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Found. Midterm RT

TermDefinition
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