Tips & Tricks: How to Keep kV Constant by Adding Scan Protocols

Athina Gorezis |  24-02-2017

CARE kV has the advantage of automatically selecting the optimal kV settings to potentially save dose. In cases where the kV needs to remain the same, such as in multiphase studies, scan entries can be grouped easily for constant scan protocols. Learn more from these tips and tricks.


CARE kV is part of the FAST CARE package of scanning technologies that automatically select the optimal kV setting appropriate to the patient and the clinical diagnostic task at hand. The aim of CARE kV is to provide the requested image quality while minimizing dose to the patient.

There are three modes in CARE kV: “Off”, “Semi”, “On” (Fig. 1).

When the “On” mode is activated, the system will recommend the optimal kV and mAs settings for that particular patient and the clinical task.

When CARE kV is set to “Semi,” a user-defined kV setting will be implemented and mAs values will be adjusted based on the specified reference values.

When CARE kV is set to “Off”, the scan is performed with the reference kV setting defined in the respective scan protocol.

All available kV settings are considered when determining the optimal choice in each case. The automatic adaption of kV and mA values when CARE kV is “On” enables dose saving. Changing the kV setting, however, alters the Hounsfield units in the resulting images. This may not be desirable in certain cases, such as to assess a lesion in a multiphase study. Here, it is preferable to keep the kV constant in multiphase studies, irrespective of the diagnostic task at hand (e.g. non-contrast CT scan vs. soft tissue arterial scan). To keep the kV constant for an examination, it is necessary to group the studies. Scan entries can be added easily to a group to fix a kV value for all scan ranges.

Below is an example of a multiphase CT abdomen study with a non-contrast CT scan, arterial and portal venous scans.

  1. Click a scan entry to be grouped in the scan chronicle on the right (Fig. 2).
  2. From the context menu, choose “Add to CARE kV group”.
  3. The scan entries belonging to a CARE kV group are then clearly marked with a paper clip symbol in the scan chronicle (Fig. 3)

All scan entries within that CARE kV group will then be scanned at the same kV value. This value is optimized based on the size of the patient and an average of the dose optimization slider positions for all the scan ranges included in the CARE kV group.

Similarly, to remove a scan entry from a CARE kV group, click a scan entry on the right and select “Remove from CARE kV group”.


About the Author

Athina Gorezis is Application Specialist at Computed Tomography, Siemens Healthineers, Germany


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