Dr. Osman is the Program Director of the Division of
Nuclear Medicine, Department of Radiology, Saint Louis University
Hospital, St. Louis, MO.
One of the most significant
transformations in patient care can be achieved simply by striking a
balance across the continuum of care. This is especially true when
managing oncology patients from diagnosis to staging to monitoring
disease, where managing tradeoffs is critical to delivering the best
As the second most common cause of death in the United
States, preceded only by cardiovascular disease (CVD), cancer accounts
for nearly 1 of every 4 deaths.1 In 2012, an estimated half-million Americans, or >1,500 people a day, were expected to die of cancer.1
The use of integrated positron emission tomography and computed tomography (PET/CT) imaging with 18F
fluorodeoxyglucose (FDG) is a widely established imaging technique with
major indications in oncology for staging, re-staging, and monitoring
response to therapy.2 In fact, at leading nuclear medicine
institutions, such as Saint Louis University School of Medicine, St.
Louis, MO, 90% of PET studies are conducted on patients with cancer,
while the other 10% is divided among neurological and cardiac
PET-imaging studies. The majority of PET studies involve lymphoma and
cancers of the lung, head and neck, colon, esophageal, melanoma, and
One of the challenges with PET/CT imaging is respiratory
motion, which can have a major degrading impact on PET-based tumor
quantification and delineation,3-7 and inhibits the ability
to define accurate target volumes in radiation oncology. This is
particularly true for small lesions found in borders between organs,
such as the lung and liver.
In lesion detection, the challenge is
the difference in the resolution. In the PET world, the accuracy of a
lesion 1 cm or less in size used to be suboptimal. It was even more
complicated if the same small-size lesion was in a patient with a high
body-mass index (BMI). In obese patients, scatter and attenuation
artifacts led to more challenges in identifying and characterizing small
Additionally, with organized industry efforts, such as ALARA (as low as reasonably achievable) and the Image Gently®
Campaign, to lower the levels of radiation dose patients are exposed to
during medical imaging exams, radiologists and nuclear medicine
physicians have been challenged to find strategies to manage dose
without degrading image quality.
The main problem we have had in
PET imaging is how to balance scanner throughput without compromising
image quality and without having to resort to higher radiotracer dose.
Up until now, balancing image quality, dose and scan time has been the
The Ingenuity TF PET/CT advantage
The need for more accurate tumor quantification and delineation has
led to the development of technology that enables high-quality PET/CT
images to be acquired at low dose levels.
Philips Ingenuity TF
PET/CT addresses the challenges of localization, specificity and low
dose in oncology and neurological imaging exams, and overcomes obstacles
for conducting cardiac perfusion and diagnostic CT studies. The system
is equipped with Astonish TF with 4-dimensional (4D) time-of-flight
(TOF) capabilities for high-speed and full-fidelity PET imaging. With
495 picoseconds (ps) timing resolution on the system, Astonish TF
provides the fastest timing resolution currently available, helping to
lead to enhanced localization of events.
Astonish TF provides TOF
technology designed to enhance image quality by reducing noise and
providing high sensitivity. The high-quality images help to improve
lesion detection and localization to increase diagnostic confidence and
preserve healthy tissue during treatment. This latest generation in TOF
technology leads to enhanced contrast by up to 30% compared to non-TOF
The 4D component of TOF is designed to provide additional
image quality and standard uptake value (SUV) quantitation improvements
to account for patient movement during respiratory-gated studies. In
fact, Astonish TF shows up to 50% improved contrast resolution, while
maintaining quantitative accuracy with up to 4 times the reconstruction
speed of previous-generation systems.
Low dose techniques for quality imaging
To address the need to manage CT dose without sacrificing image quality, the system comes available with iDose4, a CT iterative reconstruction technique.
As an iterative reconstruction technique, iDose4 gives
the user control of the dial, enabling clinicians to personalize image
quality based on the patients’ needs at low dose. iDose4 is
designed to improve spatial resolution at low dose, reduce noise with a
natural appearance, provide robust artifact prevention, and improve
image quality*. In fact, iDose4 improves spatial resolution by up to 57% on the Ingenuity CT platform.
List mode capabilities
Another important feature of Astonish TF for improving lesion
detection is list mode reconstruction capabilities. This technology
records each event and timing sequentially to enhance image resolution
and improve accuracy. By leveraging list-mode reconstruction, Astonish
TF can provide higher accuracy in SUV values without compromising
List mode reconstruction enables us to acquire all
the information with a single event at a time and to process this data
in a short amount of time. It produces a more uniform picture and better
tradeoff. What’s unique about the Astonish TF is what’s described as
full fidelity, and it is the only TOF that offers a highly accurate way
to reconstruct images in a very fast mode.
Improving lesion detection
advantage of TOF technology for PET is that it produces sharper images
that are better for lesion detection and localization. This increases
diagnostic confidence for the physician and contributes to preserving
healthy tissue during radiation therapy treatments.
advantage of the TOF is the ability to see smaller and smaller lesions
that , until recently, were unable to be detected and/or characterized.
In a recent study,7
TOF PET yielded a significant improvement in lesion detection in
oncologic studies over all contrasts and BMIs, and this improvement was
greater for lower lesion contrasts. The study evaluated 100 patients
with various body types and found that TOF PET scans improved the
signal-to-noise ratio for both liver and lung images and resulted in
improvement in lesion detection.
Fast image acquisition in TOF
PET is enabling doctors to acquire head-to-toe whole-body images
acquisitions in a reasonable amount of time without compromising the
throughput of the scanner. We are able to see smaller lesions, get
better image quality, and image head-to-toe in a reasonable amount of
In a recent case, a 65-year-old male presented with a
history of laryngeal cancer. Chest, abdomen, and pelvic contrast-CT
images revealed an esophageal lesion with no nodal or distant
metastases. The PET/CT was ordered for initial treatment strategy. The
PET/CT (Figure 1) images revealed a large FDG-avid esophageal mass as
well as a 3-mm node FDG-avid abdominal node (Figure 2). While a 3-mm
node appeared normal on a CT scan, it was very FDG-avid on PET,
demonstrating the metabolic size was significantly larger than the
anatomic size (Figure 2). A subsequent biopsy confirmed lymph-node
metastases, which changed staging and management in this case.
Expanding neuro-imaging applications
the majority of PET/CT procedures today are geared toward oncology
applications, there are a growing number of PET/CT neurological and
cardiovascular imaging studies.10 Most clinical procedures
for neurological imaging are for dementia, epilepsy, and brain tumors.
Although FDG for brain imaging is still the most important PET/CT
tracer, this may change with the recent approval of amyloid tracers for
conditions, such as Alzheimer’s Disease. Accordingly, neurological
imaging is an area that is expected to experience tremendous growth.
The recent FDA approval of amyloid imaging agents may improve diagnostic evaluation of patients with suspected dementia.8
This coupled with new promising treatment agents may open the door for
the routine incorporation of PET in clinical trials in patients with
managing patients with known or suspected coronary artery disease,
PET/CT is increasingly used to perform tests on the patient at rest or
with stress for noninvasive imaging of the perfusion of the heart.9
introduction of the F-18-based cardiac tracer may present a shift in
myocardial nuclear imaging from SPECT to PET. This is possible because
image quality in PET is much better than in the SPECT images and is must
faster. A whole stress-rest study can be completed in one hour as
opposed to 4 hours in the SPECT world.
Astonish TF and PET/CT and
F-18-based cardiac tracers will change how nuclear cardiology is being
utilized. It will open a whole new area in nuclear cardiology and PET
Tailored treatment in bariatrics
clinical condition that is transforming patient care is obesity. More
than 100 million people in the U.S. are defined as obese, 12 million of
whom have extreme obesity.10 Along with the increasing number of obese patients comes a growing challenge to diagnostic imaging.
A recent study11
showed TOF scans can help improve lung and liver lesion detectability
in heavy patients. This is critical at Saint Louis University School of
Medicine, where nearly half of all patients presenting for nuclear
medicine exams are obese.
Fundamental to improving image quality
in patients with a high BMI is higher sensitivity. The TOF serves as a
sensitivity amplifier. On average scanners, to achieve higher
detectability of smaller lesions, an injection of a significantly higher
dose of FDG may be necessary. But with TOF, small lesions may be
detected in obese patients by adjusting imaging protocols and with
minimal increase in injected dose. We therefore have higher sensitivity
due to the inherent lower signal-to-noise ratio in the TOF scanner.
With solutions like TOF, imaging patients with a large body habitus is feasible.
use the least amount of radiation, and we are able to produce
interpretable scans in patients with high BMI where at other sites these
images may be of lower quality.
Transforming patient care for the future
While the adoption of PET for neurological and cardiac imaging
promises to revolutionize the future of patient care, we are already
seeing a significant transformation today.
We have fast image
acquisition, and we are able to detect smaller lesions, produce better
quality images independent of body mass index, and on this PET/CT system
we can better manage radiation.
Balancing image quality, dose,
and scan time no longer has to be a matter of managing tradeoffs. With
Astonish TF, we can already strike that balance without compromise.
Improved image quality is defined by improvements in spatial resolution
and/or noise reduction as measured in phantom studies.
Cancer Society: Cancer Facts and Figures 2012. Atlanta, Ga: American
Cancer Society, 2012. Last accessed January 6, 2012.
Suhy, BS, CNMT, RT(N), Piotr J. Maniawski, MSc. Routine clinical
applications of 4D TOF PET/CT. Philips Healthcare – Nuclear Medicine,
Cleveland, OH. http://clinical.
- Lui C, Alessio A, Kinahan PH. Respiratory motion correction
for quantitative PET/CT using all detected events with internal—external
motion correlation. Med Phys. 2011;38: 2715-2723.
- Erdi YE, Nehmeh SA, Pan T, et al. The CT motion quantitation of lung lesions and its impact on PET-measured SUVs. J Nucl Med. 2004;45:1287-1292.
Thorndyke B, Schreibmann E, Koong A, Xing L. Reducing respiratory
motion artifacts in positron emission tomography through retrospective
stacking. Med Phys. 2006;33:2632-2641. doi: 10.1118/1.2207367.
- Nehmeh SA, Erdi YE. Respiratory motion in positron emission tomography/computed tomography: A review. Semin Nucl Med. 2008;38:167-176. doi: 10.1053/j.semnuclmed.2008.01.002.
Kawano T, Ohtake E, Inoue T. Deep-inspiration breath-hold PET/CT of
lung cancer: Maximum standardized uptake value analysis of 108 patients.
J Nucl Med. 2008;49:12231231. doi: 10.2967/jnumed.107.049296.
- Yang L, Rieves D, Ganley C. Brain Amyloid Imaging — FDA Approval of Florbetapir F18 Injection. N Engl J Med. 2012;367:885-887. September 6, 2012 DOI:10.1056/ NEJMp1208061.
Cardiac PET and PET/CT Imaging Practice Guidelines. A summary of the
recommendations and practice guidelines of professional groups. SNM PET
Center of Excellence. http://
- Gordon-Larsen P, Adair LS, Nelson MC, Popkin BM.
Five-year obesity incidence in the transition period between adolescence
and adulthood: The National Longitudinal Study of Adolescent Health. Am J Clin Nutr. 2004;80:569-575.
- El Fakhri et al. Improvement in lesion detection with whole-body oncologic time-of-flight PET. J Nucl Med. 2011; 52:347-353.