At the end of this lecture the students should be able to understand The advantages of good working relationships and close collaboration with the imaging department in planning appropriate ID: 1044358
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1. Diagnostic ImagingObjectivesAt the end of this lecture the students should be able to understand:• The advantages of good working relationships and close collaboration with the imaging department in planning appropriate investigations.• The basic principles of radiation protection.• The principles of different imaging techniques and their advantages and disadvantages in different clinical scenarios.
2. Diagnostic ImagingIntroduction:Imaging
3. Diagnostic Imaging
4. How and what to choose ?Simplest and cheapest test “hoping it will answer the question”Know the limitation and complication of each test.Availability, experience, and cost in addition to clinical presentation.Diagnostic Imaging
5. How to request imaging ? Collaboration between the radiologist and the referrer► What do you want to know ?►State the clinical problem.►Give provisional diagnosis.►If you are not sure about the best method to reach the diagnosis, consult and discuss the problem with the radiologist.►Some information are of value (past medical Hx., drugs, LMC)Diagnostic Imaging
6. Diagnostic ImagingInterpreting Images:
7. Diagnostic ImagingHazards of Imaging:☆Contrast media:(low osmolarity contrast media) LOCM X HOCM(high osmolarity contrast media)Allergic reaction and nephrotoxicity ➣ 5-10 times safer. ➣ Serious reactions 1:2500 cases. ➣ Life threatening reactions 1:25000 cases. ➣ No difference in the risk of sudden death. ➣ Allergic reaction time and treatment. “early, steroid”
8. Diagnostic Imaging➣ Patients with renal impairments: (DM) - Get a recent creatinine and urea level. - Risk X Benefit - Minimal dose of LOCM. - Patient well hydrated. - N- acetylcysteine for renal protection. - Metformin Lactic acidosis.(stop / 100ml of contrast / normal renal function)➣ Gadolinium containing contrast ??- Allergic reaction is rare (mild 1:200 – sever 1:10000)- Nephrotoxic (pre-existing renal disease)NSFC/I : neonate, RF, liver transplantation, and pregnancy.
9. Diagnostic Imaging☆ Hazard of Ionizing radiation. (15% of total human radiation) Predictable, dose dependent tissue effects lens (cataract) , chronic exposure to radiation All or nothing effects (stochastic) cancer , not dose dependent, but increased in likelihood with increased radiation dose.Plain films (chest and limbs)Cancer risk 1:1000000CT examination of abdomen and pelvisCancer risk 1:1000
10. Diagnostic Imaging - Fluoroscopy and portable machines use much more radiation to achieve the same result and possibly lower quality.When using the image intensifier, lead aprons, thyroid shields, lead glasses and radiation badges should always be worn.- Pregnancy in the female patient or staff must be excluded
11. Diagnostic Imaging
12. Diagnostic ImagingConventional radiography- Roentgen 1895.- Chest, trauma, orthopaedics.- Depends on the degree of tissue absorption of the X ray emitted from the machine (Black and White).- Air, fat, soft tissue, bone and mineralization, and metal.Advantages: Cheap Available Easily producible and comparable Relatively low dose of radiation
13. Diagnostic ImagingDisadvantage : Lack of soft tissue differentiation.➣To overcome this problem: Use of contrast materialsFluorescent screen
14. Diagnostic ImagingUltrasound:- High frequency sound waves (3-20MHz) generated by a transducer.Time and direction of waves reflection will generate an image.High frequency greater resolution. Less penetration.Abdomen 3-7 MHz for superficial structures (high frequency)- Endocavitary transducers e.g. transvaginal, transrectal, endoscopic
15. Diagnostic ImagingReflection of US waves from a moving objects (RBCs)Change in frequency of US wavesMeasure these changesSpeed and direction of movementPrinciples of Doppler US
16. Diagnostic ImagingAdvantages of US: Cheap Easily available - Assessment of liver, biliary system, and renal tract. (1st line invest.)Gynecology and Obstetric.Thyroid and testicles (High frequency transducer).Interventional radiology by using the needle for biopsy and drainage.Soft tissue foreign bodies.Ligament, tendon, and muscle injuries.
17. Diagnostic ImagingDisadvantages of US: ➣ Highly operator dependent ➣ Difficult in getting images to areas beyond bony or air filled structures. ➣ Images can not be reliably reviewed away from the patient. ➣ Needs a long learning curve in some area of expertise. ➣ Resolution depends on available machines.
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19. Diagnostic ImagingComputed tomography (CT): A great development in CT technology in the last 30 years.Conventional Helical Spiral Multidetector machine.Gantry containing X ray tubes, filters, and detectors.Revolves around the patient acquiring information at different angles and projections.The information is mathematically reconstructed to obtain 2D images.
20. Diagnostic ImagingHigher contrast resolution than conventional radiograph.Assessment of different phases (early and late) (arterial and venous).Used in thoracic, abdominal, neurological, muscloskeletal , and trauma imaging.CT angiography.Virtual colonoscopy and bronchoscopy.3D image aiding in surgical planning.
21. Diagnostic ImagingDisadvantages: Cost High dose of radiationCT abd. & pelvis = 500 CXR
22. Diagnostic ImagingMagnetic resonance imaging (MRI):Integral part of imaging arsenal with expanding indications.Nuclei have an odd number of electrons or protons that have a characteristic movement in a magnetic field (precession) producing a magnetic moment as a result of this motion.Applying a strong magnetic field by the MRI result in alignment of these nuclei within the magnetic field producing a magnetic moment.A radiofrequency pulses is then applied to alter the nuclei motion.Once the radiofrequency pulses removed, the nuclei realign themselves with the main magnetic field (relaxation). During this time they emit a radiofrequency signals that recorded to produce image.Tissue characteristics define the manner and rate at which nuclei relax.
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24. Diagnostic ImagingNuclear medicine: ➣Radioactive element or radionuclide are used in addition to ionizing radiation.➣ Gallium, Technetium, Thallium, and iodine are examples of radioactive substances.➣ A detector such as gamma camera used to detect and localize the emission of these radioactive elements from the patient.➣ Each substance had an affinity to certain tissue.(large no. of elements)➣ Nuclear medicine provides functional status of the system.
25. Diagnostic ImagingBone imaging metabolic diseases metastatic diseases arthropathy occult infection traumatic injuryGenitourinary system obstructionDynamic study (function and perfusion) renovascular hypertension renal transplant
26. Diagnostic ImagingThyroid and parathyroidCardiac diseases(ischemia)Pulmonary embolism.Inflammatory bowel diseases.Occult infection.➣Positron emission tomography (PET)18F , metabolic characters of tissue.Cost, very limited availability, and relatively low spatial resolution (PET/CT)
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28. Thank you