21
Imaging Techniques
possible. Prior to biopsy localization scans are obtained and the
patient positioned to permit the most direct access to the lesion.
Biopsy of lesions within the chest should be performed using
strict sterile technique. Local anesthesia of superficial and deep
tissues should also be utilized to minimize patient discomfort
and encourage maximal patient cooperation. For biopsy a vari-
ety of needles ranging from 18 to 25 gauge may be used. Many
interventionalists prefer a coaxial technique employing an 18-
or 19-gauge stabilizing needle through which a smaller needle
is introduced for tissue sampling. Complications of lung biopsy
include pneumothorax with 5-10% requiring chest tube place-
ment.1,11,12 For this reason, appropriate equipment for treatment
of pneumothorax should be immediately available for patients
undergoing thoracic procedures.
Mediastinum
The most frequent cancer involving the mediastinum is non-
small cell lung cancer, and FNAB of mediastinal lymph nodes
is of great importance in staging and treatment planning. CT
guidance is useful for biopsy of enlarged mediastinal nodes.
Conventional US is less useful; however, the use of endoscopes
equipped with small high-resolution ultrasound transducers
permits US guidance for biopsy of mediastinal masses13,14 and
may permit sampling of smaller nodes than is possible with CT
guidance. Endoscopic US-guided biopsy has a reported sensitiv-
ity of 92% and specificity of 100%.13
Abdominal and Pelvic organs
Both CT (Figs. 21.1B,C) and US (Figs. 21.2B,C) are effective in
providing guidance for focal lesions in the liver, kidney, adrenal,
pancreas, spleen, retroperitoneum, and pelvic masses and nodes
with sensitivity of 85 to 90% and specificity of near 100%. The
selection of the method to be used in a specific patient will be
determined by lesion visibility and location, assuming that expe-
rienced operators are available for each technique. Small lesions
lying near the dome of the liver may be difficult to approach
with US and are usually biopsied with CT guidance. Since US
guidance requires a path not impeded by interposed gas, lesions
that cannot be approached because of interposed lung or bowel
require CT guidance. CT and/or CT fluoroscopic guidance may
be desirable to better demonstrate anatomy in patients with
lesions difficult to access or in unusual or precarious locations,
when the optimal biopsy approach lies near vital structures, and
in patients with unusual anatomy.
FNAB of deep abdominal and pelvic masses is most com-
monly performed with 9- to 20-cm-long, 18- to 25-gauge spinal
or Chiba needles. A comparison of large (20 gauge or larger)
and small (21 gauge or smaller) needles for abdominal and pel-
vic FNAB has shown no significant difference in diagnostic rates
or accuracy.15 FNAB of deep retroperitoneal masses may require
an approach that traverses the stomach or intestine. With fine
needles (20-25 gauge) this is not usually a problem, with sev-
eral reports indicating minimal risk of bleeding or peritoni-
tis.16-19 When US guidance is used, transducer pressure is usually
successful in displacing overlying bowel loops from the area
of interest. With CT, posterior approaches to deep retroperi-
toneal masses are also an option to avoid the bowel. FNAB is
also an effective means for diagnosis of masses arising from the
stomach and bowel, with infrequent complications.20,21 Endo-
scopic US may also be used to provide guidance for FNAB of
abdominal masses in the region of the pancreas, duodenum,
and porta hepatis.22,23
Liver
Liver FNAB is most often performed with US or CT guidance.
Large series indicate the sensitivity of FNAB in the evaluation of
masses to range from 88 to 93% with specificity of 100%.24,25 A
complication rate of 1.9% was reported in a series of 322 liver
biopsies with a 1.2% incidence of severe hemorrhage.24 The
majority of deaths following abdominal FNAB are related to
hemorrhage following liver biopsy.26
Pancreas
FNAB of the pancreas may be performed with US or CT guid-
ance by percutaneous approaches or using endoscopic ultra-
sound.27 Reported serious complications of pancreatic FNAB
include pancreatitis, hemorrhage tumor seeding of the needle
track, and sepsis.26-28 In the series reported by Smith, the second
major cause of death following FNAB was due to pancreatitis
following pancreatic biopsy. Tumor seeding along the needle
tract was reported in 0.003-0.009% of biopsies and was most
likely following biopsy of pancreatic carcinoma.26
Kidney
Renal mass biopsy may be performed with either CT or US guid-
ance, although core biopsy is generally preferred over FNAB.
In comparing renal mass FNAB and core biopsy, Johnson et al.
obtained adequate samples in 73% of fine-needle aspirates.29 In
28% only the core biopsy provided a definitive diagnosis. When
renal lymphoma is suspected, core biopsy is generally preferred,
although flow cytometry analysis adds additional diagnostic
information to cytological examination of fine-needle aspira-
tion samples.30
Concluding Remarks
Successful diagnosis utilizing image-guided fine-needle aspira-
tion biopsy is best accomplished by combining the skills of the
cytopathologist and the imaging specialist. Patients receiving
care from a dedicated and interested team combining imaging,
interventional, and cytology skills are likely to have their diag-
noses made with minimal discomfort and inconvenience, as
well as maximal safety and efficacy. Imaging and interventional
expertise is essential in the selection of the most appropriate
imaging method, in determining the safest approach, and in
obtaining quality tissue samples from the target lesion. Like-
wise, expertise in the preparation and evaluation of the aspirated
material is essential in determining the adequacy of samples
and, through close interaction with person performing the
biopsy, in correlating the clinical, imaging, and biopsy findings.
With modern imaging technology permitting the identification
and localization of abnormalities throughout the body, the use
of image-guided FNAB, combined with modern cytopathologic
techniques, allows most patients to be spared more invasive and
potentially hazardous methods for establishing diagnosis.
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