US CIRS 062MQA CBCT electron density

USACIRS 062MQA CBCT electron density and image quality phantom

Introduction:

USAThe CIRS 062MQA CBCT electron density and image quality phantom is designed with the intent of providing a tool that can be used for electron density calibration and image quality assessment of cone beam CT systems integrated in radiotherapy equipment. The phantom's electronic calibration capabilities enhance the results of adaptive radiation therapy, while image quality features address the fine balance between optimizing image quality while minimizing radiation dose.

USAThe CIRS 062MQA CBCT electron density and image quality phantom consists of several parts: a 100mm thick body panel, a 100mm thick CBCT image quality phantom, a 50mm thick electron density phantom, and a mass consisting of a 37.5mm thick uniform plate, a 12.5 mm thick uniform slab and a 50mm thick uniform slab.

The 100mm thick body section has a central hole that accepts CBCT image quality models. Each Bolus plate is drilled to accommodate the ion chamber insert, allowing ion chamber measurements regardless of the location of the image quality insert. The thickness of the section is chosen to allow any layer containing image quality features to be positioned on the beam's central axis. Additionally, the different thicknesses of the sections reduce the increment by which the electron-dense section can deviate from the *mandrel.

The phantom support as well as the laser alignment marks allow easy and fast positioning of the model on the accelerator couch. With the help of machined grooves, the model is placed on the support rails. A bumper plate is provided to reduce artifacts from the support device and allow user access to the handle on the support plate. Flattening of the support and implicit phantom is accomplished by adjusting the horizontal legs.

USACIRS 062MQA CBCT electron density and image quality phantom features:

YesAAPM TG Report #1 Perform All CT Image QA Testing

Dosimetry using an ionization chamber

Dosimetry using an ion chamber

in multiple layersCalibrating electron density in CT and cone beam CT

execute*Spindle and offset measurements

Position simulated tissue material at17 different positions within CT and CBCT energy range

Optimized for volumetric imaging

Quickly locate and customize loading configurations

A solution for electron density calibration and image quality assessment:

CBCT image quality phantom

Phantom consists of four layers: spatial resolution, CT number linearity/slice thickness, low contrast and uniformity. Positioning of the different layers of the CBCT image quality phantom on the *mandrel can be accomplished by placing the phantom in the 100mm body section or by placing the phantom directly on the support device.

spatial resolution layer

The spatial resolution layer is designed to evaluateSpatial resolution of the IGRT system. A pattern of line pairs from 1 lp/cm to 16 lp/cm is embedded in the background. To minimize artifacts, each line pair pattern is made of material with 350HU greater than background attenuation. The line pair pattern is a 12 mm high 3D pattern along the longitudinal axis of the CBCT image quality phantom. The spatial resolution targets are arranged in a circular pattern.

CT number linear and slice thickness layers

CT number linearity and slice thickness layers were used to determine contrast-to-noise ratio, Hounsfield number accuracy, and slice thickness sensitivity. Six rods made of air, low-density polyethylene (LDPE), polystyrene, acrylic, Delrin and Teflon are used to measure CnR and Hounsfield number accuracy. Three angled air channels arranged in an equilateral triangle can be used to evaluate slice thickness sensitivity.

low contrast layer

The low-contrast layer is designed to evaluate the system's ability to detect small differences in contrast. It consists of three sets of low contrast rods with a linear attenuation difference relative to the background material.0.5%, 1% and 2%. The diameter of the low-contrast rod was chosen to provide a 0.5 ratio between two adjacent rods by cross-section and volume. Additional features are designed to evaluate the magnification in the orthogonal axis of the transverse image and serve as input for the calculation of the point spread function and subsequent modulation transfer function.

uniform layer

The uniformity layer is designed to measure a system's ability to produce a uniform image across an object's field of view, with highly uniform physical properties in all directions.

electron density phantom

Motif consists ofComposed of nested discs made of PlasticWater®. Nested disks allow simulation of head and abdominal phantom configurations. Eight different tissue-equivalent inserts can be positioned at 17 different locations within the scan field. The phantom geometry also enables the user to obtain measured offsets from the *mandrel.