Specificity and sensitivity of 99mTc-EDDA/HYNIC-Tyr³-octreotide (99mTc-TOC) for imaging neuroendocrine tumors.

OBJECTIVES: Gastroenteropancreatic neuroendocrine tumors (NETs) are cancers originating from neuroendocrine organs such as the pancreas, pituitary, thyroid, and adrenal glands and tumors arising from the diffuse neuroendocrine cells that are widely distributed throughout the body. NETs express somatostatin (SS) and contain a high density of SS receptors; therefore, they can be specifically targeted with SS-based radiopharmaceuticals. The aim of this research was to determine the validity in terms of specificity, sensitivity, and the agreement beyond chance with the biopsy (gold standard) of the 99mTc-EDDA-HYNIC-Tyr³octreotide (99mTc-TOC) to image and localize NETs and their metastases. MATERIALS AND METHODS: Freeze-dried kits containing 0.0125 mg HYNIC-octreotide and co-ligands were easily labeled and quality controlled within the hospital radiopharmacy. Fifty-six consecutive Mexican patients with a previous presumptive diagnosis of NETs underwent several clinical and laboratory studies and were referred to the Nuclear Medicine Department for a routine scan with 99mTc-TOC. The patients were injected with 500-600 MBq 99mTc-TOC, and whole-body images were obtained 2 h later with a SPECT or a SPECT/CT camera. Two nuclear medicine physicians observed the images and classified them as 17 negative and 39 positive. After correlating the image of each patient with our 'gold standard' (biopsy, clinical history, morphological images, and tumor marker assays), the 99mTc-TOC images were classified by the same two physicians as 12 true negatives, five false negatives, 38 true positives and one false positive. RESULTS: The validity of 99mTc-TOC in terms of relative frequencies with corresponding 95% confidence intervals were as follows: 92.3% (64-100%) specificity; 88.4% (78-97%) sensitivity; and the agreement beyond chance was 73% (60-84%). The positive predictive value was 97.4% (87-100%); the negative predicted value was 70.6% (48-93%); the accuracy was 89.3% (89-97%); and the prevalence was 76.8% (64-87%). CONCLUSION: Because of these high values, we strongly recommend scintigraphy with the Mexican-produced 99mTc-TOC for the localization of NETs and their metastases, and we conclude that it is a good tool for detecting neuroendocrine disease in a Mexican population.

Specificity of 99mTc-UBI for detecting infection foci in patients with fever in study.

UNLABELLED: Fever of unknown origin (FUO) represents a challenge to clinical medicine, and bacterial cultures have been considered the 'gold standard' in discriminating between fevers resulting from bacterial infection and sterile inflammations. In nuclear medicine, a synthetic radiolabeled antimicrobial peptide (Tc-UBI) is used to image the molecular localization of infectious microorganisms. OBJECTIVE: The aim of this research was to determine the absolute and relative frequencies of Tc-UBI, by molecular imaging, to detect infection foci in patients with fever in study or FUO. METHODS: Images (207) from 196 patients with FUO acquired with Tc-UBI and a Siemens gammacamera were read by two nuclear medicine physicians and classified as positive or negative for infection foci. The diagnostic value was corroborated with our gold standard, which comprises bacterial cultures of biopsies, blood and urine, plus laboratory studies, morphological images (radiographs, nuclear magnetic resonance, computed tomography) and the clinical history of each patient. The absolute and relative frequencies of Tc-UBI were calculated from the molecular images versus the gold standard. RESULTS: The specificity of Tc-UBI for localizing infection foci and for discarding sterile inflammation was 95.35%, the sensitivity was 97.52%, the positive predictive value was 96.72%, the negative predictive value was 96.47%, the accuracy was 96.62%, and the observed agreement between the bacterial culture and the molecular image was 96.62% (P=0.0001). CONCLUSION: Considering that the absolute and relative frequencies are very high, we propose that, in the future, Tc-UBI molecular imaging could be the gold standard to detect infection sites and to discard sterile inflammation.

Radioguided occult lesion localization (ROLL) versus wire-guided lumpectomy for non-palpable breast lesions: a randomized prospective evaluation.

BACKGROUND: It is important to optimize the localization technique for non-palpable breast lesions. METHODS: One hundred consecutive women with non-palpable breast lesions were randomized to radioguided occult lesion localization (ROLL) or wire localization (WL). For ROLL technique (99m)Tc-labeled particles of human serum albumin were injected under breast-imaging control. Localization of the lesion was done in the operating room with the aid of a gamma-probe. All lesions were identified in an X-ray control of the surgical specimen. Categorical variables were analyzed with the Chi-square method. Significance was considered at P < 0.05. RESULTS: All procedures were performed on the same day of excision, on ambulatory basis. Both techniques resulted in 100% retrieval of the lesions. Localization time was reduced with ROLL (P < 0.001). Clear margins were achieved in 88.9% ROLLs and 62.5% WLs (P < 0.05) reducing the requirement of re-excision. There were significant differences in the subjective ease of the procedures in favor of ROLL technique as rated by surgeons and radiologists. CONCLUSIONS: ROLL technique is as effective as WL for excision of non-palpable breast lesions, reduce localization time and probably the incidence of pathologically involved margins of excision. ROLL appears to improve the learning curve for surgical residents and cosmesis. ROLL is an attractive alternative to WL.

Abnormal SPECT myocardial perfusion imaging during periods of obstructive sleep apnea in morbid obese patients without known heart disease.

OBJECTIVE: Determine the myocardial perfusion characteristics in obstructive sleep apnea and its possible role in cardiovascular damage. METHODS AND PROCEDURES: Fourteen patients from the Obesity Clinic weighing less than 130 kg underwent myocardial perfusion studies using single photon emission computed tomography with technetium 99m-labeled sestamibi during nighttime polysomnographic recordings. Coronary angiograms were performed on patients with suspect of severe coronary obstruction according nighttime myocardial perfusion studies or pharmacological stress carried out during waking hours. RESULTS: All 14 patients manifested myocardial perfusion defects during sleep, affecting an average of 5.5 segments/patient, although only 8 presented ischemic ST segment changes and none demonstrated rhythm or conduction disturbances. Angiographic examination of the 10 patients with the most severe perfusion defects did not reveal significant coronary obstruction, and fewer perfusion defects were documented during daytime scintigraphy. DISCUSSION: In obese patients with obstructive sleep apnea, myocardial perfusion defects appear to occur with highest frequency and severity during nighttime sleep, justifying further investigation in a larger number of patients with obstructive sleep apnea and more significant obesity.

Radiopharmacokinetics, renal clearance and dosimetry of 99m Tc-MAG3

Background. Technetium-99m-mercaptoacetyltriglycine (99-mTc-MAG3) is a radiopharmaceutical for tubular function and can be prepared with 99-mtechnetium and the ligand Bz-MAG3 (Instituto Nacional de Investigaciones Nucleares, Mexico City). No radiopharmacokinetic parameters have been found for the healty adult Mexican population with 99mTc-MAG3, prepared with the nationally produced or imported Bz-MAG3 kit. Methods. The radiopharmacokinetic parametrs and the clearance of 99mTc-Mag3 in seven healthy Mexican volunteers were determined by the single-and multi-sample methods. Computer programs were used for the calculations. Results. Using several plasma samples from 0.43 min and the BIEXP program, it was show that 99mTc-MAG3 follows a two-compartment model of distribution, with an apparent volumen in the central compartment Vdcc = 6.7 + 1.0 1, T½Ó = 0.07 + 0.02 h-1, T½ ß = 0.49 + 0.15 h-1, mean residence time MRT = 0.60 + 0.17 h and clearance = 208 57 (ml/min)/1.73 m². In comparison, the clearance value with a single sample drawn 43 min post-injection and calculated with Tauxe's formula was 193 ñ 59 (ml/min)/m². Conclusions. The 15 ml difference between the two methods is neither statistically different (p= 0.11) nor important for routine clinical studies. The single-sample method is recommendad because it is reliable and can be done at the same time that dynamic renal scan is aquiered. Estimated absorbed radiation dose was calvulated for several organs

El 99mTc-alendronato como nueva opción en la gammagrafía ósea / 99mTc-Alendronate as an option in bone scanning

Objetivo. Comparar la calidad de las imágenes de gammagrafía ósea obtenidas con un radiofármaco nuevo, el 99mTc-ABP, con aquéllas obtenidas con el 99mTc-MDP. Material y métodos. Fue un estudio comparativo en un mismo sujeto. Se estudiaron 9 voluntarios sanos (5 mujeres y 4 hombres) de 23 a 39 años de edad. A todos se les inyectaron 740 MBq de los radiofármacos Tc-ABP y Tc-MDP con un intervalo de 72 horas entre uno y otro. Dos horas después de cada inyección se les realizó un gammagrama óseo de cuerpo entero con una cámara de centello MultiSpect 2 y se determinaron los parámetros radiofarmacocinéticos. Tres médicos nucleares evaluaron por separado la calidad de las imágenes mediante el trazado de regiones de interés (RDI) sobre vértebras, costillas, esternón, fémur, articulaciones y cráneo. Se obtuvieron relaciones hueso/músculo con RDI sobre diferentes huesos. Los resultados se compararon etadísticamente con las pruebas de kappa y de Wilcoxon. Resultados. La concordancia sobre la calidad de las imágenes de los dos radiofármacos por los tres observadores fue moderada (kappa 0.4). La relación fémur/músculo mostró una distribución normal y no manifestó diferencias significativas entre radiofármacos. Conclusiones. La calidad de las imágenes con ambas preparaciones fue similar. Recomendamos utilizar al 99mTc-ABP en la gammagrafía ósea debido a la menor exposición a radiación del paciente

Technetium-99m-alendronate: a new radiopharmaceutical for bone scanning

The purpose of this paper is to report the preparation of a new technetium-99m-radiopharmaceutical for bone scanning. The chelating agent for99mTc is a new bisphosphonate, alendronate, 4-amino-1-hydroxy-butylidene-1,1-bisphosphonate (ABP) used as a treatment for osteoporosis. ABP, because of its amino group, seems to be better suited to form a strong and stable complex with technetium-99m and therefore might be better than 99mTc-etidronate (HEDP) or 99mTc-medronate (MDP) for bone scanning. A sterile dry kit containing APB, a reducing agent and a stabilizer was prepared. The parameters studied were molar concentrations, pH, shelf life, labeling efficiency and radiochemical purity. the oven dried sterile kit was formulated with 5 mg ABP, 0.25 mg stannous fluoride and 0.025 mg gentisic acid at pH2.5-3.5. The labeling efficiency with 20 - 1500 MBq of pertechnetate (99mTcO4-) was over 95 percent at room temperature and was stable for 5 h. Technetium-99m-alendronate was tested in two rabbits and it proved to be a promising new radiopharmaceutical for bone scanning. Work is underway to study underway to study 99m-Tc-ABP biodistribution in a statistically significant number of laboratory animals and, later on, to determine radiopharmacokinetic parameters in normal volunteers

Variabilidad interobservadores al delimitar regiones de interés en gamagramas computarizados / Interobserver variability in RIO drawing in computerized scan processing

Antecedentes. En la actualidad, de los departamentos de medicina nuclear cuentan con cámaras de centelleo para gamagrafía computarizada. Para el radiorrenograma se adquieren 90 imágenes de 16 segundos cada una, se integran en una sola y sobre ella se trazan regiones de interés (RDI) dibujado el contorno de los riñones y de la vejiga, por medio de una palanca móvil ("joy stick"). El programa utliza la radiactividad de cada RDI para generar curvas de actividad/tiempo, y calcular el tiempo de máxima actividad renal (Tmax) y el tiempo que tarde el riñón en eliminar la mitad de esta radiactividad T½). El dibujo del contorno de órgano, al trazar las RDI, es el único paso en que interviene directamente el operador por lo que cabe la posibilidad de que los resultados dependan de su habilidad y experiencia, y por ende, que hubiera diferencias interoperadores que repercutieran en la interpretación clínica de los gamagramas. Objetivo. Establecer la variabilidad interoperadores de cuatro personas experimentadas en el trazado de RDI en imágenes renales. Material y métodos. Los cuatro operadores trazaron las RDI para obtener la Tmax Y T½ de 38 riñones de 20 pacientes (dos trasplantados). Se calculó el CV interoperadores de Tmax y T½ de los 38 riñones. Resultados. Globalmente hubo mayor variabilidad interobservadores en T½ que en Tmax. Cuatro riñones mostraron pequeñas diferencias interoperadores en Tmax y/o T½ pero suficientes para que discreparan sus clasificaciones de normal/retardado. La separación de los datos en tres grupos (T = Tmax y T½ normales; 2 = Tmax normal y T½ retardada; 3 = ambas retardadas) mostró que había diferencias intergrupos significativas en el CV interobservadores de la Tmax (Kruskal-Wallis p = 0.032) que obedecían a que la variabilidad fue mayor en el grupo 2 (6 de 11 riñones con CV >4 por ciento) que en los grupos 1 y 3 (ninguno con CV >4 por ciento). Conclusiones. 1. Las discrepancias interoperadores tuvieron repercusión sólo en algunos casos en que los parámetros estaban ligeramente retardados (8-9 min en Tmax, 15-20 min en T½). 2. No tenermos una explicación de por qué hubo mayor variabilidad interoperadores en Tmax de los riñones del grupo 2 (Tmax normal con T½ retardada). 3. Creemos que un estudio de la variabilidad interoperador de estas mismas cuatro personas puede aclarar algunas de las observaciones de este estudio