Prognostic value of genetic alterations and 18F-FDG PET/CT imaging features in diffuse large B cell lymphoma.

The current standard front-line therapy for patients with diffuse large-B cell lymphoma (DLBCL)-rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP)-is found to be ineffective in up to one-third of them. Thus, their early identification is an important step towards testing alternative treatment options. In this retrospective study, we assessed the ability of 18F-FDG PET/CT imaging features (radiomic + PET conventional parameters) plus clinical data, alone or in combination with genomic parameters to predict complete response to first-line treatment. Imaging features were extracted from images prior treatment. Lesions were segmented as a whole to reflect tumor burden. Multivariate logistic regression predictive models for response to first-line treatment trained with clinical and imaging features, or with clinical, imaging, and genomic features were developed. For imaging feature selection, a manual selection approach or a linear discriminant analysis (LDA) for dimensionality reduction were applied. Confusion matrices and performance metrics were obtained to assess model performance. Thirty-three patients (median [range] age, 58 [49-69] years) were included, of whom 23 (69.69%) achieved long-term complete response. Overall, the inclusion of genomic features improved prediction ability. The best performance metrics were obtained with the combined model including genomic data and built applying the LDA method (AUC of 0.904, and 90% of balanced accuracy). The amplification of BCL6 was found to significantly contribute to explain response to first-line treatment in both manual and LDA models. Among imaging features, radiomic features reflecting lesion distribution heterogeneity (GLSZM_GrayLevelVariance, Sphericity and GLCM_Correlation) were predictors of response in manual models. Interestingly, when the dimensionality reduction was applied, the whole set of imaging features-mostly composed of radiomic features-significantly contributed to explain response to front-line therapy. A nomogram predictive for response to first-line treatment was constructed. In summary, a combination of imaging features, clinical variables and genomic data was able to successfully predict complete response to first-line treatment in DLBCL patients, with the amplification of BCL6 as the genetic marker retaining the highest predictive value. Additionally, a panel of imaging features may provide important information when predicting treatment response, with lesion dissemination-related radiomic features deserving especial attention.

Nuclear-medicine probes: Where we are and where we are going.

Nuclear medicine probes turned into the key for the identification and precise location of sentinel lymph nodes and other occult lesions (i.e., tumors) by using the systemic administration of radiotracers. Intraoperative nuclear probes are key in the surgical management of some malignancies as well as in the determination of positive surgical margins, thus reducing the extent and potential surgery morbidity. Depending on their application, nuclear probes are classified into two main categories, namely, counting and imaging. Although counting probes present a simple design, are handheld (to be moved rapidly), and provide only acoustic signals when detecting radiation, imaging probes, also known as cameras, are more hardware-complex and also able to provide images but at the cost of an increased intervention time as displacing the camera has to be done slowly. This review article begins with an introductory section to highlight the relevance of nuclear-based probes and their components as well as the main differences between ionization- (semiconductor) and scintillation-based probes. Then, the most significant performance parameters of the probe are reviewed (i.e., sensitivity, contrast, count rate capabilities, shielding, energy, and spatial resolution), as well as the different types of probes based on the target radiation nature, namely: gamma (γ), beta (ß) (positron and electron), and Cherenkov. Various available intraoperative nuclear probes are finally compared in terms of performance to discuss the state-of-the-art of nuclear medicine probes. The manuscript concludes by discussing the ideal probe design and the aspects to be considered when selecting nuclear-medicine probes.

Pilot performance of a dedicated prostate PET suitable for diagnosis and biopsy guidance.

BACKGROUND: Prostate cancer (PCa) represents one of the most common types of cancers facing the male population. Nowadays, to confirm PCa, systematic or multiparametric MRI-targeted transrectal or transperineal biopsies of the prostate are required. However, due to the lack of an accurate imaging technique capable to precisely locate cancerous cells in the prostate, ultrasound biopsies sample random parts of the prostate and, therefore, it is possible to miss regions where those cancerous cells are present. In spite of the improvement with multiparametric MRI, the low reproducibility of its reading undermines the specificity of the method. Recent development of prostate-specific radiotracers has grown the interest on using positron emission tomography (PET) scanners for this purpose, but technological improvements are still required (current scanners have resolutions in the range of 4-5 mm). RESULTS: The main goal of this work is to improve state-of-the-art PCa imaging and diagnosis. We have focused our efforts on the design of a novel prostate-dedicated PET scanner, named ProsPET. This system has small scanner dimensions defined by a ring of just 41 cm inner diameter. In this work, we report the design, implementation, and evaluation (both through simulations and real data) of the ProsPET scanner. We have been able to achieve < 2 mm resolution in reconstructed images and high sensitivity. In addition, we have included a comparison with the Philips Gemini-TF scanner, which is used for routine imaging of PCa patients. The ProsPET exhibits better contrast, especially for rod sizes as small as 4.5 mm in diameter. Finally, we also show the first reconstructed image of a PCa patient acquired with the ProsPET. CONCLUSIONS: We have designed and built a prostate specific PET system, with a small footprint and improved spatial resolution when compared to conventional whole-body PET scanners. The gamma ray impact within each detector block includes accurate DOI determination, correcting for the parallax error. The potential role of combined organ-dedicated prostate-specific membrane antigen (PSMA) PET and ultrasound devices, as a prebiopsy diagnostic tool, could be used to guide sampling of the most aggressive sites in the prostate.

FDG-PET/CT Focal Uptake on an Ocular Prosthesis.

We present a case of an unexpected focally increased radiotracer uptake in an artificial eye in an FDG-PET/CT scan that was performed on a woman with a history of choroidal melanoma. It is crucial to know the type of prosthesis used and the timing of replacement for a correct interpretation of the findings. Recently, an FDG PET/CT was proposed to monitor the vascularity of the prosthesis instead of gadolinium MRI or of Tc bone scintigraphy.

La minigammacámara intraoperatoria en la cirugía del hiperparatiroidismo primario / The intraoperative mini gamma camera in primary hyperparathyroidism surgery

Introducción y objetivos: La evolución del tratamiento quirúrgico del hiperparatiroidismo primario se ha visto favorecido por la aparición de nuevas técnicas que permiten una mejor localización de las glándulas paratiroides. Recientemente se ha desarrollado una minigammacámara portátil (MGP), que permite realizar gammagrafías paratiroideas intraoperatorias. El objetivo del estudio ha sido valorar la utilidad de esta técnica. Métodos: Estudiamos prospectivamente 29 pacientes con hiperparatiroidismo primario y evaluamos la validez diagnóstica de la MGP comparando los resultados obtenidos con las técnicas preoperatorias (ecografía+gammagrafía Tc99m-sestamibi). Resultados: La sensibilidad y especificidad de la minigammacámara es superior a las técnicas preoperatorias, tanto por lado como por cuadrante del cuello (por lado: sensibilidad del 89,6% y especificidad del 96,15% frente a un 79,31 y 92,59% respectivamente, y por cuadrante: sensibilidad y especificidad del 83,33 y 90,91% versus 48,39 y 72,73%). Conclusiones: La MGP localiza de forma precisa las glándulas paratiroides patológicas, por lo que podría resultar útil al plantear una cirugía radioguiada mínimamente invasiva paratiroidea(AU)

Introduction and objectives: The evolution of primary hyperparathyroidism surgical treatment has been improved by the arrival of new techniques that allow for better parathyroid gland tracking. A mini gamma camera has recently been developed that makes it possible to take intraoperative parathyroid gammagraphies. The objective of this study was to evaluate the utility of this technique. Method: We prospectively studied 29 patients with primary hyperparathyroidism, comparing the diagnostic effectiveness of the MGP with the results obtained with preoperative techniques (ultrasound scan plus Tc99m-sestamibi gammagraphy). Results: The sensitivity and specificity of the mini gamma camera was superior to those of the preoperative techniques, applied to the lateral neck as well as to the face of the neck (lateral: 89.6% sensitivity and 96.15% specificity compared to 79.31% and 92.59% respectively; and neck face: sensitivity and specificity 83.33% and 90.91% against 48.39% and 72.73%). Conclusions: The portable mini gamma camera accurately tracks pathologic parathyroid glands. In that sense, it could be useful when considering a radio-guided surgery with minimal parathyroid invasion(AU)

The intraoperative mini gamma camera in primary hyperparathyroidism surgery.

INTRODUCTION AND OBJECTIVES: The evolution of primary hyperparathyroidism surgical treatment has been improved by the arrival of new techniques that allow for better parathyroid gland tracking. A mini gamma camera has recently been developed that makes it possible to take intraoperative parathyroid gammagraphies. The objective of this study was to evaluate the utility of this technique. METHOD: We prospectively studied 29 patients with primary hyperparathyroidism, comparing the diagnostic effectiveness of the MGP with the results obtained with preoperative techniques (ultrasound scan plus Tc(99m)-sestamibi gammagraphy). RESULTS: The sensitivity and specificity of the mini gamma camera was superior to those of the preoperative techniques, applied to the lateral neck as well as to the face of the neck (lateral: 89.6% sensitivity and 96.15% specificity compared to 79.31% and 92.59% respectively; and neck face: sensitivity and specificity 83.33% and 90.91% against 48.39% and 72.73%). CONCLUSIONS: The portable mini gamma camera accurately tracks pathologic parathyroid glands. In that sense, it could be useful when considering a radio-guided surgery with minimal parathyroid invasion.

A voxel-based analysis of FDG-PET in traumatic brain injury: regional metabolism and relationship between the thalamus and cortical areas.

The objective was to study the correlations and the differences in glucose metabolism between the thalamus and cortical structures in a sample of severe traumatic brain injury (TBI) patients with different neurological outcomes. We studied 49 patients who had suffered a severe TBI and 10 healthy control subjects using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET). The patients were divided into three groups: a vegetative or minimally-conscious state (MCS&VS) group (n=17), which included patients who were in a vegetative or a minimally conscious state; an In-post-traumatic amnesia (In-PTA) group (n=12), which included patients in PTA; and an Out-PTA group (n=20), which included patients who had recovered from PTA. SPM5 software was used to determine the metabolic differences between the groups. FDG-PET images were normalized and four regions of interest were generated around the thalamus, precuneus, and the frontal and temporal lobes. The groups were parameterized using Student's t-test. Principal component analysis was used to obtain an intensity-estimated-value per subject to correlate the function between the structures. Differences in glucose metabolism in all structures were related to the neurological outcome, and the most severe patients showed the most severe hypometabolism. We also found a significant correlation between the cortico-thalamo-cortical metabolism in all groups. Voxel-based analysis suggests a functional correlation between these four areas, and decreased metabolism was associated with less favorable outcomes. Higher levels of activation of the cortico-cortical connections appear to be related to better neurological condition. Differences in the thalamo-cortical correlations between patients and controls may be related to traumatic dysfunction due to focal or diffuse lesions.

Multimodality imaging techniques.

In multimodality imaging, the need to combine morphofunctional information can be approached by either acquiring images at different times (asynchronous), and fused them through digital image manipulation techniques or simultaneously acquiring images (synchronous) and merging them automatically. The asynchronous post-processing solution presents various constraints, mainly conditioned by the different positioning of the patient in the two scans acquired at different times in separated machines. The best solution to achieve consistency in time and space is obtained by the synchronous image acquisition. There are many multimodal technologies in molecular imaging. In this review we will focus on those multimodality image techniques more commonly used in the field of diagnostic imaging (SPECT-CT, PET-CT) and new developments (as PET-MR). The technological innovations and development of new tracers and smart probes are the main key points that will condition multimodality image and diagnostic imaging professionals' future. Although SPECT-CT and PET-CT are standard in most clinical scenarios, MR imaging has some advantages, providing excellent soft-tissue contrast and multidimensional functional, structural and morphological information. The next frontier is to develop efficient detectors and electronics systems capable of detecting two modality signals at the same time. Not only PET-MR but also MR-US or optic-PET will be introduced in clinical scenarios. Even more, MR diffusion-weighted, pharmacokinetic imaging, spectroscopy or functional BOLD imaging will merge with PET tracers to further increase molecular imaging as a relevant medical discipline. Multimodality imaging techniques will play a leading role in relevant clinical applications. The development of new diagnostic imaging research areas, mainly in the field of oncology, cardiology and neuropsychiatry, will impact the way medicine is performed today. Both clinical and experimental multimodality studies, in humans and animals, will have to demonstrate an efficient use of the imaging information provided by the modalities to affect the future of medical imaging.

Voxel-based statistical analysis of thalamic glucose metabolism in traumatic brain injury: relationship with consciousness and cognition.

OBJECTIVE: To study the relationship between thalamic glucose metabolism and neurological outcome after severe traumatic brain injury (TBI). METHODS: Forty-nine patients with severe and closed TBI and 10 healthy control subjects with (18)F-FDG PET were studied. Patients were divided into three groups: MCS&VS group (n = 17), patients in a vegetative or a minimally conscious state; In-PTA group (n = 12), patients in a state of post-traumatic amnesia (PTA); and Out-PTA group (n = 20), patients who had emerged from PTA. SPM5 software implemented in MATLAB 7 was used to determine the quantitative differences between patients and controls. FDG-PET images were spatially normalized and an automated thalamic ROI mask was generated. Group differences were analysed with two sample voxel-wise t-tests. RESULTS: Thalamic hypometabolism was the most prominent in patients with low consciousness (MCS&VS group) and the thalamic hypometabolism in the In-PTA group was more prominent than that in the Out-PTA group. Healthy control subjects showed the greatest thalamic metabolism. These differences in metabolism were more pronounced in the internal regions of the thalamus. CONCLUSIONS: The results confirm the vulnerability of the thalamus to suffer the effect of the dynamic forces generated during a TBI. Patients with thalamic hypometabolism could represent a sub-set of subjects that are highly vulnerable to neurological disability after TBI.