Download SPECT-CT: From “Unclear Medicine” to New

SPECT-CT: From “Unclear
Medicine” to New-Clear
Medicine!
John Bauman, M.D.
Nuclear Medicine,
Diagnostic Radiology
OVERVIEW:
Nuclear Medicine,
the imaging of disease
processes by detecting
radiation emitted from
patients who have
John Bauman, M.D.
been administered
radioactive isotopes, was preceded only by
plain x-ray as a diagnostic technique and
predates CT, Ultrasound and MRI. Nuclear
Medicine was also the first specialty to
“go digital” and make extensive use of
computerized imaging and data processing
to enhance image quality and improve
diagnosis. Nuclear Medicine is based on
binding a radioactive isotope, such as
99m-Technetium (99mTc), to a physiologically active molecule which transports
the isotope to areas of clinical interest in
the body. For a bone scan, 99m-Tc is bound
to a diphosphonate compound that will be
chemisorbed into the skeleton. For a
myocardial perfusion scan, the same 99m-Tc
is bound to a molecule that is taken up by
the myocardium in direct proportion to
variations in blood flow. Several other
isotopes and physiologic compounds are
used to create unique radiopharmaceuticals
for a variety of diagnostic and therapeutic
uses. The patient is imaged with a gamma
camera and computer system that generates
images of the radiopharmaceutical’s biodistribution to assess for the presence or
absence of disease.
THE PROBLEM:
The inherent physics of imaging radiopharmaceuticals results in very “noisy” images
that are limited in resolution and information
density such that they can look like “spots &
dots” to the uninitiated. Nonetheless, due
to the unique and valuable pathophysiologic
nature of the information provided, conventional planar Nuclear Medicine remains a
powerful diagnostic tool.
Single Photon Emission Computed Tomography (SPECT), is to planar nuclear medicine
imaging what CT is to plain X-ray: a method
to generate 3-D, multiplanar images. SPECT
has been in use for over 30 years. However,
early SPECT cameras were very limited in
their imaging resolution and accuracy.
Figure 1:
Use of SPECT-CT has revolutionized pre-operative localization
of parathyroid adenomas. The adenoma is identified with the
SPECT agent, 99mTc-Sestamibi, and confidently localized on
fused SPECT-CT images. Not only is the size of the adenoma
provided, the surgeon is also given a roadmap with specific
measurements to guide dissection for rapid and accurate
surgical excision. Information about possible aberrant vessels
and other potential operative hazards is also provided. In this
case, planar imaging failed to identify the small adenoma,
readily seen at SPECT-CT.
Figure 2:
SPECT-CT has also been of significant benefit in localization
and characterization of pain in small bones of the cervical spine,
wrist and foot. Here a sesamoid fracture is localized (“hot”)
on bone scan and confirmed to be due to a micro-fracture on
0.33mm CT image obtained concurrently. The SPECT-CT at
VMC has the highest bone CT resolution available – greater
than conventional CT.
Valley Medical Center
and Vantage Radiology
would like to recognize
Patient Accounts
Manager, Krisse Bartels
Krisse Bartels, Patient Accounts
Manager at Vantage Radiology &
Diagnostic Services, was born and
raised in Bellevue and still resides
there today. Krisse obtained her
Business Finance degree from
Seattle University in 1988.
Serving in multiple capacities
over the years, Krisse has worked
for Valley Radiologists/Vantage
Radiology since 1986. She is
currently Director of Finance
as well as the Patient Accounts
Manager and also supervises the
authorization team, a testament to
her noteworthy ability to multitask. Krisse is a credit to Vantage
Radiology having cultivated a
committed and skilled team
of billing and accounting
professionals. She is amazingly
adept at managing all the various
demands of the practice’s
business. Vantage Radiology is
proud and very fortunate to have
a leader of Krisse’s skill and
depth on its team.
Krisse has three children who
keep her very busy with their
academics and athletic pursuits.
(continued on reverse)
www.valleymed.org
Vantage Radiology & Diagnostic Services, a professional service
corporation, in association with Valley Medical Center.
www.vrads.com
SPECT-CT: From “Unclear
Medicine” to New-Clear
Medicine! (continued from front)
CURRENT STATUS:
Recent advances in both hardware and software
have resulted in greatly enhanced diagnostic
capability for Nuclear Medicine. The arrival of
low-cost super computers enabled the use of
improved image reconstruction algorithms. The
inclusion of individual camera characteristics,
distance of the camera from the patient, and
other factors in the reconstruction algorithm
corrects for flaws that otherwise reduce image
quality. Finally, the modern combination of lowdose co-axial CT scanning with SPECT gamma
camera imaging, such as we have here at VMC,
adds the ability to correct the Nuclear Medicine
images for variations in body density as well as to
co-register the Nuclear Medicine information (in
color) with the CT information (grayscale). With
this system, CT radiation exposure is extremely
low, and billing is similar to SPECT alone.
These advances have resulted in spatial
resolution for SPECT-CT images in the range
of 6-7 mm, similar to that obtained with PETCT imaging. These advances provide an
accuracy of anatomic localization of radiopharmaceutical distribution within the body
that, quite frankly, is stunning.
Figure 3:
Another useful orthopedic application is evaluation of
painful prosthetic joints – hips, knees, ankles, etc. In
particular, evaluation of knee prostheses has been
problematic by conventional scintigraphy, plain
radiographs are frequently unrewarding and MRI is
not possible. SPECT-CT frequently finds causes for
pain other than prosthesis loosening. Here is a case
of a large peri-prosthetic cyst with a fractured wall.
Note the greater information provided by the
SPECT-CT image versus the planar image.
A News Publication from
Vantage Radiology &
Diagnostic Services and
Valley Medical Center
Summer 2014