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Current Medical
Imaging Reviews
ISSN: 1573-4056
Current Medical Imaging Reviews
Volume 1, Number 3, November
2005
Contents
Electrical Impedance Scanning – A New Diagnostic
Tool in Cancer Detection: Current Status and Recent Developments
Pp.209
Ansgar Malich, Mirjam Facius, Dorothee Fischer and Bernhard
Scholz
[Abstract]
Methodological Aspects and Applications of In
Vivo Imaging of Apoptosis in Oncology: An Illustrative
Review Pp.221
Marina S. Kartachova, Marcel Verheij, Cornelis A. Hoefnagel,Berthe
L. van Eck and Renato A. Valdés Olmos
[Abstract]
Current Issues in the Utility of Blood Oxygen Level
Dependent (Bold) MRI for the Assessment of Modulations in
Tumor Oxygenation Pp.229
Christine Baudelet and Bernard Gallez
[Abstract]
Issues of Quantitative Metabolic Brain Imaging with
Small Animal PET in Mice Pp.245
Hiroshi Toyama
[Abstract]
Can Motion Artifacts be Completely Removed from fMRI-Activation
Maps? Pp.253
Elisabeth De Castro Caparelli
[Abstract]
Comparison of the Image Quality on Low-dose Urinary
Tract Multidetector CT Examinations with 80 kVp and 120 kVp
(Original Research) Pp.265
Ensar Yekeler, Candan Ozdemir, Sabri Yilmaz, Alim Topcu,
Hakan Genchellac, Atadan Tunaci and Gulden Acunas
[Abstract]
Current Clinical Applications of In Vivo
Magnetic Resonance Spectroscopy and Spectroscopic Imaging
Pp.271
Margaret R. Lentz, Jennifer L. Taylor, D. Ashley Feldman
and Leo L. Cheng
[Abstract]
Virtual Colonoscopy Pp.303
Andrea Laghi
[Abstract]
Transient Focal Lesions in the Splenium of the Corpus
Callosum with Restricted Diffusion: An Enigma Pp.313
Masayuki Maeda and Hirokazu Tsukahara
[Abstract]
Extended Concepts of Occipital Retinotopy Pp.319
Christopher W. Tyler, Lora T. Likova, Chien-Chung Chen,
Leonid L. Kontsevich, Mark M. Schira and Alex R. Wade
[Abstract]
Neuroimaging in Obsessive-Compulsive Disorder Pp.331
Peter L. Remijnse, Odile A. van den Heuvel and Dick J.
Veltman
[Abstract]
Abstracts
[Back to top]
Electrical Impedance Scanning – A New Diagnostic
Tool in Cancer Detection: Current Status and Recent Developments
Ansgar Malich, Mirjam Facius, Dorothee Fischer and Bernhard
Scholz
Due to insufficiencies of the currently available imaging
modalities in breast cancer diagnosis the development of improved
technical systems has been a main field of activities in the
medical engineering community for years, including thermography,
laser mammography and impedance based technologies.
Up to now none of these technologies reached the break-through
into routine application due to several reasons.
Also electrical impedance scanning being free of side effects,
non invasive, cheap, and flexible to handle, is a promising
diagnostic tool especially in breast cancer detection.
This review aims to describe the physical background, clinical
application, already useful applications, limitations and
future developments.
[Back to top]
Methodological Aspects and Applications of In
Vivo Imaging of Apoptosis in Oncology: An Illustrative
Review
Marina S. Kartachova, Marcel Verheij, Cornelis A. Hoefnagel,
Berthe L. van Eck and Renato A. Valdés Olmos
In vivo monitoring of apoptosis during anticancer
therapy has attracted intense research interest as a potential
assay to predict treatment outcome.
From all apoptosis-detecting radioligands, the group of Annexin
V-based tracers is currently the most widely used for real
time imaging of apoptosis in patients with various malignant
and non-malignant diseases.
In this article, we discuss the current status of in
vivo imaging of apoptosis by means of 99mTc -Annexin
V scintigraphy: the biodistribution of the tracers will be
illustrated and the methodological aspects of gamma camera
imaging procedure will be outlined. In addition, recently
developed phosphatidylserine-targeting tracers for PET imaging
of programmed cell death will be highlighted.
We will specify the opportunities to improve visual assessment
of the scintigraphic images. A four-step grading scale and
SPECT/SPECT, SPECT/CT and SPECT/MRI fusion models will be
discussed in order to overcome technical limitations caused
by low tumour-to-background ratio. Furthermore, possible clinical
applications of this technique in oncology will be illustrated
in detail, with a major accent on the group of patients with
malignant lymphoma, lung cancer and head and neck squamous
cell cancer.
[Back to top]
Current Issues in the Utility of Blood Oxygen Level
Dependent MRI for the Assessment of Modulations in Tumor Oxygenation
Christine Baudelet and Bernard Gallez
It has been known for some time now that hypoxia is an important
physiological parameter in tumor growth and response to therapy.
The development and application of non invasive methods to
determine the extent of tumor hypoxia as well as its modulation
will improve cancer treatment strategies. Magnetic Resonance
sequences that are based on the BOLD effect use the endogenous
contrast agent deoxyhemoglobin as a source of contrast. This
technique can be used to monitor the evolution of tumor oxygenation
since there is a good correlation between the evolution of
the partial pressure of oxygen (pO2) and the NMR parameters
measured. The information provided by BOLD NMR is essentially
qualitative in nature due to the complexity of the relationship
between the pO2 and the NMR parameters measured. The factors
at the origin of this complex relationship are discussed in
this review. The advantages of the BOLD technique are non
invasiveness and high spatial and temporal resolution. The
method has been successfully applied in experimental and human
tumors to monitor changes after respiratory challenges and
pharmacological treatments. Additionally, the method has been
used to provide maps of mature and functional tumor vessels
and maps of spontaneous fluctuations of oxygenation and blood
perfusion related to tumor acute hypoxia.
[Back to top]
Issues of Quantitative Metabolic Brain Imaging with
Small Animal PET in Mice
Hiroshi Toyama
Positron emission tomography (PET) allows imaging of molecular
and physiological events in living subjects. Recent technical
advances have made it possible to use PET for small animals.
A major advantage of small animal PET studies compared to
necropsy studies is that the former allows longitudinal within-subject
design. Fully quantitative PET studies require information
on the time course of tracer delivery to the tissue. In practical
terms, one disadvantage of small animal PET imaging is the
need to control the animal’s motion during the study
in order to obtain good quantitative in-vivo dynamic imaging
results. Thus, animals must be either physically restrained
or placed under anesthesia. Anesthesia is known to have significant
effects on the central nervous, cardiovascular and respiratory
systems. Restraining devices lead to extremely high stress
levels, which can create conditions that poorly reflect normal
physiology of an animal. In this paper, we assess feasibility
and limitations of quantitative metabolic brain imaging with
small animal PET in mice based on our recent published papers
using [18F]FDG and small animal PET. Future perspectives in
quantitative metabolic brain imaging with PET in small animals
are also discussed.
[Back to top]
Can Motion Artifacts be Completely Removed from fMRI-Activation
Maps?
Elisabeth De Castro Caparelli
Most functional magnetic resonance imaging (fMRI) studies
are based on the detection of small time-dependent signal
variation induced by changes in blood oxygenation during brain
activation. However, since this signal change is very small
(typically 1–5%; even under optimal conditions and high
magnetic field strengths), head motion as small as 1 mm translation
or 1o rotation, can also produce spurious activation, if correlated
with the stimulus paradigm. Several methods have been proposed
to retrospectively (during image post-processing) or prospectively
(in real time) correct for motion, however these techniques
generally correct only for geometric rigid-body effects. Head
motion can also change the magnetic field homogeneity, altering
the effective relaxation rates of tissues (R2*), and producing
time-dependent geometrical distortions in fMRI studies. Unfortunately
these non-linear motion-related artifacts become worse at
high field strengths and cannot be corrected by standard image
realignment methods; therefore, the range of motion is restricted
for in vivo fMRI studies, especially at high field
strengths. Real-time motion monitoring during fMRI can provide
highly accurate information on whether subject motion during
an fMRI scan was acceptable or excessive, and whether repeat
scans with excessive motion are necessary.
[Back to top]
Comparison of the Image Quality on Low-dose Urinary
Tract Multidetector CT Examinations with 80 kVp and 120 kVp
(Original Research)
Ensar Yekeler, Candan Ozdemir, Sabri Yilmaz, Alim Topcu,
Hakan Genchellac, Atadan Tunaci and Gulden Acunas
Purpose: To compare the image quality on
low-dose urinary tract multidetector CT examinations with
80 kVp and 120 kVp.
Materials and Methods: Seventy-six patients
with urinary tract symptoms were evaluated for urinary tract
calculi by unenhanced multidetector CT. The examinations were
performed with a four-row detector CT scanner. In all patients,
two low-dose CT examinations with different kVp and mAs values
(120 kVp, 30 mAs and 80 kVp, 95 mAs) were performed. The other
scanning parameters were kept constant. Weighted-CT dose index
was equal in both examinations. Both CT examinations were
quantitatively compared with calculating the HU values of
kidneys, subcutaneous fat, calculus, and phleboliths and the
HU ratio of urinary calculi to the kidney. Both scans were
also qualitatively compared for image quality of upper and
lower abdomen.
Results: One hundred and two calculi were
detected in 50 of 76 patients. One or more phleboliths were
present in 20 patients. HU values of the phleboliths and urinary
calculi were higher on images obtained with 80 kVp than those
obtained with 120 kVp. HU ratio of the calculi to the kidney
was higher on scans with 80 kVp. Adipose tissue was less noisy
and had lower HU value on 80 kVp images. Image quality of
the upper abdomen and major pelvis were better on 80 kVp images,
and the majority of these patients were normal (n=28) and
overweight (n=20). Minor pelvis mostly (60%) revealed poorer
image quality on 80 kVp images. However, the majority were
overweight (n=22) or obese (n=6). In patients with osteoporosis,
image quality was relatively better when compared with similar
weighed patients without osteoporosis on 80 kVp images. Small
renal, proximal and middle ureteral calculi were better demarcated
on 80 kVp images.
Conclusion: Low-dose urinary tract multidetector
CT examination with 80 kVp, compared to 120 kVp provides better
image quality in the upper abdomen and major pelvis. In overweight
and obese patients, minor pelvis may not be evaluated thoroughly
on 80 kVp images. Detection of small renal, proximal and middle
ureteral calculi could be improved by using 80 kVp setting.
[Back to top]
Current Clinical Applications of In Vivo Magnetic
Resonance Spectro-scopy and Spectroscopic Imaging
Margaret R. Lentz, Jennifer L. Taylor, D. Ashley Feldman
and Leo L. Cheng
Magnetic resonance imaging (MRI) infused Radiology with
rejuvenating vigor in the 1980s, owing credit to a couple
of magnetic resonance spectroscopy (MRS) experiments performed
in 1973. MRI has since been embraced by the radiology and
medical communities. If the goal of MRS is to measure many
chemicals in a homogeneous magnetic field, then the function
of MRI is, in general, to measure one chemical – water
– in an artificially created inhomogeneous field.
Combining spectroscopy principles with technologies developed
over the past two decades for MRI presented the philosophical
appeal of non-invasively measuring metabolic molecules in
living tissue, and led to the explosive developments in the
last decade of in vivo MRS, and more recently MRSI,
in the settings of diagnostic radiology.
This review is intended to discuss the basic technologies
of the current trends in the field of in vivo MRS
and MRSI, especially the inherent predilections of individual
techniques to the study of certain disease states. Following
a historical introduction, individual techniques and their
clinical applications, found in publications between January
2000 and October 2004, are reviewed in connection with related
ex vivo results, after which the practical aspects
of in vivo MRS and MRSI in clinical settings are
discussed.
[Back to top]
Virtual Colonoscopy
Andrea Laghi
Virtual colonoscopy (VC), also known as CT colonography,
is a noninvasive imaging method for the examination of the
colon. The technique is easy, less labour-intensive than barium
enema and conventional colonoscopy and is inherently safer
since no adverse event or procedure-related complications
have ever been reported. The success rate of VC is approximately
100%, if bowel preparation and distension are optimal and
no sedation is required. From the patient’s perspective,
the major advantages of VC include the very brief time required
to perform the examination, the absence of contrast enemas
and the potential for same-day colonoscopy when polyps are
detected. To date several studies have reported sensitivity
and specificity comparable with conventional colonoscopy in
the detection of clinically significant polyps. However, the
smaller the polyp size, the lower the sensitivity. The currently
accepted clinical uses include the evaluation of patients
who have undergone unsuccessful or incomplete conventional
colonoscopy, patients with obstructing colorectal cancer,
and those whose medical problems make them unsuitable for
conventional colonoscopy. Current uses generally do not include
the screening of asymptomatic persons, although recently published
work has demonstrated no statistically significant differences
between VC and conventional colonoscopy regardless of polyp
size. A practical approach is to consider virtual colonoscopy
‘as a currently credible alternative screening method
and as a reasonable alternative to the other colorectal cancer
screening tests when a patient is unable or unwilling to undergo
conventional colonoscopy’.
[Back to top]
Transient Focal Lesions in the Splenium of the Corpus
Callosum with Restricted Diffusion: An Enigma
Masayuki Maeda and Hirokazu Tsukahara
Small transient lesions in the central part of the splenium
of the corpus callosum (SCC) have been reported in MR examinations,
particularly in patients with encephalitis or encephalopathy,
and in patients with or without epilepsy who are receiving
antiepileptic drugs. The MR findings are characteristic: an
ovoid T2-high signal lesion in the SCC, no enhancement after
contrast agent, restricted diffusion shown by diffusion MR
imaging, and complete disappearance on follow-up MR examinations.
Most noteworthy is that these lesions have restricted diffusion
but are reversible, which is distinct from infarction lesions
seen in energy failure. The exact mechanism of these transient
lesions remains uncertain and enigmatic. We review previously
reported patients to show these unique MR findings and describe
possible pathogenesis of particular SCC lesions.
[Back to top]
Extended Concepts of Occipital Retinotopy
Christopher W. Tyler, Lora T. Likova, Chien-Chung Chen,
Leonid L. Kontsevich, Mark M. Schira and Alex R. Wade
Retinotopic mapping is a key property of organization of
occipital cortex, predominantly on the medial surface but
increasingly being identified in lateral and ventral regions.
The retinotopic organization of early visual areas V1-3 is
well established, although anatomical landmarks can help to
resolve ambiguities in poorly-defined functional maps. New
morphing techniques are now available to define the metric
mappings quantitatively within each retinotopic area. In the
dorsal occipital regions, there is fair agreement that area
V3A should be split into separate V3A and V3B maps, and that
beyond them lies a further area, V7. We specify the eccentricity
mapping of both V3B and V7 for the first time, showing how
the latter is roughly parallel to the meridional mapping and
offering formal accounts of such paradoxical behavior. In
ventral occipital cortex, we support the analysis of Zeki
and Bartels [1] and Wade et al. [2] that V4 maps
the full hemifield, and show the existence of two more areas,
a ventromedial map of the lower quadrant, emphasizing the
upper vertical meridian, and an adjacent area with a dominant
foveal representation. In lateral cortex, the motion area
defined by a motion localizer shows pronounced retinotopy,
particularly in the eccentricity parameter. A dorsolateral
map between the motion area and V3B, which represents the
lower quadrant with an emphasis the foveal part of the lower
vertical meridian, may be a counterpart to the ventromedial
map.
[Back to top]
Neuroimaging in Obsessive-Compulsive Disorder
Peter L. Remijnse, Odile A. van den Heuvel# and Dick J.
Veltman
Neurobiological models of obsessive-compulsive disorder
(OCD) have emphasized the mediation of clinical symptoms by
aberrant frontal-striatal circuits. A recent neurobiological
model for normal human emotion perception has proposed distinct
ventral and dorsal processing systems corresponding with differential
levels of emotion perception. This construct appears also
relevant for elucidating the pathophysiology of OCD, being
an anxiety disorder.
In the present paper, we present a comprehensive review of
the neuroimaging literature in OCD, with the aim of critically
appraising the current status of imaging-based knowledge on
neurophysiological factors in the pathogenesis of OCD, along
with the methodological possibilities and limitations of each
imaging paradigm for OCD research. Moreover, we intend to
relate these experimental findings to the frontal-striatal
model and to the model of normal emotion perception.
Results of imaging studies point to the need for adjustments
in current models, with respect to the involvement of frontal-striatal
circuits in OCD, as a ventral-dorsal dissociation may be distinguished.
Moreover, data from pediatric OCD patient samples have commenced
to shed light on developmental characteristics of OCD. Furthermore,
longitudinal designs, in combination with pre-post treatment
comparisons, are of great value for assessing the state-trait
duality. Finally, the use of multimodal study designs holds
great promise for the near future.
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