Fund. 103 Study Guide

Hyperechoic and hypoechoic:

comparisons of echo intensities. lighter= hyperechoic, darker=hypoechoic

Define window width

rayscale (contrast scale); number of densities that are visualized

Define echoes:

reflections produced by tissue interaction

Define AEC:

Automatic exposure control- Employs photo timers to measure x-ray intensity and quality.

Identify types of contrast commonly used in radiology procedures:

Barium for GI procedures. Iodine contrast for GU and IR procedures

Bone marrow syndrome

- Hematopoietic syndrome. Results in infection, hemorrhage and anemia

CNS syndrome

- Seizures, coma, eventual death due to increased ICP.

How thin should high-resolution CT be:

0.625-mm to 1.5-mm slice thickness

Describe three radiation syndromes:

Bone Marrow syndrome, GU Syndrome, CNS Syndrome

Give CT numbers for each tissue

Bone: +400 - +1000 Soft tissue: +40 - +80 Water: 0 Fat: -60 - -100 Lung: -400 - -600 Air: -1000

Anechoic

Echo free, appear dark.

Latent stage

Feel well but body is undergoing biologic changes that lead to..

Manifest stage

Feels full effects, leading to recovery or death.

Genetic

Future generations as result of damage to germ cells. Affected cell is fertilized and develops. Children are more radiosensitive than adults and irradiation of fetus should be avoided.

Define CT number:

Hounsfield scale. CT image (pixel) is expressed in terms of Hounsfield units (HU) corresponding to the x-ray attenuation (or tissue density

Name and describe the imaging features radiologists use:

Location - Area where changes in anatomic features are evident Size - Measurements of changes Density and structure - Abnormal appearance compared to normal Shape and demarcation - Describe anatomic structure changes and involvement Perfusion - Abnormal tissue, relates to vascularity, distinguishes between cystic and solid lesions Integrated - Space occupying in the anatomic structure

GI syndrome

Massive diarrhea, nausea, vomiting, and fever.

Advantages of IR

Most procedures performed on an outpatient basis or require short hospital stay. General anesthesia usually not required. Risk, pain and recovery time are often significantly reduced. Procedures are sometimes less expensive than surgery.

Prodromal stage

Nausea, vomiting, and diarrhea

How is PET scans utilized

images of blood flow or other biochemical functions. images of glucose metabolism in the brain, or rapid changes in activity in various areas of the body

List advantages of ultrasound:

Safety; no effect on tissue. Modality for children and pregnant patients. Quick & inexpensive

Define SPECT

Similar to PET but radioactive substances have longer decay times and emit single instead of double gamma rays. Provides information about blood flow and distribution of radioactive substances in body. Images have less sensitivity and less detailed that PET, but is less expensive. Cardiovascular imaging to chart flow of blood through heart and blood vessels

Describe the late effects of radiation exposure

Somatic Genetic

Who discovered x-rays? When?

Wilhelm Conrad Roentgen in 1895

How did early CT scanners acquire images?

Acquired by rapid rotation of the x-ray tube 360 degrees around the patient.

List advantages to digital mammography:

Acquired in less than a minute. Spot view digital systems are available to help guide breast biopsy. Superior contrast resolution especially in dense breast tissues. Offers possibility of 3D breast tomography using relatively low doses.

Advantages of CT:

CT readily available in most hospitals; Increasingly rapid imaging modality with excellent image resolution, enabling faster and more accurate diagnostic evaluation of patients over a wide spectrum of clinical indications; Data acquired in one scan can subsequently be manipulated to provide multiplanar and 3D reconstructions.

Describe fusion imaging:

Combines anatomic images with physiologic functional images. Provides high degree of clarity to view pathophysiologic changes.

Describe fluoroscopy:

Continuous x-rays to show processes, typically GI. Common exams now being replaced by CT and MRI, but used in interventional radiology.

Name the views used in mammography:

Craniocaudal view and mediolateral oblique view

How ultrasound works

Cross-sectional anatomy at low cost, availability, ability to differentiate cystic, solid, and complex tissues. Non-invasive high frequency sound waves produced by electrical stimulation.

Discuss the need for compression of breast:

Decreases thickness of the breast, reducing scattered radiation and improves contrast. Decreases kinetic blur. Reduces geometric unsharpness by homogenously bringing the object close to the film. Makes breast thickness uniform in film density. Differentiates easily compressible cysts and fibroglandular tissue from more rigid carcinomas. Separates super imposed breast lesions. Reduces radiation dose to breast tissue.

Define window level

Density or brightness; midpoint of total number of densities viewed

Bone scanning

Detects radiation from radioactive substance, collects in bone tissues. Useful for detecting tumors, which have high metabolic activity.

What does nuclear medicine exam show:

Detects tumors, aneurysms, or inadequate blood flow to various tissues, blood cell disorders and inadequate functioning of organs, such as thyroid and pulmonary function deficiencies.

Somatic

Develop in individual. Typically cataract formation and carcinogenesis. Lens very sensitive to radiation. Skin cancers, leukemia, thyroid cancers.

What are the advantages and disadvantages of SPECT:

Disadvantage - Only allows imaging of a small area of interest, the size of camera. Limited imaging parameters causes long exam times. Advantages - Provides useful information for coronary artery disease, ventricular function abnormalities, infection, tumor, stroke, seizures and TBI.

Describe components of x-ray machine:

Equipment include x-ray tube, table with bucky tray, wall mounted bucky. Collimator used to size and shape x-ray field coming out of tube. Film goes in bucky tray.

Briefly explain how x-rays are produced:

Process by which a beam of radiation is reduced in energy when passing through tissue or other materials. Denser the tissue, more x-rays are attenuated. ie more attenuation in bone than air.

Describe stages of early effects of radiation exposure:

Prodromal, Latent, & Manifest stage

Define PET:

Produces images of body by detecting radiation emitted from radioactive substances. Substances are injected into body and usually tagged with a radioactive atom that has a short decay time. These atoms are formed by bombarding normal chemicals with neutrons to create short-lived radioactive isotopes. Detects gamma rays given off at the site where a positron emitted from the radioactive substance collides with an electron in the tissue.

Describe helical scanning

Pt moves through gantry, faster scanning without respiratory motion, provides volumetric data that is reconstructed in coronal, sagittal and axial planes. Used for all imaging now at UCLA

Disadvantages of CT:

Radiation Artifacts: Motion; streak (caused by high-density objects-metal); partial voluming (different tissue within a single voxel leads to averaging of data) Poor tissue contrast when compared to MRI. Occurs in thin adults and children due to lack of intra- abdominal fat separating various tissue planes. Relatively high cost and limited portability. Contrast allergies and renal toxicity.

Disadvantages of IR:

Radiation Iodine used, may compromise kidney function, allergy risk Hematomas at insertion site

Define scatter radiation:

Radiation produced from x-ray photon interactions with matter in such a way that the resulting photons have continued in a different direction.

List ways IR is being used:

Radiologists insert catheter via guidewire, under fluoroscopy, through femoral or radial arteries in order to visualize blood vessels, place stents, remove clots, place chemo directly into tumor and increase effectiveness of medicine without damaging surrounding healthy tissue. Must hold pressure on site for at least 20min.

Explain interventional radiology

Radiology specialty which provides minimally invasive image-guided diagnosis and treatment of disease

Thyroid scans:

Thyroid concentrates iodine, so by injecting radioactive iodine into blood stream, certain tumors can be detected.

Discuss ways to protect from radiation exposure for patients and as technologists

Time - Minimize length of exposure. Distance - Further away from radiation decreases risk. Shielding - Lead aprons, gonadal shielding, thyroid shields.

Describe how different tissues look on x-rays:

Tissue densities show a range of greyness depending on thickness of each tissue. Air is black, metal or contrast material is white. Bodily tissues are varying degrees of grey depending on density and thickness.

Explain how nuclear medicine works:

Uses radioactive substances to image body and treat disease. Looks at both physiology (functioning) and the anatomy of the body in establishing diagnosis and treatment.

Explain how CT works:

Uses x-rays to generate cross-sectional, two-dimensional images. Transmitted radiation is measured by a ring of sensitive radiation detectors located on the gantry around the patient.

Describe doppler ultrasound:

Vascular or color-flow Doppler studies assess patency of major blood vessels, evaluating for clots, plaques and emboli. motion/direction of blood flow.

Describe equipment in mammography

X-ray tube; Target-molybdenum and rhodium; Beryllium window-minimizes absorption of radiation within tube; Molybdenum filter-absorbs unwanted radiation; Compression device

List limitations of ultrasound:

barriers, air, bone, and barium

Who developed CT? When?

in 1972 by Sir Godfrey Hounsfield.

Describe how PET works

injected with radioactive substance. contains the circular gamma ray detector array, scintillation crystals, photomultiplier tube. Crystals convert gamma rays, emitted from the patient, to photons of light and the photomultiplier tubes convert and amplify the photons to electrical signals. Signals are then processed by the computer to generate images. series of thin slice images of body over the region of interest. Thin slices can be assembled into 3D representation of pt's body.

Stress thallium test

injected with radioactive thallium compound, exercised on a treadmill and imaged with a gamma ray camera.

Isoechoic:

two structures that have same echogenicity even though tissue is not the same.