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  5. A Quantification of the Accuracy of Proton Radiography for Patient Alignment of Intracranial Targets

A Quantification of the Accuracy of Proton Radiography for Patient Alignment of Intracranial Targets

M Pankuch1*, E DeJongh2 , A Panchal3 , S Boyer4 , D Alexander5 , N Kamens6 , A Pruneau7 , M Weirich8 , D DeJongh9 , V Rykalin10 , G Coutrakon11 , C Sarosiek12 , N Karonis13 , C Ordonez14 , J Winans15 , K Duffin16 , R Schulte17 , J Welsh18 , W Hartsell19 , (1) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (2) ProtonVDA, Naperville, IL, (3) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (4) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (5) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (6) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (7) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (8) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (9) ProtonVDA Inc, Naperville, IL, (10) ProtonVDA, Naperville, IL, (11) Northern Illinois University, Dekalb, IL, (12) Northern Illinois University, Dekalb, IL, (13) Northern Illinois University, Dekalb, IL, (14) Northern Illinois University, Dekalb, IL, (15) Northern Illinois University, Dekalb, IL, (16) Northern Illinois University, Dekalb, Illinois, (17) Loma Linda University, Loma Linda, CA, (18) ,,,(19) Northwestern Medicine Chicago Proton Center, Warrenville, IL

Presentations

(Sunday, 7/29/2018) 3:00 PM - 3:30 PM

Room: Exhibit Hall | Forum 5

Purpose: To quantify the accuracy of positional correction vectors obtained from TOPAS-simulated orthogonal proton radiographs of a patient head.

Methods: A clinical x-ray CT image set of a patient head was misaligned by 11 random positional offsets. The offset CT images were resampled back into the DICOM space of the original CT. X-ray and proton digitally reconstructed orthogonal radiographs (X-DRRs, p-DRRs) were generated for each of the 11 offset scenarios. X-DRR’s of the offset CTs were generated with a commercial treatment planning system. The p-DRR’s were simulated using the TOPAS model of a pCT radiography system currently under construction. The simulated detector data was fed into an iterative most reconstruction algorithm to produce the p-DRRs. Four experienced radiological technicians used a clinically available alignment software to obtain the correction vectors from each of the 30 DRR image sets. Correction vectors for both X-DRR’s and p-DRR’s were averaged and compared to the known misalignments from each offset CT image sets.

Results: The average alignment errors observed using the X-DRR’s in the Lt/Rt, Sup/Inf, Ant/Post directions were -0.002cm, -0.004cm, and 0.001cm, with standard deviations of 0.022cm, 0.019cm and 0.016cm, respectively. Translational errors observed with p-DRR’s were -0.011cm, 0.010cm, and 0.016cm, with standard deviations of 0.033 cm, 0.038 cm and 0.037 cm, respectively.

Conclusion: Whereas the primary benefit of proton radiography is the pre-treatment verification of water-equivalent proton pathlength in beam direction, these result show that 2D alignment accuracy and precision of p-DRRs for head alignments is comparable to that of X-DRRs.

Keywords

Protons, Radiography, Target Localization

Taxonomy

TH- External Beam- Particle therapy: Proton therapy - Development (new technology and techniques)

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