Radiofrequency Ablation in a Porcine Lung Model: Correlation Between CT and Histopathologic Findings
Akira Yamamoto1,
Kenji Nakamura1,
Toshiyuki Matsuoka1,
Masami Toyoshima1,
Tomohisa Okuma1,
Yoshimasa Oyama1,
Yoshihiro Ikura2,
Makiko Ueda2 and
Yuichi Inoue1
1 Department of Radiology, Osaka City University Graduate School of Medicine,
1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
2 Department of Pathology, Osaka City University Graduate School of Medicine,
Abeno-ku, Osaka 545-8585, Japan.
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Fig. 1A —Group A: swine sacrificed immediately after radiofrequency
ablation. CT image shows ablated lesion immediately after radiofrequency
ablation. Area with ground-glass attenuation is observed.
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Fig. 1B —Group A: swine sacrificed immediately after radiofrequency
ablation. Photograph shows ablated lesion after fixation. Ablated lesion has
two-layered structure presenting as ring shape and is surrounded by brown
strips (arrows) situated at outer layer. Boundary between ablated and
nonablated areas is not clear.
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Fig. 1C —Group A: swine sacrificed immediately after radiofrequency
ablation. Low-power photomicrograph of H and E-stained section, fixed by
Heitzman's method, of tissue presented in B shows outermost layer
(arrows).
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Fig. 1D —Group A: swine sacrificed immediately after radiofrequency
ablation. Photomicrograph shows H and E section of tissue presented in
B. Histopathologically, normal lung (N), congestion in outermost layer
(C), and effusion in pulmonary alveoli lumens in intermediate layer (E) are
observed. (H and E, x40)
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Fig. 1E —Group A: swine sacrificed immediately after radiofrequency
ablation. Photograph of H and E-stained frozen section of ablated lesion shows
outermost layer (C, arrows), intermediate layer (E),
and normal lung parenchyma (NL). (H and E, x20)
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Fig. 1F —Group A: swine sacrificed immediately after radiofrequency
ablation. Photograph of nicotinamide adenine dinucleotide (NADH)
diaphorase-stained section of tissue presented in E shows outermost
layer observed on H and E-stained frozen section is found on border of NADH
diaphorase-stained lesions. In its internal regions (E),
not-NADH-stained lesion conforms to ablated lesion, which is same as
coagulation necrosis. However, outermost layer contains admixture of stained
and not-stained cells (arrows). (NADH diaphorase, x20)
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Fig. 2A —Group C: swine sacrificed 10 days after radiofrequency
ablation. CT image shows lesion as ring-shaped structure
(arrows).
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Fig. 2B —Group C: swine sacrificed 10 days after radiofrequency
ablation. On low-power photomicrograph of H and E-stained section, two layers
are observed. Outer layer is seen (arrows).
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Fig. 2C —Group C: swine sacrificed 10 days after radiofrequency
ablation. Photomicrograph of H and E-stained section of tissue shows two
layers. Normal lung (L), strong infiltration of inflammatory cells, and
increased granulation tissues rich in collagen fibers (F) are recognized. In
layer (N), lesion contains completely coagulated tissue with no viable cells.
(H and E, x40)
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Fig. 3A —Group D: swine sacrificed 4 weeks after radiofrequency
ablation. Photograph shows slice of tissue after fixation. Pale lesion is
considered to be obstructive pneumonitis only in periphery of ablated areas
(arrows). Decreased size of inner layer area results in decrease of
overall size as compared with group C.
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Fig. 3B —Group D: swine sacrificed 4 weeks after radiofrequency
ablation. CT image shows slice of ablated lesion tissue presented in A
with obstructive pneumonitis. Ablated lesion observed on CT is larger than
ablated lesion seen at macroscopic examination. Pale lesion only in periphery
of ablated areas plus ablated lesion on macroscopic examination is observed as
wedge-shaped high-density masslike lesion (arrows).
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Fig. 3C —Group D: swine sacrificed 4 weeks after radiofrequency
ablation. Photomicrograph of H and E-stained section of tissue presented in
A shows that polyplike formation of granulation tissues
(arrows), which originated from organization of necrotic layers, is
found in bronchus in ablated lesion. (H and E, x100)
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Fig. 4 —Graph shows that diameters of high-density area observed on
CT and those of ablated lesion observed in macroscopic examination (Macro) are
correlated significantly (p < 0.05) in groups A, B, and C.
r = correlation coefficient.
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Fig. 5A —Group C: swine sacrificed 10 days after radiofrequency
ablation. CT image shows cavity is similar to pulmonary abscesses.
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Fig. 5B —Group C: swine sacrificed 10 days after radiofrequency
ablation. Low-power photomicrograph of H and E-stained section of tissue in
A shows border of this cavity is covered with granulation tissues in
outer layer, which are found in groups C and D
(Fig. 2B), and inner layer are
necrotic tissues or not found.
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Fig. 6A —Schematic representations of ablated lesion immediately after
radiofrequency ablation. Ablated lesion is observed as area with ground-glass
attenuation. Maximum diameter on CT is measured.
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Fig. 6B —Schematic representations of ablated lesion immediately after
radiofrequency ablation. Histopathologically, ablated lesion presents
three-layered structure, outermost layer (hemorrhagic rim) mainly consists of
congestion (C); intermediate layer mainly consists of effusion in pulmonary
alveoli lumens (E); and innermost portion mainly consists of cytoplasm, which
shows acidophilic change and nuclei that have condensed chromatin (N). Maximum
diameter on macroscopic (macro) examination is measured. Completely necrotic
lesion is intermediate layer and innermost portion (E + N). Maximum diameter
on macroscopic examination is inner necrotic lesion plus outermost layer
(hemorrhagic rim). Maximum diameter on CT and on macroscopic examination is
significantly correlated. Therefore, area with ground-glass attenuation on CT
leads to overestimation of necrotic lesion.
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Copyright © 2005 by the American Roentgen Ray Society.
