Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
Hostname: page-component-848d4c4894-wg55d Total loading time: 0 Render date: 2024-05-19T20:58:44.692Z Has data issue: false hasContentIssue false

8 - Computed tomography

Published online by Cambridge University Press:  05 July 2011

Shahzad Ilyas ,
Tomasz Matys ,
Nasim Sheikh-Bahaei ,
Adam K. Yamamoto  and
Martin J. Graves
By
N. Sheikh-Bahaei
Shahzad Ilyas
Affiliation:
Addenbrooke’s Hospital, Cambridge, UK
Tomasz Matys
Affiliation:
Addenbrooke’s Hospital, Cambridge, UK
Nasim Sheikh-Bahaei
Affiliation:
Addenbrooke’s Hospital, Cambridge, UK
Adam K. Yamamoto
Affiliation:
Addenbrooke’s Hospital, Cambridge, UK
Martin J. Graves
Affiliation:
Addenbrooke’s Hospital, Cambridge, UK
N. Sheikh-Bahaei
Affiliation:
Cambridge University Hospitals NHS Foundation Trust
Get access

Summary

  1. Regarding computed tomography (CT) number (CTn):

  1. It represents the linear attenuation coefficient of each tissue

  2. It is directly proportional to μwater

  3. It depends on kV, but not on filtration

  4. It is between 20 and 30 for brain white matter

  5. Air and water can be used for calibration of CTn

  1. Regarding the partial volume effect:

  1. A thin high-contrast object at an oblique angle is less visible

  2. Because of the partial volume effect, a small high-contrast object that is smaller than the display pixel size is not visible

  3. It reduces the visibility of low-contrast detail

  4. It depends on the thickness of the tissue

  5. It depends on the thickness of the transaxial slice

  1. In CT:

  1. The total number of detectors is around 500–1000 in each row

  2. The gantry cannot tilt in the cranio-caudal direction

  3. A bone algorithm improves the spatial resolution

  4. The anode–cathode axis is perpendicular to the z-axis to reduce the heel effect

  5. The main filter is usually 3 mm of aluminium

  1. In CT geometry:

  1. There are typically two focal spots and the smallest is 0.6 mm

  2. The heating capacity is 0.4 MJ

  3. The filter in first-generation scanners was copper to remove high-energy photons and aluminium for low-energy photons

  4. Post-patient collimation is necessary in a multi-slice scanner to get an accurate thickness

  5. […]

Type
Chapter
Information
Physics MCQs for the Part 1 FRCR , pp. 98 - 109
Publisher: Cambridge University Press
Print publication year: 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Save book to Kindle

To save this book to your Kindle, first ensure coreplatform@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×