front 1 similarities between conventional radiograph & CT | back 1 both based on same principles, both use X-rays and get attenuated by the body's tissues and produce images based on tissue radiodensity |
front 2 differences between conventional radiograph & CT | back 2 CT uses many projections from different angles that get captured by up to 1,000 detectors encircling the patient and creates images based on these slices |
front 3 what are the three planes viewed as slices in a CT? | back 3 images as collected are not limited to axial plane (volumetric scanning) but can be constructed in any plane and rotated in 3 dimensions. Viewed in axial (transverse), saggital, and coronal (frontal). |
front 4 Windowing | back 4 operator selects radiodensities displayed in an image to determine what tissues are emphasized (ie. bone v soft tissue) |
front 5 What does CT image best? | back 5 Bone: subtle and or complex fractures, degenerative changes, spinal stenosis (especially when combined with CT myelography), and measurement of osseus allignment in any plane. BEST MODALITY FOR evaluation of loose bodies in a joint, and can be combined with diskogram to evaluate intervertebral discs in the spine. Also, imaging choice in serious trauma because it can detect injuries to muscle tissue types, less time-consuming than MRI or ultrasound, less expensive than MRI. 3D imaging. |
front 6 limitations of CT | back 6 identifies tissues based on radiodensity and some tissues are similar in that regard making them difficult to distinguish. HIGH RADIATION EXPOSURE. |
front 7 T1 | back 7 return to longitudinal magnetization when protons lose energy to surrounding molecules, faster recovery=stronger signal, shorter T1 SIGNAL CAUGHT EARLY AND CAN NOTE DIFFERENCE IN FAT & WATER TR= short time to repitition, TE= time to echo |
front 8 highest signal intensity on T1 (brightest) | back 8 yellow bone marrow and fat, ACUTE HEMMORAGHE |
front 9 lowest signal intensity on T1 (darkest) | back 9 cortical bone, ligament, tendon, fluid |
front 10 T2 | back 10 relaxation of transverse magnetization toward equilibrium slower the decay=stronger the signal long TR: long time to repition long TE: long time to echo |
front 11 highest signal intensity on T2 (brightest) | back 11 water and inflammation (reluctant to release energy) SOFT TISSUE TUMORS AND CHRONIC HEMMORAGHE |
front 12 what does MRI image best? | back 12 soft tissue details (sport injury), changes in bone marrow (stress fracture), disk herniation, staging of neoplasm, alternative to invasive procedures |
front 13 limitations of MRI | back 13 low signal intensity of corticol, increased time to produce image (high cost) |
front 14 contradictions and health concerns related to MRI | back 14 metals can become projectile, surgical clips can become displaced & can be fatal, claustrophobia |
front 15 advantages of MRI > CT | back 15 greater contrast of soft tissues and ability to image organs surrounded by bone, no ionizing radiation, various visibility using different sequences decrease the risk of missing a pathology |
front 16 what are the disadvantages of MRI as compared to CT? | back 16 MRI more expensive & less available/takes longer. Thicker slices and less resolution of corticol bone and image quality can be lost due to motion. Contraindications with metal or metal implants. |