PMID- 11699497
OWN - NLM
STAT- MEDLINE
DCOM- 20011204
LR  - 20190708
IS  - 0360-3016 (Print)
IS  - 0360-3016 (Linking)
VI  - 51
IP  - 3
DP  - 2001 Nov 1
TI  - An anatomy-based beam segmentation tool for intensity-modulated radiation therapy 
      and its application to head-and-neck cancer.
PG  - 849-59
AB  - PURPOSE: In segmental intensity-modulated radiation therapy (IMRT), the beam 
      fluences result from superposition of unmodulated beamlets (segments). In the 
      inverse planning approach, segments are a result of ''clipping'' intensity maps. 
      At Ghent University Hospital, segments are created by an anatomy-based 
      segmentation tool (ABST). The objective of this report is to describe ABST. 
      METHODS AND MATERIALS: For each beam direction, ABST generates segments by a 
      multistep procedure. During the initial steps, beam's eye view (BEV) projections 
      of the planning target volumes (PTVs) and organs at risk (OARs) are generated. 
      These projections are used to make a segmentation grid with negative values 
      across the expanded OAR projections and positive values elsewhere inside the 
      expanded PTV projections. Outside these regions, grid values are set to zero. 
      Subsequent steps transform the positive values of the segmentation grid to 
      increase with decreasing distance to the OAR projections and to increase with 
      longer pathlengths measured along rays from their entrance point through the skin 
      contours to their respective grid point. The final steps involve selection of 
      iso-value lines of the segmentation grid as segment outlines which are 
      transformed to leaf and jaw positions of a multileaf collimator (MLC). Segment 
      shape approximations, if imposed by MLC constraints, are done in a way that 
      minimizes overlap between the expanded OAR projections and the segment aperture. 
      RESULTS: The ABST procedure takes about 3 s/segment on a Compaq Alpha XP900 
      workstation. In IMRT planning problems with little complexity, such as laryngeal 
      (example shown) or thyroid cancer, plans that are in accordance with the clinical 
      protocol can be generated by weighting the segments generated by ABST without 
      further optimization of their shapes. For complex IMRT plans such as paranasal 
      sinus cancer (not shown), ABST generates a start assembly of segments from which 
      the shapes and weights are further optimized. CONCLUSIONS: ABST is a fast 
      procedure to generate a set of segments for IMRT planning. The plan is finalized 
      by assigning weights to the segments or by direct optimization of segment shapes 
      and weights. ABST allows us to avoid the step of translating optimized intensity 
      maps to sequences of segments.
FAU - De Gersem, W
AU  - De Gersem W
AD  - Division of Radiotherapy, Ghent University Hospital (GUH), Belgium.
FAU - Claus, F
AU  - Claus F
FAU - De Wagter, C
AU  - De Wagter C
FAU - De Neve, W
AU  - De Neve W
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Int J Radiat Oncol Biol Phys
JT  - International journal of radiation oncology, biology, physics
JID - 7603616
SB  - IM
MH  - *Algorithms
MH  - Female
MH  - Head and Neck Neoplasms/*radiotherapy
MH  - Humans
MH  - Laryngeal Neoplasms/radiotherapy
MH  - Neck/*anatomy & histology
MH  - Physical Phenomena
MH  - Physics
MH  - Radiotherapy Planning, Computer-Assisted/*methods
MH  - Radiotherapy, Conformal/*instrumentation
MH  - Software
EDAT- 2001/11/09 10:00
MHDA- 2002/01/05 10:01
CRDT- 2001/11/09 10:00
PHST- 2001/11/09 10:00 [pubmed]
PHST- 2002/01/05 10:01 [medline]
PHST- 2001/11/09 10:00 [entrez]
AID - S0360-3016(01)01727-8 [pii]
AID - 10.1016/s0360-3016(01)01727-8 [doi]
PST - ppublish
SO  - Int J Radiat Oncol Biol Phys. 2001 Nov 1;51(3):849-59. doi: 
      10.1016/s0360-3016(01)01727-8.