The concept of a dual-modality positron emission tomography and
computed tomography (PET/ CT) scanner was first proposed in 1994 by
physicist David W. Townsend, PhD, and engineer Ronald Nutt, PhD,
while working at the University of Geneva in Switzerland. The goal
was to provide an integrated imaging system that would produce
accurately aligned, clinical-quality PET and CT scans. With funding
from the National Cancer Institute, the prototype PET/CT scanner
was built and, in 1998, it was donated to the University of
Pittsburgh for testing. In October 2000, the United States Food and
Drug Administration approved PET/CT for use as a diagnostic and
therapeutic tool for cancer treatment, and commercial shipment of
PET/CT systems began.
Now that many physicians have gained extensive experience with
this technology and are reaching the top of the learning curve on
its basic use, they would like to increase its usefulness and to
improve the reading experience. "This is something that I and other
physicians who have been using the PET/CT have been discussing,"
said Jacqueline Brunetti, MD, Director of Radiology, Holy Name
Hospital, Teaneck, NJ. "With PET/CT, we have high resolution and we
have high accuracy. We have scans that give us very good
specificity. But the bottom line is that we need a way to deal with
all that data. Up front we have a superb tool to identify cancers
and to stage patients, but the issue is the ability to track these
lesions and to monitor changes. We need to be able to look at the
data in a meaningful way. We need speed, and we need more
functionality to perform measurements and to deal with the volume
of images and data that we have."
At the 54
Annual Meeting of the Society of Nuclear Medicine (SNM), June 2-6,
in Washington, DC, GE Healthcare (Waukesha, WI) will introduce new
software that is designed to address these issues. The PET VCAR
(Volume Computer-Assisted Reading) software works on the GE
Advantage Windows (AW) Workstation. PET VCAR has undergone testing
at 3 preclinical sites and 7 clinical evaluation sites. GE expects
to be in full production by the end of 2007.
The software automatically highlights and bookmarks regions of
metabolic activity in the PET component of the PET/ CT image and
provides measurements of standard uptake value (SUV) and volume of
the metabolic activity (Figure 1). The software, which was designed
to monitor disease progression or response to treatment using
multiexam comparison, bookmarks these locations using the CT data
and provides anatomic tracking and automatic registration when
multiple studies of a single patient are opened.
"PET VCAR has been cleared for use by oncology clinicians to
help with the diagnosis, staging, treatment planning, and
management of treatment response," explained Kelly Piacsek, PhD,
Global Oncology Product Manager, GE Healthcare. "The goal of PET
VCAR is to provide an analytic environment so that the user can
track critical parameters in evaluating tumor response to various
therapies. The software provides an identification of high
metabolic areas and performs automatic segmentation of those
areas," she continued (Figure 2). "It provides information such as
SUV maps, SUV mean, and what we call a 'functional volume,' which
defines the total number of voxels appropriate for a particular
tumor. It then coordinates that information over time, so you can
have a baseline scan and an unlimited number of follow-up exams
that you can track and report percent change of those critical
"The functional volume information is a result of 3 different
built-in segmentation algorithms," Piacsek added. "Additional user
preferences can be set depending on what the user desires, the
acquisition parameters, and the ideal settings for a particular
Once the data is acquired and analyzed by the software, the
results are complied and presented in the Interactive Data Analysis
(IDA) spreadsheet. The IDA organizes the information in an
interactive format that is synchronized with the image display. The
user can click on information in the spreadsheet to be directed to
the corresponding spot on the image.
"The results are given in a tabular format," explained Piacsek.
"Our patented data presentation, IDA, allows the user to click in
the table and triangulate to various tumors in the image volume
set. Then the parameters in the table can be exported into separate
files that are supported in Excel." The final reports can then be
stored and accessed on the facility's picture archiving and
communication system (PACS) or on compact disks (CDs)."
"The program has a portable CD reporting tool that can be used
on any PC, or it can be moved to a PACS, where you actually collect
preferred images and analytical information, along with the
report-critical images," said Piacsek.
Brunetti commented, "One of the things that I think is very
important is that the graphs, trends, and all of the data must be
translatable onto the PACS. It also must have a method of recording
data so that the report can be sent to the referring physicians.
The referring physician needs to have a measure of what he or she
is doing and whether or not it is effective. Medical oncologists,
particularly, want to know what changes are occurring, if the
current treatment is effective, if there is new disease, and so on.
I think this will give them a depiction in the form of a graph of
trends and changes in the patient's malignancy. I think this will
help them in utilizing the PET/CT."
"Once the tumor delineation and baseline exam are completed,
bringing in future studies is very easy," explained Piacsek. "The
software has autoregistration that happens immediately when
multiple exams are opened and has automatic bookmark propagation.
With a single button click, the user can propagate all the original
tumor bookmark information to the new image data set. It is very
efficient management of data from multiple time points."
"I think one of the most powerful pieces of the VCAR is the
ability to track, to have a more objective way of looking at what's
happening, and of trending changes," added Brunetti. "As people are
more involved in PET/CT, you get patients who are coming back for
their fifth or sixth PET/CT exam--or sometimes for even more of
them. How do you deal with all this data? It's so important to be
able to look at not just a point in time but a larger time frame.
Most radiologists will not just look at the last CT in their cancer
patients, but they tend to pull up the prior exams as well because
it gives them a better idea of what's happening to the
Piacsek sees particular value in this software for patients with
metastatic disease. "The system's workflow and detection
capabilities will be extremely useful for tracking a large number
of lesions over time," she noted. "Also for patients who have
cancer in remission who are having annual follow-ups; this is a
product that will allow you to bring in all your previous
information and look very quickly to see if there is anything
"Certainly, for the patient themselves, I think it gives another
level of confidence and maybe another level of comfort," added
Brunetti. "We have an additional piece of solid information that
can be translated into their reports to give another level of
information as to how their therapy is progressing."
"PET VCAR allows us to look at trends in an organized fashion,"
said Brunetti. "It gives us the ability to graph changes so that we
can pictorially look at trends, which I think can be very helpful
in monitoring patients," said Brunetti. "Going forward, I think
some studies should be conducted to determine exactly what we are
viewing and to identify the meaning of these changes."
"I think the obvious next step is to bring in more of the
quantitative CT tools to add to this as well as some of the
radiation oncology capabilities," added Piacsek. "We already have
built in the ability to export a radiotherapy (RT) structure set
for RT planning, but I believe the next step is to bring in more of
these pieces, including respiratory gating and full simulation
"You need the functionality of the PET/CT workstation to be as
powerful as the front end with the high resolution and the
exquisite anatomic detail," concluded Brunetti. "What do we do with
all that information? I think the PET VCAR addresses this in a very
efficient and quick manner, and it provides a comprehensive way to
tabulate and trend some of the information that we obtain on the