Aims and objectives
CT is used in many hospitals as first-line imaging modality in cervical trauma,
due to the higher accuracy compared to conventional radiography.
However radiation dose is a major concern,
due to the fact that many younger patients are scanned,
and the presence of radiosensitive tissue(thyroidglands) in the scan range.
The use of beam filters in radiography is a proven way to reduce dose from low-energy photons absorbed in the patient.
The Siemens SOMATOM FORCE scanner can scan at 150 kVp with tin beam filtration.
Use...
Methods and materials
Retrospective study of 20 consecutive patients,
half of whom were scanned with old protocol (120 kVp) and half with new protocol at 150Sn kVp.
Image quality parameters were identical for both protocols: Reference kVp 120,
Quality reference mAs 190,
pitch 0,6,
collimation 192x0,6mm.
In the 150Sn protocol rotation time was increased from 0,5 to 1 second,
to allow enough photons through the tin filter.
CT Dose Index (CTDIvol)and Dose-Length-Product (DLP) was recorded from the scanner generated patient protocol.
Scan range was from outer auditory canal...
Results
Patients in the 120 kVp group had a mean age of 35,6 years compared to 38,4 in the 150Sn kVp group,
whichdidnot differsignificantly (p=0,63).
CTDI and DLP values can be seen in the table below,
and the difference in bothwas statistically significant between 120 and 150Sn kVp groups (p<0,0001).
Numbers in parenthesis represent standard deviation).
kVp
mean CTDI (mGy)
mean DLP (mGycm)
120
19,65 (2,66)
487,10 (59,58)
150Sn
5,93(0,50)
136,17 (21,83)
Distribution of both readers' image quality score can be seen below,
by criteria.
In...
Conclusion
Theuse ofspectral filtration,
150 kVp and tube current modulation,
can potentially reduce radiation dose by more than 70%,
compared to 120 kVp,while maintaining diagnostic image quality.
Further studies,
including more patients,are recommended to confirm these findings,
including different patient sizes' impact upon results.
Personal information
The author would like to thank doctors Kaj Åge Hansen and Janus Mølgaard Christiansen for time spent in reviewing images.
References
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