This is a sample checklist to be used as a guide for establishing a scanning procedure for constancy measurements as a part of a QA program. 

Choosing Parameters

Parameters of any clinical protocol can be used as long as the scan and display FOV is adapted to the testing requirements and phantom size. Suggested scanning parameters for optimal testing can be found in our help pages. 

• Use scan FOVs close to the centered phantom diameter (210 to 250mm) unless using an annuli.
• In general use reconstruction FOVs that are close the phantom diameter (~210 mm).
  
  • For measuring slice width 1 mm or thinner use reconstruction FOV ~100 ­- 120 mm.
  • For measuring higher (10lp/cm) spatial resolution use reconstruction FOV ~100­ - 120 mm and reconstruction slice thickness ~3­5 mm. For standard resolution, use ~210­ - 250 mm FOV.
• Off centered zooms are only supported if centered on the MTF bead.

Creating a Protocol

For consistent results, using a pre­programmed protocol is recommended. Typical technique: 120 kVp, 200­300 mA, 0.5­1.0 sec (In rare cases the max loading of the small focal spot can be as low as 150mA)

1. Orientation: supine - head first. 
2. Position the slice groups at the center of the modules as indicated by the measurements on the phantom drawing, using either the first center dots (light alignment or the crossing of the CPT404 wire ramps (localizer view).
3. Recommended settings (see also Suggested scanning parameters for optimal testing in our help pages).
4. Store the protocol with a descriptive name (indicating it is not a clinical protocol).

CTP404 - Sensitometry

• A least one 5mm slice

CTP404 - Slice Thickness (Wire ramp)

• 1 or more slices for thick slice thickness (>2mm) to be measured

CTP591 - Slice Thickness (Bead ramp)

• 1 or more slices for thin slice thickness (<=2mm) to be measured
• Use of small focal spot may be required for highest resolution

CTP528 - Spatial Resolution

• Two or more adjacent slices for each test covering ~5 mm
• Scanning slice thickness 0.5 ­- 3 mm
• Recon slice thickness ~3 -­ 5 mm
• Use of small focal spot may be required for highest resolution

CTP515 - Low Contrast

• Four or more adjacent slices
• Slice thickness 5 or 10 mm (being careful to not exceed the module width)

CTP486 - Uniformity

• One or more adjacent slices
• Slice thickness 5 or 10 mm (being careful to not exceed the module width)

Before Scanning

1. Use the Catphan® model and serial # for name and ID (ex: Catphan 600, 600119)
2. Enter the name of the test person as a referring physician (optional).
3. Select the scan protocol.
4. Align the phantom using the laser guide lines and spirit level.
5. Reset the table position to 0.00mm (if possible) when the laser is on the first white alignment pins of the phantom.

Scanning

1. Make a localizer scan (optional).
2. Using clear landmarks in the phantom for spacing and distance information, position a slice or slice groups according to the Catphan® model (optional if using the localizer).
3. Make the scan according to previously stored protocol. Additional protocols can be performed if desired.
4. For constancy measurements, the same protocol should be repeated at all times.