Computed Tomography (CT, was CAT, Computerized Axial Tomography)rev 2016-02-20this is now slide 1 do not print it to pdf

things to do (check off when complete):

add revision date to cover pageremove trianglescreate list for pages to print in the handout

2-10,12-17,20-22,29-31add captions for photo slidesincorporate notes taken during presentationadd Key Points page 3

useful characters: ° degrees Ω ohms μ micro ☑ checkbox ☐ slash-zero ØCO2 O2 SpO2 N2O ® ™ trademarks

à 224 E0á 225 E1â 226 E2ã 227 E3ä 228 E4å 229 E5æ 230 E6ç 231 E7Ð 208 D0è 232 E8é 233 E9ê 234 EAë 235 EBì 236 ECí 237 EDî 238 EEï 239 EFÑ 209 D1Ò 210 D2Ó 211 D3Ô 212 D4Õ 213 D5Ö 214 D6Ø 216 D8ß 223 DFÞ 222 DEÙ 217 D9Ú 218 DAÛ 219 DBÜ 220 DCÝ 221 DDÞ 222 DEß 223 DF

Computed Tomography[was: Computerized Axial Tomography]CT scanners [or CAT scanners]

© D. J.

© D. J. McMahon 150504 rev cewood 2016-02-20

Key PointsComputed Tomography (CT):

Know the essential components of a CT scanner (handout image)

Know the general idea of how CT scanners capture an image

What value do more detectors offer?

Understand the principle of Multislice Spiral Computed Tomography (MSCT)

“Tomography” :an image from many slices (Greek: tomos = slice)

Digital geometry processing is used to generate a three-dimensional image of the inside of the body from a large series of two-dimensional X-ray images taken around a single axis of rotation.

Individual slice data is generated using an X-ray source that rotates around the patient;

X-ray sensors are positioned on the opposite side of the circle from the X-ray source and also move, staying 180° from the source.

These sensors use scintillation systems based on photo diodes.

Many data scans are progressively taken as the body is gradually passed through the gantry.

The images are combined together by mathematical procedures known as tomographic reconstruction.

Contrast between soft tissues can be increased by injection of iodine-based solutions.

Evolution of CT scanning -

Increased beam size, and increased number of detectors.

Most current installations are third and fourth generation.

https://www.youtube.com/watch?v=M-4o0DxBgZk

More detectors and smaller detectors give better resolutionor faster image capture (e.g. to capture a beating heart) or both.

Enhanced image data can be reconstructed thru algorithms

Current CT machines can have 320 detectors yielding 256 slices.

Multislice Spiral Computed Tomography (MSCT)

Sampling Patterns of a 4-slice spiral scan at different pitch values.

At pitch 1 and 2, each z-position is sampled 4 and 2 times respectively.

The spacing between samples decreases from d to d/2 when going from pitch 1 to pitch 1.5, then increases again to d when increasing the pitch to 2.

At a pitch of 4, each sample is acquired once and the sampling distance is d (d denotes the slice collimation)

64-slice CT unit -

T X-ray tubeD X-ray

detectorsX X-ray beamR Gantry

rotation

That gantry rotates at 180 - 240 r.p.m.

Open CT running http://www.youtube.com/watch?v=2CWpZKuy-NE

Toshiba “Aquilion” - 80 detectors, 160 slices

http://medical.toshiba.com/products/ct/aquilion-prime/index.php

Specifications First CT Scanner(circa 1970)

Recent CT Scanner

Time to acquire one CT image: 5 minutes 0.5 seconds

Pixel size: 3 mm x 3 mm 0.5 mm x 0.5 mm

Number of pixels in an image: 6,400 256,000

Early scan, ~1975 Scan, ~2003

Siemens “Definition”scanner: Dual-source CT

Two x-ray tubes are operated at different tube potentials: one at a low energy (e.g. 80 or 100 kV), and the other at a high energy (e.g. 140 kV).

Different tube energies allow for differentiation between materials such as iodine, calcium and uric acid, and is used to distinguish bone or iodinated contrast material, as well as the visualization of blood perfusion.

Dual-energy CT can also be used to identify the composition of materials in the body, and to identify renal stone type or to detect uric acid deposits in joints.

Typical applications for CT:

Chest: Lungs, heart, esophagus, major blood vessels, the tissues in the center of the chest, lung cancer, pulmonary embolism.

Abdomen: Infection, tumors, an aneurysm, foreign objects, bleeding.

Urinary tract: Kidneys, urethra, and bladder (called a KUB). Liver: A CT scan can find liver tumors, liver diseases.

Pancreas.

Gallbladder and bile ducts.

Adrenal glands.

Spleen.

Pelvis: Problems of organs in the pelvis.- Uterus, fallopian tubes, etc- Prostate

http://upload.wikimedia.org/wikipedia/en/e/ea/SADDLE_PE.JPG

Typical CT study of a skull :

Three-dimensional CT scanning:

pixels

voxels

http://upload.wikimedia.org/wikipedia/commons/4/4a/Ct-workstation-neck.jpg

Revealing bone densities and vessels by manipulation of the data

http://medical.toshiba.com/resources/img/products/computed-tomography/aquilion-prime/Prime-Overview-Clincial-Example-01.gif

Two views of a femoral fracture -

Enhanced imaging --

How much ??4-slice scanner: $85,000 - $115,000

16-slice scanner: $145,000 - $225,000

64-slice scanner: $250,000 - $450,000

Service contracts: $100,000 - $135,000

CT tube replacement: $50,000 - $100,000

Major players in CT scanners:

G.E. Medical ( GEMS)Philips

SiemensToshiba

Major players in CT service and tubes: