Evaluation of Scintigraphic Image Quality in Thyroid Nodules

Abstract

Aim: The main goal of this study was to analyze the imaging parameters that impact image quality of nodular thyroid scintigraphy for more accurate diagnosis in nuclear medicine. Method: This work consists of two components: phantom and patients’ study. A properly designed phantom was used to mimic human’s thyroid gland. The phantom was scanned using small field of view (SFOV) gamma camera (Mediso Nucline TH-22 model) at 1 cm and 10 cm distance from the collimator. Contrast (C) and contrast-to-noise ratio (CNR) were evaluated based on ROI counts analysis. Additionally, the above mentioned C and CNR were investigated on actual thyroid images acquired up to 200.000 counts. Results: It was demonstrated that both C and CNR were higher when the distance between the detector and collimator was 1 cm. This image was also considered the optimum according to evaluation made by two experienced nuclear medicine physicians. Conclusion: The phantom and patients scintigraphy performed on gamma camera showed superior contrast and CNR with closed distances to the detector. Besides, acquisition up to 200.000 counts seems to be feasible for thyroid scintigraphy in nuclear medicine

Keywords

• Thyroid phantom,contrast (C),contrast-to-noise ratio (CNR),lesion detectability,thyroid scintigraphy

Tiroid Nodüllerinde Sintigrafik Görüntü Kalitesinin Değerlendirilmesi

Abstract

Amaç: Bu çalışmada, tiroid nodüllerinde tanısal doğruluğu yüksek sintigrafik görüntü kalitesinin elde edilebilmesi için uygun çekim parametrelerinin belirlenmesi amaçlanmıştır. Yöntem: Çalışma iki aşamada gerçekleştirildi: Fantom ve hasta çalışması. Fantom çalışmasında, insan tiroidini temsil eden bir fantom Mediso Marka Nucline TH-22 model küçük görüş alanlı (SFOV) gama kamerada 99mTc kullanılarak 1 cm ve 10 cm mesafelerde görüntülendi. Fantomdaki lezyonlardan ve zeminden ilgi alanları (ROI) çizilerek kontrast (C) ve kontrast-gürültü oranı (CNR) hesaplandı. 200.000 toplam sayım değerinde çekilmiş hasta tiroid sintigrafilerinden C ve CNR parametreleri hesaplandı. Bulgular: Fantom-kolimatör mesafesi 1 cm olan sintigrafik görüntülerde, toplam sayım miktarı 200.000 olana kadar görüntülerde C ve CNR değerleri arttı. Görüntüler 2 ayrı nükleer tıp uzmanı tarafından değerlendirildi. 1 cm mesafede 200.000 sayımlı görüntü en iyi olarak yorumlandı. Kantitatif değerlendirmede ise 1 cm mesafede 200.000 sayımlı görüntünün en yüksek C ve CNR değerlerini verdiği belirlendi. Sonuç: Gama kamerada çekilen tiroid sintigrafilerinde hem fantom hem de hasta çalışmasında hastanın kolimatöre 1 cm mesafede tutulması ve çekimin 200.000 sayımda sonlandırılmasının en iyi sintigrafi kalitesi sağladığı sonucuna varıldı.

Keywords

• Tiroid fantomu, kontrast (C), kontrast-gürültü oranı (CNR), lezyon saptanabilirliği, tiroid sintigrafisi

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