Description of the methodology for dosimetric quantification in treatments with 177Lu-DOTATATE. / Descripción de la metodología para la cuantificación dosimétrica en tratamientos con 177Lu-DOTATATE.

Implementation of dosimetry calculations in the daily practice of Nuclear Medicine Departments is, at this time, a controversial issue, partly due to the lack of a standardized methodology that is accepted by all interested parties (patients, nuclear medicine physicians and medical physicists). However, since the publication of RD 601/2019 there is a legal obligation to implement it, despite the fact that it is a complex and high resource consumption procedure. The aim of this article is to review the theoretical bases of in vivo dosimetry in treatments with 177Lu-DOTATATE. The exposed methodology is the one proposed by the MIRD Committee (Medical Internal Radiation Dose) of the SNMMI (Society of Nuclear Medicine & Molecular Imaging). According to this method, the absorbed dose is obtained as the product of 2factors: the time-integrated activity of the radiopharmaceutical present in a source region and a geometrical factor S. This approach, which a priori seems simple, in practice requires several SPECT/CT acquisitions, several measurements of the whole body activity and taking several blood samples, as well as hours of image processing and computation. The systematic implementation of these calculations, in all the patients we treat, will allow us to obtain homogeneous data to correlate the absorbed doses in the lesions with the biological effect of the treatment. The final purpose of the dosimetry calculations is to be able to maximize the therapeutic effect in the lesions, controlling the radiotoxicity in the organs at risk.

PET/CT with 18F-Fluordesoxyglucose in patients with suspected endovascular prosthesis infection. / PET/TC con 18F-Fluordesoxiglucosa en pacientes con sospecha de infección de prótesis endovasculares.

OBJECTIVE: Infection of large vessel prostheses is a rare but critical complication. The aim of this work is to assess the impact of PET/CT with 18F-Fluordesoxyglucose (PET-FDG) on the diagnosis of infection in our environment. MATERIAL AND METHODS: Thirty-five patients (38 scans) were evaluated for suspected prosthetic infection. A qualitative analysis was performed taking into account the distribution of the radiopharmaceutical, categorizing the studies as positive or negative for infection. Those with focal or multifocal deposits along the vascular prosthesis were considered positive, and negative if a homogeneous and diffuse distribution over the whole prosthesis was observed, or a total absence of uptake. A semi-quantitative analysis was performed using SUVmax and average SUV values, and a metabolic index was calculated (SUVmax of the graft / average SUV of the normal vascular pool). RESULTS: The PET-FDG study was positive in 20 patients, with a diagnostic accuracy of 84%. The 38 PET-FDG scans performed showed positive capture patterns (focal in 6, multifocal in 15, diffuse in 4) and negative pattern in the remaining 13. The sensitivity, specificity, positive and negative predictive values obtained for the PET-FDG were 95%, 89%, 90% and 94%, and for the AngioTC study 50%, 73%, 73% and 50%, respectively. The area values under the ROC curve were as follows: for the AngioTC 0.642 (not significant), and for the SUVmax values of 0.925 (p<0.005), average SUV of 0.922 (p<0.005) and for the metabolic index of 0.917 (p<0.005). CONCLUSIONS: The PET-FDG proves to be a tool with high diagnostic accuracy in the infection of vascular prosthesis, both visual analysis according to patterns and semi-quantitative.

Contribution of brain perfusion SPECT in the diagnosis of a case of cerebral malaria. / Aportación diagnóstica de la SPECT de perfusión cerebral en un caso de malaria cerebral.

Cerebral malaria is a serious complication of infection with Plasmodium falciparum. Its pathophysiological mechanisms and clinical manifestations are still currently being studied. Structural imaging techniques such as CT and MRI provide non-specific information during the diagnostic process. However, there are hardly any references on the use and potential benefits of radioisotope procedures for this pathology. In this article we present the case of a patient diagnosed with cerebral malaria treated in our centre, subjected to progressive monitoring using SPECT perfusion.

Role of SPECT-CT in breast cancer sentinel node biopsy when internal mammary chain drainage is observed.

INTRODUCTION: SPECT-CT in the detection of the sentinel lymph node (SLN) of breast cancer offers known advantages over conventional planar lymphoscintigraphy. Sometimes, it shows atypical findings like mediastinal lymphatic drainage. We have evaluated these atypical findings showed by SPECT-CT performed in patients with migration to the internal mammary chain (IMC) and their roles in the management of the patients. MATERIALS AND METHODS: We reviewed the 56 lymphoscintigraphies (planar and SPECT-CT) of 56 women (average age: 55 years) diagnosed with breast cancer with IMC migration observed in the planar images. We compared the two techniques, obtaining the number of depicted nodes, atypical locations, their exact anatomical location and their role in the management of the patient. RESULTS: Planar images showed a total number of 81 IMC nodes. SPECT-CT showed 74 nodes in the IMC territory and 14 mediastinal lymphatic nodes in 6 patients. Out of the 81 IMC nodes reported by planar images, seven corresponded to mediastinal nodes. Planar and hybrid images showed 110 and 130 axillary nodes, respectively. SPECT-CT showed additional findings in five patients: three infraclavicular and two supraclavicular nodes that were exactly located. One intramammary node was discarded by the SPECT-CT as a focal skin contamination. CONCLUSION: Mediastinal nodes are unexpected, but not uncommon findings that are important in the planning of SLN biopsy. SPECT-CT found more nodes than planar images, being able to separate mediastinal and IMC nodes, helping to exactly depict the SLN and its relations with anatomical structures.

Coexistence of two different types of lymphoma in a patient with Sjögren's syndrome. The usefulness of the PET-CT.

Sjögren syndrome is a chronic systemic autoimmune disease in which there is an increased risk of developing non-Hodgkin's lymphoma. Neoplastic lung involvement and the coexistence of different histological types of lymphoma are uncommon in these patients. These patients frequently have associated infectious processes, most of them due to oral candidiasis. When there is immunodeficiency, the hematogenous spread of the fungus may affect the lungs. We present the case of a female patient diagnosed with follicular non- Hodgkin lymphoma within the context of long-term Sjögren syndrome. In addition to the neoplastic nodal and splenic disease, the PET-CT study showed extensive lung involvement. Due to suspicion of a false positive result for pulmonary Candida infection, antifungal treatment was initiated, with no response. A further histological study showed the presence of a second and different type of lymphoma.

[Radioguided surgery of intestinal carcinoid tumor relapse. Role of SPECT-CT]. / Cirugía radiodirigida de metástasis de tumor carcinoide intestinal. Importancia de la realización de SPECT-TAC.

We present a patient with clinical suspicion of intestinal carcinoid relapse confirmed by a somatostatin receptor scintigraphy. A very intense somatostatin avid abdominal lesion was located and radioguided surgery was proposed. Prior to the procedure, we performed a SPECT-CT that made it possible to detect and localize the lesion anatomically, thus facilitating the performance of the radioguided procedure. Furthermore, it modified the planning of the intervention with the adequate physical and human resources to prevent the possible surgical complications.

[Optimization of sentinel lymph node biopsy in breast cancer by intraoperative axillary palpation]. / Optimización de la biopsia selectiva de ganglio centinela en el cáncer de mama mediante palpación axilar intraoperatoria.

INTRODUCTION: Sentinel node biopsy (SNB) by radioisotopes is a widely accepted and reliable surgical method for staging breast cancer in patients with unknown positive axillary lymph nodes involvement. The main limitation of this method is due to the appearance of false negatives that may be caused by tumor lymph node blockage of the sentinel lymph node and uptake in the neighboring lymph nodes. Infiltered sentinel nodes are generally increased in size and firm. Thus, they can be detected by intraoperative palpation, even when there is no uptake by the radiotracer. AIM: To reduce the false negative rates by applying intraoperative axillary palpation after SNB. METHOD: Over a two-year period, we complemented the SNB in 168 patients with careful intraoperative axillary palpation, detecting and removing all the palpable suspicious lymph nodes (SLN) that were analyzed as sentinel nodes RESULTS: In 32 out of 168 patients, 50 palpable SLN were found. In 3 out of 32 patients, 4 infiltrated SLNs were demonstrated with negative SNB and positive axillary lymphadenectomy. Thus, intraoperative palpation avoided false negative results. In one patient, one palpable SLN with tumor involvement was observed and SNB was also positive. In the remaining 28 patients, the histological analysis of 45 SLN was negative for tumor but SNB was positive in 3 patients. CONCLUSION: Intraoperative axillary palpation, once the SNB was done, reduced the false negative rate. Thus, we consider that it should be included as one more part of this procedure.

[Negative predictive value of (123)I Ioflupane SPECT in movement disorders]. / Valor predictivo negativo del SPECT con Ioflupano (123)I en los trastornos del movimiento.

OBJECTIVE: A non-degenerative etiology is supported by a normal SPI [normal SPECT with 123I-Ioflupane (SPI)] in a patient with movement disorders (MD). METHOD: A total of 196 SPIs were conducted during the period of 2004/05. Of these, 44 were selected in order to rule out degenerative MD (DMD), the results being normal in these patients. The clinical background of these patients were reviewed in a minimum period of 24 months (range 24-40), collecting the diagnoses reached by the neurology specialists. The SPI were evaluated using a consensus, according to subjective criteria and quantification. RESULTS: Thirty-six of the 44 patients (81%) were identified at 2 years of having nondegenerative movement disorders: 18 as essential tremor, 5 as drug-induced disorder, 4 as vascular disease, 3 as peripheral polyneuropathy, 2 postural tremors, 1 writer's cramp, 1 psychogenic tremor, 1 intercranial hypertension and 1 fibromyalgia. The remaining 8 patients were diagnosed with Parkinson's disease in 5 cases, 1 corticobasal degeneration, 1 multisystemic atrophy and another degenerative Parkinsonism with unclear etiology. CONCLUSION: The SPI in our hospital has a lower negative predictive value than the data reported in the literature. The false negatives could be explained because most of our patients come from neurologist physicians who are not movement disorder experts. In addition, a small proportion of degenerative Parkinsonism could evolve with normal SPI.

Detección de recidiva pleuropulmonar en carcinoma de mama / Detection of pleuropulmonary relapse in breast cancer

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[Positron emission tomography (PET) imaging in head and neck cancer]. / La Tomografía por Emisión de Positrones (PET) en la patología oncológica de cabeza y cuello.

Positron Emission Tomography (PET) with 18F-Fluordeoxyglucose is a diagnostic imaging technique very useful in the management of head and neck cancer, better than anatomic imaging in most cases. PET shows higher diagnostic accuracy in the detection of local and regional tumor recurrences. PET is also indicated for the identification of unknown primary tumors when regional nodal metastasis is the presenting feature. The improved planning of radiation therapy with hybrid cameras PET-CT, the earlier diagnosis of post-radiotherapy residual disease and the possibility of monitoring the effects of chemotherapy makes PET imaging an important tool in evaluating tumor response to treatment.

La Tomografía por Emisión de Positrones (PET) en la práctica clínica oncológica / Positron emission tomography (PET) in oncological clinical practice

La Tomografía por Emisión de Positrones con 18F-fluorodeoxiglucosa (PET-FDG) es una técnica de diagnóstico por imagen cuyo uso se ha generalizado en España durante la última década. Existen una serie de indicaciones concretas, en las cuales la PET-FDG ha demostrado sobradamente su superioridad con respecto a los métodos convencionales de diagnóstico. Es recomendable, por ello, realizar un estudio PET-FDG únicamente en las siguientes situaciones: la estadificación de tumores pulmonares y linfomas, la re-estadificación de tumores de tiroides, colorrectales, de cabeza-cuello, linfomas y melanomas; la localización de tumores de origen desconocido; la caracterización del nódulo pulmonar solitario; y, por último, el diagnóstico diferencial recidiva/radionecrosis en tumores cerebrales (AU)