MVCT QA w/TomoHDA & Ray6 HOME

2018_06_28

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At Tomo

• Before Starting: powered up, software running, 5-minute warmup, AIRSCANS

• Select Patient: ‘_CT Number Calibration’ [ normal pitch, 2mm slices x 19 ]

  • Select all slices → Accept slices … Prepare scan → OK → Setup → Yes

• Setup cheese phantom (+ PWx20), green lasers

  • Main → Ready → Yes … Key → Image → Key
  • Record air-HU and water-HU from screen → OK

• Tools → Clear selected patient

• Tools → Dicom Options → Export Items

  • Export to: RaySearch … select correct ‘CTrue Image’ (4 slices)
  • Send Now → Close

• Insert density plugs w/test pattern pointed in, orient plug side into gantry

  

  Cheese Phantom
  Inserts
  Plastic Water
  Cortical Bone
  Liquid Water
  Resolution Test Object
  Air

• Select Patient: ‘ZZ-06_TomoPhant’, plan-3

  • ~20 slices covering inner part of plugs, fine pitch, 1mm slices
  • Accept Slices … Prepare scan → OK → Setup → Yes
  • Setup on green lasers … Main → Ready → Yes … Key → Image → Key

• Tools → Clear selected patient

• Tools → Dicom Options → Export Items

  • Export to: RaySearch … Select CTrue Image,
  • Send Now → Close

At RayStation

• Patient Data / Patient Information

  • Import new patient → [ ‘Storage SCP’, ‘_CT Number Calibration’, ‘CT Series’]
  • ‘Import’ → if prompted, ‘Create a new patient’ then ‘OK’
  • Image Sets / Properties
  • confirm correct density table, then ‘OK’

• Patient Modeling / Structure Definition / ROI Tools

  • New ROI geometry / Structure templates / Create structures from template…
  • Template → ‘MVCT QA’
  • Initialization → ‘Align image centers’
  • Structures → ‘Select All’
  • OK, then confirm contour alignment
  • Double-click ROIs, record ‘Intensity Avg’, click ‘Cancel’
  • Center: 24.66 … calculate +/- 40 as HU range, e.g. -15 → 60

  

  Cheese Phantom
  Q1	1.85
  Q2	2.79
  Q3	17.66
  Q4	13.21

  New ROI geometry / Thresholding / Gray level threshold …

  Set threshold levels → ‘-15’ [HU] ‘60’

  Output / Create geometry for: / Existing ROI → ‘+/- 40 HU’ and click ‘OK’

  Are you sure that you want to replace the existing geometry: → ‘Yes’

  • Expression A → ‘+/- 40 HU’
  • Operator → ‘intersection’
  • Expression B → ‘center_slice’
  • Ouput → no expansion, Create geometry for: / Existing ROI / ‘noise_volume’ → OK

  Are you sure that you want to replace the existing geometry: → ‘Yes’, long delay

  Inspect ‘noise_volume’ for artifacts

  Double-click ROIs, record ‘Volume [cm3]’, click ‘Cancel’

  noise_volume	33.89
  center_slice	45.30

  Calculate %-enclosed: 78% vs tolerance of 65%,

• Patient Modeling / Structure Definition / POI Tools

  Adjust pin_1, pin_2, and pin_3 to center of metal pins in the image slice

  Double-click POIs, record coordinates R-L, I-S, P-A, click ‘Cancel’

  pin_1	9.37	0.05	11.23
  pin_2	14.52	0.05	-2.63
  pin_3	9.50	0.05	-11.37

• Patient Data / Patient Information → ‘Close’

  • Modifications must be saved before closing the current patient.
  • Do you want to save the changes? → ‘Yes’

• Patient Data / Patient Information

  • Import new patient → [‘Storage SCP’, ‘ZZ-06_TomoPhant’, ‘CT Series’]
  • ‘Import’ → if prompted, ‘Create a new patient’ then ‘OK’
  • Image Sets / Properties
  • confirm correct density table, then ‘OK’

• Patient Modeling / Structure Definition / ROI Tools

  • Inspect for number of high-contrast objects visible: 4
  • New ROI geometry / Create New ROI → ‘bone’, ‘liquid_water’, ‘air’
  • Use the brush on single slice, structure covers about central half of the plug
  • Double-click ROIs, record ‘Intensity Avg’, click ‘Cancel’

  bone	651.48	11.23
  liquid_water	6.44	-2.63
  air	0.05	-911.74

At Excel

VI.B.2.a, VI.B.2.b

• Constancy

  • Tomo HU +/- 10 from expected, phantom=25, air=-1000

• Uniformity

  • Each quadrant periphery within 25 HU of center
  • center = phantom slice, radius 1 → 12 cm (excl outer 3 cm)
  • Q1, Q2, Q3, Q4 = slice quadrant, radius 13 → 14 cm

• SNR of NLT 28 dB

  • i.e. NLT 65% (typical 75%) of center volume within 40 HU of mean value

• Pin-to-pin distances within 1 mm of true value

  	Expected
  pin_2 →3	101.2 mm
  pin_1 →2	148.0 mm
  pin_1 →3	226.7 mm

• VI.B.2.c, VI.B.2.d, VI.B.2.e

  • NLT 3 resolution objects visible (1.6 mm)
  • Density objects within tolerance of expected HU

  bone	Expect	Tolerance
  Cortical Bone	668.8	50 HU (6%)
  Water	0.0	30 HU (10%)
  Air	-916.3	reasonableness