PMID- 34894408
OWN - NLM
STAT- MEDLINE
DCOM- 20220211
LR  - 20220211
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 49
IP  - 2
DP  - 2022 Feb
TI  - Technical note: Advancing size-specific dose estimates in CT examinations: Dose 
      estimates at longitudinal positions of scans.
PG  - 1303-1311
LID - 10.1002/mp.15402 [doi]
AB  - PURPOSE: American Association of Physicists in Medicine (AAPM) (Report 204) 
      introduced the size-specific dose estimate (SSDE) for the average dose to the 
      center of a fixed-mA scan. International standards establish a method that CT 
      manufacturers and radiation dose index monitoring software may use to calculate 
      SSDE(z) at longitudinal positions of scans with fixed mA or tube current 
      modulation, and its scan range average SSDE(z)  . We sought to test how accurate 
      SSDE(z) is in tracking the average dose to the transverse slab of an axial image 
      slice (D(slice) ), evaluated with Monte Carlo calculation, in the chest and 
      abdominopelvic examinations. METHODS: We retrospectively identified 65 
      consecutive adult patients undergoing whole-body CT for transcatheter aortic 
      valve implantation planning. Examination parameters (kV, mA, CTDI(vol) ) were 
      extracted from the DICOM headers. Patient water equivalent diameter D(W) (z) was 
      calculated at each image slice, excluding the patient table. A previously 
      validated Monte Carlo simulation (Geant4) program was used to evaluate D(slice) 
      from the chest and abdominopelvic examinations. Alternatively, SSDE(z) was 
      calculated at each slice. The results of the two methods were compared with 
      descriptive statistical outcomes (R, version 4.0.2). RESULTS: In chest and 
      abdominopelvic CT examinations, D(slice) largely changed with anatomic location 
      and uniformly fell off toward scan range edges. Scan range averages SSDE(z)  and 
      Dslice  were consistent within 2.5%-3.1% (median) and 6.3%-10.4% (maximum) in two 
      examinations. On individual image slices, SSDE(z) could be lower or higher than 
      D(slice) , with deviation ranging from -18.3% to 85% in two edges (2 x 5 cm) of 
      scan range and from -35.2% to 18.7% in the remaining central region of the scan. 
      CONCLUSION: This study provides critical inputs for quality assurance programs. 
      SSDE(z)  is useful to track the average dose of all image slices, but further 
      development may be useful for tracking patient dose at the level of individual 
      image slices, especially near a scan range edge.
CI  - (c) 2021 American Association of Physicists in Medicine.
FAU - Li, Xinhua
AU  - Li X
AD  - Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 
      Boston, Massachusetts, USA.
FAU - Marschall, Theodore A
AU  - Marschall TA
AD  - Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 
      Boston, Massachusetts, USA.
FAU - Yang, Kai
AU  - Yang K
AD  - Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 
      Boston, Massachusetts, USA.
FAU - Liu, Bob
AU  - Liu B
AD  - Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 
      Boston, Massachusetts, USA.
LA  - eng
PT  - Journal Article
DEP - 20211222
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
SB  - IM
MH  - Adult
MH  - Humans
MH  - Monte Carlo Method
MH  - Radiation Dosage
MH  - Retrospective Studies
MH  - *Software
MH  - *Tomography, X-Ray Computed
OTO - NOTNLM
OT  - average dose to image slice
OT  - comparison
OT  - computed tomography
OT  - longitudinal position
OT  - size-specific dose estimate
EDAT- 2021/12/12 06:00
MHDA- 2022/02/12 06:00
CRDT- 2021/12/11 17:03
PHST- 2021/10/29 00:00 [revised]
PHST- 2021/07/26 00:00 [received]
PHST- 2021/11/22 00:00 [accepted]
PHST- 2021/12/12 06:00 [pubmed]
PHST- 2022/02/12 06:00 [medline]
PHST- 2021/12/11 17:03 [entrez]
AID - 10.1002/mp.15402 [doi]
PST - ppublish
SO  - Med Phys. 2022 Feb;49(2):1303-1311. doi: 10.1002/mp.15402. Epub 2021 Dec 22.