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Current Medical
Imaging Reviews
ISSN: 1573-4056
Current Medical Imaging Reviews
Volume 2, Number 2, May
2006
Contents
Trends in Medical Image Compression Pp. 165-185
Gloria Menegaz
[Abstract]
Small Animal PET: A Review of Commercially Available
Imaging Systems Pp. 187-192
Michele Larobina, Arturo Brunetti and Marco Salvatore
[Abstract]
Review of the Contribution of Radiolabelled Tracers
for Tumour Cell Status Imaging Pp. 193-203
Perek Nathalie, Le Jeune Nathalie, Denoyer Delphine,
Prevot Nathalie and Francis Dubois
[Abstract]
Functional Imaging Techniques for the Evaluation of
Hepatocellular Carcinoma Using Dynamic 11C-Acetate
PET Imaging Pp. 205-214
Sirong Chen, Chi-Lai Ho and Dagan Feng
[Abstract]
A Systematic Review of the Efficacy of 18F-FDG
PET in Unknown Primary Tumors Pp. 215-225
Roberto C. Delgado-Bolton, José L. Carreras
and Ma. Jesús Pérez-Castejón
[Abstract]
Imaging Malignant Gliomas with 99mTc-MIBI
Brain Single-Photon Emission Computed Tomography Pp.
227-235
P. Beauchesne, R. Pedeux and C. Soler
[Abstract]
The Role of Functional Neuroimaging in Mild Cognitive
Impairment Pp. 237-246
Alberto Marcos, Ana Barabash, Pedro Gil, Marta
Encinas, Ramón de Juan, María Payno, Inés
Ancín, Blanca Vázquez and José Antonio
Cabranes
[Abstract]
A Review of Wavelet Denoising in MRI and Ultrasound
Brain Imaging Pp. 247-260
Aleksandra Pizurica, Alle Meije Wink, Ewout Vansteenkiste,
Wilfried Philips and Jos B.T.M. Roerdink
[Abstract]
Lymphatic Drainage in Patients with Primary Cutaneous
Melanoma - the Role of Lymphoscintigraphy in Sentinel Lymph
Node Biopsy Pp. 261-270
Roger F. Uren, John F. Thompson, Robert Howman-Giles
and David Chung
[Abstract]
Pelvic Floor Ultrasound Pp. 271-290
Hans Peter Dietz
[Abstract]
Abstracts
[Back to top]
Trends in Medical Image Compression
Gloria Menegaz
This paper presents an overview on the state-of-the-art in
the field of medical image coding. After a summary of the
more representative 2D and 3D compression algorithms, a versatile
model-based coding scheme for three-dimensional medical data
is introduced. The potential of the proposed system is in
the fact that it copes with many of the requirements characteristic
of the medical imaging field without sacrificing compression
efficiency. Among the most interesting features are progressively
refinable up-to-lossless quality of the decoded information,
object-based functionalities and the possibility to decode
a single 2D image of the dataset. Furthermore, such features
can be combined enabling a swift access to any two-dimensional
object of any image of interest with refinable quality. The
price to pay is a slight degradation of the compression performance.
Though, the possibility to focus the decoding process on a
specific region of a certain 2D image allows a very efficient
access to the information of interest, which can be recovered
to the desired up-to lossless quality. This is believed to
be an important feature for a coding system meant to be used
for medical applications, which largely compensates for the
eventual loss in compression that could be implied.
[Back to top]
Small Animal PET: A Review of Commercially Available
Imaging Systems
Michele Larobina, Arturo Brunetti and Marco Salvatore
More than ten years ago, several research groups started
to develop Positron Emission Tomography (PET) systems dedicated
to animal studies. The growing interest in pre-clinical imaging
studies, both in biological and medical basic research, and
in pharmaceutical industry, has recently induced the world-leading
manufacturers of medical image equipment to invest in this
market. Some of the proposed scanner prototypes in an overhauled
and/or enhanced version, turned into commercial systems, and
five PET scanners dedicated to small animals (mice and rats)
are today commercially available: “Explore Vista”
from General Electric Healthcare (Waukesha, Wisconsin, USA),
“microPET Focus” from Concorde Microsystems, Inc.,
(Knoxville, Tennessee, USA), “quad-HIDAC” from
Oxford Positron Systems Ltd. (Weston-on-the-Green, Oxfordshire,
UK), “Mosaic” from Philips Medical Systems (Milpitas,
California, USA) and “Yap-PET” from I.S.E. Srl
(Migliarino Pisano, Pisa, Italy).
This paper reviews the commercially available systems describing
each tomograph in terms of gantry geometry, detector material,
detector size and configuration, and reporting the parameters
(field of view, spatial resolution and sensitivity) characterizing
the imaging capability. A critical discussion on some aspects
related to the use of these systems is reported.
[Back to top]
Review of the Contribution of Radiolabelled Tracers
for Tumour Cell Status Imaging
Perek Nathalie, Le Jeune Nathalie, Denoyer Delphine,
Prevot Nathalie and Francis Dubois
Cancer develops as a result of an imbalance between cell
proliferation and programmed cell death or apoptosis. Tumour
cells are characterised by prolonged survival and uncontrolled
proliferation. Tumour cells also acquire new functions, such
as the capacity to migrate and colonise other organs by forming
metastases. Cancer chemotherapy mainly acts by inducing apoptosis.
However, resistance of human malignancies to multiple chemotherapeutic
agents remains a major obstacle to the efficacy of treatment.
Radiolabelled tracers used in Single Photon Emission Computed
Tomography (SPECT) and more recently in Positron Emission
Tomography (PET) screening in nuclear medicine have been developed
to directly visualise in vivo biochemical and physiological
parameters of tumour cells. These functional and molecular
techniques have become an excellent research tool to study
in vivo tumour biology. For instance, proliferation,
apoptosis and multidrug resistance tracers have been complexed
and studied on in vitro cellular models and several
in vivo applications have been developed in the management
of cancer patients. In this review, we focus on the radiotracers
elaborated in the field of proliferation, apoptosis and MDR.
We summarise the most recent studies in SPECT and PET imaging
and their possible applications in oncology.
[Back to top]
Functional Imaging Techniques for the Evaluation of
Hepatocellular Carcinoma Using Dynamic 11C-Acetate
PET Imaging
Sirong Chen, Chi-Lai Ho and Dagan Feng
It was widely reported that 18F-fluorodeoxyglucose
(FDG) positron emission tomography (PET) could not detect
40-50% of hepatocellular carcinoma (HCC), one of the most
common malignancies worldwide. Recent research had demonstrated
that 11C-acetate (ACT) was a complementary tracer
to FDG and these 2 tracers together could maximize the detection
accuracy of this tumor. Quantitative functional imaging techniques
were, therefore, conducted to further characterize the underlying
kinetic basis of this tracer in the detection of HCC. To describe
the 11C-acetate molecular kinetic behavior in liver,
a three-compartment model with fixed-weight dual-input function
was initially proposed, together with a new physiologic parameter
defined as the “local hepatic metabolic rate-constant
of acetate (LHMRAct)”. Preliminary results
had shown that the LHMRAct of HCC was significantly
higher than that of the non-tumor liver tissue. This tracer
kinetic modeling technique provided the first quantitative
and kinetic evidence that 11C-acetate was indeed
metabolically incorporated in certain types of HCC. In real
pathology, however, both tumor and non-tumor liver tissues
were actually quite heterogeneous in the distribution and
proportion of the two hepatic blood supplies: hepatic artery
(HA) and portal vein (PV). To further improve the accuracy
of our previous quantitative analysis, the individual proportion
of HA/PV in different regions of interest (ROIs) was further
studied. An extra parameter called “αv”,
defined as the “relative portal venous contribution
to the hepatic blood flow”, was proposed (in substitute
of the previously fixed weight HA:PV contribution) for the
11C-acetate dual-input liver model. Ten ROIs extracted
from six patients were used to test the models with fixed/non-fixed
weight dual-input function. The weighted non-linear least
squares (NLS) algorithm was used to estimate all the parameters.
Results showed that the new model structure could provide
better characterization of the 11C-acetate kinetic
behavior in liver by statistical study. The analysis was also
able to provide a better understanding of the blood supply
mechanism in the liver, proposing that the new parameter αv,
as a quantitatively derived vascular factor, might also provide
useful diagnostic information for detection of HCC, particularly
in situations when confounding hyperaemic variables such as
dysplastic and regenerative nodules coexist in the setting
of severe cirrhosis.
[Back to top]
A Systematic Review of the Efficacy of 18F-FDG
PET in Unknown Primary Tumors
Roberto C. Delgado-Bolton, José L. Carreras
and Ma. Jesús Pérez-Castejón
Patients with unknown primary tumors (UPT) represent a challenge
for clinicians, as management decisions depend on the localization
of the primary tumor and accurate staging. In this article
we systematically reviewed the evidence on the efficacy of
18F-FDG PET in patients with UPT, analyzing the
diagnostic performance, impact on management and patient outcome
efficacy. The performance of 18F-FDG PET in primary
tumor detection was high, as it detected the primary tumor
in >40% of patients with high sensitivity and intermediate-high
specificity. Most cases in which no primary tumor was found
remained true-negative after follow-up. Moreover, most studies
included patients with negative conventional imaging methods.
Studies presented variable results regarding changes in management,
reporting a high impact on management in 44% of patients in
the pooled data (range 14%–69%). However, this variability
could be due to differences in study design. Patient outcome
efficacy was discussed by several studies, with conflicting
and inconclusive results. Future studies must supply high
quality evidence regarding impact on management, patient outcome
efficacy, and cost-effectiveness issues; additionally, the
role of PET/CT must be evaluated. In our opinion, 18F-FDG
PET should be performed at the onset of the diagnostic work-up;
this may improve management decisions and patient outcome.
[Back to top]
Imaging Malignant Gliomas with 99mTc-MIBI
Brain Single-Photon Emission Computed Tomography
P. Beauchesne, R. Pedeux and C. Soler
Malignant glioma, the main primary brain tumor, has a dismal
prognosis. Current therapies extend a patient’s survival
(usually 2-3 months) by only about 9 months to 1 year on average.
Early and reliable assessment of an individual patient’s
prognosis and response to therapeutics is therefore essential
to determine whether continued therapies are beneficial.
Functional imaging methods have been proposed for the evaluation
of treatment efficacy and are claimed to be more specific
than are conventional radiological investigations. Yet the
question remains as to how best to incorporate this newly
acquired insight into the clinical context. SPECT and PET
assess tumor viability by specific intracellular uptake in
malignant cells. TI-201thallium SPECT accuracy
is similar to that of 18FDG PET. 99mTc-MIBI
is used as an alternative to TI-201thallium for
the study of myocardial perfusion and has also been proposed
as an imaging agent for various tumors such as gliomas. MIBI
brain SPECT has shown more specificity and sensitivity than
TI 201thallium brain SPECT. MIBI brain SPECT may
help in differentiating a high grade glioma recurrence from
a radiation necrosis. In this review, we describe the roles
of MIBI SPECT in the management and follow up of malignant
glioma patients.
[Back to top]
The Role of Functional Neuroimaging in Mild Cognitive
Impairment
Alberto Marcos, Ana Barabash, Pedro Gil, Marta
Encinas, Ramón de Juan, María Payno, Inés
Ancín, Blanca Vázquez and José Antonio
Cabranes
Mild Cognitive impairment (MCI) is a frequent problem in
the elderly, since many of MCI subjects progress into Alzheimer’s
disease (AD). Recently new treatment options have been developed
that may alter or delay the rate of AD deterioration. Wherefore,
detecting and recognising patients that have a higher risk
of developing dementia allows for the planning of correct
treatments, future care and research purposes. Although there
are no markers that certainly predict the progression to dementia,
some useful clinical or biological features have been reported.
A reduced perfusion, glucose metabolism or atrophy in local
areas of the cerebral cortex assessed by functional or conventional
imaging technics, some genes, CSF proteins and psychological
test, have been described as risk factors for the development
of AD. Even if there is not one single diagnostic method with
enough sensibility or specificity to allow a sure outcome,
combining early clinical, regional cerebral blood flow and
genetics markers we can improve accuracy on predicting the
progression from MCI to AD. We review the clinical diagnostic
criteria of MCI, the increasing literature about its diagnosis,
and we describe the recent findings under the light of our
experience following up patients during 5 years.
[Back to top]
A Review of Wavelet Denoising in MRI and Ultrasound
Brain Imaging
Aleksandra Pizurica, Alle Meije Wink, Ewout Vansteenkiste,
Wilfried Philips and Jos B.T.M. Roerdink
There is a growing interest in using multiresolution noise
filters in a variety of medical imaging applications. We review
recent wavelet denoising techniques for medical ultrasound
and for magnetic resonance images and discuss some of their
potential applications in the clinical investigations of the
brain. Our goal is to present and evaluate noise suppression
methods based on both image processing and clinical expertise.
We analyze two types of filters for magnetic resonance images
(MRI): noise suppression in magnitude MRI images and denoising
blood oxygen level-dependent (BOLD) response in functional
MRI images (fMRI). The noise distribution in magnitude MRI
images is Rician, while the noise distribution in BOLD images
has been recently shown to follow a Gaussian model well. We
evaluate different methods based on signal to noise ratio
improvement and based on the preservation of the shape of
the activated regions in fMRI.
A critical view on the problem of speckle filtering in ultrasound
images is given where we discuss some of the issues that are
overlooked in many speckle filters like the relevance of the
“speckled texture”, expert-defined features of
interest and the reliability of the common speckle models.
We analyze the use of multiresolution speckle filters to improve
the automatic processing steps in the clinical research of
non-cystic periventricular leukomalacia. In particular we
apply speckle filters to ultrasound neonatal brain images
and we evaluate the influence of the filtering on the effectiveness
of the subsequent classification and segmentation of flares
of affected tissue in comparison with the manual delineation
of clinicians.
[Back to top]
Lymphatic Drainage in Patients with Primary Cutaneous
Melanoma - the Role of Lymphoscintigraphy in Sentinel Lymph
Node Biopsy
Roger F. Uren, John F. Thompson, Robert Howman-Giles
and David Chung
Lymphatic drainage of the skin is highly variable from patient
to patient and unexpected patterns of lymph drainage are not
uncommon. Drainage can occur from the skin of the back through
the posterior body wall to nodes in the retro-peritoneal,
paravertebral and para-aortic areas. Drainage from the skin
of the back to nodes in the triangular intermuscular space
occurs in 10% of back melanomas and drainage from the back
over the shoulders to SLNs in the neck is seen in 20% of patients.
In the head and neck lymph drainage can occur up the neck
from the base to nodes in the occipital and upper cervical
regions and drainage can occur from high on the scalp directly
to nodes in the supra-clavicular fossa completely bypassing
nodes higher in the neck. Lymphatic drainage is common across
the midline to contralateral SLNs and interval nodes are seen
as SLNs in 7% of patients with melanoma.
For SLN biopsy to be accurate high quality lymphoscintigraphy
is vital to ensure that all SLNs are biopsied in every patient
regardless of their location.
[Back to top]
Pelvic Floor Ultrasound
Hans Peter Dietz
Over the last 20 years, ultrasound has largely replaced radiological
methods in the investigation of pelvic floor disorders. Transrectal,
transvaginal/ introital and transperineal/ translabial methods
have been investigated, with the transperineal/ translabial
approach currently the most widespread due to ease of use
and the fact that equipment is available almost universally.
Position and mobility of the bladder neck, bladder wall thickness,
pelvic floor muscle activity and pelvic organ prolapse can
be quantified, and Color Doppler may be used to document stress
urinary incontinence. As a consequence, both preoperative
assessment and audit activities in the field of pelvic reconstructive
surgery have been markedly enhanced. This has been most evident
in the evaluation of new synthetic slings and implants which
usually are highly echogenic, making ultrasound the imaging
method of choice for the evaluation of such grafts.
Most recently, 3D translabial and transvaginal ultrasound
have given access to the axial plane, allowing imaging of
paravaginal spaces, the levator hiatus and the pubococcygeus/
puborectalis muscles, i.e., the inferior aspects of the levator
ani. The observation of manoeuvres such as a pelvic floor
contraction or a Valsalva in the three orthogonal planes,
rendered 3D volumes and 4D volume cine clips open up new possibilities
for the assessment of functional anatomy, superior to what
is currently possible with Magnetic Resonance Imaging. With
the latest development, Volume Contrast Imaging (VCI), pelvic
floor ultrasound has now reached the spatial resolution of
MRI in all three dimensions, while providing far superior
temporal resolution. It has become clear that, while there
is a wide range of ‘normality’ in pelvic organ
mobility and the dimensions of the levator ani and the hiatus
itself, childbirth has a distinct effect on the dimensions
of the hiatus and may cause significant soft- tissue trauma
that is not apparent at the time of delivery. However, the
clinical relevance of such traumatic changes remains to be
determined. Much work will need to be done before the full
potential of 3D/ 4D pelvic floor ultrasound is realized, both
in research and in clinical practice.
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