurements are, even if they are far from the accepted value. Measurements that are both precise and accurate are repeatable and very close to true values. Thank you!  Measurements standard and units Physical quantities are classified into fundamental quantities such as mass, length, time and derived quantities such as velocity, acceleration, force, energy….  Units in Medicine In the medical area some units are more used than those of the S.I units, such as: The use of calorie as unit for energy than the Joule (1 𝑐𝑎𝑙 = 4.2 𝐽) The millimeter of mercury for the pressure than the Pascal (1𝑚𝑚𝐻𝑔 = 133.32 𝑃𝑎) or the liter for the volume than the meter cube.  The Scientific notation A number is said to be in scientific notation when it is written as a number between 1 and 10,times a power of 10. For example 0.000000521 can be written as 5.21 × 10−7 When a number is written with the powers of 10, we can use the following prefixes Conversion of the units Examples Thank you!