PMID- 19610314
OWN - NLM
STAT- MEDLINE
DCOM- 20090827
LR  - 20220331
IS  - 0094-2405 (Print)
IS  - 0094-2405 (Linking)
VI  - 36
IP  - 6
DP  - 2009 Jun
TI  - Image-guided respiratory-gated lung stereotactic body radiotherapy: which target 
      definition is optimal?
PG  - 2248-57
AB  - In stereotactic body radiotherapy (SBRT), the respiratory tumor motion makes 
      target definition very important to achieve optimal clinical results for 
      treatment of early stage lung cancer. In this article, the authors quantitatively 
      evaluated the influence of different target definition strategies on image-guided 
      respiratory-gated SBRT for lung cancer. Twelve lung cancer patients with 4D CT 
      estimated target motion of >1 cm were selected for this retrospective study. An 
      experienced physician contoured gross target volumes (GTVs) at each 4D CT phase 
      for all patients. Three types of internal target volumes (ITVs) were generated 
      based on the contoured GTVs:(1) ITVBH: GTV contoured on deep expiration 
      breath-hold (BH) CT with an isotropic internal margin (IM) of 5 mm; (2) ITV50: 
      GTV contoured at the end-expiration (50%) phase with an isotropic IM of 5 mm; (3) 
      ITVGW: Composite volume of all GTVs within the gating window, defined as several 
      phases around phase 50% with residual target motion of <5 mm. Planning target 
      volumes (PTVs) were generated by adding 3 mm isotropic setup error margin to 
      ITVs. Three treatment plans, namely, PlanBH, Plan50, and PlanGW, were created 
      based on the three PTVs. Identical beam settings and planning constraints were 
      used for all three plans for each patient. The prescription dose was 60 Gy in 
      three fractions. The potential toxicities to the critical organs were quantified 
      by mean lung dose (MLD), lung volume receiving >20 Gy (V20), mean heart dose 
      (MHD), and spinal cord dose (SCD). It is shown that the tumor volume and dose 
      coverage are comparable for PlanBH and Plan50. On average, PTVGW are 38% less 
      than PTV50. Although for most patients PTV50 encompasses the entire PTVGW, up to 
      5.48 cm3 (6%) of PTVGW is outside PTV50. Compared to Plan50, prescribed 
      percentage is about 2% higher for PlanGW, and the average dose decreases in 
      critical organs are 0.78 Gy for MLD, 1.02% for V20, 0.61 Gy for MHD and 0.59 Gy 
      for maximum SCD. For the cases receiving high lung and heart dose with Plan50, 
      the dose reduction is 1.0 Gy for MLD and 1.14 Gy for MHD with PlanGW. Our 
      preliminary results show that a patient-specific ITV, defined as the composite 
      volume of all GTVs within the gating window, may be used to define PTV in 
      image-guided respiratory-gated SBRT. This approach potentially reduces the 
      irradiated volume of normal tissue further without sacrificing target dose 
      coverage and thus may minimize the risk of treatment-related toxicities.
FAU - Zhao, Bo
AU  - Zhao B
AD  - Department of Radiation Oncology, University of Pittsburgh Cancer Institute, 5230 
      Centre Avenue, Pittsburgh, Pennsylvania 15232, USA.
FAU - Yang, Yong
AU  - Yang Y
FAU - Li, Tianfang
AU  - Li T
FAU - Li, Xiang
AU  - Li X
FAU - Heron, Dwight E
AU  - Heron DE
FAU - Huq, M Saiful
AU  - Huq MS
LA  - eng
PT  - Clinical Trial
PT  - Journal Article
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
SB  - IM
MH  - Aged
MH  - Aged, 80 and over
MH  - Female
MH  - Humans
MH  - Lung Neoplasms/*surgery
MH  - Male
MH  - Middle Aged
MH  - Radiosurgery/*methods
MH  - Reproducibility of Results
MH  - Respiratory-Gated Imaging Techniques/*methods
MH  - Sensitivity and Specificity
MH  - Surgery, Computer-Assisted/*methods
MH  - Tomography, X-Ray Computed/*methods
MH  - Treatment Outcome
EDAT- 2009/07/21 09:00
MHDA- 2009/08/28 09:00
CRDT- 2009/07/21 09:00
PHST- 2009/07/21 09:00 [entrez]
PHST- 2009/07/21 09:00 [pubmed]
PHST- 2009/08/28 09:00 [medline]
AID - 10.1118/1.3129161 [doi]
PST - ppublish
SO  - Med Phys. 2009 Jun;36(6):2248-57. doi: 10.1118/1.3129161.