Greg Freiherr, Industry Consultant
Greg Freiherr, Industry Consultant

Greg Freiherr has reported on developments in radiology since 1983. He runs the consulting service, The Freiherr Group.

Blog | Greg Freiherr, Industry Consultant | PET-CT| April 06, 2016

How to Achieve the Quantitative Promise of PET/CT

How to Achieve the Quantitative Promise of PET/CT

Image courtesy Siemens Healthcare

The good news for molecular imaging is that the latest generation of PET/CT can visualize more and subtler signs of disease. Even better, these souped-up machines can more precisely measure standard uptake values (SUVs). This adds credence to their role in quantifying what has long been a subjective process of diagnosing, prognosing and following patients.

Unfortunately, that is also the bad news.

The increased precision possible with the latest PET/CT scanners, replete with point-spread function and time-of-flight, is a welcome development for diagnosticians. But it can be a double-edged sword for those who replace an older generation system with a newer one.

Scanning patients on newer, more powerful PET/CTs can reveal lesions that were overlooked earlier, giving the appearance that a therapy is ineffective or the disease has returned. This may happen when the latest images show what were too small to spot on less powerful machines. Additionally, the quantitative measurements may be higher because the latest equipment is more sensitive. Different protocols, some of which may be introduced with the availability of new equipment, may further skew interpretations.

Quantitative measurements — standard uptake values — can be particularly vexing. Ones recorded prior to oncologic therapy provide the baselines against which those acquired during and after therapy are compared. SUVs may be used to set PERCIST (PET response criteria in solid tumors) thresholds for individual patients. Research has documented that an increase of 30 percent or more above the PERCIST threshold indicates poor patient response and that a change in therapy should be considered. Conversely, a decline of 30 percent or more indicates a likely positive effect and that the therapy is working.

SUVs represent a sea of change in medical diagnostics. Their quantitative nature offers a respite from the subjectivity and skill-based diagnostics that characterize modern medicine. The importance of meeting the challenge of data harmonization, presented by data variability, takes on a new dimension when considering multi-site clinical trials. SUVs can be the pivotal metric in trials designed to test the efficacy of experimental therapies. Conclusions may be called into question, if the data are not adjusted to account for technical differences among the sites.

There are ways to handle this apples-and-oranges dilemma. Guidelines developed by international organizations serving the MI community have laid out the process for adjusting SUVs to make them comparable. But the process is not easy. The staff conducting multi-center clinical trials may have the wherewithal to do it, but the everyday practitioner may not.

This is especially disappointing considering the potential of SUVs to increase certainty and confidence in the management of patients. PET/CT is positioned to play a major role in the coming age of value medicine, but only if its quantitative capability results in improved patient outcomes. To have a substantial impact on public health, solutions that allow accurate interpretation must be easy to use. Progress toward this goal is being made.

French researchers have developed a mathematical formula that allows the comparison of data captured using different generations of scanners. They proved this formula can be used to harmonize data obtained during multi-center research on patients with non-small cell lung cancer. The formula has since been productized by an equipment vendor and, in this form, proved to work on data from patients with a wide range of cancers.

Notably, this software has been validated only on generations of equipment made by the vendor that has productized it. Work to extend its ability reach to translate SUVs obtained using generations of scanners made by different manufacturers is underway.

Until the means for translating data is achieved and widely embraced, the benefit that might be derived from quantitatively assessing follow-up patients will be on hold … and with it the hope that molecular imaging might bring increased precision to patient management.

Editor’s note: This is the first blog in a series of four by industry consultant Greg Freiherr on Where Molecular Imaging Fits in Managing the Cancer Patient. To read all of Greg's blogs, click here.

Related Content

Improving Molecular Imaging Using a Deep Learning Approach
News | Nuclear Imaging | March 21, 2019
Generating comprehensive molecular images of organs and tumors in living organisms can be performed at ultra-fast speed...
News | PET-CT | February 06, 2019
Technological advancements in positron emission tomography/computed tomography (PET/CT) offer both clinicians and pat
Videos | SPECT-CT | December 12, 2018
This is a walk around of the new Spectrum Dynamics Veriton SPECT-CT nuclear imaging system introduced at the 2018 ...
GE Healthcare Recalls Millennium Nuclear Medicine Systems
News | Nuclear Imaging | November 15, 2018
GE Healthcare announced it is recalling its Millennium Nuclear Medicine Systems due to an incident in which the the top...
MEDraysintell Projects Increasing Mergers and Acquisitions in Nuclear Medicine
News | Nuclear Imaging | November 07, 2018
With the recent announcement by Novartis to acquire Endocyte , interest from the conventional pharmaceutical industry...
The Siemens Biograph Vision PET-CT system was released in mid-2018.

The Siemens Biograph Vision PET-CT system was released in mid-2018.

Feature | Nuclear Imaging | September 07, 2018 | By Dave Fornell
Nuclear imaging technology for both single photon emission computed tomography (SPECT) and positron emission tomography...
Abnormal Protein Concentrations Found in Brains of Military Personnel With Suspected CTE

Researchers are using the tracer, which is injected into a patient, then seen with a PET scan, to see if it is possible to diagnose chronic traumatic encephalopathy in living patients. In this image, warmer colors indicate a higher concentration of the tracer, which binds to abnormal proteins in the brain. Credit UCLA Health.

News | PET Imaging | August 24, 2018
August 24, 2018 — In a small study of
Siemens Healthineers Announces FDA Clearance of syngo.via VB30 Molecular Imaging Software
Technology | Nuclear Imaging | July 16, 2018
At the 2018 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI), June 23-26 in Philadelphia...
Nuclear imaging scan showing very good tissue delineation. Scan performed on a Biograph Vision positron emission tomography/computed tomography (PET-CT) system from Siemens Healthineers.

Nuclear imaging scan showing very good tissue delineation. It offers crisp overall image quality and sharply delineates the muscle and fat planes, vertebral margins and end plates, billiary radicals, renal calyces, aortic wall and papillary muscles of the heart. Scan performed on a Biograph Vision positron emission tomography/computed tomography (PET-CT) system from Siemens Healthineers.

Technology | PET-CT | June 05, 2018
June 5, 2018 — The U.S.