Estimation of thyroid mass in Gravesʼ disease by a scintigraphic method

Abstract

scintigraphic method for the estimation of the thyroid mass in patients with Graves' disease is described. The method was first standardized using thyroid phantoms with eight different volumes ranging from 5 to 110 cm(3). The planar and single photon emission computed tomography (SPECT) images of each phantom were acquired with four different activities [3.7 MBq (100 microCi), 11.1 MBq (300 microCi), 22.2 MBq (600 microCi) and 37 MBq (1.0 mCi) of 99mTc-pertechnetate] with a 20% window symmetrically placed over the photopeak of 99mTc. The thyroid lobes were enclosed with the help of regions of interest (ROI) tools and a threshold was selected to identify the thyroid boundaries. The same threshold was used in all slices of an image. In the phantom study, a 20% threshold for planar images and a 30% threshold for SPECT were found to be optimum for measuring the thyroid volume. The volume from planar images was calculated by the formula described by Allen and Goodwin (The scintillation counter as an instrument for in-vivo determination of thyroid weight. Radiology 1952; 58: 68-79), whereas, in SPECT images, the sum of the slice areas was multiplied by the slice thickness. The estimated volume of each phantom was compared and correlated with its actual volume. After standardization of the technique with phantom studies, planar scintigraphy (with 20% threshold) in 51 patients and SPECT (with 30% and 35% threshold) in 40 patients with Graves' disease were performed to estimate the thyroid size. The thyroid size was also estimated by ultrasonography, which showed good agreement with the scintigraphic method, particularly with SPECT.

High pre-therapy [99mTc]pertechnetate thyroid uptake, thyroid size and thyrostatic drugs: predictive factors of failure in [131I]iodide therapy in Graves' disease

“…The area of the frontal silhouette of the lobe in square millimetres and the height of the lobe in millimetres were noted. The volume of the gland was calculated using the method of Pant et al [25] in patients with Graves' disease.…”

Correlação entre volume tireoidiano determinado pelo método de ultrassonografia versus cintilografia e sua implicação em cálculos dosimétricos na terapia com radioiodo na doença de Graves

“…Há descrições da importância do uso do método cintilográfico na mensuração da massa da tireoide como alternativa ao método ultrassonográfico, evitando a total dependência deste, como publicado por Pant e cols. (5). Embora seja bastante relevante a diferença entre as massas estimadas pelos diferentes métodos de imagem, poucos estudos procuraram dar a devida atenção a esse tópico, bem como a suas implicações.…”

“…Foi realizada avaliação de massa glandular pela USG e pela cintilografia. Como exemplificado na figura 1, o cálculo de massa pela USG foi feito pelo método do elipsoide, em que o volume de cada lobo, considerado uma estrutura ovoide, é definido pelo produto da medida dos diâmetros anteroposterior (AP), transversal (T) e longitudinal (L) multiplicado pelo fator de correção 0,523 (5).…”

Single Photon Emission Tomography (SPECT) and 3D Images Evaluation in Nuclear Medicine

“…SPECT is used in image analysis studies to extract information about areas and volumes or amounts of radioactivity in specific regions of interest. The information that derived from these studies is then applied to aid in clinical diagnoses or even to estimate radiation dosimetry or determination of volume or mass (De Sadeleer et al, 1996;Erdi et al, 1995;Pant et al, 2003;). Many methods for precise and accurate measurements of volume and the amount of radioactivity in a specific region of interest are used (Boudraa & Zaidi, 2006;Hansen, 2002a).…”

“…Gradient shading was used to surface images, by a gradient factor up to 5% low. Determination of thyroid volume leads to the calculation of the thyroid mass and the accurate activity to be administered for patient specific therapeutic purposes (Pant et al, 2003). …”