PMID- 28519496
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20191120
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 39
IP  - 6Part4
DP  - 2012 Jun
TI  - SU-E-I-45: Measurement of CT Dose to An HDPE Phantom Using Calorimetry: A 
      Feasibility Study.
PG  - 3635
LID - 10.1118/1.4734760 [doi]
AB  - PURPOSE: Radiation dose in CT is traditionally evaluated using an ionization 
      chamber calibrated in terms of air kerma in a phantom of specific dimensions. The 
      radiation absorbed dose, J/kg, can also be realized directly by measuring the 
      temperature rise in the medium. We investigate using this primary method to 
      determine the CT dose at a point (a few mm), using the recently proposed (APMM 
      TG220) high density polyethylene (HDPE) phantom as a medium. METHODS: The 
      calorimeter detection scheme is adapted from the second generation NIST water 
      calorimeter using sensitive thermistors in a Wheatstone bridge powered by a 
      lock-in amplifier. The temperature sensitivity is about 3 microK. The expected 
      temperature rise in PE is about 0.6 mK per Gy. The thermistor sensors were placed 
      inside a 26 cm dia. x 10 cm HDPE phantom. Two preliminary tests were made: at a 
      linear accelerator with a 6 MV photon beam, and at a 16-slice CT scanner with a 
      120 kV beam, each with the thermal sensor and with a calibrated ionization 
      chamber. RESULTS: The 6 MV photon beam with 10 on/off cycles at 60 s each yielded 
      the (uncorrected) run-to-run average dose of 3.06 Gy per cycle (sdm 0.3%), about 
      8% higher than the Result from the ionization chamber (calibrated in terms of 
      absorbed to water). The CT measurements were also made in the middle section of 
      the TG200 30 cm phantom. Twenty consecutive axial scans at 250 mA, which delivers 
      a nominal accumulated dose (CTDIvol) of 705 mGy in 50 s at three axial and three 
      radial locations were measured. The accumulated dose measured by the ionization 
      chamber at the center of the smaller phantom was 347 mGy. CONCLUSIONS: The 
      calorimeter data show qualitative tracking of the chamber measurements. Detailed 
      thermal and electrical analysis of the system are planned to obtain quantitative 
      results.
CI  - (c) 2012 American Association of Physicists in Medicine.
FAU - Chen-Mayer, H
AU  - Chen-Mayer H
AD  - National Institute of Standards and Technology, Gaithersburg, MD.
FAU - Tosh, R
AU  - Tosh R
AD  - National Institute of Standards and Technology, Gaithersburg, MD.
FAU - Bateman, F
AU  - Bateman F
AD  - National Institute of Standards and Technology, Gaithersburg, MD.
FAU - Zimmerman, B
AU  - Zimmerman B
AD  - National Institute of Standards and Technology, Gaithersburg, MD.
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
OTO - NOTNLM
OT  - Amplifiers
OT  - Calorimeters
OT  - Computed tomography
OT  - Ion beam detectors
OT  - Ionization chambers
OT  - Ionizing radiation
OT  - Linear accelerators
OT  - Photons
OT  - Temperature measurement
OT  - Thermistors
EDAT- 2012/06/01 00:00
MHDA- 2012/06/01 00:01
CRDT- 2017/05/19 06:00
PHST- 2017/05/19 06:00 [entrez]
PHST- 2012/06/01 00:00 [pubmed]
PHST- 2012/06/01 00:01 [medline]
AID - 10.1118/1.4734760 [doi]
PST - ppublish
SO  - Med Phys. 2012 Jun;39(6Part4):3635. doi: 10.1118/1.4734760.