Feasibility study of a SiPM-fiber detector for non-invasive measurement of arterial input function for preclinical and clinical positron emission tomography.

Pharmacokinetic positron emission tomography (PET) studies rely on the measurement of the arterial input function (AIF), which represents the time-activity curve of the radiotracer concentration in the blood plasma. Traditionally, obtaining the AIF requires invasive procedures, such as arterial catheterization, which can be challenging, time-consuming, and associated with potential risks. Therefore, the development of non-invasive techniques for AIF measurement is highly desirable. This study presents a detector for the non-invasive measurement of the AIF in PET studies. The detector is based on the combination of scintillation fibers and silicon photomultipliers (SiPMs) which leads to a very compact and rugged device. The feasibility of the detector was assessed through Monte Carlo simulations conducted on mouse tail and human wrist anatomies studying relevant parameters such as energy spectrum, detector efficiency and minimum detectable activity (MDA). The simulations involved the use of 18F and 68Ga isotopes, which exhibit significantly different positron ranges. In addition, several prototypes were built in order to study the different components of the detector including the scintillation fiber, the coating of the fiber, the SiPMs, and the operating configuration. Finally, the simulations were compared with experimental measurements conducted using a tube filled with both 18F and 68Ga to validate the obtained results. The MDA achieved for both anatomies (approximately 1000 kBq/mL for mice and 1 kBq/mL for humans) falls below the peak radiotracer concentrations typically found in PET studies, affirming the feasibility of conducting non-invasive AIF measurements with the fiber detector. The sensitivity for measurements with a tube filled with 18F (68Ga) was 1.2 (2.07) cps/(kBq/mL), while for simulations, it was 2.81 (6.23) cps/(kBq/mL). Further studies are needed to validate these results in pharmacokinetic PET studies.

Incidental 68Ga-DOTATOC PET/CT Uptake in Hemorrhagic Transformation of Stroke in a Patient With Cervical Paraganglioma.

ABSTRACT: We present a case of a 75-year-old woman with clinical suspicion of stroke whose cranial CT showed ischemic changes in right precentral region, without visible vascular occlusion, and a right vagal lesion suggestive of paraganglioma. Two weeks later, 68Ga-DOTATOC PET/CT with IV iodine-based contrast administration (Biograph 6 True Point equipment; Siemens) was performed for characterization of this lesion and staging. Intraparenchymal 68Ga-DOTATOC uptake was visualized in right frontal lobe suggestive of hemorrhagic transformation of the previous stroke.

Validation technique and improvements introduced in a new dedicated brain positron emission tomograph (CareMiBrain).

The goal of developing a PET dedicated to the brain (CareMiBrain) has evolved from its initial approach to diagnosis and monitoring of dementias, to the more ambitious of creating a revolutionary clinical pathway for the knowledge and personalized treatment of multiple neurological diseases. The main innovative feature of CareMiBrain is the use of detectors with continuous crystals, which allow a high resolution determination of the depth of annihilation photons interaction within the thickness of the scintillation crystal. The technical validation phase of the equipment consisted of a pilot, prospective and observational study whose objective was to obtain the first images (40 patients), analyze them and make adjustments in the acquisition, reconstruction and correction parameters, comparing the image quality of the CareMiBrain equipment with that of the whole-body PET/CT. Thanks to the team meetings and the joint analysis of the images, it was possible to detect its weak points and some of its causes. The calibration, acquisition and processing processes, as well as the reconstruction, were optimized, the number of iterations was set to achieve the best signal-to-noise ratio, the random correction was optimized and a post-processing algorithm was included in the reconstruction algorithm. The main technical improvements implemented in this phase of technical validation carried out through collaboration of the Services of Nuclear Medicine and Neurology of the Hospital Clínico San Carlos with the Spanish company Oncovision will be exposed in a project financed with funds from the European Union (Horizon 2020 innovation program, 713323).

Clinical relevance of incidental focal breast uptake on fluorine-18 fluorodeoxyglucose PET/computed tomography studies: an experience in a high-load center of Spain.

AIM: We aimed to determine the frequency and clinical significance of breast incidental uptake (BIU) detected through fluorine-18 fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) in a single, high-load center. PATIENTS AND METHODS: In this retrospective study, we analyzed a total of 13 763 PET/CT studies performed from January 2017 to January 2020. After excluding 3148 scans, the maximum standardized uptake value (SUVmax) and maximum diameter (cm) of each BIU were measured. Clinical management, ultrasound/mammography and pathology reports were analyzed. RESULTS: We found BIU in 27 scans of 26 patients (0.3% of the studies). Mean age was 62.2 years and 88.5% were women; 84.6% underwent PET/CT for oncological indications. Ultrasound/mammography was consequently performed in 23 patients (88.5%), and histological correlations were available for Breast Imaging Reporting and Data System categories 4 and 5. Finally, lesions were benign in 14 patients (60.9%; two of them with low/intermediate risk of malignancy) and malignant in nine patients (39.1%). The remaining three patients had no ultrasound/mammography reports. Mean SUVmax of benign and malignant lesions were 2.6 ± 1.4 and 5.8 ± 3.5, respectively (P = 0.002). Considering a SUVmax cut-off value of 4.0, the sensitivity and specificity for differentiating benign vs. malignant lesions were 67 and 93%, respectively. Benign lesions were smaller than malignant in CT (maximum diameter:1.3 ± 0.5 cm vs. 2.0 ± 1.0 cm, P = 0.02). CONCLUSION: Although BIU detected by 18F-FDG PET/CT is infrequently found, the risk of malignancy remains very high (39.1%). Both SUVmax and maximum diameter were greater in malignant than in benign lesions. An exhaustive study with ultrasound/mammography and selective histopathological correlation is mandatory after BIU findings, even in small lesions.

Assessment of extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia detected on 18F-FDG PET-CT studies.

BACKGROUND: Lung involvement in patients with coronavirus disease 2019 (COVID-19) undergoing PET-CT has been previously reported. However, FDG uptake outside lung parenchyma was poorly characterized in detail. We evaluated the extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia through 18F-FDG PET-CT. METHODS: A total of 1079 oncologic 18F-FDG PET-CT were performed between February 2 and May 18, 2020. Confirmed COVID-19 pneumonia was defined as characteristic ground-glass bilateral CT infiltrates and positive genetic/serologic tests. Nonmetastatic extra-parenchymal lung PET-CT findings were evaluated through qualitative (visual), quantitative (measurements on CT), and semiquantitative (maximum standardized uptake value: SUVmax on PET) interpretation. Clinical data, blood tests, and PET-CT results were compared between patients with and without COVID-19 pneumonia. RESULTS: A total of 23 18F-FDG PET-CT scans with pulmonary infiltrates suggestive of COVID-19 and available laboratory data were included: 14 positive (cases) and 9 negative (controls) for COVID-19 infection, representing a low prevalence of COVID-19 pneumonia (1.3%). Serum lactate dehydrogenase and D-dimers tended to be increased in COVID-19 cases. Extra-parenchymal lung findings were found in 42.9% of patients with COVID-19, most frequently as mediastinal and hilar nodes with 18F-FDG uptake (35.7%), followed by incidental pulmonary embolism in two patients (14.3%). In the control group, extra-pulmonary findings were observed in a single patient (11.1%) with 18F-FDG uptake located to mediastinal, hilar, and cervical nodes. Nasopharyngeal and hepatic SUVmax were similar in both groups. CONCLUSION: In cancer patients with asymptomatic COVID-19 pneumonia, 18F-FDG PET-CT findings are more frequently limited to thoracic structures, suggesting that an early and silent distant involvement is very rare. Pulmonary embolism is a frequent and potentially severe finding raising special concern. PET-CT can provide new pathogenic insights about this novel disease.

[FROM THE CT-PET TO THE MRI-PET]. / DEL PET-TAC AL PET-RM.

CT-PET is a multimodality imaging technique which diagnostic utility has been demostrated especially in oncology and neurosciences. There is about 100 equipments of this modality in Spain. MRI-PET ia a new multimodality imaging technique recently installed in Spain. Its main advantages over CT-PET are: the reduction in the absorbed dose of radiations and the better contrast between normal and pathological tissues, especially in soft tissue tumors and neurological disorders.

Malignant melanoma.

Nuclear medicine plays an essential role in the correct staging of patients suffering from melanoma. Both sentinel lymph node biopsy (SLNB) and positron emission tomography (PET) represent its main diagnostic tools. SLNB is the choice procedure for lymphatic regional staging of these patients, including the result of this technique in the 2002 American Joint Cancer Committee melanoma staging. SLNB sensitivity is superior than PET/CT for the detection of lymphatic micrometastases in early stages of the disease. PET/CT is mainly used in confirming clinical metastases suspected, detection of recurrences, and recurrence restaging. PET/CT has also shown superiority against conventional diagnostic methods in the detection of distant metastases, being able to detect illness even six months earlier than those methods.

[Present role of CT/PET in diffuse large B-cell lymphoma]. / Papel actual del PET-TAC en el linfoma difuso de células B grandes.

The Diffuse Large B-Cell Lymphoma is the most frequent non Hodgkin Lymphoma. The role of CT/PET in this relatively homogeneous group of lymphomas is controversial. It rarely changes the management of the patients in the initial staging. Recents publications, clinical trials and experts consensus meetings have demonstrated its utility in the evaluation of the response at the end of the treatment. The interest of CT/PET in the evaluation of the response during the treatment, with the objective of implement a "Risk Adapted Therapy", in increasing.

[PET-CT in the oncological translational platforms]. / PET-TAC en las plataformas translacionales oncológicas.

Molecular Imaging is changing the development of new therapies. Conventional imaging methods evaluate response based in the reduction of tumour size, which often is a late effect and, therefore, it can take months to confirm the efficacy of an antitumoral therapy. Systems based in imaging biomarkers or radiotracers, as PET and PET-CT can detect the response as soon as a few days after initiation of therapy. A large number of imaging radiotracers has been proposed. They are capable of supplying a varied information: metabolism, cellular proliferation, DNA replication, protein or membrane lipids synthesis, amino acid transport, angiogenesis, hypoxia, apoptosis, etc.

[New help from nuclear medicine to surgery]. / Nuevas ayudas de la medicina nuclear a la cirugía.

New Nuclear Medicine techniques to help the surgeon in the operation room are now being introduced. They aim to get a better location of the objective or a shorter duration of the surgical process. The selective radioguided biopsy of the sentinel node included in the clinical practise guidelines for the surgery of tumours as breast cancer and malignant melanoma is the paradigm of this new techniques. Other techniques are intraoperatory detection with probes or portable gammacameras of tumour lesions as parathyroid adenomas, metastatic neuroendocrine tumours and other tumours.

[Systematic review and meta-analysis of diagnostic accuracy of 18F-FDG PET in suspected recurrent head and neck cancer]. / Revisión sistemática y metaanálisis de la eficacia diagnóstica de la PET 18F-FDG en recurrencia tumoral de cánceres de cabeza y cuello.

OBJECTIVES: A meta-analysis of the literature was performed in this article in order to evaluate the diagnostic accuracy of 18F-FDG PET in suspected recurrent head and neck cancer. MATERIAL AND METHODS: A systematic review of the literature was performed using 1987 to 2007 MEDLINE and CANCERLIT databases, applying selection criteria to the studies found. Sensitivity, specificity, positive and negative likelihood ratios, and odds ratio were calculated. The diagnostic accuracy was evaluated with ROC (receive-operating-characteristics) curves. RESULTS: Nineteen articles were included in the meta-analysis. Sensitivity of 18F-FDG PET was 94 %, specificity 80 %, and the summary ROC curve showed a good trade-off between sensitivity and specificity. CONCLUSIONS: 18F-FDG PET was useful in patients with suspected recurrence of head and neck cancer, showing a high sensitivity and intermediate-high specificity.

Revisión sistemática y metaanálisis de la eficacia diagnóstica de la PET 18F-FDG en recurrencia tumoral de cánceres de cabeza y cuello / Systematic review and meta-analysis of diagnostic accuracy of 18F-FDG PET in suspected recurrent head and neck cancer

Objetivos: En este trabajo se realizó un metaanálisis de la literatura para evaluar la exactitud diagnóstica de la PET 18F-FDG en la sospecha de recurrencia de cánceres de cabeza y cuello. Material y métodos: Inicialmente se realizó una búsqueda sistemática de la literatura en las fuentes MEDLINE y CANCERLITE hasta mayo de 2007, aplicando unos criterios de cribado a los estudios hallados. Se calcularon los valores de sensibilidad, especificidad, cocientes de probabilidad positivo y negativo y la odds ratio diagnóstica. El rendimiento diagnóstico se valoró mediante curvas ROC (receive-operating-characteristic). Resultados: Fueron incluidos 19 artículos en el metaanálisis. La sensibilidad de la PET 18F-FDG fue del 94 %, la especificidad del 80 % y la curva ROC mostró una buena relación entre sensibilidad y especificidad. Conclusiones: La PET 18F-FDG fue útil en pacientes con sospecha de recurrencia tumoral por cáncer de cabeza y cuello; mostró una sensibilidad alta y una especificidad intermedia-alta

Objectives: A meta-analysis of the literature was performed in this article in order to evaluate the diagnostic accuracy of 18F-FDG PET in suspected recurrent head and neck cancer. Material and methods: A systematic review of the literature was performed using 1987 to 2007 MEDLINE and CANCERLIT databases, applying selection criteria to the studies found. Sensitivity, specificity, positive and negative likelihood ratios, and odds ratio were calculated. The diagnostic accuracy was evaluated with ROC (receive-operating-characteristics) curves. Results: Nineteen articles were included in the meta-analysis. Sensitivity of 18F-FDG PET was 94 %, specificity 80 %, and the summary ROC curve showed a good trade-off between sensitivity and specificity. Conclusions: 18F-FDG PET was useful in patients with suspected recurrence of head and neck cancer, showing a high sensitivity and intermediate-high specificity

Impacto de la tomografía por emisión de positrones en el tratamiento de pacientes con sospecha de enfermedad residual o recurrente de cáncer diferenciado de tiroides / Impact of positron emission tomography on therapeutic decisions in patients with suspected residual or recurrent differentiated thyroid cancer

Objetivo: Valorar las modificaciones en el tratamiento inducidas por la tomografía por emisión de positrones con 18F-desoxiglucosa (PET-FDG) en pacientes con sospecha de enfermedad residual o recurrente de cáncer diferenciado de tiroides (CDT) con tiroglobulina (Tg) elevada y rastreo corporal total (RCT) con 131I negativo. Pacientes y método: Se analizó de forma retrospectiva a un grupo de 50 pacientes (35 mujeres y 15 varones) tratados de CDT, a los que se hizo estudio PET-FDG (51 exploraciones) por elevación de Tg con RCT con 131I negativo. La comprobación de resultados se hizo según la anatomía patológica, respuesta al tratamiento o seguimiento clínico. Valoraron el impacto los médicos, que indicaron cómo influyó esta técnica en las decisiones terapéuticas, y se clasificó como alto, moderado, bajo o sin impacto, según los criterios de Hicks modificados. Resultados: La PET-FDG tuvo alto impacto en 18 (35,3%) pacientes, en los que se modificó la estrategia terapéutica; en 2 (3,9%) el impacto fue moderado, ya que no se aplicó tratamiento pero el resultado negativo de la PET-FDG evitó la realización de otros métodos diagnósticos; en 18 (35,3%), el impacto fue bajo, ya que no modificó el tratamiento; en 13 (25,5%) no tuvo impacto, pues no se tuvo en cuenta a la hora de decidir el tratamiento. Conclusiones: La PET-FDG resulta una técnica diagnóstica útil para la toma de decisiones terapéuticas en pacientes con sospecha de enfermedad residual o recurrente de CDT que presentan Tg elevada y RCT con 131I negativo (AU)

Objective: To assess FDG-PET-induced treatment modifications in patients with suspected recurrent or residual differentiated thyroid cancer (DTC) with elevated thyroglobulin (Tg) and negative 131I whole body scan (WBS). Patients and method: Fifty-one FDG-PET studies due to elevated Tg with negative WBS were retrospectively analyzed in 50 patients treated for DTC (35 women and 15 men). The results were verified by pathological analysis, treatment response or clinical follow-up. The impact of FDG-PET was assessed by asking the physicians to indicate how this technique had affected their therapeutic decisions and the influence was classified as high, moderate, low or nil according to Hicks' modified criteria. Results: The impact of FDG-PET was high in 18 patients (35.3%), in whom the therapeutic strategy was modified. A moderate impact was found in 2 patients (3.9%) since no treatment was applied; however, in these patients, negative FDG-PET results obviated the need for other diagnostic methods. Impact was low in 18 patients (35.3%) as treatment was not modified, and was null in 13 (25.5%) since this technique was not considered when therapeutic decisions were made. Conclusions: FDG-PET is a useful diagnostic technique for therapeutic decision-making in patients with suspected residual or recurrent DTC, elevated Tg and negative 131I-WBS (AU)

[CT-PET: a new light in the diagnostic tunnel]. / PET-TAC: una nueva luz en el túnel del diagnóstico.

Positron Emission Tomography (PET) has got an important role in oncology. Since its introduction in 1995, more than 40 PETs have been installed in Spain. New hybrid CT-PET equipment that have appeared in the last three years have the anatomical and functional information of both techniques. The addition of CT makes it possible to reduce the duration of the PET study, to ameliorate the image quality, to ameliorate its diagnostic performance and to increase its indications. The new equipment being installed are all CT-PET and they will soon be more numerous than the previous PETs.

[The value of 18F-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) in diagnosis of neoplastic diseases]. / Valor de la tomografía por emisión de positrones mediante 18F-fluoro-2-desoxi-D-glucosa (PET-FDG) en el diagnóstico de las neoplasias.

Positron emission tomography (PET) has the ability to detect cancer based on molecular and biochemical processes within the tumor tissues. The most widely used radiotracer in oncology at this time is the glucose analogue 18F-fluoro-2-deoxy-D-glucose (18F-FDG). Like glucose, 18F-FDG is transported into cells by a glucose transporter protein and rapidly converted into 18F-FDG-6-phosphate. PET imaging with 18F-FDG is able to diagnose, stage, and restage many cancers with accuracies ranging from 80% to 90%. Responses to therapy can be identified earlier and with greater accuracy than is possible with anatomic imaging modalities. The prognostic information available through 18F-FDG PET is superior to that of conventional imaging for many cancers. The aim of this review article is to show the most promising clinical indications for the use of PET in oncology.