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CT Seeram: Components of a CT Scanner Major Components Scanner room Imaging system Generator (?) Electronics Room Power Computer (?) Generator (?) Operator’s Area Display / recording / storage Computer (?) Gantry Provides Structural Framework for x-ray tube modern tubes very large & heavy external cooling (oil heat exchanger) generator / transformer (slip ring technology) Extreme mechanical stability requirements Very tight tolerances for vibration Give / sag Gantry Provides Structural Framework for collimators filters Detectors / electronics Gantry Size Must Accommodate The gantry is pre-assembled at the factory patients size of room Truck transport to hospital Gantry Size Must Accommodate Transport within hospital hallways doors elevators Typical weight: 3500 lb. Special Clinical Gantry Concerns Patient aperture Tilt range Cooling of electrical components x-ray tube Patient Couch Vertical travel minimum height for stretcher transfer Horizontal travel reduces need for re-positioning patient accuracy Patient Couch Weight capacity Strength cantilevered Rigidity Patient Couch Requirements Safe for patients Easy to clean Radiolucency Speed Pretty? Siemens offers colors Imaging System Produces x-rays Shapes & filters (hardens) beam collimates attenuates for uniformity May detect (measure) pre-patient beam intensity Provides digital intensity data to computer Imaging System Components X-ray tube Generator supplies power to x-ray tube filament high voltage Collimators restricts beam to slice of interest Imaging System Components Filter protects patient from low-energy photons provides a beam closer to mono-energetic provides a more uniform beam Detector & electronics also called data acquisition system (DAS) includes A-D converter provides digital information to reconstruction computer Computer System Components Input / output devices Detectors Printer Central processing units • • • • (CPU’s) Array Processor Reconstruction Hardware Interfaces to other computers Remote service RIS Archive Web browser Communications hardware Software • enables above hardware operation • image manipulation • scanning control Reconstruction Computer Receives digital data from DAS Reconstructs cross-sectional image Image display, manipulation, & processing windowing enhancement zoom quantitative measurements multi-planar & 3D reconstruction Image Display, Record, Storage Display output image Facilitate storage / retrieval of digital data Provide permanent hard-copy for referring physician (?) Computer & Image Processing Hardware Special processing architecture Software Processing Architecture Multi-processing capability scanning reconstructing archiving Distributed processing architecture many independent processors each controls specific function CT Software Functions Operator console Allows operator to communicate with computer & scanner keyboard touch screen mouse / trackball Control • • • • • of scanner Gantry tilt scout / axial field of view x-ray technique slices » how many » thickness » overlap CT Software Functions Control of imaging selection of pre-stored image protocols Selection of reconstruction algorithm Operating System often UNIX multiuser multitasking controls hardware Image Display, Storage, & Recording Display CRT or flat panel images in gray shade non-image data in color or B/W often hi-resolution Can display 4-on-1 or zoomed image at full resolution Display processor provides display functions image manipulation Image Storage Typical CT image 512 X 512 pixels 8-12 bits deep often stored as 2 bytes / pixel (16 bits / pixel) Multiply image size by # images Image Size 512 X 512 image = 262,144 pixels 262,144 pixels X 2 bytes / pixel = 524,288 bytes per image ~ 512 KB ~ 0.5 MB Image Storage (cont.) Assume 0.5 Mbytes per image If 100 images / patient 50 Mbytes / patient 25 patients / day X 50 MBytes / patient = 1.25 GBytes per day High Capacity Image Storage Types Magnetic disk Magnetic tape Digital videotape Optical disks Optical Tape Considerations Capacity Access Speed Rewritable? Size / space Longevity On line? $$$ CT Hard Copy on Laser Printer Stringent quality requirements broad grayscale contrast resolution high spatial resolution No film processor required CT Hard Copy on Laser Printer Requires special film Film’s spectral sensitivity must match laser Laser types solid state gas (He-Ne) Laser Printing Film exposed by scanning line by line with laser Laser Printer Features Contains image buffer (computer memory) Buffer stores images in memory until printed Camera prints multiple images on one film Camera can receive & buffer multiple image sources images simultaneously CT Console Keyboard Mouse Display CRT Flat panel Touch panel CT Console Allows Operator to Control Gantry tilt scanning parameters Slice thickness Spacing Technique image manipulation multiplanar reformatting 3D zoom / pan CT Available Automatic Control Functions Archiving Voice instruction to patient Visual instructions to patient Auto-film protocols (?) Window / level Format (12 on 1 for example) Optional Purchases CT Hardware Archival systems Independent workstations Physicians 3D Printing Laser Multi-format CT Options Bone mineral analysis Dynamic scan rapid sequential scans of single slice Multiplanar reformatting 3D image reconstruction Regional cerebral blood flow analysis CT Angiography Dental CT (surgery planning, implants) Networking CT Room Layout Gantry Couch Room for Resuscitation team Emergency equipment Stretchers Medical Gasses Shielding CT Room Layout Equipment room not always necessary as scanners become smaller Control room Film recording may be combined with control room Purchasing CT; Specifications List of Items Major components Optional equipment Major technical features should be measurable CT Specifications Who’s Involved? Radiologist Technologist Physicist Administrators Technical Specifications X-ray generator parameters operational parameters maximum kVp kW rating X-ray tube • heat capacity • cooling rates Detector efficiency Reconstruction time Throughput CT Specifications Gantry aperture size tilt range laser positioning aids controls Couch strength / weight limits movement characteristics Speed Limits CT Specifications; Operator’s Console Display, keyboard, mouse, touch panel characteristics Software design Choice box of available options vs. manual typing Film recording & archival considerations CT Specifications Physician’s console & other workstations functions available speed Simultaneity Computer storage requirements CPU networking CT Specifications Interfaces PACS hooks & DICOM compatibility Worklist management Pulling patient demographics from RIS Image storage Transfer of images to archive / PACS Computer Software CT Specifications image reconstruction options FOV filters display options annotation analysis options regions of interest CT Specifications Hardcopy devices & interface laser printer Quality control equipment phantoms software Remote Diagnostics CT Specifications Acceptance Testing Who performs What tests done Technology Changes “Latest model available at time of delivery” Service Warranty Binding service contract prices Purchasing CT Room planning in consultation with equipment vendor Property ownership. Who owns? And when does ownership transfer? service manuals diagnostic software operating system Property ownership dictates hidden software costs & service options CT Specifications: Training For whom? Technologists How many? Where? Vendor site On-site Local What’s included Registration Books Travel expenses