3DVH. Introduction. Utilizzo di una gamma function 3D (3DVH) e la sua integrazione per tecniche IMRT/Volumetriche

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Armando Fadda
6 anni fa
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Utilizzo di una gamma function 3D (3DVH) e la sua integrazione per tecniche IMRT/Volumetriche Sara

? Are they clinically significant? What are the best passing criteria?

distribution and patient DVH analysis, the plan verification has to be based on the same features analysis.

1 Utilizzo di una gamma function 3D (3DVH) e la sua integrazione per tecniche IMRT/Volumetriche Sara Bresciani D.O. Fisica Sanitaria, IRCCS Candiolo sara.bresciani@ircc.it What do these errors mean?? Are they clinically significant? What are the best passing criteria? Beyond the planar verification Considering that the plan approval criteria on TPS consist on 3D dose distribution and patient DVH analysis, the plan verification has to be based on the same features analysis. 3DVH Introduction Application that uses the classical 2D/3D QA measures to perturb the patient dose planned on TPS to obtain the equivalent 3D plan actually erogated. 1

Patient RT Structure device RT Dose device

(PDP) Anatomy Specific Dose Evaluation PDP

per-beam dose contributions Each Patient

2 Patient RT Dose towards real DVH on CT patients phantom patient Patient RT Plan Patient RT Structure device RT Dose device measurement 3DVH Planned Dose Perturbation (PDP) Anatomy Specific Dose Evaluation PDP Algorithm Each Error Map is ray-traced through the TPS Patient Dose Grid Each Patient Dose Voxel is divided into per-beam dose contributions Each Patient Dose voxel is perturbed based on beam/errors D Pa Corrected 2

Case 1: significative increase of Dmax to PTV N /PTV Boost QC pre-treatment Tolleranze 3%-3mm

1 Campo 3 98.0 95.6 Campo 4 92.9 85.7 Campo 5 97.7 88.7 Media 95.8 89.

6 Tolleranze 3%-3mm 2%-2mm 1%-1mm Gamma* Campo 1 95.0 86.1 51.3 Campo 2 98.3 91.1 58.

5 Campo 7 91.9 82.7 51.8 Media 94.4 85.7 54.9 Local Gamma Index %GP=93.1; 97.

3 Case 1: significative increase of Dmax to PTV N /PTV Boost QC pre-treatment Tolleranze 3%-3mm 2%-2mm Gamma* Campo Campo Campo Campo Campo Media Global Gamma Index Tolleranze 3%-3mm 2%-2mm Gamma* Campo Campo Campo Campo Campo Media Local Gamma Index Case 2: significative reduction of D95 to PTV Boost %GP=91.9; 98.6 Tolleranze 3%-3mm 2%-2mm 1%-1mm Gamma* Campo Campo Campo Campo Campo Campo Campo Media Local Gamma Index %GP=93.1; 97.6 Tolleranze 3%-3mm 2%-2mm 1%-1mm Gamma* Campo Campo Campo Campo Campo Campo Campo Media Global Gamma Index 3

4 Comparison between TPS DVH (solid line) and 3DVH (dashed line) PTV Boost IMRT: 4.5% D95 in comparison with the approved plan Clinical Impact? Insufficient coverage of PTV Case 3: good plan with %GP < 95% % Gamma Pass with a 3% 3mm threshold 94.1% Brainsterm Dmean=-3.5% 4

Patients 27 PP patients 15 HN patients Pretreatment verifications were performed for all patients plans 2D-Array: MapCheck 2D-Array: MapCheck 2

the% GP: average %GP calculated for PP and HN patients For all of the patients we evaluated the %GP using two different calculation methods and three

5 Patients 27 PP patients 15 HN patients Pretreatment verifications were performed for all patients plans 2D-Array: MapCheck 2D-Array: MapCheck 2 routinely used in our Institute, with absolute dose calibration, and the software SNC patient (Sun Nuclear Corporation, Melbourne, FL) Evaluation of the% GP: average %GP calculated for PP and HN patients For all of the patients we evaluated the %GP using two different calculation methods and three different acceptance criteria, as previously described. In the overall sample, we calculated a total number of 252 %GP data points. Maximum and minimum values %GP 5

6 DVH values PTV: we took into account as relevant dose values D Mean and D 95%. OAR: D 2% (dose to 2% volume) for the spinal cord and D Mean for parotids (HN patients), V 50Gy and V 70Gy are taken into account for rectum and D Mean for bladder (PP patients) Anatomical Region Structure Analyzed Dose PTV1 (Pelvic Lymph Nodes) D Mean, D 95 PP PTV2 (Boost) D Mean, D 95 Rectum V 50, V 70 Bladder D Mean PTV Boost D Mean, D 95 HN Spinal Cord D 2% Parotid R D Mean Parotid L D Mean Dose comparison and differences estimation HR Prostate Head & Neck The t-test results between the planned and estimated DVH values showed that mean values were comparable (p> 0.05) this indicates that there were no systematic errors 6

7 Range and average absolute errors (%) for clinically relevant metrics in the case of all plans (N) meeting a specific %GP threshold ( 95%) (for 3%/3mm and 2%/2mm criteria). Observed errors (%) in DVH metrics for plans exceeding >95% GP Structures Mean absolute error (%) 3%/3mm (3%/3mm and 2%/2mm criteria) 2%/2mm Global (N=41)/ Local (N=26) Global (N=7)/ Local (N=1) PP patients PTV1 (-5.07, 1.18)/(-1.64, 1.18) D Mean 1.20 / 1.12 (-2.71, 1.84)/(-7.86, 0.81) D / 1.44 (-3.45, 0.85)/(-3.01, 0.85) DMean 2.79 / 2.28 PTV2 (-11.95, 3.61)/(-11.95, 4.23) D / 3.16 (-8.06, 6.69)/(-2.57, 6.69) Rectum D Mean 2.97 / 3.03 (-3.83, 2.16)/(3.83, 2.16) Baldder D Mean 2.09 / 2.82 (-0.06, 0.88)/ no range only 1 pts 0.78 / 0.55 (0.55, 1.10) 0.36 / 0.06 (-4.64/-1.64) 2.28 / 0.92 (-3.01, -0.92) 3.33 / 1.64 (-2.56, -1.41) 1.82 / 1.50 (-0.62, 0.46) 0.43 / 0.62 Structures Mean absolute error (%) Observed errors (%) in DVH metrics for plans exceeding >95% GP (3%/3mm and 2%/2mm criteria) 3%/3mm 2%/2mm Global (N=41)/ Local (N=26) Global (N=7)/ Local (N=1) HN patients (-4.35, 1.09)/(-2.37, 1.09) 1.43 / 1.00 PTV boost (-7.10, 0.27)/(-6.18, 0.27) / 1.59 Spinal Cord D 2% (-4.40, 0.71)/(-1.53, 0.71) 1.22 / 0.42 (-0.64, 0.611)/ no range only 1 pts 0.44 / 0.64 (-1.40, -0.20) 0.72 / 1.40 (-0.90, 0.18) 0.42 / 0.23 R- Parotid D Mean (-15.38, 4.46)/(-15.38, 4.46) 2.64 / 1.78 L-Parotid D Mean ( , 4.32)/(-11.03, 4.32) 2.53 / 1.28 (-0.28, 4.46) 1.78 / 4.46 (-1.81, -0.23) 1.28 / 1.61 Gamma index is a good diagnostic test? 7

8 Sensitivity + Specificity The sensitivity of a clinical test refers to the ability of the test to correctly identify those pre treatment QA with the errors. FN : all the cases that have DVH errors higher than 5% or 3% and %GP higher than 95% TP : all the cases that have DVH errors higher than 5% or 3% and %GP lower than 95%. Sensitivity Specificity Tolerance 3% 3%/3mm 2%/2mm -local global local global Tolerance 5% 3%/3mm 2%/2mm -local global local global Clinical impact Gamma criteria 3%/3mm globale <95%: 1 3%/3mm locale <95%: 11 3DVH OAR: QUANTEC reccomendation All plans respect dose constraints Target: ICRU reccomendation D95%>95% 12 /27 not approvable 8

techniques PACS MRI TC Software QA (SNC patient, 3DVH) RT dose PET TC

9 Towards the integration: ita PACS Patient-specific QA is continuing to evolve towards more specific and sensitive measurement and analysis techniques PACS MRI TC Software QA (SNC patient, 3DVH) RT dose PET TC Treatment Planning System: Eclipse, Pinnacle, Oncentra, 4 Tomo workstations 9

10 Thank you for your attention! 10

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