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Current Medical
Imaging Reviews
ISSN: 1573-4056
Current Medical Imaging Reviews
Volume 2, Number 3, August
2006
Contents
Innovation in Contrast Agents for Magnetic Resonance
Imaging Pp. 291-298
Pasquina Marzola, Federico Boschi and Andrea Sbarbati
[Abstract]
Usefulness of Magnetic Resonance Imaging in Cardiac
and Enovascular Intervention Pp. 299-313
Maythem Saeed
[Abstract]
Adenosine Myocardial Perfusion Imaging Pp. 315-327
Gilbert J. Zoghbi and Ami E. Iskandrian
[Abstract]
Characterization of Breast Lesions by Magnetic
Resonance Imaging (MRI) and Spectroscopy (MRS) Pp.
329-340
Uma Sharma, Raju Sharma and Naranamangalam R. Jagannathan
[Abstract]
Sentinel Node Imaging Pp. 341-346
Annette H. Chakera, Krzysztof T. Drzewiecki, Christian Ingvar,
Torben Steiniche and Birger Hesse
[Abstract]
Clinical Applications of Pinhole Single Photon Emission Tomography
Pp. 347-352
Alain Seret and Roland Hustinx
[Abstract]
The Ultrasonographic Diagnosis of Polycystic Ovary Syndrome
Pp. 353-363
Cesare Battaglia, Nicola Persico, Fulvia Mancini, Arianna
Cianciosi, Paolo Busacchi and Domenico de Aloysio
[Abstract]
Fractional Moving Blood Volume Measurement Using Power Doppler
Ultrasound as an Estimation of Fetal Organ Blood Perfusion
Pp. 365-372
Edgar Hernandez-Andrade, Tomas Jansson and Karel Marsál
[Abstract]
Contrast Enhanced Ultrasonography for Focal Liver Lesions
Characterization: Clinical Perspective Pp. 373-383
Michele Bertolotto, Tommaso Vincenzo Bartolotta, Loretta
Calderan, Stefano Cernic, Ada Mandic and Maria Assunta Cova
[Abstract]
Abstracts
[Back to top]
Innovation in Contrast Agents for Magnetic Resonance
Imaging
Pasquina Marzola, Federico Boschi and Andrea Sbarbati
In magnetic resonance imaging (MRI), contrast between
different tissues depends on a number of parameters including
transversal and longitudinal relaxation times (T1,
T2),
susceptibility, proton density and flow. Despite this multiparameter
dependence, the usefulness of contrast agents has been recognized
since MRI was first introduced. Contrast agents in MRI are
chemicals which by virtue of their unpaired electrons induce
relaxation in the water molecules in their vicinity. Depending
on their chemical structure, different contrast agents may
alter the signal in specific regions of the image or in specific
pathologies. Established and widely used contrast agents are
small Gd chelates which, after injection into the bloodstream,
rapidly extravasate into the extravascular space. More recently,
a different class of contrast agents has been developed with
the property of remaining in the vascular space (blood pool
contrast agents). Blood pool contrast agents have been used
to investigate vasculature in tumors (angiogenesis) and in
the brain (cerebral blood volume and functional MRI). In the
last few years, great attention has been devoted to the use
of contrast agents for cellular and molecular imaging. It
has been realized that cells, opportunely marked with contrast
agents, can be visualized in vivo with MRI. The technique
has been applied successfully to in vivo detection
of stem cells after transplantation. Moreover, contrast agents
have been applied to imaging phenomena at the molecular level
in vivo, for instance to investigate gene expression
in tissues. In this article we describe some innovative applications
of contrast agents for MRI.
[Back to top]
Usefulness of Magnetic Resonance Imaging in Cardiac
and Enovascular Intervention
Maythem Saeed
Assessment of ischemic heart disease is an important
application of magnetic resonance imaging (MRI). This noninvasive
diagnostic technique has the potential to evaluate different
aspects of ischemic heart disease such as myocardial function,
perfusion and the extent of acute and chronic infarctions.
MRI is becoming an alternative technique for assessment of
myocardial viability by predicting systolic recovery of stunned
and hibernating myocardium after revascularization. MR contrast
agents provide additional information on residual myocardial
viability, myocardial perfusion, coronary angiography and
microvascular integrity. Recent technologic improvements in
scanners, sequences and post-processing of images showed the
potentiality of MR-guided procedures. This review begins with
a brief overview of magnetic resonance properties and MR contrast
agents and proceeds to their applications in cardiac imaging
and endovascular intervention. The next generation of MR contrast
agents will likely focus on increase detection sensitivity
so that minor tissue changes can be detected, prolonging intravascular
retention (blood pool contrast agents), improving tissue targeting
(tissue and molecule specific contrast agents and probes)
and molecular imaging. MRI will play viable role in cardiovascular
imaging and intervention in the near future and it may have
the potential to complement other commonly used diagnostic
modalities.
[Back to top]
Adenosine Myocardial Perfusion Imaging
Gilbert J. Zoghbi and Ami E. Iskandrian
Adenosine myocardial perfusion imaging is a commonly
used modality for the evaluation of patients with known or
suspected coronary artery disease (CAD). In this review we
discuss the pharmacology of adenosine and its effects on myocardial
blood flow and the generation of perfusion defects during
myocardial perfusion imaging (MPI), the indications and contraindications
of MPI, stress protocols, side effects, hemodynamic and electrocardiographic
changes, comparison to other stress MPI modalities, the role
of adenosine MPI in special patient populations and the recent
advances in the field with the emergence of the new selective
adenosine agonists.
[Back to top]
Characterization of Breast Lesions by Magnetic
Resonance Imaging (MRI) and Spectroscopy (MRS)
Uma Sharma, Raju Sharma and Naranamangalam R. Jagannathan
Breast cancer is a major health problem in women, worldwide.
A combination of physical examination, mammography, ultrasound
and fine needle aspiration cytology (FNAC) or core biopsy
is currently the mainstay for preoperative diagnosis of breast
lesions. Magnetic resonance imaging (MRI) has been proposed
as a useful complimentary modality to provide additional information.
It has shown potential in the detection, diagnosis and management
of breast cancer. It can be used to improve preoperative staging,
follow response to therapy, and to detect local recurrences.
Contrast enhanced MRI (CEMRI) has evolved as an important
tool in the evaluation of breast abnormalities with high sensitivity
(94-100%), but with poor specificity. Recently, diffusion
and perfusion MRI techniques have been applied to breast lesion
characterization and show promise but warrant further investigations.
Characterization of breast lesions may also be assisted by
using information of the cellular chemistry provided by in
vivo proton MR spectroscopy (MRS). Recent reports have
shown that neoplastic breast tissue contains elevated levels
of choline containing compounds, which can be used as a biochemical
marker for differentiating benign versus malignant tumor and
for monitoring treatment response. Presently, the various
MR techniques show promise primarily as adjunct to the existing
standard detection techniques, and its acceptability as a
primary screening method will increase only if specificity
can be increased. This review presents the current status
of MRI and MRS in breast imaging.
[Back to top]
Sentinel Node Imaging
Annette H. Chakera, Krzysztof T. Drzewiecki, Christian Ingvar,
Torben Steiniche and Birger Hesse
Breast cancer and melanoma metastasize predominantly
via the lymphatic route. It has long been known that invasion
into one or a few nodes draining the primary tumour, the sentinel
nodes (SN), is the most important, early sign of dissemination.
If no malignant cells are detected in the SN, dissemination
is unlikely to be expected. For the last 10 years SN biopsy
has become an important tool in staging cancers. Two kinds
of tracers are used for SN detection: The blue dye, injected
during operation, and radioactively labelled colloid, injected
before operation. The lymphatic drainage can then be mapped
by following the blue dye by visual inspection during the
operation, and with gamma camera imaging before and probe
detection during the operation. The variations in the tracers
used, and the injection and imaging techniques are discussed.
The pathologic examination has also undergone a rapid evolution
with more detailed analysis including immunohistochemistry.
The use of the SN technique has quickly spread worldwide for
melanoma and breast cancer but is also being tested in several
other cancers. Reports on the influence on morbidity and mortality
reduction are becoming increasingly convincing. The near future
of SN examination is finally briefly outlined.
[Back to top]
Clinical Applications of Pinhole Single Photon Emission Tomography
Alain Seret and Roland Hustinx
For some planar scintigraphic explorations, like thyroid
or hip, the pinhole collimator is usually preferred to the
usual parallel hole collimators because it allows a superior
resolution. Progress in 3D tomography reconstruction methods
allows single photon emission tomography (SPET) to be today
performed using the pinhole collimator with again the advantage
of a higher resolution. Pinhole collimator imposes a short
distance (a few centimetres) to the target area and a restricted
field of view. Over the last ten years, the potential of pinhole
SPET has been essentially investigated for the ankle and the
hind foot, the detection of thyroid nodules or abnormal parathyroid
glands, the exploration of axillary lymph nodes. The technique
was usually compared to planar scintigraphy performed with
parallel hole or pinhole collimator. Sometimes a comparison
to standard (with parallel hole collimator) SPET or to a morphologic
imaging technique was also available. All studies highlight
the improvement in resolution afforded by the use of the pinhole
collimator. In bone scintigraphy, the delineation of the structures
was largely superior allowing the visualisation of significant
details usually never seen on scintigraphic images. In thyroid
scintigraphy, the better resolution allowed to detect more
nodules (essentially infra-centimetre nodules), and to reduce
the number of equivocal cases. For abnormal parathyroid gland
detection, the number of false negative cases decreased, with
a concomitant increase of true positive cases; the glands
were more sharply delineated on the images. Pinhole SPET with
Tc-99m-tetrofosmin was the only scintigraphic method able
to successfully reveal the number of involved lymph nodes
in patients with breast cancer. In conclusion pinhole single
photon appears as a promising new scintigraphic method allowing
to explore small areas with a high resolution.
[Back to top]
The Ultrasonographic Diagnosis of Polycystic Ovary Syndrome
Cesare Battaglia, Nicola Persico, Fulvia Mancini, Arianna
Cianciosi, Paolo Busacchi and Domenico de Aloysio
Polycystic ovary syndrome (PCOS) is one of the most controversial
endocrine disease, for its clinical and biochemical heterogeneity.
Many authors focused on the possible role of genetic, environmental
and hormonal factors in the development of the syndrome, but
the etiopathogenesis still remains unclear.
The diagnostic criteria for the definition of PCOS are as
heterogeneous as the disease itself and underwent more than
one revision throughout the last years.
Ultrasonography has been widely accepted as an important criterion
for the detection of polycystic ovaries. Furthermore, Doppler
flow analysis of both intraovarian and uterine arteries seems
to provide an insight to the pathological state and the degree
of progression of the disease. In this review, we provide
the state of the art for a correct diagnosis of PCOS, pointing
out the capacity of ultrasonography and color Doppler imaging
in the early detection of the syndrome and the possibility
to obtain additional information about its pathophysiology.
Since PCOS patients have higher cardiovascular risk the precocity
and the precision of the diagnosis is extremely important
to improve the long-term prognosis.
[Back to top]
Fractional Moving Blood Volume Measurement Using Power Doppler
Ultrasound as an Estimation of Fetal Organ Blood Perfusion
Edgar Hernandez-Andrade, Tomas Jansson and Karel Marsál
Fractional moving blood volume (FMBV) estimated using
power Doppler ultrasound (PDU) is a sensitive technique to
detect slow blood movement. However, several factors as; depth,
attenuation and blood characteristics can affect the PDU signals.
The aim of this study was to standardized and validate the
FMBV measurement compensating for the factors that can affect
the final results, in order to accurate estimate blood movement
in a specific region of interest (ROI) of fetal organs as
an estimation of blood perfusion.
FMBV measurement for the fetal lung blood perfusion was standardized
in 29 healthy fetuses at 35-37 weeks of gestation. Clear definition
of the ROI in both fetal lungs was proposed. FMBV values were
in the range of 27-42% (mean 36.2%) and showed a coefficient
of variation of 0.14. No significant differences between the
FMBV values obtained from the left and the right lungs, or
between cardiac systole and diastole were observed. A phantom
experimental study showed good sensitivity for slow blood
movement.
FMBV was then compared with blood perfusion measurements evaluated
with radioactive labeled microspheres (RMS) in the adrenal
gland of 5 fetal lambs exposed to severe asphyxia. There was
a high correlation between FMBV and RMS (r=0.90, range 0.43-0.99).
The reproducibility and agreement analyses showed an intraclass
correlation coefficient of 0.92 (95% confidence intervals
[CI] 0.78-0.96), and a mean difference between observers of
0.06 (SD, 3.7).
Conclusion. The estimation of the fractional moving blood
volume measurement using power Doppler ultrasound can be reliable
correlated with true fetal organ blood perfusion. FMBV is
a reproducible method that can offer valuable information
about adaptive fetal blood flow changes in the presence of
pregnancy associated complications.
[Back to top]
Contrast Enhanced Ultrasonography for Focal Liver Lesions
Characterization: Clinical Perspective
Michele Bertolotto, Tommaso Vincenzo Bartolotta,
Loretta Calderan, Stefano Cernic, Ada Mandic and Maria Assunta
Cova
Gray-scale and color Doppler ultrasonography have limited
accuracy in characterization of focal liver lesions because
a significant overlapping exists between the echo pattern
and vascularity of benign and malignant lesions. Several clinical
studies have demonstrated that characterization of focal liver
lesions that are indeterminate at conventional ultrasonography
could be improved using microbubble contrast agents with contrast
specific modes. In particular, latest generation ultrasound
contrast agents allow evaluation of lesion vascularity in
real time using low acoustic power contrast specific modes
with the resolution afforded with gray-scale imaging.
In this review article the enhancement pattern of different
types of benign and malignant focal liver lesions using low
acoustic power contrast specific modes is described, and the
current role of contrast enhanced ultrasonography in liver
lesion characterization is discussed.
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