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How is PET/CT different from traditional PET imaging?

Posted on: 10.12.17

Today, most of the Positron Emission Tomography (PET) scanners you find in hospitals, or delivered via mobile imaging, are actually PET/CT cameras. Modern PET/CT scanners combine both PET and Computed Tomography (CT) scans almost simultaneously to provide a greater amount of clinical data to assist in the diagnosis process.

Combining the benefits of PET and CT

A PET/CT scan includes two parts: a PET scan and a CT scan. The CT portion of the scan produces a 3-D image that shows a patient’s anatomy. The PET scan demonstrates function and what’s occurring on a cellular level. The PET scan is unique because it images the radiation emitted from the patient while the CT records anatomical x-rays, showing the same area from another perspective.

The role of attenuation correction

PET/CT scans not only pinpoint localization; they also offer significant help with attenuation correction, a huge advantage. During a CT scan, the system records numbers, called Hounsfield units, which measure the density of the tissue that it travels through. Not only does the CT produce images, but they also have numbers assigned to each individual pixel.

The PET scan measures the level of radiation coming from the patient and compiles information that the system needs to decipher. It uses algorithms and corrections, including the Hounsfield units from the CT scan, and adjusts the images in accordance with the corrected densities for each region.

In the 1990’s or early 2000’s, a PET-only scan would have used a transmission scan for attenuation correction or forgone it completely. Today, however, there is better technology available. Using both CT and PET to cross-check data and corroborate each other is a way to increase confidence and reduce guesswork. It gives significantly more data points to reference in order to determine a diagnosis and treatment plan.

PET/CT is more than just oncology

One of the biggest misconceptions about PET/CT is that its benefits are limited to diagnosing cancer. There are many new uses that are benefiting from PET/CT technology that fall outside of oncology. For example, in neurology, a brain CT or MRI only looks at the structure. The benefit of looking at function through an FDG-PET scan is that a functional change on the cellular level will be seen before a possible structural change. The same can be said for cardiac imaging, epilepsy, Alzheimer’s disease, dementia, infection and inflammation and a host of others. These are areas that could benefit from taking advantage of the advancements in the PET/CT world.

How to prep a site before offering mobile CT, PET

Posted on: 08.17.17

Whether it’s used while you upgrade and remodel, to accommodate increased volume, or for disaster recovery, a mobile CT or PET/CT unit might be the ideal solution either on a short-term or long-term basis. Independent of the mobile imaging provider you choose, there is some lead-time needed to prepare your facility for the service from a regulatory standpoint as well as from a site planning position.

Regulatory requirements

Adding a mobile CT unit to your facility requires the x-ray tube to be registered with the state and an annual evaluation performed by a licensed physicist. Some states also require initial acceptance testing be performed by a licensed in-state physicist. Ideally, the mobile provider’s Radiation Safety Officer will coordinate this service. The process could take anywhere from 2 weeks to 3 months, depending upon the state.

In the case of a PET/CT unit, if the mobile company does not currently hold a radioactive materials license in a particular state, a new application must be submitted. While the approval process can take between three and six months, in many states, the company also has the ability to work under reciprocity for a temporary time period until the new application is approved.

When a current radioactive materials license is already in place, only an amendment to include the additional location address and authorized user is needed. An amendment can take one to three months, depending upon the state. As with a dedicated CT unit, the PET/CT x-ray tube must be registered with the state, and an annual physicist evaluation will be performed on both the CT and the PET portion of the scanner.

A memorandum of understanding must also be signed by both the facility and the PET/CT provider. This document outlines the responsibilities of each party and as evidenced by their signatures, their agreement to the assignments. It is required in all states.

Physical site requirements

Choosing a physical site for the mobile unit is an important decision. Space, shielding design, proximity to your building, and occupancy of the surrounding areas are important factors to consider. The recommended support pad for the mobile unit is concrete and is 10’11” x 40’8”; the measurements for the recommended service pad are 21’ x 58’, which will allow full-service access to the unit.

You’ll also need to consider the size and weight of the trailer when deciding on an area. Its overall weight is 57,000+ pounds, and it is 53’ long. The designated area should provide ample space and be able to adequately support the trailer’s weight without concern of shifting or sinking. Asphalt is ideal because it allows for a firm, level surface, but tightly packed gravel is an option, as is grass in some situations.

Power requirements

Another consideration is power to the mobile unit. A single electrical power source, 3/N/PE AC 480V service fused at 150 amperes, is required for operation of a PET/CT system. It should be located within 300 feet of the main power source. A Lockout/Tagout provision in accordance with OSHA Standard 1910.147 is also required.

Telephone and data service requirements

The mobile unit will have three telephone connections. For use at the site, you’ll need to purchase and install one Hubbell all-weather telephone connection. 50’ phone cords are included with the mobile unit, and the unit is also supplied with 2 CAT5 data line connections, along with the required 50’ data connection cables.

Site Planning Guide

These are the major highlights of the planning phase that you’ll need to consider. Once you decide to move forward, many companies will offer a site-planning guide that delivers more detail, including model numbers and requirements specific to their service to ensure smooth delivery, set up, and proper functionality.

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