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Dosimetric impact of different CT datasets for stereotactic treatment planning using 3D conformal radiotherapy or volumetric modulated arc therapy.

Oechsner M, Odersky L, Berndt J, Combs SE, Wilkens JJ, Duma MN - Radiat Oncol (2015)

Bottom Line: Only small differences were found for PTV parameters between the four CT datasets.PCT, AIP and MidV resulted in similar doses.If a 4DCT is acquired PCT can be omitted using AIP or MidV for treatment planning.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675, Munich, Germany. markus.oechsner@mri.tum.de.

ABSTRACT

Background: The purpose of this study was to assess the impact on dose to the planning target volume (PTV) and organs at risk (OAR) by using four differently generated CT datasets for dose calculation in stereotactic body radiotherapy (SBRT) of lung and liver tumors. Additionally, dose differences between 3D conformal radiotherapy and volumetric modulated arc therapy (VMAT) plans calculated on these CT datasets were determined.

Methods: Twenty SBRT patients, ten lung cases and ten liver cases, were retrospectively selected for this study. Treatment plans were optimized on average intensity projection (AIP) CTs using 3D conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT). Afterwards, the plans were copied to the planning CTs (PCT), maximum intensity projection (MIP) and mid-ventilation (MidV) CT datasets and dose was recalculated keeping all beam parameters and monitor units unchanged. Ipsilateral lung and liver volumes and dosimetric parameters for PTV (Dmean, D2, D98, D95), ipsilateral lung and liver (Dmean, V30, V20, V10) were determined and statistically analysed using Wilcoxon test.

Results: Significant but small mean differences were found for PTV dose between the CTs (lung SBRT: ≤2.5 %; liver SBRT: ≤1.6 %). MIPs achieved the smallest lung and the largest liver volumes. OAR mean doses in MIP plans were distinctly smaller than in the other CT datasets. Furthermore, overlapping of tumors with the diaphragm results in underestimated ipsilateral lung dose in MIP plans. Best agreement was found between AIP and MidV (lung SBRT). Overall, differences in liver SBRT were smaller than in lung SBRT and VMAT plans achieved slightly smaller differences than 3D-CRT plans.

Conclusions: Only small differences were found for PTV parameters between the four CT datasets. Larger differences occurred for the doses to organs at risk (ipsilateral lung, liver) especially for MIP plans. No relevant differences were observed between 3D-CRT or VMAT plans. MIP CTs are not appropriate for OAR dose assessment. PCT, AIP and MidV resulted in similar doses. If a 4DCT is acquired PCT can be omitted using AIP or MidV for treatment planning.

No MeSH data available.


Related in: MedlinePlus

Lung and a liver volumes of all patients. In MIP CTs the determined lung volume was always smaller and the liver volume was always larger than in the other CT datasets. AIP: average intensity projection CT, PCT: planning CT, MIP: maximum intensity projection CT, MidV: mid-ventilation CT
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Fig2: Lung and a liver volumes of all patients. In MIP CTs the determined lung volume was always smaller and the liver volume was always larger than in the other CT datasets. AIP: average intensity projection CT, PCT: planning CT, MIP: maximum intensity projection CT, MidV: mid-ventilation CT

Mentions: Figure 2 shows the lung and liver volumes of all patients. In MIP CTs the lung volume was significantly smaller than in all other CT datasets (p ≤ 0.01). The largest volumes were contoured in PCTs but that was not statistically significant. The best agreement for lung volumes was found between MidV and AIP CTs (−1.5 ± 3.0 %). For the liver SBRT cases, the largest liver volume was always contoured in MIP CTs (p ≤ 0.01). The smallest differences were found between PCT and AIP (0.5 ± 4.8 %). PCT and AIP achieved also the smallest liver volumes as compared to the other CT datasets.Fig. 2


Dosimetric impact of different CT datasets for stereotactic treatment planning using 3D conformal radiotherapy or volumetric modulated arc therapy.

Oechsner M, Odersky L, Berndt J, Combs SE, Wilkens JJ, Duma MN - Radiat Oncol (2015)

Lung and a liver volumes of all patients. In MIP CTs the determined lung volume was always smaller and the liver volume was always larger than in the other CT datasets. AIP: average intensity projection CT, PCT: planning CT, MIP: maximum intensity projection CT, MidV: mid-ventilation CT
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4666088&req=5

Fig2: Lung and a liver volumes of all patients. In MIP CTs the determined lung volume was always smaller and the liver volume was always larger than in the other CT datasets. AIP: average intensity projection CT, PCT: planning CT, MIP: maximum intensity projection CT, MidV: mid-ventilation CT
Mentions: Figure 2 shows the lung and liver volumes of all patients. In MIP CTs the lung volume was significantly smaller than in all other CT datasets (p ≤ 0.01). The largest volumes were contoured in PCTs but that was not statistically significant. The best agreement for lung volumes was found between MidV and AIP CTs (−1.5 ± 3.0 %). For the liver SBRT cases, the largest liver volume was always contoured in MIP CTs (p ≤ 0.01). The smallest differences were found between PCT and AIP (0.5 ± 4.8 %). PCT and AIP achieved also the smallest liver volumes as compared to the other CT datasets.Fig. 2

Bottom Line: Only small differences were found for PTV parameters between the four CT datasets.PCT, AIP and MidV resulted in similar doses.If a 4DCT is acquired PCT can be omitted using AIP or MidV for treatment planning.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675, Munich, Germany. markus.oechsner@mri.tum.de.

ABSTRACT

Background: The purpose of this study was to assess the impact on dose to the planning target volume (PTV) and organs at risk (OAR) by using four differently generated CT datasets for dose calculation in stereotactic body radiotherapy (SBRT) of lung and liver tumors. Additionally, dose differences between 3D conformal radiotherapy and volumetric modulated arc therapy (VMAT) plans calculated on these CT datasets were determined.

Methods: Twenty SBRT patients, ten lung cases and ten liver cases, were retrospectively selected for this study. Treatment plans were optimized on average intensity projection (AIP) CTs using 3D conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT). Afterwards, the plans were copied to the planning CTs (PCT), maximum intensity projection (MIP) and mid-ventilation (MidV) CT datasets and dose was recalculated keeping all beam parameters and monitor units unchanged. Ipsilateral lung and liver volumes and dosimetric parameters for PTV (Dmean, D2, D98, D95), ipsilateral lung and liver (Dmean, V30, V20, V10) were determined and statistically analysed using Wilcoxon test.

Results: Significant but small mean differences were found for PTV dose between the CTs (lung SBRT: ≤2.5 %; liver SBRT: ≤1.6 %). MIPs achieved the smallest lung and the largest liver volumes. OAR mean doses in MIP plans were distinctly smaller than in the other CT datasets. Furthermore, overlapping of tumors with the diaphragm results in underestimated ipsilateral lung dose in MIP plans. Best agreement was found between AIP and MidV (lung SBRT). Overall, differences in liver SBRT were smaller than in lung SBRT and VMAT plans achieved slightly smaller differences than 3D-CRT plans.

Conclusions: Only small differences were found for PTV parameters between the four CT datasets. Larger differences occurred for the doses to organs at risk (ipsilateral lung, liver) especially for MIP plans. No relevant differences were observed between 3D-CRT or VMAT plans. MIP CTs are not appropriate for OAR dose assessment. PCT, AIP and MidV resulted in similar doses. If a 4DCT is acquired PCT can be omitted using AIP or MidV for treatment planning.

No MeSH data available.


Related in: MedlinePlus