A visual and semi-quantitative assessment of 99m Tc-EDDA/HYNIC-TOC scintigraphy in differentiation of solitary pulmonary nodules
2004
BACKGROUND: The aim of the study was the assessment of the clinical usefulness
of scintigraphy with 99m Tc-EDDA/HYNIC-TOC for purposes of a differential diagnosis
of SPNs by means of a visual inspection and semi-quantitative assessment of uptake
intensity of the radiopharmaceutical (RPh). MATERIAL AND METHODS: In 53 patients (32 males and 21 females at the ages
between 38 and 78 years, mean value 57) with SPN on chest radiographs or CT scans,
of diameters from 1 to 5.5 (mean 2.3) cm a SPECT acquisition was performed, 2–4
h after administration of 740 MBq of RPh. Additionally, aiming at the implementation
of a correction of a partial volume effect resulting from finite resolution of
this technique, the measurement of the resolution of this technique was performed
on an thorax phantom. Scintigraphic studies were inspected visually visually and
semi-quantitatively, restoring real concentration of the RPh in nodules in comparison
with the peritumoral background (tumour-to-backgroud ratio) by the application
of resolution recovery coefficients for the respective nodule diameters. The threshold
values of tumour-to-background ratio providing optimal differentiation between
malignant and benign nodules of sizes smaller and larger than 2 cm in diameter
were determined. Verification of scintigraphic results was based on pathological
examinations of tumour samples (histopathology or cytology) and in some cases
on bacteriological studies. The additional criterion of tumour benignity was accepted,
based on its stable size in a time interval no shorter than 3 years. RESULTS: In 32 patients the following malignant tumours were diagnosed:
12 adenocarcinomas, 6 squamous cell carcinomas, 6 non-small cell lung cancers
of unspecified more detailed morphology, 2 large cell carcinomas, 2 small cell
lung cancers, 2 carcinoids and 2 metastatic lesions (malignant melanoma and leiomyosarcoma).
In 21 patients benign etiologies were found: 6 tuberculomas, 2 other granuloma,
4 hamartomas, 2 non-specific inflammatory infiltrate, 1 alien body with inflammatory
reaction and 1 suppurating inflammatory lesion, 1 abscesses, 1 peripheral carcinoid
of morphological features of a benign tumour, 2 tumours of unspecified etiology
with sizes stable over 3 and 5 years, and 1 ectopic lesion of thyroid tissue.
A visual inspection of scintigrams revealed enhanced uptake of RPh at 29 of 32
sites corresponding to locations of malignant nodules, in 2 cases (1 adenocarcinoma
and 1 metastatic lesion of malignant melanoma) results were negative and in 1
(metastatic leiomyosarcoma) equivocal; in 13 of 21 benign nodules true negative
results were obtained, in 4 — positive (foreign body with inflammatory reaction,
abscess, suppurating inflammatory lesion and tuberculoma), in the next 4 — equivocal
(2 tuberculomas, 1 hamartoma, 1 tumour of unspecified aetiology, but with a stable
size over 3 years). The mean values of tumour-to-back-ground ratio without resolution
recovery in malignant and benign nodules equalled 4.6 (sd 5.9) and 1.8 (sd 1.2),
resp. (p = 7 × 10 -4 ), while after resolution recovery coefficients — 7.8 (sd 7.2)
and 2.7 (sd 2.8), resp. (p = 2 × 10 -4 ). The semi-quantitative method resulted
in true positive results in 29/32 malignant cases and true negative in 15/21 benign
cases. CONCLUSIONS: 99m Tc-EDDA/HYNIC-TOC scintigraphy is a very promising method
for the differentiation of SPNs. The semi-quantitative method using resolution
recovered tumour-to-background ratio enables the differentiation of malignant
and benign SPNs based on the intensity of RPh uptake and facilitates the making
of a decision as to the positive or negative scintigraphic character of the equivocal
lesions.
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