Intesity Modulated Radiation Therapy Quality Assurance

Patent-Specific IMRT QA: ِِA Developed Program/Software for Dose Distributions Evaluation (Gamma Calculation)

The work is about the dose evaluation of two dose distributions (reference and evaluated distributions, or measurement and plan dose distributions). We developed a program does the calculation of dose difference (DD), distance to agreement (DTA) and gamma index. The program is validated with Daniel Low results for two synthesized relative dose distributions that published in AAPM TG-120 report. 

Fig. 1: Validation our program with Daniel Low works (AAPM TG-120). Left, Daniel Low works: a) reference distribution, b) evaluated distribution, c) dose difference (b) – (a), d) distance to agreement (DTA), e) composite (gamma binary), and f) gamma index (3% 3 mm)., and Right, Reproducing Daniel low works for verification (our program results).

The program is also validated with I'mRT MATRIX software for one clinical case (prostate) and the amma index results are compared.

Fig. 2: Validation the program with ImRT MATRIX software (IBA Dosimetry) for a clinical case (prostate).  Left, Gamma index for a prostate case (ImRT MATRIX software).  Right, Gamma index for a prostate case (our program). 

Patient-Specific IMRT/VMAT QA: A Developed Program/Software for Patient-Specific IMRT/VMAT QA using Log File Analysis (Calculations-based Method)

Current QA is performed as 1) Pre-treatment verification of fields (Checks of leaf motion, Transfer of data, & General deliverability of plan), 2) Second check software, and /or 3) Frequent imaging.

What is missed? Verification of correct delivery when the plan is delivered to the patient on a daily basis. 

The American College of Radiology (ACR) recently (August 2015) published a statement on their website answering the question of whether the ACR Radiation Oncology Practice Accreditation (ROPA) program considers log files generated from the treatment machine an acceptable “alternative” measurement for IMRT/VMAT for patient QA. The ACR states that log files are acceptable as long as they are generated using the patient’s IMRT/VMAT plan before the start of patient treatment, and that the medical physicist, along with the radiation oncologist have assured that the measurements verify the actual radiation doses the patient will receive. Two-dimensional detector arrays are specified as another ‘alternative’ method in the ACR-ASTRO Practice Guidelines for IMRT.

We have developed a software to analyze the MLCs performance during the IMRT delivery.

Fig. 1. IMRT QA using DynaLog file analysis method. a) leaf position error (mm), b) leaf gap error (mm), c) velocity error (cm/s), d) photon fluence error (%), and e) leaf deviation value (mm) (root mean square of leaf position).

Fig. 2: A hand-made DMLCs sequence.