Comparison of Whole-Body Dosimetry Measurements in 131I Therapy Using Ceiling-Mounted Geiger-Müller Detectors and γ-Camera Scans: An Agreement Analysis.

Background: In 131I therapies internal dosimetry is crucial for determining the mean absorbed dose to organs at risk, particularly the bone marrow, which has a dose constraint of 2 Gy. Traditionally, multicompartmental models have been used for bone marrow dosimetry, necessitating whole-body absorbed-dose assessments. However, noninvasive techniques, such as γ-camera scans or ceiling-mounted Geiger-Müller (GM) counters, can estimate the aforementioned. This study was aimed to evaluate the agreement between whole-body mean absorbed dose using γ-camera scans and ceiling-mounted GM in patients with thyroid carcinoma undergoing 131I therapy. Methods: This study included 31 patients with thyroid cancer who were treated with 131I. The whole-body time-integrated activity (TIA) and mean absorbed dose were estimated using the elimination curves obtained with γ-camera scans and ceiling-mounted GM. In addition, statistical analysis was performed on the data to determine the Coefficient Correlation Coefficient and the Bland-Altman limits of agreement for both parameters, as well as for the elimination curves' effective half-life. Results: The study revealed correlations of 0.562 and 0.586 between whole-body TIA and mean absorbed dose, respectively. The Bland-Altman limits of agreement were found to be below -3.75% and within 12.75% of the bone marrow dose constraint of 2 Gy. The nonparametric evaluation revealed that whole-body TIA and mean absorbed dose medians from GM were lower than those from γ-camera scans (p < 0.001). Effective half-life estimation mean was significantly lower in the GM than in the γ-camera of 13 and 23 h. Conclusions: Although GM calculates the whole-body absorbed dose with margins of error within clinical acceptance, underestimation of the effective half-life makes it an unacceptable substitute method for γ-cameras in clinical practice. Further research should be conducted to evaluate single-point GM measurement substitutions in time-activity curves.

Riesgo de recurrencia dinámico en pacientes con microcarcinoma de tiroides con y sin ablación con Yodo-131 / Dynamic risk of recurrence in patients with thyroid microcarcinoma with and without iodine-131 ablation

Introducción: El cáncer diferenciado de tiroides ha incrementado su incidencia en las últimas 3 décadas debido al sobrediagnóstico de tumores pequeños o microcarcinomas, las nuevas tendencias en su manejo hacen de la cirugía y la terapia con iodo radioactivo el tratamiento de elección para casos seleccionados. El manejo actual de microcarcinoma de tiroides se basa en el riesgo de recurrencia inicial y su seguimiento en el tiempo con el riesgo de recurrencia dinámico. Objetivo: El presente trabajo se enfocó en analizar el riesgo de recurrencia dinámico en pacientes con microcarcinoma de tiroides que recibieron o no terapia ablativa con Iodo 131 posterior a tratamiento quirúrgico en el Hospital Teodoro Maldonado Carbo durante los años 2016 ­ 2018. Métodos: Se realizó un estudio ambispectivo, no experimental, descriptivo, analítico, transversal y correlacional. Se analizaron 51 pacientes atendidos en la unidad técnica de endocrinología. Resultados: De un total de 51 casos de microcarcinoma, el 60% fue tratado con terapia ablativa, la respuesta inicial fue excelente en el 53.3% de pacientes ablacionados y en el 66.7% de los casos no ablacionados. El riesgo de recurrencia inicial fue significativamente más bajo en el grupo no tratado mediante ablación (100%), mientras que en el tratado con ablación fue bajo, intermedio y alto en 16 (53.3%), 7 (23.3) y 7 (23.3), respectivamente. Conclusiones: Existe un riesgo bajo de recurrencia dinámico, independientemente de la indicación de terapia ablativa con I131, la estratificación del riesgo de recurrencia constituye una herramienta útil para seleccionar aquellos pacientes que deben recibir iodo radioactivo.

Introduction: Differentiated thyroid cancer has increased its incidence in the last 3 decades due to overdiagnosis of small tumors or microcarcinomas; new trends in its management make surgery and radioactive iodine therapy the treatment of choice for selected cases. The current management of thyroid microcarcinoma is based on the initial risk of recurrence and its follow-up over time with the dynamic risk of recurrence. Objective: The present work focused on analyzing the risk of dynamic recurrence in patients with thyroid microcarcinoma who received or did not receive ablative therapy with Iodine 131 after surgical treatment at the Teodoro Maldonado Carbo Hospital during the years 2016 - 2018. Methods: An ambispective, non-experimental, descriptive, analytical, cross-sectional, and correlational study was carried out. Fifty-one patients treated at the endocrinology technical unit were analyzed. Results: Of 51 cases of microcarcinoma, 60% were treated with ablative therapy, and the initial response was excellent in 53.3% of ablated patients and 66.7% of non-ablated cases. The initial recurrence risk was significantly lower in the group not treated by ablation (100%). In contrast, in the group treated with ablation, it was low, intermediate, and high in 16 (53.3%), 7 (23.3), and 7 (23.3), respectively. Conclusions: There is a low risk of dynamic recurrence, regardless of the indication for ablative therapy with I131; a recurrence risk stratification is a helpful tool for selecting those patients who should receive radioactive iodine.

Rectal Neuroendocrine Tumor With Inferior Vena Cava Tumor Thrombosis Diagnosed With 68Ga-DOTANOC PET/CT.

A 69-year-old man with a history of back pain, urinary obstruction, and deep vein thrombosis of both lower extremities 4 years earlier was diagnosed with rectal neuroendocrine tumor, grade 2, Ki-67 index 3%. Ga-DOTANOC PET/CT images showed a left pelvic mass extended to the lumen of the inferior vena cava with a high affinity for somatostatin receptor. A tubular focus of radiotracer accumulation after the course of inferior vena cava with filling defect was suggestive of tumor thrombus.

Detection of muscle calcifications by thigh CT scan in neurocysticercosis patients.

Twenty-five patients with calcified neurocysticercosis (two to four intraparenchymal brain calcifications) were asked to have a non-contrasted computed tomography (CT) scan of the thighs to determine the frequency of muscle calcifications detected by this technique. Thirteen (52%) showed one or more muscle calcifications. The numbers of calcifications in the thighs and the brain were not correlated. Patients with a positive CT scan for muscle calcifications were also examined by X-rays to compare both methods. Only 6 of 13 had visible calcifications on X-ray. Thigh CT scans can demonstrate muscle calcifications in a significant proportion of patients with calcified neurocysticercosis.