Huestis•Cascade NT™ — Frequently Asked Questions

We've listed answers to some of our most common radiotherapy simulator questions for your convenience.

A radiotherapy simulator “simulates” the motions and treatment angles of a radiotherapy treatment unit. It is used to help delineate tumor areas and treatment volumes with the use of radiographic and fluoroscopic imaging instead of high-energy radiation used by a typical treatment unit. The simulator can be used to localize the tumor, document its position, and mark the treatment area. It can help duplicate accurate patient positioning and develop parameters for the treatment unit to deliver a homogeneous dose of radiation to the tumor while minimizing the dose to surrounding normal tissues.

What is a radiotherapy simulator composed of?

A radiotherapy simulator consists of an array of X-ray components and mechanical positioning systems that are capable of reproducing typical functions and movements of a radiotherapy treatment unit. In radiotherapy, tumor volumes are defined in relation to a specific reference point called the isocenter. The isocenter remains constant throughout the treatment process. Radiotherapy simulators physically position the patient and X-ray components in order to localize the tumor in a manner that would minimize irradiation of healthy organs and tissue during an actual treatment. Other treatments that are non-isocentric can be also simulated. Using either method, the simulator's mechanical systems must match the motions of the treatment unit in relation to the isocenter to ensure accurate patient positioning and treatment angles.

What are the most important mechanical aspects of proper positioning?

The simulator must be able to match positioning parameters consistent with the common motions of typical treatment units. Gantry rotation, Source-to-axis (SAD) adjustment, collimator rotation, image intensifier movement and table movements must all match the treatment unit. Mechanical tolerances, anti-collision systems, and readout consistencies must also be maintained. Simulator performance should be a precise match to the treatment unit with the only exception being that the simulator delivers low-energy diagnostic X-rays instead of high-energy radiation.

How do you address stability and reliability over the lifetime of the system?

Our rugged, freestanding gantry supports the X-ray tube, collimator, and image intensifier and provides proper alignment with the central axis of the x-ray beam and the gantry's axis of rotation. This detailed, overbuilt construction ensures isocentric accuracy of ± 1 mm (at 100 cm).

Are there any installation considerations with your system?

The Huestis•Cascade NT™ Simulator was purposely designed so that it could be installed with minimal modification to an existing facility. Huestis•Cascade NT™ Simulator's freestanding design is quick and easy to install because there is no pit required as with other models. Installation time is also drastically shortened with an average one week setup.

Is your couch compatible with my treatment unit?

Our radiolucent, carbon-fiber couch helps prevent image degradation and is compatible with all treatment units. Extremely rugged, it elevates up to 500 Lbs. (226 kg) and can be lowered to 70 cm for easy patient access. It includes motorized movement in x, y, and z axes, strategically placed emergency switches, a mounted hand control pendant and “free-float” capability.

What type of X-ray generator does the Huestis•Cascade NT™ simulator use?

We offer different generator models contingent on the available power supply to the facility. Our constant potential high frequency X-ray generators utilize self-diagnostic circuitry and are controlled by multiple microprocessors to ensure consistent and repeatable X-ray operation. We typically use a three-phase generator which has advantages of higher tube currents at short exposure times, constant potential, higher kVp, and small ripple in voltage waveform that translate into less strain on the cables compared to single-phase designs.

What type of X-ray tube is used?

We use a Rhenium, Tungsten, Molybdenum X-ray tube that provides proven performance and extended life over multiple exposures without overheating. Our small 0.6 mm focal spot offers enhanced details and minimal width of the image of the treatment area. Our 12° target angle covers a 40 cm2 field. The Anode heat storage is 400,000 HU with a maximum anode dissipation rate of 100,200 HU/min. Our high-speed rotation of up to 10,000 RPM (3,200 minimal) provides increased radiographic ratings.

What size is the image intensifier?

Our high resolution image intensifier features motorized movement in x, y and z axes and includes auto-centering lateral and longitudinal movement and anti-collision protection. This high contrast, high resolution intensifier includes a Cesium Iodide I.I. tube, and covers a large X-ray field. Our tri-field 9”, 6”, 4.5” (22.8, 15.2, 11.4 cm) I.I. covers the maximum X-ray field on the patient at clinically used source-to-skin (SSD) distances. It features a 20 mm output field size, “S” distortion correction and automatic brightness for fluoro.

What size cassettes can be used with the Huestis•Cascade NT™ simulator?

Our radiographic cassette holder accepts 35 x 43 cm (14” x 17”) cassettes. The entire holder rotates 90° for quick and easy access. It features and anti-collision touch guard, safety locks, and accepts a radiation grid to absorb scatter.

How do I mount block trays to the simulator?

An included custom block tray adapter matches your source-to-tray distance. Our snap-in positive locking design is lightweight and will hold the same trays as your treatment machine.

Can I simulate half-blocked fields?

Our asymmetrical and symmetrical field wires and motorized collimator rotation of ± 95° facilitates simulation of half-blocked fields for matching of radiotherapy units.

What is the maximum treatment field size?

Our precise positioning flexibility handles field sizes from 0 x 0 cm to 45 x 45 cm (at 100 cm SAD) for complete compatibility with treatment planning systems. We provide a convenient, visible margin around the maximum treatment field size (40 x 40 cm at 100 cm SAD) for all treatment units.

Are there any additional components that I will have to purchase?

Our included custom features offer unmatched simulator value. Fluoroscopic capability, (4) four diode line lasers, a custom block tray adapter fabricated to match your radiotherapy treatment unit, and (2) two grid trays (80 cm, 100 cm) are all included. Optional accessories including cassette adapter inserts, additional block trays/ lasers, and Huestis installation and maintenance options are also available.