Introduction to Diagnostic Imaging and the Modalities - Radiology - Spring 2022

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Patient with progressive SOB and CP over the past several days to weeks. What is the initial study of choice?

1) CXR
2) MRI
3) CT
4) Nuclear
5) Echo
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Terms in this set (87)
Use ionizing radiation to produce an imageRadiating imaging modalitiesWhat are some imaging services that are considered radiating imaging modalities?-Radiography, which includes fluoroscopy (planar) -Computer Tomography (CT) (3D cross-sectional) -Nuclear Medicine (uses gamma radiation), which includes (PET) (positron emission)What are some imaging services that are considered non-radiating imaging modalities?MRI and UltrasonographyDo not use ionizing radiation to produce an imageNon-radiating imaging modalitiesFor the pelvic region, what do we typically want to avoid if there are other options?Radiation exposure, but sometimes its the best modality. This is where we would weigh the risk vs benefitForm of energy that acts by removing electrons from atoms and molecules of materials that include air, water and living tissueIonizing radiationDoes not have enough energy to remove electrons from atoms and moleculesNon-ionizing radiationWho discovered X-rays?RoentgenRefers to the medical images that are the "shadows" projected onto a flat plane (planar) when x-rays pass through a patientRadiographyUtilizes a screen-film system within a film cassette as the x-ray detectorFilm Radiography-In place of film uses an imaging plate -the plate is run through a special laser scanner, or CR readerComputed radiography-Provides a filmless and cassette less system for capturing x-ray images in digital format -direct read-out detectors produce an immediate digital radiographic imageDirect radiographyActual thickness and composition of the object, affects x-ray absorption/transmissionPhysical densityWhat are the four basic physical densities?-Air -Fat -Soft tissue -Bone/MetalDegree of blackness on the radiographic imagesRadiographic density - (black to white on a radiologic image)Absorbs the least x-rays and appears "blackest" on conventional radiographsAirGray, somewhat darker (blacker) than soft tissueFatThe most dense, naturally occurring material; absorbs most x-raysCalcium (Bone)Usually absorbs all x-rays and appears the "whitest"MetalDenser structures block x-rays better, appear white on radiographRadiopaqueLess dense structures allow x-rays to pass through, appear gray to black on radiographRadiolucentUnit of exposure in airRoentgenAdvantages of radiographyfast, inexpensive, high spatial resolution, widely available, portable, low amount of ionizing radiation to patient, contrast between bone, soft tissue, lung and airDisadvantages of radiography-Poor differentiation between different soft tissue -2D image of a 3D object-Allows real-time observation -digital images are displayed on a television monitor and are recorded as a movie clipFluoroscopy-Low dose x-ray imaging -only method of screening for breast cancerMammography-routine examination consists of two views of each breast (Craniocaudal and mediolateral oblique) -asymptomatic patientScreening Mammogram-initial procedure for evaluating screening-detected calcifications that are not typically benign -begins with the two-view standard mammogram -additional views dictated by history, physical examination, and findings on initial mammography -women with a history of breast cancer and on those with breast implantsDiagnostic Mammogram-Referred to as 3D mammography -allows the breast to be viewed in a 3D format as multiple thin-slice images spanning the entire breastDigital breast tomosynthesis (DBT)Patient comes in with no symptoms, just a routine checkupScreening MammogramIf a patient has a lump, mass or any other sign of potential breast cancer, then what kind of testing do we do?Diagnostic MammogramWhat is the difference between a MRI and a CT?MRI has no ionizing radiation + CT Scan only takes images in the trans-axial angle. MRI is sequences you can take it in any angle-An x-ray beam that rotates along a 360° circular pattern with detectors rotating along the opposite side -Measurements of attenuation of x-rays at different locations and angels are acquired -a cross-sectional image of the body is producedComputed Tomography (CT)This imaging modality is composed of a matrix of thousands of tiny squares called pixels, each of which is computer-assigned a number from -1000 to +1000 HUCTIf a CT descriptor is "high attenuation" what does that mean as far as density?Radiodense or whiterIf a CT descriptor is "low attenuation" what does that mean as far as density?Radiolucent or darkerMeasure of the beam attenuation capability of a specific structure. Also called pixel values, density numbers or CT numbersHounsfield UnitsThe appearance of CT images depends on what two things?Window and level set by userEnhanced (multi-phase) CT, most commonly used in liver, adrenal, and pancreatic imaging, as well as CT arteriography and venorgaphyDynamic contrastWhat imaging modality are indications of: 1) Bone: useful for characterization of fractures or other local changes in bone such as neoplasm or infection 2) Anything well calcified: such as lung nodules 3) In trauma situations when acute hemorrhage is suspected; head injury or possible hemorrhagic stroke patients, for example, can get rapid assessment for intracranial bleeding with non-contrast CT 4) Useful for visualizing internal organs; chest and abdomen 5) Pelvic fractures/trauma (often acute emergencies) usually best seen on ______? - which will depict not just bone but all the tissues, structures, and organ systems involved 6) Usually not used first in children/young adults due to risk of radiation to reproductive organs.CT Scan (these are all CT indications; when to use CT scan)Is blood radiopaque or radiolucent in the brain?Radiopaque; blood creates its own contrast so we don't use contrast for trauma to the headWhat are some advantages of a CT scan?-Speed: relatively quick + large area of coverage in patients with severe/multi-system acute trauma -Contrast resolution b/w different tissues; can see difference between hemorrhage, calcium, or gasWhat are some disadvantages of a CT scan?-higher radiation exposure (10-100x more radiation than conventional x-rays) -patient movement can cause artifacts -cannot differentiate soft tissue injury -IV contrast hazards -not portable (patient must go to the CT scan machine; cannot be done at bedside like a portable x-ray)What is the only imaging modality that depends on contrast agents; gives functioning of body due to the radioactive pharmaceutical given to the patient; the camera is not the radioactive aspect, the patient is.Nuclear MedicineThis imaging modality uses radioactive compounds called radiopharmaceuticals or radiotracersNuclear (Molecular) MedicineVarious body organs have a specific affinity for, or absorption of, different biologically active chemicals. So, what do we give a patient to view how the organ is functioning? And, what is the imaging modality we use to view this?Radiopharmaceutical + Nuclear MedicineProvides targeted therapy for a variety of diseasesNuclear MedicineAcquires many 2D images from multiple angles, which are then reconstructed by computer into a 3D data set that can be manipulated to demonstrate thin slices in any projectionSingle photon emission computer tomography (SPECT)-Operate on a molecular level to produce 3D images that depict the body's biochemical and metabolic processes -They are performed with a positron producing radioisotope attached to a targeting pharmaceuticalPositron emission tomography (PET)What is the most commonly used target molecule in a PET scan?Fluorodeoxyglucose (FDG)-Most often used in the diagnosis and treatment follow-up of cancer -Frequently used to locate hidden metastases from a known tumor or to detect recurrence -Oncologic ____ scans make up about 90% of the clinical use of this imaging -Some tumors take up more of the radio tracer than others and are referred to as FDG avid tumorsPET Scans / FDGCombines anatomic images with metabolic function images, increases the accuracy of a diagnosis.Fusion imagingWhat are some advantages of Fusion Imaging?-highly sensitive -functional and anatomical informationWhat are some disadvantages of Fusion Imaging?-Non-specific -Uses ionizing radiation -Cost of equipment -Extra care in handling of radioactive materialIn an MRI, what is the particle that will align in the same direction as the main magnetic field?Hydrogen protonsGo over MRI slide, no flashcard on thatThe brighter an area on an MRI = the (greater/fewer) the concentration of hydrogen protons?GreaterThe darker an area on an MRI = the (greater/fewer) the concentration of hydrogen protons?FewerWhat is a T1-weighted MRI image?an image on which fat appears white or brightWhat is a T2 MRI image?an image on which fluids appear white or bright; higher water content-Brain tumors or ischemic strokes; Tumors more visible with gadolinium -Any soft tissue pathology; ligament or meniscal tears in the knee, spinal disc herniation, nerve root impingement, bone marrow changes -Pelvic imaging (both because of the lack of radiation exposure to reproductive organs and because of good soft tissue discrimination); ex: uterine fibroids -MRI angiograms can be useful in the study of coronary or cerebral vasculatureMRI; these are the indications of when to order an MRIWhat are some advantages of MRI?-Superb contrast between different soft tissues -Lack of artifact from adjacent bone -Higher resolution than CT -Highlights pathological changes -No ionizing radiation -3D data acquisition/multi-planar -May be fused with CT scansWhat are some disadvantages of MRI?-Machines are more expensive than CT -Patient's are sometimes claustrophobic -Presence of sensitive equipment (pacemakers, cochlear implants (chris), artificial heart valves, ports, pins and screws) -Reduced sensitivity for small calcification and acute hemorrhageSound waves travel into the body and hit a boundary between tissuesUltrasonographyThe body surface that is scanned may be: 1) external, such as in trans-abdominal sonography 2) internal, such as in trans-vaginal, trans-rectal, trans-esophageal, and endovascular sonographyUltrasonographyUltrasonography: 1) White on ultrasound = 2) Light Gray = 3) Gray = 4) Black 5) Blurry =1) Hyperechoic; reflects more echoes, brighter and whiter 2) Isoechoic; equal in echoes to surround structures 3) Hypoechoic; transmits more echoes (reflects less), darker 4) Anechoic; completely black 5) Heterogeneous; nonuniform texture (fluids with internal debris or intestinal contents)Provides valuable information regarding the presence, direction, and velocity of blood flowDoppler SonographyIf we see yellow, orange or red on a doppler sonography what does that mean as far as direction of blood?Towards the transducerIf we see blue, green on a doppler sonography what does that mean as far as direction of blood?Away from transducerWhat imaging modality would we use for the following clinical scenarios: 1) Gynecologic exams 2) Echocardiography 3) Abdominal exams 4) Checking for DVT 5) Severity of carotid artery blockage 6) Procedures 7) Examining breast masses 8) Focused assessment with sonography for traumaUltrasoundWhat are some advantages of Ultrasound?-lack of ionizing radiation -low cost -portability -lack of use of contrastWhat are some disadvantages of ultrasound?-Cannot penetrate gas or bone so lesions within/behind/ above cannot be visualized -Obese patients may be difficult to penetrate -Dependent on the skills of the operator scanningIn a patient with normal renal function, the kidneys eliminate almost all the contrast agents. What is imperative that we order as providers before administrating contrast agents?B.U.N. and creatinineWhat is recommended if a patient is allergic/hyper sensitive to contrast?Pretreatment on re-exposure; antihistamines and corticosteroidsWhat should we keep in mind when giving contrast?Renal function is keyWhat is the contrast used today for MRI?GadoliniumWhen is Gadolinium contraindicated?pregnancy, lactation, renal failure