Advanced imaging modalities of the liver

 The role of diagnostic imaging in the

assessment of liver disease continues to
gain an importance. The classic
techniques used for liver imaging are
ultrasonography, CT and MRI.
 New imaging modalities were developed
to accurately characterized the hepatic
lesions which is important in treatment
plan and follow up process.

Contrast-enhanced Ultrasound
(CEUS)

 Microbubble contrast enhanced ultrasound (CEUS) is
becoming an established technique with proven

accuracy. CEUS has the advantage that it avoids the use
of ionizing radiation, may be performed during the same
patient visit as the B-mode scan and negates the need
for more invasive investigations, such as formal
angiography or biopsy. Advantages of CEUS are
particularly relevant in cases where repeat follow-up
imaging is required, for example, post-radiofrequency
ablation, and there is a desire to reduce the patients’
exposure to ionizing radiation. The usual way of
administration is an intravenous bolus injection.

Focal fatty sparing. (a) An area of low reflectivity (arrow) close to the lower
aspect of the right lobe of the liver, close to the gall-bladder fossa; a common
site for an area of focal fatty sparing. (b) Following the administration of
microbubble contrast, imaging in the portal-venous phase (at 100 s), there is
uniform enhancement of the area under investigation (arrow) indicating that this
is ‘normal’ liver tissue.

Haemangioma. (a) A large mixed
reflective lesion in the right lobe of
the liver.
(b) Following the administration of
microbubble contrast, imaging in
the arterial phase (at 20 s), there is
peripheral nodular enhancement
(arrows)
with
absence
of
enhancement in the centre of the
lesion.
(c) Imaging in the portal-venous
phase (at 40 s), demonstrates
gradual ‘in-filling’ of the lesion.

Liver abscess. (a) A large
‘solid’ predominantly low
reflective lesion (arrows)
occupies most of the right
liver lobe, displacing the
portal vein.
(b) Imaging in the portalvenous phase (at 40 s),
demonstrates
multiple
septum of a large abscess

Figure 6. (a) Focal nodular hyperplasia. An
iso-reflective lesion (long arrow) in the right
lobe of the liver with the suggestion of a
‘central scar’ (short arrow). (b) Following the
administration of microbubble contrast,
imaging in the arterial phase (at 15 s),
demonstrates radial branches from the
‘central scar’. (c) Imaging in the portalvenous phase (at 45 s), clearly demonstrates
the ‘central scar’ (arrow) with the lesion
showing avid enhancement.

Hepatocellular carcinoma. (a) Two low
reflective lesions (arrows) in the left lobe of
the liver in a patient with hepatitis C.
(b) Imaging in the arterial phase (16 s), both
the
lesions
demonstrate
marked
enhancement (arrows) relative to the
surrounding liver.
(c) Imaging in the portal-venous phase (92 s),
the central aspects of the lesions are
demonstrating enhancement ‘washout’.

Multi-modality imaging (MMI)
(Hybrid Imaging Modalities)
 - A new standard of clinical care
 - Diagnosis and staging
 - Treatment planning
 - Response assessment

- Structural / morphological imaging
 • CT
 • MR
-Functional / molecular imaging
 • PET
 • SPECT

PET/CT and SPECT/CT
 Comparing the functional images of Nuclear

Medicine with the more anatomical modalities like
CT has been done in the past with side-by-side
comparison techniques or by the use of software
based fusion, overlaying the two sets of data
information.

Why Hybrid?
 Hybrid PET/CT, and

SPECT/CT can combine the
functional imaging capabilities of PET and SPECT
with the precise anatomical overlay of CT images, all
performed in the one imaging session. The CT
provides accurate anatomical localization of the
functional information obtained from positron
emission tomography (PET) and single photon
emission computed tomography (SPECT) scan.

Justification of Dual Modality PET/CT
• PET and CT images taken at different time on separate
scanners can only be easily co-registered through rotation and
translation with rigid structures, such as the brain or bones.
• It is very difficult, if at all possible, to perfectly co-register
soft, deformable or moving tissues, such as in the thorax and
abdomen.
• Acquisition of anatomic and functional images without having
to move the patient from one scanner to another:
 avoids patient repositioning and the inevitable anatomic
variations resulting from motion of internal structures
 provides automatically aligned images
 avoids need for complex mathematical co-registration
techniques to fuse images
 enables exact localization of lesions and improved
quantification.

 The obstacle to a wider dissemination of

PET/CT and PET/MRI is the difficulty and cost
of
producing
and
transporting
the radiopharmaceuticals used for PET
imaging, which are usually extremely shortlived (for instance, the half life of
radioactive
fluorine18
used
to
trace
glucose
metabolism
(using
fluorodeoxyglucose, FDG) is two hours only.
Its
production
requires
a
very
expensive cyclotron as well as a production
line for the radiopharmaceuticals.

SPECT/CT
16 slice CT machine with double detector Gamma Camera

Nuclear medicine fusion study. (A) Contrast-enhanced CT scan shows
barely visible low attenuation lesions in the right lobe of the liver
(arrows).
(B) Hybrid fusion image from combined SPECT / CT scan shows two large
lesions in the liver (arrows) that are not readily apparent on the contrastenhanced CT.

Differential uptake of FDG. Axial fused FDG PET–CT images of patient with colon
cancer shows metastases to the liver. The metastases demonstrate differential
FDG uptake in proportion to their metabolic activity. The necrotic centers of the
metastases (straight solid arrow) show negligible uptake compared with their
hypermetabolic peripheries (open arrows). Arrowheads represent physiologic FDG
activity in the left kidney, wavy arrow is simple hepatic cyst without metabolic
activity.

metastatic colorectal adenocarcinoma after multiple liver radiofrequency ablation
procedures with recurrent/residual tumor delineated by PET/CT.
A, Scan from unenhanced CT portion of examination shows multiple large and
small, low- and mixed-density lesions throughout liver likely representing
combination of ablation defects and recurrent/residual tumor.
B, Fused PET/CT image from same examination shows three foci of increased 18FFDG uptake, clearly distinguishing tumor from ablation change and providing
precise localization for radiofrequency ablation planning.

PET/MRI
 Integrate the PET detectors into the MRI scanner

which would allow simultaneous data
acquisition, resulting in combined functional and
morphological images with an excellent soft
tissue contrast, very good spatial resolution of
the anatomy and very accurate temporal and
spatial
image
fusion.
Additionally,
since
MRI
provides
also
functional
information, PET/MRI could even provide multifunctional information of physiological processes
in vivo.

A separate MRI and PET scanners
The patient turns 180° on a floor-based turntable to enter
separate MRI and PET scanners

Hybrid PET/MRI scanner
The PET detector and MR coils are built into the gantry of the new Siemens
PET/MRI, allowing simultaneous acquisition of PET and MR data.

PET/MRI of patient has a hepatic tumor
with left lung metastasis

Angiogenesis imaging of
liver tumors
 Hepatic CT perfusion

Measures of permeability, blood flow, blood
volume, and MTT can now be routinely
acquired for tumors as part of clinical practice
as well as for chronic liver disease. The
development of modern, 128-slice CT
hardware with accompanying software
advances has allowed both whole organ and
tumor perfusion analysis.

Hepatic CT Perfusion
Normal liver perfusion
image. A: Selection of
ROI at aorta, portal
vein and liver; B: Timedensity curve (TDC) for
ROI (up left: aorta; up
right: portal vein;
down left: liver); C:
Pseudo-color image of
HBF.

CT perfusion functional maps of blood
flow (BF), blood volume (BV), and
mean transit Time (MTT) in a patient
with hepatocellular carcinoma in the
right lobe of the liver. Preferential
arterial supply to the tumor results in
higher BF, BV, and a lower MTT value.

Elastography: Imaging of
Tommorow
 Elastography is a method of imaging that

produces a type of image, called an
elastogram.
It
is
a
promising
diagnostic, noninvasive technique used to
evaluate the stiffness of soft tissues. It is done
in correlation with a conventional sonogram
or MRI.

Transient Elastography
(Fibroscan)
Transient elastography, commercially
known as FibroScan®, uses a modified
ultrasound probe to measure the velocity
of a shear wave created by a vibratory
source. It uses mechanical waves that are
sent through the liver. The speed of
these waves through tissue provides
data about the condition and stiffness of
the liver and thus can indicate a liver
fibrosis. The velocity of the wave
correlates with tissue stiffness: the
wave travels faster through denser,
fibrotic tissue

Fibroscan score
A staging system for evaluating fibrosis in nonalcoholic
liver disease categorized into five stages: no fibrosis (F0),
perisinusoidal fibrosis (F1), perisinusoidal fibrosis plus
periportal fibrosis (F2), bridging fibrosis (F3), and cirrhosis
(F4).
By TE
 At a cut off point of ≥7 KPs, significant hepatic ﬁbrosis
could be predicted.
At a cut off point of ≥ 16.5 kPa, hepatic cirrhosis could be
predicted.

MR Elastography (MRE)
 Magnetic resonance elastography appears

more
promising
than
ultrasound
elastography. It uses a vibration device to
induce a shear wave in the liver. The wave
is detected by a modified magnetic
resonance imaging machine, and a colorcoded image is generated that depicts the
wave velocity, and hence stiffness,
throughout the organ.

MRE Score for liver
stiffness

Malignant liver tumors had significantly greater mean shear
stiffness than benign tumors with cut off value of 5 Kpa
(kilopascals) . in the absence of focal mass, fibrotic and cirrhotic
liver has a high shear stiffness more than 5 Kpa

Top row: Conventional
MR images of two
different
patients.
Middle
row:
Elastographic
wave
image. Bottom row:
Wave
images
are
processed to generate
quantitative
images
showing stiffness of
tissue
(elastograms).
Patient on right has
markedly elevated liver
stiffness, averaging 7 kPa
(normal value 2 kPa seen
in patient on left),
indicating presence of
moderate liver fibrosis.

MR elastography of
HCV-related fibrosis.
MR
elastographic
wave images (left) and
color-coded
elastograms
(right), obtained at 3 T
in three patients with
chronic
HCV
infection,
show
biopsy-proved stage
F1 (a), F2 (b), and F4
(c) .

Patient with hepatic adenoma.
A, T2-weighted MR image (A) shows hyperintense 8-cm adenoma (arrow) in right lobe of liver.
B, Gadolinium-enhanced MR image shows intense arterial phase enhancement (arrow).
C, Axial MR elastographic wave image shows good illumination of tumor (circle). Waves in tumor
have slightly longer wavelength than those in surrounding normal liver parenchyma.
D, Elastogram with region of interest corresponding to tumor shows shear stiffness value of
tumor is 3.1 kPa and of surrounding liver is 2.4 kPa.

Patient with liver cirrhosis and biopsy-proven hepatocellular carcinoma.
A and B, Dynamic gadolinium-enhanced T1-weighted MR images show
enhanced tumor (arrow) in right lobe of liver during arterial phase (A) with
washout during portal venous phase (B). C, MR elastographic wave image
shows shear waves with long wavelength (arrow) within tumor. Waves in
surrounding liver also have longer wavelength than normal. D, Elastogram
shows mean stiffness of tumor (arrow) is about 8 kPa.

Patient with metastatic colon cancer
A, T2-weighted image shows single hyperintense lesion (arrow) in periphery of
right lobe of liver. B, Wave image shows prolongation of shear wave through
tumor (arrow) compared with surrounding normal liver parenchyma.
C, Elastogram shows tumor (arrow) as hot spot with stiffness value of 6.2
kPa, suggestive of malignant tumor. Finding was confirmed at surgery to be
metastasis from colon cancer.

Conclusion:
 Contrast-enhanced

ultrasound
CEUS
continues to grow in importance as a tool
that may be used for the detection and
characterization of focal liver lesions. As a
general rule, benign lesions are characterized
by the persistence of contrast enhancement
during the late phase and a malignant lesion
is characterized by loss of contrast
enhancement in the late phase.

Conclusion:
Indication to perform a HYBRID MMI
(PET-SPECT/CT and PET/MRI)
• High suspicion for active disease, or known
structural pathology, as hybrid MMI may
localize multiple sites and define extent of
disease
• Planning treatment (medical, surgical, or
radiation therapy)
• Monitoring response to treatment.
• Absence of overt structural pathology in the
presence of high clinical suspicion.

Conclusion:
Fibroscan is a reliable screening tool for liver
fibrosis or cirrhosis in high risk groups and it
may be used in assessment of treatment
response in liver fibrosis.
fibroscan may replace invasive liver biopsies .
MR elastography is a promising noninvasive
technique for assessing hepatic fibrosis and
cirrhosis as well as solid liver tumors.

Advanced imaging modalities of the liver

Advanced imaging modalities of the liver

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