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Found. Midterm RT
| Term | Definition |
|---|---|
| Brems stop | X ray in tube |
| PACS | Picture archiving and communication system Store images that can be accessed from RT dept or hospital |
| DICOM | Digital imaging and communication in medicine Ensures images are communicated properly to standards and specific protocols HL7 |
| Conventional/Axial scanners | Require Pt to be at a fixed point and tube rotates 360 |
| HIS | Is Dr ordered |
| EMR | Is EPID/EPIC? |
| VSIM | Verifies port films |
| RIS | Is ARIA |
| Helical/Spiral CT | Where Pt is at a fixed point while x ray tube roared and creates slinky form |
| Slice thickness CT reconstruction parameter | Determines thickness of reconstructed images |
| Slice increment | Determines distance B/W center of CT slices |
| Smaller effective detector sizes | Thinner slices for reconstruction |
| Wider slice thickness | Can be reconstructed by combining the signal from multiple rows |
| Aperture | Bore size |
| DAS | Data acquisition system Measures radiation beam, binary coding and transmission binary data to the computer |
| Array processors | Multiple images are reconstructed per second |
| Process CT formation | Includes DAS, image reconstruction and image display |
| SFOV | Scanned field of view means scan field of view is smaller than bore of gantry |
| DFOV | Defined field of view can be less than or equal to SFOV |
| DFOV includes | Anatomy to be viewed |
| Increase in spatial resolution | Increase in noise |
| Artifacts | Discrepancy on images |
| Interpolation | Missing data using math and estimated attenuation B/W 2 points |
| Algorithms | Specific set of instructions to get specific output to reconstruct raw data into reconstructed data A+B=0 c+d=1 a+c=1 b+d=0 |
| Raw data | Bits in different projections |
| Filter | Mathematic function |
| Hounsfield scale | -1000= air 0= water -800 to -200= lungs -100= fat 20= blood 50= muscle and brain 1000= bone |
| WL | Central HUs of all CT #s with WW |
| WW | Range of #s displayed contrast on CT |
| Image matrix | Images seen in rows and columns 512*512=262,144 pixels |
| Pixel | Each cell on image matrix is 2D of corresponding tissue |
| Voxel | slice thickness/volume |
| Isotropic imaging increases | Spatial resolution and enhances 3D reconstruction |
| WL of 50 | Used for abdominal imaging |
| WL of 500 | Good lung detail in thorax |
| WW is narrowed for | Greater contrast and sharper changes in shades of gray |
| ROI | Region of interest |
| Low HU | Fatty tissue |
| High HU | Maybe cancer |
| WW will decrease | Contrast |
| Narrow WW | Increase contrast |
| WW=600 WL=100 | range=-200 to 400 |
| Spatial resolution | High contrast |
| Smaller focal spot | Smaller detector size so better resolution |
| Noise is affected by | kVp/mA/exposure time/collimation/reconstruction algorithm/filter/helical pitch/table/speed/isocenter distance and detector |
| Artifacts caused by | Pt movements, anatomy, design of scanner and system failure |
| Beam hardening artifacts | Dark bands often bear bone |
| Partial volume artifacts | Occur when thick slices are obtained |
| Star artifacts | Occur from surgical clips or other metallic objects within Pt |
| Faster scanners | Help reduce motion artifacts especially when Pt holds their breath during the scan |
| Helical scanning of thorax and abdomen | Can lead to object distortion because of breathing |
| Water phantom scans | Check noise levels by comparing the HU# of water at various areas of the phantom +-3 to 0 |
| CT | Localized treatment isocenter, defines shape and size of Tx volume according to normal tissues |
| Conventional sim improvements were made to | 2D imaging and the display of these images |
| Virtual sim | Provides ability to design fields without conventional sim with better visualization of internal structures by using 3D images on computer |
| Simulation is a | Single/multiple step process carried out by RT under supervision of RO |
| Localization | Position/extent of tumor/anatomical structure by reference of surface marks that can be used for Tx setup purposes |
| Verification | Final check to ensure each planned Tx beam covers the tumor target volume and does not irradiate critical normal tissues |
| Radiopaque markers | Material with high atomic # lead/copper/solder wire and can be used on Pt body surface or body cavity also called reference marks |
| Separation | Measurement of thickness of Pt along the central axis or any other point within irradiated volume/calipers also called intra/inner field distance (IFD) |
| Intrafraction | Change in target position during Tx like breathing or coughing |
| CTV | Clinical target volume is gross palpable or visible tumor and surrounding volume of tissue with microscopic disease |
| PTV | Planning target volume and is CTV plus margins for geometric uncertainty like motion, beam penumbra or Tx set up differences |
| Beam penumbra | Is like scatter but geometric to beam |
| Pt positioning | Needs to be reproducible and is essential for Tx |
| 3D lasers | Transverse, coronal and sagittal planes |
| Support conditions prescribed in Tx plan | Fascilitate Pts condition and Tx unit limitations |
| Entire HC system is based on | Effective communication and education |
| Contrast increases | Dose but a thorough medical history is to be obtained and reactions are not real or true |
| Ionic or nonionic iodine contrast | Induced neuropathy |
| Barium is not | Water soluble |
| Ionic | Has high osmolality which causes water to move into blood vessels |
| Nonionic | Made for power injectors but can be painful to Pt because of the viscosity or thickness of substance of contrast medium concentration and size of molecule |
| Pt should be positioned carefully so that | The area of interest is in center of the CT bore and SFOV which is the area for protection data collected for CT scan which eliminates artifacts and provides best image quality and ensures FOV |
| Small tumor | Small slice thickness |
| DFOV | Pitch resolution/slice thickness/increment/rotation speed/scan length/filters WL&WL/dose saving techniques/collimation/image matrix |
| Shift method | Procedure where reference marks are placed on Pt before CT scan in an arbitrary location close to desired anatomical Tx isocenter |
| Isocenter localization | Procedures are divided into 3 methods 1. External fiducials/computing isocenter/placement of isocenter based on Tx volume/contour 2. Compute isocenter based on field border placement 3. Tx volume/contour based delineation of segment target volume |
| RAS | Right and left Anterior and posterior Superior to inferior |
| DIBH | Deep inspiration breath hold or fully exhale |
| 4D CT | Had low pitch scan data |
| Breast tumor in inner upper lower quadrant what's lymph nose drainage? | Internal mammary |
| Located at L4 | Umbilicus |
| Inferior angle of scapula | T7 |
| 2cm anterior and 2cm superior to EAM | Sella turcica |
| Thoracic lymph duct begins in abdomen where | L2 |
| Relationship of esophagus to trachea and vertebra column | Esophagus is posterior to trachea and anterior vertebral column |
| Lymph drainage from right lung to its return in cardiovascular system | Pulmonary intrapulmonary, hilar bronchopulmonary, carinal inferior mediastinal and paratracheal |
| Where is rotters node | Infraclacicular fossa |
| Sella turcica is depression of | Sphenoid bone and holds pituitary gland |
| Hounsfield unit for fat | -100 |
| Conventional simulators are designed to simulate | Mechanical |
| Ct numbers are | Hounsfield units |
| Most ct scanners are | Third generation |
| Light photons are produced and transmitted electronically through to a video image where | Output phosphor |
| Central axis of beam is | Only area divergent and aligned with isocenter |
| What's difference in completing axial scan and spiral ct | Table moves for spiral ct |
| Matrix size determined by | Pixel |
| Takes into consideration how an area on the other side of an irradiated wall will be used | Occupancy factor |
| Positioning lasers are located | Overhead, Sagittal and lateral |
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callieyates060513
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