PMID- 15763313
OWN - NLM
STAT- MEDLINE
DCOM- 20050711
LR  - 20191210
IS  - 0167-8140 (Print)
IS  - 0167-8140 (Linking)
VI  - 74
IP  - 3
DP  - 2005 Mar
TI  - Clinical impact of the detector size effect in 3D-CRT.
PG  - 315-22
AB  - OBJECTIVE: The detector size artificially increases the measured penumbra of 
      radiotherapy fields. The aim of this work is to determine the influence of the 
      detector size when planning three-dimensional conformal radiation therapy 
      (3D-CRT) treatments. MATERIAL AND METHODS: Two anatomical sites of interest in 
      3D-CRT were studied: prostate and hypophysis chordoma. Conventional 3D-CRT 
      treatments for two cases in these locations were planned with a FOCUS 4.0.0 
      (Computerized Medical Systems, USA) treatment planning system (TPS) equipped with 
      Fast Fourier Transform Convolution (FFTC) and Multigrid Superposition (MGS) 
      algorithms, making use of beams modelled from radiation profiles measured either 
      with a 2.0 mm diameter detector (PFD(3G) diode) or with a 5.5 mm diameter 
      detector (PTW-31002 ionisation chamber). These detectors cover up the range of 
      detector sizes commonly used to measure radiation profiles for 3D-CRT. 
      Dose-volume histograms (DVHs), radiobiological indexes, tumor control probability 
      (TCP) and normal tissue complication probability (NTCP) were analysed and 
      compared for planning target volumes (PTVs) and organs at risk (OAR) studied. 
      RESULTS: Important differences in DVH were found. OAR received higher dose levels 
      when a 5.5 mm detector was used to measure profiles compared to the case in which 
      a 2.0 mm detector was used. A 2 Gy increment in the mean rectal dose was found 
      when the larger detector was used. In the same way, NTCP of brain stem in 
      hypophysis chordoma treatments was doubled when this detector was used. 
      CONCLUSION: The current use of ionisation chambers of about 5 mm active diameter 
      to get the necessary data to model treatment machines in radiotherapy treatment 
      planning systems (TPS) implies a significant overirradiation of OAR close to the 
      PTV in 3D-CRT treatments due to errors in the measured penumbra of beam profiles. 
      To avoid this overirradiation, the measured profiles should either being acquired 
      with a suitable detector size (2-3 mm active diameter) or being deconvoluted.
FAU - Garcia-Vicente, Feliciano
AU  - Garcia-Vicente F
AD  - Department of Radiation Oncology and Medical Physics, Hospital Universitario de 
      la Princesa, Diego de Leon 62, 28006 Madrid, Spain.
FAU - Bejar, Maria Jose
AU  - Bejar MJ
FAU - Perez, Leopoldo
AU  - Perez L
FAU - Torres, Juan J
AU  - Torres JJ
LA  - eng
PT  - Evaluation Study
PT  - Journal Article
DEP - 20041125
PL  - Ireland
TA  - Radiother Oncol
JT  - Radiotherapy and oncology : journal of the European Society for Therapeutic 
      Radiology and Oncology
JID - 8407192
SB  - IM
MH  - *Algorithms
MH  - Chordoma/radiotherapy
MH  - Humans
MH  - Imaging, Three-Dimensional
MH  - Male
MH  - Pituitary Neoplasms/radiotherapy
MH  - Prostatic Neoplasms/radiotherapy
MH  - Radiation Injuries/prevention & control
MH  - Radiometry
MH  - Radiotherapy, Conformal/*instrumentation/*methods
MH  - Reproducibility of Results
MH  - Sensitivity and Specificity
EDAT- 2005/03/15 09:00
MHDA- 2005/07/12 09:00
CRDT- 2005/03/15 09:00
PHST- 2004/04/19 00:00 [received]
PHST- 2004/10/11 00:00 [revised]
PHST- 2004/10/28 00:00 [accepted]
PHST- 2005/03/15 09:00 [pubmed]
PHST- 2005/07/12 09:00 [medline]
PHST- 2005/03/15 09:00 [entrez]
AID - S0167-8140(04)00514-6 [pii]
AID - 10.1016/j.radonc.2004.10.012 [doi]
PST - ppublish
SO  - Radiother Oncol. 2005 Mar;74(3):315-22. doi: 10.1016/j.radonc.2004.10.012. Epub 
      2004 Nov 25.