Acquisition Phase

Phase Included

Scan Delay

Respiration Phase

Anatomical Coverage

Non Contrast

Yes

N/A

Inspiration

Carina through the apex of the heart

Arterial Phase

Yes

Bolus triggered

Inspiration

Apex of the lungs through the diaphragm

Venous Phase

N/A

N/A

N/A

N/A

Delayed Phase

N/A

N/A

N/A

N/A

Scan Comments: The term triple r/o is really a misnomer because several pathologies can be evaluated using this protocol. The clinical indication for using this protocol is when optimal contrast opacification is required in both the pulmonary arteries and great vessels without resulting in beam hardening artifact from the SVC. For larger patients, it is helpful to utilize a DSXXL based scan protocol that allows for the temporal resolution to be adjusted even after the scan has been completed. Increasing the temporal resolution times will allow for a reduction in image noise at the expense of the increased cardiac motion. Typically, a calcium score is also performed (see calcium score protocol for scan details). All scans are performed using the ALARA principle. A 3D Post Processing is performed with this protocol.

 

Technical Parameters

Parameters

kVp

120

Effective mAs

CareDose

Care Dose Reference mAs

320

Time (Rotation)

0.28 sec

Average Acquisition Time

HR Dependent

Collimation

128 x 0.6mm

Pitch Value

HR Dependent

Scan Direction

Craniocaudal

Comments: Both the pitch and the scan time will vary based upon the patient's heart rate. 120kVp is necessary to limit beam hardening artifact from occurring at the SVC, which can obstruct pathology on the great vessels. ECG dose modulation is always performed to limit patient exposure. CareDose is used to reduce patient dose.

 

Reconstruction Parameters

Soft Tissue

Thin Data

Lung

Slice Thickness

 3mm

 0.75mm

 3mm

Reconstruction Spacing

 3mm

 0.5mm

 3mm

Reconstruction Algorithm

 B30f

 B26f ASA / I41f

 B80f

Window Width and Level

 410/10

 500/100

 1600/-500

Reconstruction Comments: A 1.0mm x 0.6mm multiphase reconstruction is generated across the ECG pulsing range every 5-10% of the R-R interval. An additional smaller DFOV reconstruction that only includes the heart/aorta will increase spatial resolution of the coronary vessels. Iterative reconstructions are performed to improve image noise. Coronal and sagittal image reconstructions are also performed.

 

Contrast Parameters

Parameters

Contrast Type

Non ionic

Contrast Volume

120ml

Saline Flush

30ml (80% nonionic contrast/20% saline)

Injection Rate

5ml/sec

Oral Contrast

N/A

Contrast Volume

N/A

Comments: Bolus tracking is ideal with 230HU trigger value on the ascending aorta. A diluted flush (80% contrast to 20% saline) is used to soften the SVC and limit beam hardening artifact.



Other Comments: Selecting the correct range for ECG dose modulation is based primarily on the patient's heart rate and clinical indication. When multiphase images are not clinically indicated, the use of ECG dose modulation, specifically Siemens MinDose application, can significantly reduce the patient's exposure. See Cardiac CT Flow Chart below for more information on selecting the correct protocol based on the patient's heart rate and rhythm. Coronary CTA images should visualize the coronary arteries and left ventricle with adequate opacification of IV contrast. Images should limit venous contamination while flushing contrast out of the right ventricle to prevent image artifacts.