PART TWO
Diagnostic Cytology
Table 21.1
Advantages of Image Guidance
Allows biopsy of lesions not visible or palpable
provides safe approach for biopsy of deep lesions
Reduces chance of injury to adjacent or overlying structures
permits confirmation and documentation of sampling location
AIIows selection of the sampling site within a lesion to avoid areas of
necrosis, etc.
permits rapid identification of complications.
AIIows conversion to core biopsy if necessary
or lying deep within the chest, mediastinum, abdomen, or pelvis
are accessible for image-guided fine-needle or core biopsy. Image
guidance permits planning and implementation of a biopsy
approach that minimizes injury to adjacent organs or vessels,
allowing for safe and effective sampling of these sites. Image guid-
ance also permits sampling of specific sites within a lesion, target-
ing areas most likely to contain viable tissue and avoiding areas
of suspected necrosis, thus improving the reliability of cytological
analysis. Imaging allows confirmation and permanent documen-
tation of sampling sites. If FNAB is not adequate for diagnosis,
conversion to core biopsy is possible in most instances. Finally,
image guidance permits rapid identification and management of
complications such as bleeding or pneumothorax, if they arise.
Imaging Methods
The ideal imaging method for biopsy guidance should provide
sufficient spatial and contrast resolution to permit the precise
identification and localization of small masses embedded in
normal organs such as the liver. High temporal resolution is
required to permit real-time or near real-time observation of nee-
dle placement. There should be little or no exposure to ioniza-
tion radiation and the method should be relatively inexpensive.
For use at the bedside or in the operating room, portability is
also desirable. Although no single imaging method provides all
of these attributes, several methods that provide many or most
of these advantages when used appropriately are currently avail-
able. With the increasingly large number of options for perform-
ing image-guided biopsy, no single method stands out as better
than the others. Selection of the most appropriate approach for
a given patient is influenced by many factors, the most impor-
tance of which is the skill and experience of the individual per-
forming the biopsy with the localization method selected.
Modern diagnostic imaging uses a variety of techniques, each
with unique advantages and disadvantages in providing guid-
ance for tissue sampling. In general, imaging methods may be
divided into those which provide only 2-dimensional planar
information, such as conventional radiography and fluoros-
copy, and those providing 3-dimensional cross-sectional imag-
ing capability, namely US, CT, and MRI. The advantages and
disadvantages of imaging methods commonly used for FNAB
guidance are shown in Table 21.2.
conventional Radiography and Fluoroscopy
Radiography and fluoroscopy utilize X-rays to create a 2-
dimensional image by the recording of X-ray energy that passes
through the patient onto film or a digital receptor. The image
Table 21.2
Imaging Methods
Imaging method
Advantages
Disadvantages
Fluoroscopy
Real-time
Low tissue contrast
Best for high-contrast
2-dimension
lesions in bone or
summation
lungs
image
Inexpensive
May result in
significant radiation
exposure
Computed
precise guidance and
Expensive
tomography
documentation of
Angled approaches
sample site.
are difficult
Less operator-
May require the use of
dependent than
intravenous contrast
ultrasound.
agents to display
Cross-sectional
lesions
imaging provides
May result in
3-dimensional spatial
significant radiation
localization of lesion.
exposure
Magnetic resonance
Excellent contrast
Requires special
No ionizing radiation
equipment compat-
Cross-sectional
ible with magnetic
imaging provides
3-dimensional spatial
localization of lesion.
environment.
Ultrasound
provides real-time
Limited by overlying
imaging
gas or bone
portable
relatively inexpensive
Rapid
endoscopic, transvagi-
nal, and transrectal
approaches possible
Doppler permits
imaging of vascular
structures
No ionizing radiation
Cross-sectional
imaging provides
3-dimensional spatial
localization of lesion.
Well suited for angled
approaches
User-dependent
produced is a summation of the superimposed shadows of all
structures in the image field, and needle localization in three
dimensions is possible only by repositioning the fluoroscope
or the patient, or by the use of complex biplane fluoroscopic
equipment. Compared to US, CT, and MRI, tissue contrast
is poor. Fluoroscopy is best suited for lesions that exhibit
high contrast from their surroundings, such as lung or bone
masses.
Like ultrasound, fluoroscopy provides a dynamic real-time
image of the needle and the lesion during manipulation. With
fluoroscopy, lengthy or complex procedures may result in
significant radiation exposure to the patient. If fluoroscopy is
used for FNAB guidance, the equipment used should offer a
high-resolution imaging chain with adequate shielding and col-
limation. Ability to perform complex angle (e.g. anteroposterior,
lateral, or oblique) fluoroscopy views is often necessary to
ensure proper needle placement. Overhead fluoroscopic tube
600
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