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Updated: Oct 29, 2025
Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
Planning target volume density impact on treatment planning for lung stereotactic body radiation therapy
Milovan Savanović1,2, Dražan Jaroš3, Jean-Noël Foulquier2
1Faculty of Medicine, University of Paris-Saclay, Le Kremlin-Bicêtre, France.
Background:
To evaluate the impact of the planning target volume (PTV) density on treatment planning for lung Stereotactic Body Radiation Therapy (SBRT).
Material And Methods:
The PTV coverage was analyzed in two groups of 40 lung SBRT patients. One group had PTV density <0.5 g/cm3, while the other group had PTV density >0.5 g/cm3. The treatments were planned in Pinnacle 9.10, using the collapsed cone convolution (CCC) algorithm. The prescribed dose was 60 Gy to the PTV in 4-8 fractions. Respecting constraint for the PTV coverage (D98% > 95%), we compared changes in the isodose line prescription, the number of monitor units (MU), maximum dose (Dmax), irradiated volume covered with 30 Gy (V30Gy), and the optimization planning volume (OPV).
Results:
For the same median values of the PTV coverage (98.3%), the differences are presented with median values between lower and higher density than 0.5 g/cm3. The isodose line prescription was 83 vs. 90% (p < 0.0001), the MUs were 2294 vs. 1655 MU (p < 0.0001), Dmax was 74.26 vs. 68.09 Gy (p < 0.0001), V30Gy was 117.03 vs. 104.81 cc (p = 0.04), and OPV was 28.48 vs. 39.35 cc (p < 0.001). By overriding the ITV density to 0.8 g/cm3, the isodose line prescription decreases. The Dmax and MUs decrease by 7%, V30Gy by 34%, and OPV by 70%.
Conclusion:
To obtain similar PTV coverage for PTV which is <0.5 g/cm3, a larger margin irradiating a large OPV was used. More MUs and a higher maximum dose were delivered. For the PTV density of ≤0.36 g/cm3, overriding is recommended to reduce the dose and irradiated volume.
