Introduction to Radiology (Part 1) Lecture Notes PDF

Introduction to Radiology (PART 1)  Table of contents 01 Safety. 02 Introduction to Radiology.  Radiation Protection SAFETY Aims to reduce unnecessary radiation exposure As to minimize harmful effects of ionizing radiation ALARA As Low as Reas...

Introduction to Radiology (PART 1)  Table of contents 01 Safety. 02 Introduction to Radiology.  Radiation Protection SAFETY Aims to reduce unnecessary radiation exposure As to minimize harmful effects of ionizing radiation ALARA As Low as Reasonably Achievable BIG THREE OF SAFETY Time Distance Shielding SHIELDING ❑ Avoid the primary X-ray beam. ❑ Be ware of the position of the beam ❑ Know how to position themselves and the machine for the minimum dose. ❑ Wear protective equipments PPE: ❑ Personnel protective equip. Lead Thyroid Leaded Leaded aprons collars goggles gloves Dosimeter  Use shielding Mobile Lead shields curtains Gonadal shields NB ❑Safe dose to be exposed to radiation not to exceed 5000millirems ❑Lifetime do not exceed the age X 1000milliremsLead can effectively attenuate certain radiations due to its high denitsy and high atomic number (82) ❑Radiation weighting factor for x ray is expressed by Siveret (SV) ( old unit : rem –1 SV= 100 rem ❑After 5 yrs the lead aprons must be rejected  Radiological methods of examination 1-X-ray. 2-Computed tomography (CT). 3-Ultrasound (us). 4-Magnetic resonance image (MRI)  X-Ray What is X ray ? 1-A very energetic form of ionizing electromagnetic radiation. 2-Used to take images of the human body. 3- They are produced by an x-ray tube, using a high voltage to accelerate the electrons produced by its cathode. 4-The produced electrons interact with the anode, thus producing x-rays.  X-Ray X-Ray  X-Ray How can X ray produce images of internal structure of the body ? 1Difference in body tissue densities allow us to seen what inside the body by creating shadowgram. 2 The body is composed of may structures of different atomic numbers (the numbers of protons in nucleus). 3 The higher the atomic number the higher the density, & more effectively the X ray is blocked.  X-Ray What are the five basic radiologic densities ? *Metal (bright white) *Mineral (white) *Fluid /Soft tissue (grey) *Fat (dark grey) *Air (black).  X-Ray What are the three key elements of radiation safety? 1- Time ( reduce the time of exposure). 2-Distance (X ray dose is inversely proportional to the distance squared). 3- Shielding ( aprons composed of metals that block X-rays). How can Iorder X ray ? 1- Write complete request contains: A- The personal data of the patient B- Provisional diagnosis. C- Requested image & its positions. D-Other clinical &laboratory data. X-Ray How Iknow if the X ray of diagnostic quality? As physicians we are not only responsible for the pathology in the X ray, but also to assess the quality of the X ray film. 1-An over penetrated film (overexposed) is too dark and may obscure important structures. 2- An under penetrated (underexposed) film can make normal structures as pathological structures. 3- Also the patient should be well centered & well positioned. X-Ray Over exposed Under exposed  CT What is CT? 1-CT provides us with images showing slice through the body. 2-We can vary the thickness of the slice , so we are looking at thin two-dimensional picture representing a volume of tissue.  CT How dose CTworks ? 1-CT uses X ray to produce image. 2-X ray is blocked (attenuated) by tissues depending on their densities. 3-To obtain CT image X ray source rotates around the body in an arc while X ray detector rotates opposite to the source on the opposite side of the body. 4-The computer analyze the number and density of the transmitted X ray creating picture elements (pixels) that will make the final picture. CT CT CT What are Hounsfield units (HU) ? -Sir Godfrey Hounsfield was instrumental in development of the CT. His name is used for the number associated with the grey scale produced during CT scan. Example of CT assigned attenuation value: -Air -1000 HU. - Fat -5 to -50 HU. -Water 0 HU. -Soft tissue +40 to +80 HU. -Calcium +100 to +400 HU. -Cortical bone +1000 HU  CT Limitations of CT: 1 CT can’t distinguish soft tissue as magnetic resonance imaging (MRI). 2 Metals can create artifacts and blurs in the image. 3CT is limited in brain posterior fossa compared to MRI because of dense bones of skull. 4 CT is limited in use with pregnancy. CT What are window setting and how are they used ? -Window widths (Ww) and window levels(WL) are used to optimize visualization of specific structures. -The window level is the midpoint of the gray scale. -The window width is the number of grey shades. If window level is 0 and window width is 1000, they grey scale will be from -500 to +500. The most obvious example of windowing is CT chest. CT Mediastinal window Pulmonary window  CT What is contrast CT? 1 Contrast fluid material is administrated via intravenous route. 2 Itis used in imaging of the vessels , imaging of the chest, abdomen and pelvis , it is very useful in diagnosis of vascular lesions , tumors and inflammatory lesions. 3 Contrast material can be administrated via the oral and or rectal route also.  CT What is coronal , sagittal and 3D reformatted images? Software can covert serial of axial images into coronal or sagittal images and 3D reformatted images.