For more than two decades “quality” and “quality management systems” have been leading buzzwords in the business world. Numerous consultants have built their careers around these topics, and quality issues in business have been responsible for the development of new organizations and even industries, for instance, the American Society for Quality and Six Sigma consulting. The notion of quality in business focuses on the savings and additional revenue that organizations can realize if they eliminate errors throughout their operations and produce products and services at the optimal level of quality desired by their customers. Errors can take almost any form—for example, producing the wrong number of parts, sending bank statements to customers who have already closed their accounts or sending an incorrect bill to a client. All of these errors are very common, and the costs incurred seem minimal. But over time when mistakes are repeated the costs add up to a significant amount, so eliminating errors can result in significant increases to the bottom line of a business. Chapter

Quality management systems

The goal of this research was to study the widely used criteria in Iraq and the suggested criteria from the American association of physics in medicine (AAPM). The breast cancer patients treated at Al-Andalus private hospital underwent a CT simulation. The data were exported to Monaco 5.1 treatment planning system for planning purposes using the intensity-modulated radiation therapy technique with X-ray energies of 6 or 10 MV. The planning was transferred to Agility linear accelerator for irradiation to Octavius-4D phantom detector for pre-treatment verification. The results show that there is no significant difference between the prescribed and measured point dose. In addition, the dose difference is acceptable and there was no significant correlation between the dose error and the result of gamma passing rates for all criteria. A high significant difference appeared between the 3%/2 mm and 3%/3 mm criteria for both local and global gamma passing rates at the two studied thresholds 5% and 10%. All the values of 10% thresholds were highly significant than 5% in local %GP but not significant for the global %GP. The number of segments and the total number of monitor units show an inverse relationship with gamma passing rates. The results clearly show that criteria and thresholds depend on the situation and health of the patient. This means the criteria are to be set at 3%/2 mm for plans which use high doses to organs at risk, while 3%/3 mm may be used for simpler plans with lower doses to organs at risk.

Dosimetric assessment of IMRT treatment planning for unilateral breast cancer patient using Octavius phantom detector

Basic radiotherapy physics and biology

Introduction: According to the American Society of Radiation Oncology, all patients receive radiation therapy during their illness, where radiation is delivered by the medical linear accelerator (Linac). The aim of this study was to evaluate the quality assurance (QA) of the Linac in analyzing the used dose profile in the treatment of cancer tumors. Material and Methods: This experimental study was performed using Linac (synergy device type) at Baghdad Radiotherapy and Nuclear Medicine laboratories, Baghdad, Iraq. The Star Track device was used for the routine quality assurance of the Linac, using photon beam for the reference Dmax and source to surface distance of 100 cm. The Star Track consists of 453 vented parallel plate ionization chambers. Results: The flatness and symmetry of beams for the reference field size did not exceed from ±2%, as they were within the allowed range. Moreover, the penumbra region showed a change in value that did not exceed from ±0.2 cm. using the Star Track method; maximum differences in beam symmetry and beam flatness were measured at 0.76%±2% and 1.17%±2%, respectively. Moreover, the maximum difference in the penumbra region was estimated at 0.12±0.2 cm. Conclusion: The results indicated, the Star Track could successfully calculate the characteristics of dose profile during a time period of 2,500 ms, showing the superiority of this instrument over other verification devices.

http://ijmp.mums.ac.ir/article_13460_040a4e03762f70aa4632e2017fe44867.pdf

Quality Assurance of LINAC by Analyzing the Profile of 6-MV and 10-MV Photon Beams Using Star Track Device

Aim: The main aim of our study was to compare the variation of Gamma Index (GI) in Pre-treatment Verification Procedure in Intensity Modulated Radiotherapy (IMRT) Plans with Varying Grid Sizes Using 2D Array Detectors. Choosing an optimum grid size plays a vital role for planning in radiotherapy cases especially while treating with IMRT. A minimal change of even 1 mm of grid size can result in large variation in treatment planning and is reflected in quality assurance results also.
Methods and Material: We compared IMRT plans for a total of 12 patients. Out of these 12 patients 4 were head and neck, 4 were pelvic and 4 were brain patients respectively. For each patient three plans were generated with three different grid sizes. The plan acceptance criteria were 95% of PTV to receive at least 95% of prescribed dose and dose to 1% of PTV not to exceed 107% of prescribed dose. Dose for the organs at risk were respected as per the QUANTEC guidelines. After plan acceptance corresponding Pre-treatment Verification Procedure for IMRT was executed by PTW 729 array detector. The Gamma index (GI) results of each plan were recorded for the three different grid sizes. The passing criteria were kept to be 3% Dose Difference (DD) and 3 mm Distance to Agreement (DTA) for all cases.
Results: We estimated the variations in GI quality assurance results for patients undergoing IMRT planning with varying grid sizes of 3 mm, 5 mm and 10 mm respectively. We also evaluated 2% DD and 2 mm DTA, 3% DD, 3 mm DTA and 5% DD, 5 mm DTA criteria for passing result. Stastical analysis: We have calculated the average and standard Deviations (Std. Dev.) for each passing criteria for 2% DD, 2 mm DTA, 3% DD, 3 mm DTA and 5% DD, 5 mm DTA for each IMRT plans with varying grid sizes.
Conclusions: Though the present results suggest the gamma criteria of 5% DD and 5 mm DTA as the most suitable criteria for IMRT quality assurance. This gamma criterion of 5% DD and 5 mm DTA favourably exceeds 95% in each case and grid sizes but it is not recommended for strict verification procedure in Intensity Modulated Radiotherapy (IMRT). The criteria of 2% DD and 2 mm DTA, and 3% DD and 3 mm DTA gamma values show below 90% for 5 mm and 10 mm grid sizes but exceeds 95% for the 3 mm grid sizes. Hence 3 mm or less grid sizes should be routinely used in pre-treatment verification procedure IMRT plans using 2D Array Detectors.

Dosimetric Study on Variations of Gamma Index (GI) in Pre-TreatmentVerification Procedure in Intensity Modulated Radiotherapy (IMRT) Planswith Varying Grid Sizes Using 2D Array Detectors

Background: Step and shoot (SS) IMRT treatment technique is one of the modern planning techniques used in radiotherapy. It conforms to the dose to the possible minimum as to the OARs. Dosimetric error calculations used to estimate the sensitivity of reading and the dose difference between TPS and phantom detector. Monitor units (MUs) are measured by monitor chambers, which are ionization chambers that measure the dose delivered by a beam and are built into the treatment head of radiotherapy linear accelerators. Material and Method: Thirty cases of two regions (25 HN and 5 pelvic cases) performed with SS IMRT using MONACO5.1 Treatment Planning System (TPS). Then the QA tested using OCTAVIUS 4D-1500 phantom in Baghdad Center for Radiotherapy and Nuclear Medicine, Baghdad, Iraq. Gamma index and %GP calculated index by comparing the actual QA (using Octavius) with virtual QA (using MONACO TPS). Dosimetric error percentage with global and local %GP and the total Monitor Unit (MU) correlation with global and local %GP were measured. Results: The %GP was ≥95%, where 20% for local %GP for all cases and 73.3 % for global passing rate. A significant correlation found between the %DEs resulted in the %GP for both local and global. There was a correlation between the total MUs for global %GP. For a local %GP, it was statistically not correlated with MUs. Conclusion: There is a correlation found between dosimetric error percentage (%DE) and %GP for both local and global. There is a correlation between the total Monitor Unit (MU) and global %GP but not with local.

https://www.journal.atmph-specialissues.org/uploads/179/8761_pdf.pdf

The Correlation of Total MU Number and Percentage Dosimetric Error in Step and Shoot IMRT with Gamma Passing Rate Using OCTAVIUS 4D-1500 Detector Phantom

The linear accelerator is used in radiotherapy to treat tumors whether it was benign or malignant. The megavoltage electron beam is used to treat superficial tumors that do not exceed 5cm depth. In this work the dose distribution before irradiating the patient to check whether the prescribed dose is matched with the irradiated dose to help the physicist to fix the errors or deviations if it is detected. The quality assurance (QA) measured of electron beam with energy 12 MeV at common different depths and field sizes using StarTrack 2D detector and to ensure that it does not exceed the recommended limits. The equipped QA device is a StarTrack 2D detector under the linear accelerator infinity from Elekta at 100 cm from source-to surface distance SSD. The tested energy 12 MeV at depths 0.5 cm and 1.5 cm for field sizes 6cm×6cm, 10cm×10 cm and 14cm×14cm as limits measured according to the International Electrotechnical Commissioning (IEC) protocols. Results show that the revealed an error in the output dose at 6cm×6cm and 10cm×10 cm field sizes for 1.5 cm depth but for 14cm×14cm field size at 0.5 cm depth, the dose found to be above the tolerance. Also it’s found that the output dose is highly reached to 1.5 cm depth than the 0.5 cm. Furthermore, all the rotation axis of the collimator are within the limits with a few noises in the signal at the inline and the crossline axis. We conclude that there was an error in the output does need to be recalibrated before irradiating the patients to electron beam therapy at 12 MeV to assure that the treatment is qualified and efficient.

Measurements of Electron Beam Dose Distributions in Perspex Block for Different Field Size

Electron beam therapy using linear accelerator done for patients with superficial cancerous tumors. Daily quality assurance is preferable to assess a good treatment for the patients. This study focuses on penumbra, flatness, and symmetry determination for four types of an electron beam using StarTrack 2D array for quality assurance. Eelectron beam with energies: 6MeV, 9MeV, 12 MeV, and 15MeV for both in-plane (x-axis) and cross-plane (y-axis) using Elekta synergy linac exposed to StarTrack 2D array readings during 16 weeks for testing the performance and stability of StarTrack. The testing protocol used is IEC.The beam profile estimation of variation, when compared with standard values of penumbra, flatness, and symmetry of electron beam energy at the time of commissioning, reveals that all had a variation but these variations are within the limits. It is concluded that StarTrack 2D array detector is favourable in the QA process. Their implementation is not only easy, but gives information about the beam’s temporal stability and is particularly suitable for beam steering mounting.

Electron Beam Profile Assessment of Linear Accelerator Using Startrack Quality Assurance Device

Intensity modulated radiation therapy (IMRT) is an effective treatment planning technique for various types of tumors such as head and neck (H&N) or pelvis. A complexity algorithm was invented to predict the deliverability and the accuracy for IMRT plans called the Modulation Complexity Score ranging from 0 to 1. The %GP is a metric depends on %DD /DTA to find the variation between the calculated dose from TPS and the measured dose from the phantom during the QA. This study is trying to assess the correlation between the MCS and planning verification outcome. Thirty-four patients treated with step and shoot IMRT technique for anatomical sites: H&N and pelvis. The planning process performed using Monaco 5.1 TPS then exported to Elekta Synergy linear accelerator. The phantom is used for the QA procedure is Octavius 4D-1500 with Verisoft 7.1 software analysis to evaluate the gamma passing rate for commonly used criteria 3%/3 mm at a 5% threshold. The MCS calculated using MATLAB 2019a. It results that the H&N plans are significantly more complex than the pelvis once with p-value 0.0192. The analysis shows a weak correlation between the MCS and MU for both treated sites. The complex H&N plans give a good value for %GP. Also, simpler pelvis plans obtain better global %GP results. Thus, modulation Complexity score can give a simple indication for pretreatment verifications of the IMRT plans for H&N and pelvis sites.

https://iopscience.iop.org/article/10.1088/1742-6596/1829/1/012017/pdf

Nabaa M. Alazawy

Papers

The Correlation of Total MU Number and Percentage Dosimetric Error in Step and Shoot IMRT with Gamma Passing Rate Using OCTAVIUS 4D-1500 Detector Phantom

Measurements of Electron Beam Dose Distributions in Perspex Block for Different Field Size

Electron Beam Profile Assessment of Linear Accelerator Using Startrack Quality Assurance Device

The Effect of Modulation Complexity Score (MCS) on the IMRT Treatment Planning Delivery Accuracy