Usefulness of circumference difference for estimating the likelihood of malignancy in small solitary pulmonary nodules on CT.
OBJECTIVE
The presence of a small solitary pulmonary nodule (SSPN) is a common finding on chest computed tomography (CT); however, preoperative diagnosis of SSPN is often difficult. We measured the extent of ground-glass opacity (GGO) and our own original method of circumference difference (CD) as an additional approach in classifying SSPN revealed on CT, and evaluated the likelihood of malignancy.


METHODS
In total, 214 single SSPN with diameter <15mm were studied. All SSPN were histologically examined with surgical resection; preoperative CT findings and pathological diagnosis were evaluated retrospectively. The extent of the ratio of GGO and CD was evaluated using NIH image, where CD is defined as the ratio of the nodule margin distance to the circumference of the predicted circle with an area equal to that of the nodule.


RESULTS
The thresholds for differentiating SSPN are 70% of GGO and 68% of the CD ratio. Differentiation of malignancy from benign tumor using our algorithm had sensitivity of 96.6%, specificity of 86.1%, and positive predictive value of 94.1%.


CONCLUSIONS
Combined with other malignant likelihood parameters such as extent of GGO, CD ratio is a useful additional factor for estimating the likelihood of malignancy of SSPN on CT.
Department of Surgery, Akita University School of Medicine, 1-1-1 Hondo, Akita City 010-8543, Japan. hsaito@doc.med.akita-u.ac.jp
Hajime
H
Saito
Yoshihiro
Y
Minamiya
Hideki
H
Kawai
Taku
T
Nakagawa
Manabu
M
Ito
Yukiko
Y
Hosono
Satoru
S
Motoyama
Manabu
M
Hashimoto
Koichi
K
Ishiyama
Jun-Ichi
J
Ogawa
D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D003074:Solitary Pulmonary Nodule / Q000473:pathology*; D015996:Survival Rate; D014057:Tomography, X-Ray Computed / Q000379:methods*