High-resolution computed tomography (HRCT)
June, 2018
Exam: CT Thorax for interstitial lung disease
Protocol:
- Oral Contrast: none
- IV Contrast: none
- Acquisitions:
1) Supine, Inspiration
Breathing instructions for inspiratory scout and CT acquisition:
“For the first part of this study I am going to give you specific breathing instructions. Try to follow as best you can.”
“Take in a deep breath….and let it out.”
“Take in another deep breath….and let it out.”
“Take in another deep breath, and hold your breath in. Keep holding your breath!”
Scout views: PA and Lateral to include all of chest
Scan Range: Lung apices to base
Inspiratory CT acquisition parameters
Detector Collimation | kV | mAs | Pitch | Rotation | Tube current modulation |
Helical 1.2mm | 120 (may be lower as tolerated by interpreting physician | 230 (may be lower as tolerated by interpreting physician | ~1.0 | 0.5sec (or faster) | on |
Image reconstruction parameters
Image Processing Plane | Field of view | Reconstruction algorithm | Slice reconstruction thickness | Slice reconstruction interval | Window | Source |
Axial | Variable | Soft tissue (e.g. Siemens B31f, GE standard, Philips B, Toshiba Body Std.) | 3 mm | 3 mm | Mediastinum | raw |
Axial thin section | ≤ 2 cm beyond lung margin | Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE Bone, Philips D or YB, Toshiba lung std.) | 1 mm | 1 mm | Lung | raw |
Optional Axial thick section | ≤ 2 cm beyond lung margin | Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE Bone, Philips D or YB, Toshiba lung std.) | 3 mm | 3 mm | Lung | raw |
Axial MIP | ≤ 2 cm beyond lung margin | Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE Bone, Philips D or YB, Toshiba lung std.) | 6 mm | 3 mm | Lung | raw |
Coronal | ≤ 2 cm beyond lung margin | Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE Bone, Philips D or YB, Toshiba Lung Std.) | 2.5 mm | 2.5 mm | Lung | raw |
Sagittal | ≤ 2 cm beyond lung margin | Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE Bone, Philips D or YB, Toshiba Lung Std.) | 2.5 mm | 2.5 mm | Lung | raw |
* Technologist must review scans immediately after acquisition and repeat as appropriate if there is motion artifact or inadequate inspiration (in clearly non-diagnostic cases) or must contact a radiologist immediately while the patient is on the scanner gantry to determine whether repeating or adding any additional scans is necessary. Also perform prone scans if there is dependent density on supine images.
2) Supine, Expiration
Breathing instructions for expiratory scout and CT acquisition:“For the next part of this study we will ask you to breathe out and hold your breath.”
“Take in a deep breath….and let it out.” “Take in another deep breath….and let it out.”
“Take in another deep breath, let it out and hold your breath out! Do not breathe!”
Scout views: PA and Lateral to include all of chest
Scan Range
2cm below lung apices to base
Expiratory CT acquisition parameters
Detector collimation | kV | mAs | Scan interval | rotation | Tube current modulation |
Axial 2 x 1.0mm | 120 | 150 | 20 mm | 1.0 sec | on |
* Technologist must review scans immediately after acquisition and repeat as appropriate if there is motion artifact or inadequate expiration.
Image reconstruction parameters
Image Processing Plane | Field of view | Reconstruction algorithm | Slice reconstruction thickness | Slice reconstruction interval | Window | Source |
Axial thin section | ≤ 2 cm beyond lung margin | Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE Bone, Philips D or YB, Toshiba Lung Std.) | 2 mm | 20 mm | Lung | raw |
3) Prone, Inspiration (do this series only if dependent density noted on HRCT)
Breathing instructions for prone inspiratory scout and CT acquisition:“Take in a deep breath….and let it out.” “Take in another deep breath….and let it out.”
“Take in another deep breath, and hold your breath in. Keep holding your breath!”
Scout views: PA and Lateral to include all of chest
Scan Range: Carina to lung base
Prone Inspiratory CT acquisition parameters
|
Detector Collimation |
kV |
mAs |
Scan interval |
rotation |
Tube current modulation |
|
Axial 2 x 1.0mm
|
120 |
150 |
20 mm |
1.0 sec |
on |
Image reconstruction parameters
|
Image Processing Plane |
Field of View |
Reconstruction algorithm |
Slice reconstruction thickness |
Slice reconstruction interval |
Window |
Source |
|
Axial thin section |
≤ 2 cm beyond lung margin |
Moderate edge- enhancing algorithm (e.g. Siemens B45f, GE BonePhilips D or YB, Toshiba Lung Std.) |
2 mm |
20 mm |
Lung |
raw |
* Technologist must review scans immediately after acquisition and repeat as appropriate if there is motion artifact or inadequate inspiration.