PMID- 25370643
OWN - NLM
STAT- MEDLINE
DCOM- 20150624
LR  - 20170214
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 41
IP  - 11
DP  - 2014 Nov
TI  - Radiation dose calculations for CT scans with tube current modulation using the 
      approach to equilibrium function.
PG  - 111910
LID - 10.1118/1.4898124 [doi]
AB  - PURPOSE: The approach to equilibrium function has been used previously to 
      calculate the radiation dose to a shift-invariant medium undergoing CT scans with 
      constant tube current [Li, Zhang, and Liu, Med. Phys. 39, 5347-5352 (2012)]. The 
      authors have adapted this method to CT scans with tube current modulation (TCM). 
      METHODS: For a scan with variable tube current, the scan range was divided into 
      multiple subscan ranges, each with a nearly constant tube current. Then the dose 
      calculation algorithm presented previously was applied. For a clinical CT scan 
      series that presented tube current per slice, the authors adopted an efficient 
      approach that computed the longitudinal dose distribution for one scan length 
      equal to the slice thickness, which center was at z = 0. The cumulative dose at a 
      specific point was a summation of the contributions from all slices and the 
      overscan. RESULTS: The dose calculations performed for a total of four constant 
      and variable tube current distributions agreed with the published results of 
      Dixon and Boone [Med. Phys. 40, 111920 (14pp.) (2013)]. For an abdomen/pelvis 
      scan of an anthropomorphic phantom (model ATOM 701-B, CIRS, Inc., VA) on a GE 
      Lightspeed Pro 16 scanner with 120 kV, N x T = 20 mm, pitch = 1.375, z axis 
      current modulation (auto mA), and angular current modulation (smart mA), dose 
      measurements were performed using two lines of optically stimulated luminescence 
      dosimeters, one of which was placed near the phantom center and the other on the 
      surface. Dose calculations were performed on the central and peripheral axes of a 
      cylinder containing water, whose cross-sectional mass was about equal to that of 
      the ATOM phantom in its abdominal region, and the results agreed with the 
      measurements within 28.4%. CONCLUSIONS: The described method provides an 
      effective approach that takes into account subject size, scan length, and 
      constant or variable tube current to evaluate CT dose to a shift-invariant 
      medium. For a clinical CT scan, dose calculations may be performed with a 
      water-containing cylinder whose cross-sectional mass is equal to that of the 
      subject. This method has the potential to substantially improve evaluations of 
      patient dose from clinical CT scans, compared to CTDIvol, size-specific dose 
      estimate (SSDE), or the dose evaluated for a TCM scan with a constant tube 
      current equal to the average tube current of the TCM scan.
FAU - Li, Xinhua
AU  - Li X
AD  - Division of Diagnostic Imaging Physics and Webster Center for Advanced Research 
      and Education in Radiation, Department of Radiology, Massachusetts General 
      Hospital, Boston, Massachusetts 02114.
FAU - Zhang, Da
AU  - Zhang D
AD  - Division of Diagnostic Imaging Physics and Webster Center for Advanced Research 
      and Education in Radiation, Department of Radiology, Massachusetts General 
      Hospital, Boston, Massachusetts 02114.
FAU - Liu, Bob
AU  - Liu B
AD  - Division of Diagnostic Imaging Physics and Webster Center for Advanced Research 
      and Education in Radiation, Department of Radiology, Massachusetts General 
      Hospital, Boston, Massachusetts 02114.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
SB  - IM
MH  - *Radiation Dosage
MH  - Tomography, X-Ray Computed/*methods
EDAT- 2014/11/06 06:00
MHDA- 2015/06/25 06:00
CRDT- 2014/11/06 06:00
PHST- 2014/11/06 06:00 [entrez]
PHST- 2014/11/06 06:00 [pubmed]
PHST- 2015/06/25 06:00 [medline]
AID - 10.1118/1.4898124 [doi]
PST - ppublish
SO  - Med Phys. 2014 Nov;41(11):111910. doi: 10.1118/1.4898124.