Positron emission tomography (PET) imaging is a powerful tool, especially beneficial in cancer diagnosis and management. The objective of every oncology clinician using PET technology is to detect lesions and tumors clearly. Clear images can mean a patient gets into treatment faster, fostering the best possible outcome. Digital PET scans bring great promise to that goal.
The digital difference
In the simplest terms, analog is infinite – a waveform approximation based on the possibilities. Digital is finite, defined by a discrete, limited set of values. Looking at an analog clock, you gauge the time based on the position of the hour and minute hands in relation to numbers on the face. A digital clock displays the exact time.
Medical devices often use a combination of analog and digital technologies that transfer signals (inputs and outputs) via wires or through the air on radio frequency waves. These signals are time-varying quantities carrying information in the form of encoded data.
PET scans illustrate the distribution of the radiopharmaceutical tracer in the patient's body, with accumulations indicating potentially cancerous cells. Traditional PET imaging equipment uses an analog detector to record scintillation flashes, converting them to an optical display. These flashes of light are produced when photons emitted by tracers collide with crystals in the detector. Digital detectors take the concept a step further, counting the individual photons. This higher level of exactness translates to clearer images disclosing smaller abnormalities.
Radiopaedia describes "noise" in imaging as "unwanted change in pixel values in an otherwise homogenous image. Often, noise is defined loosely as, the grainy appearance on cross-sectional imaging; more often than not, this is quantum mottle."1 Analog detectors generate electronic noise during amplification of the waveform and conversion to digital output, which degrades the image somewhat. Binary signals produced by digital detectors do not require amplification and conversion, which reduces image noise. This higher "signal to noise ratio" results in a clearer image showing more detail. You might think of it as the difference between the picture on your television screen with standard (low) resolution, compared to high-resolution HDTV.
According to the Centers for Disease Control and Prevention, more than 1.6 million new cases of invasive cancer were reported in 2016. The overall incidence rate of 436 per 100,000 people is driven by prostate, lung, and colorectal cancer in men; and breast, lung, and colorectal cancer in women.2 Clearly, the need for timely, accurate diagnosis and staging exists, as well as monitoring the spread of disease and success of treatment. PET scan technology plays a vital role.
The outlay for a healthcare organization, however, is substantial. A 2017 report cites the establishment of a PET/CT station without a cyclotron and chemistry module to cost more than $3.5 million U.S. dollars.3 In addition to the initial installation, the facility must factor in operating costs such as:
- Consumables and supplies (including radiopharmaceutical tracers)
- Personnel training and staffing
- Equipment maintenance
Considering the high demand for oncology scanning services (and thus revenue generation for the facility), and the human benefits to the individual patient and community, the expense is justified.
Analysis of investment in a new PET scanning center or an upgrade should be focused on the unique utilization needs and resources of the healthcare organization.
With the speed of advancement in technology, temptation to purchase the "newest and best" often prevails. In the case of PET scan instrumentation, that means a shift to digital detectors. Yet for many organizations, analog still makes sense. It is a solid solution in use in most imaging departments today. With advanced image reconstruction capabilities, an analog detector PET/CT can be quite serviceable.4
Digital detectors became available about five years ago for academic institutions (university hospitals) and are now more widely available. Within the next decade, digital is likely to be the standard in hospitals across the globe, as it becomes more affordable and easier to implement.4
Savvy healthcare administrators, cognizant of this movement, may choose to be early adopters. Investing in a scalable solution now, allows the hospital to start with a digital PET/CT system that fits their current needs and economic model, and can be upgraded (rather than fully replaced) in the future supporting cost-effectiveness for a decade or more.
Evaluation of overall quality is essential. One way for manufacturers to lower the up-front price of the system is to make compromises. For example, scintillation crystals are typically the most expensive component of the system. Reducing the number of crystals lowers cost, but also degrades sensitivity. Thus, a lower-quality digital detector may produce images that are no better than an analog system.
Digital technology alone does not ensure optimal scan quality. Digital detection must be matched up with high sensitivity and reconstruction technology.
The real promise of digital PET
An organization's decision to consider digital PET scan technology reflects a commitment to:
- Earlier cancer detection for potentially life-saving oncology care and patient peace of mind.
- Improved patient experience, requiring less time on the table for ill patients.
- Elevated facility reputation as the front-runner in providing leading-edge services.
- Advancing the future of cancer treatment. Large-scale, real-life use of new technologies push boundaries for related research and treatment. In the case of cancer, digital PET scans are propelling innovations in new tracers, treatments such as immunotherapies, and emerging combination protocols.
Preserving lives and extending quality of life for cancer patients – that this the real promise of digital PET scans.
- Noise (computed tomography). Radiopaedia.https://radiopaedia.org/articles/noise-computed-tomography?lang=us July 30, 2019.
- United States Cancer Statistics (USCS). Centers for Disease Control and Prevention.https://www.cdc.gov/cancer/uscs/about/data-briefs/no8-USCS-highlights-2016-incidence.htm July 30, 2019.
- Unit Cost Analysis of PET-CT at an Apex Public Sector Health Care Institute in India. Indian Journal of Nuclear Medicine.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5317060/ July 30, 2019.
- Interview with GE Healthcare Global Marketing Director Amy Burris. July 25, 2019.