Infection de prothèse vasculaire : TEP-FDG vs scintigraphie aux leucocytes marqués (planaires et TEMP/TDM)

Vascular prosthesis infection is an uncommon but life-threatening complication. Its diagnosis is difficult to establish especially due to the low specificity of computed tomography (CT). The aim of this preliminary study was to compare the diagnostic value of positron emission tomography with¹⁸FDG (¹⁸FDG-PET) and ^99mTc-HMPAO-labeled leukocytes scintigraphy in this indication. ¹⁸FDG-PET/CT and ^99mTc-HMPAO-labeled leukocytes scintigraphy (planar at 6th and 24th hours after injection + SPECT/CT at the 6th hour) were prospectively performed in 11 patients (total of 22 vascular prosthesis with 14 clinical suspicions of infection). Both scans were retrospectively and blindly assessed by two independent nuclear medicine physicians. Interpretation was based on visual analysis. The gold standard was bacteriology findings or clinical follow-up greater than 6 months. Eight prostheses were considered as infected. PET found eight true-positive and one false-positive. Scintigraphy found eight true-positive and no false-positive. A focal or heterogeneous FDG-uptake higher or equal than hepatic uptake was considered as positive in PET. A focal prosthetic activity, stable or increased at the 24th hour was considered as positive in labeled leukocyte scintigraphy. SPECT/CT gave accurate anatomic localization and differentiated clearly infections of soft tissues from those of prostheses. ¹⁸FDG-PET could be performed in first-line in suspicion of vascular prosthesis infection. In litigious cases, a^99mTc-HMPAO-labeled leukocytes scintigraphy in association with SPECT/CT could bring additional arguments for infection diagnosis.     

Recommendations of the Spanish Societies of Radiation Oncology (SEOR), Nuclear Medicine & Molecular Imaging (SEMNiM), and Medical Physics (SEFM) on 18F-FDG PET-CT for radiotherapy treatment planning

Positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) is a valuable tool for diagnosing and staging malignant lesions. The fusion of PET and computed tomography (CT) yields images that contain both metabolic and morphological information, which, taken together, have improved the diagnostic precision of PET in oncology. The main imaging modality for planning radiotherapy treatment is CT. However, PET-CT is an emerging modality for use in planning treatments because it allows for more accurate treatment volume definition. The use of PET-CT for treatment planning is highly complex, and protocols and standards for its use are still being developed. It seems probable that PET-CT will eventually replace current CT-based planning methods, but this will require a full understanding of the relevant technical aspects of PET-CT planning. The aim of the present document is to review these technical aspects and to provide recommendations for clinical use of this imaging modality in the radiotherapy planning process.     

Syndromes paranéoplasiques : intérêt de la tomographie par émission de positons (TEP) au 18F-fluoro-déoxyglucose (FDG)

BackgroundWe evaluated the performance of ¹⁸F-fluorodeoxyglucose (¹⁸FDG) positon emission tomography (PET) in the diagnosis of underlying malignancy in cases of suspected paraneoplastic syndrome (PS).Methods¹⁸FDG-PET was performed in 31 patients, clinically suspected to have PS. The PS were 34, among which 12 neurological diseases, eight endocrine, seven rheumatological, one dermatological and six vascular. We compared computed tomography (CT), iodine-enhanced most of the time, and ¹⁸FDG-PET reports to clinicians definitive conclusion at the end of the work-up and a follow-up period of, at least, two months.ResultsWe obtained a histological diagnosis of cancer for ten patients, but could only identify the primary site of malignancy for nine of them. ¹⁸FDG-PET showed six primary sites among which three were not seen on CT. CT disclosed four primary sites, among which one was not seen on ¹⁸FDG-PET. In one case, ¹⁸FDG-PET disclosed regional lymph node metastases whereas these were not identified by CT. Eleven non-neoplasic causes were evidenced, among which ¹⁸FDG-PET played a major role in three cases. Ten causes were still undetermined at the end of the study.ConclusionWhole-body ¹⁸FDG-PET study plays an important role in the identification of underlying malignancy in clinically suspected paraneoplastic syndromes; either by identifying the primary tumor or by directing biopsy of metastases. Furthermore, it can identify non-neoplasic causes.     

Clinical value of (18)F-FDG PET/CT in postoperative monitoring for patients with colorectal carcinoma

Objective: To evaluate the clinical value of ¹⁸F-FDG PET/CT in postoperative monitoring for patients with colorectal carcinoma. Methods: 66 postoperative patients with colorectal carcinoma underwent whole-body FDG PET/CT. The final histopathological and formal clinical follow-up findings were used as gold standard to determine the sensitivity and specificity of FDG PET/CT and enhanced CT of the same periods. Results: The sensitivity and specificity of FDG PET/CT in detecting recurrence are 96.30%, 94.87% (while enhanced CT are 70.37% and 87.18% respectively). The sensitivity and specificity in detecting metastasis are 95.35%, 82.61% (enhanced CT are 61.90%, 75.00%). SUVmax was significantly higher in malignant lesions [range 4.16–22.00, mean ± standard deviation (x ± s) 8.06 ± 4.30] than in benign ones (range1.18–6.25, x ± s 2.82 ± 1.02). Conclusion: At present, whole-body ¹⁸F-FDG PET/CT is an advanced diagnostic imaging technique in detecting loco-regional recurrence and metastasis in postoperative patients with colorectal carcinoma for its higher sensitivity and specificity.     

Apport du TDM en imagerie multimodalité : le point de vue du physicien médical

The recent introduction of hybrid systems SPECT/CT and PET/CT in nuclear medicine, greatly improved the diagnostic accuracy for particular clinical indications, due to the possible attenuation correction of functional images and the availability of helpful anatomic information. The introduction of CT in the nuclear diagnostic process results in a significant increase of the patient dose. This increase should be justified and optimized considering both the clinical question and the CT settings available on these systems. The choice of CT settings directly affects the effective dose. It varies basically as the square of the tube voltage, linearly with the length of the scan and the product of the current by the rotation time of the tube. It is also inversely proportional to the pitch. For attenuation correction, the literature shows that it is possible to use a low CT tube current without significant effect on tumor FDG uptake or lesion size. Conversely low CT voltage must be used with caution, depending on the algorithm implemented in the CT hybrid device to transform CT Hounsfield units to the attenuation map at the appropriate energy. The radiation dose for anatomic correlation can be substantially lower than for diagnostic-quality CT. It is possible to reduce the patient's radiation dose by a factor of 2 or 3 by acquiring a low-dose PET/CT scan for anatomic correlation of adequate image quality if compared with diagnostic ¹⁸FDG PET/CT. Using specific CT settings, the effective dose can range 7.3–11.3 mSv depending on the patient weight and age.     

Comparative Oncology: Evaluation of 2-Deoxy-2-[18F]fluoro-D-glucose (FDG) Positron Emission Tomography/Computed Tomography (PET/CT) for the Staging of Dogs with Malignant Tumors

Introduction

2-Deoxy-2-[18F]fluoro-D-glucose PET/CT is a well-established imaging method for staging, restaging and therapy-control in human medicine. In veterinary medicine, this imaging method could prove to be an attractive and innovative alternative to conventional imaging in order to improve staging and restaging. The aim of this study was both to evaluate the effectiveness of this image-guided method in canine patients with spontaneously occurring cancer as well as to illustrate the dog as a well-suited animal model for comparative oncology.

Methods

Ten dogs with various malignant tumors were included in the study and underwent a whole body FDG PET/CT. One patient has a second PET-CT 5 months after the first study. Patients were diagnosed with histiocytic sarcoma (n = 1), malignant lymphoma (n = 2), mammary carcinoma (n = 4), sertoli cell tumor (n = 1), gastrointestinal stromal tumor (GIST) (n = 1) and lung tumor (n = 1). PET/CT data were analyzed with the help of a 5-point scale in consideration of the patients’ medical histories.

Results

In seven of the ten dogs, the treatment protocol and prognosis were significantly changed due to the results of FDG PET/CT. In the patients with lymphoma (n = 2) tumor extent could be defined on PET/CT because of increased FDG uptake in multiple lymph nodes. This led to the recommendation for a therapeutic polychemotherapy as a treatment. In one of the dogs with mammary carcinoma (n = 4) and in the patient with the lung tumor (n = 1), surgery was cancelled due to the discovery of multiple metastasis. Consequently no treatment was recommended.

Conclusion

FDG PET/CT offers additional information in canine patients with malignant disease with a potential improvement of staging and restaging. The encouraging data of this clinical study highlights the possibility to further improve innovative diagnostic and staging methods with regard to comparative oncology. In the future, performing PET/CT not only for staging but also in therapy control could offer a significant improvement in the management of dogs with malignant tumors.     

直径小于1 cm孤立性肺结节的18F-FDG PET/CT诊断研究进展

孤立性肺结节的鉴别诊断一直是胸部影像学的研究热点。早期且准确地鉴别肺内小结节的良恶性,对于患者治疗方案的确定以及随访情况的评估均具有重要的临床意义。~(18)F-FDG PET/CT在鉴别诊断恶性肿瘤方面具有明显优于其他传统检查的高特异性和高敏感性,其公认的恶性肿瘤的诊断阈值是最大化标准摄取值(maximum standard uptake value, SUVmax)为2.5,然而部分临床数据显示一些直径小于1 cm的恶性肺结节的SUVmax数值小于2.5。因此在早期研究中,~(18)F-FDG PET/CT在诊断直径较小的肺结节的其临床价值仍存在争议。为了尽量降低SUVmax的测量误差,提高~(18)F-FDG PET/CT诊断的准确率,衍生出了许多SUVmax辅助诊断方法以及优化的重建算法、放射性显像剂的联合应用等手段。本文将对~(18)F-FDG PET/CT鉴别诊断直径小于1 cm孤立性肺结节的研究进展进行综述。     

早期动态18F-FDG PET/CT成像在实体肿瘤评估中的应用

~(18)F-FDG PET/CT常规代谢成像反应肿瘤的葡萄糖代谢及乏氧情况,而~(18)F-FDG PET/CT早期动态成像能反映PET/CT成像早期肿瘤的灌注情况。由于肿瘤的异质性,在早期动态~(18)F-FDG PET/CT成像,即~(18)F-FDG PET/CT灌注成像中,存在独立于常规60 min~(18)F-FDG PET/CT代谢成像的SUVmax(最大标准摄取值)高摄取区。因此,在临床工作中应用~(18)F-FDG PET/CT早期动态成像,能够进一步对实体肿瘤的活性区域进行评估,能够更好评价患者预后、完善治疗方案。当前~(18)F-FDG早期动态成像已经应用在肝癌、肾癌以及膀胱癌等实体肿瘤诊断中。早期动态~(18)F-FDG PET/CT成像结合常规标准~(18)F-FDG PET/CT代谢成像,对实体肿块进行一站式成像方法,能够更好的对肿瘤进行评估。     

Évaluation de la réponse thérapeutique par tomographie par émission de positons (TEP) au fluoro-désoxyglucose (FDG) en oncologie-hématologie

¹⁸Fluoro-deoxyglucose (FDG) positron emission tomography (PET) is an imaging technique which studies the cellular glucidic metabolism. It is particularly indicated in oncology, especially for cancer diagnosis (with a potential prognosis interest) or detection of recurrence. Because of its functional approach to the tissues, its use has logically evolved into the evaluation of cancer treatments, both for the individual care of patients for clinical trials of new therapies. Also, it tends to displace conventional imaging in this indication, whose main limitation is not to assess the viability of residual masses, potentially necrotic or fibrous after treatment. However, the use of FDG-PET requires a rigorous methodology for both the exams achievement but also for the quality of their interpretation, including the choice of the comparison tool. Based on an increasing literature on the subject, were published and updated interpretation criteria for both lymphoma and solid cancers. For lymphoma, standardized assessment criteria were proposed in 2007 during an International Harmonize Project (IHP). For solid cancers, Positron Emission tomography Response Criteria In Solid Tumors (PERCIST) recommendations version 1.0 were recently proposed by an American workshop in 2009 in order to clarify and standardize practices.     

Corrélations des profils TEP au 18F-FDG,IRM et clinico-biologiques des encéphalites dysimmunitaires

IntroductionDysimmune encephalitis (DE) are rare and serious diseases. Their diagnosis is based on a set of arguments, in absence of gold standard. The discovery of anti-neuronal antibodies, although specific, is inconstant. FDG PET has a high sensitivity in this indication. Accordingly, its place is increasing in the diagnosis and monitoring of DE. We looked for associations between different patterns found in ¹⁸FDG PET in ED, and different data from the medical file, including biology, MRI, and EEG.Material and methodsWe collected retrospectively the medical records data of 30 patients of the Marseille La Timone hospital, having had a diagnosis of DE, and benefited from both a ¹⁸FDG cerebral PET/CT and a lumbar puncture in a time lapse of maximum of 15 days, from January 2010 to September 2015.ResultsThe statistical analysis showed significant associations between brain hypermetabolism and intrathecal synthesis. The second interesting finding concerned brain hypometabolism, which was significantly associated with more serious conditions, both paraclinically, with MRI more often pathological, and antibodies identified in CSF more frequently, and clinically. It also proved that the patterns of cerebral ¹⁸FDG PET, although pathological, most often varied widely, and no specific pattern was found.DiscussionFuture research will determine if there are associations between cerebral ¹⁸FDG PET findings, and prognostic factors, particularly in terms of therapeutic response in the DE.     

Role and Cost Effectiveness of PET/CT in Management of Patients with Cancer

PET/CT is a relatively new imaging technology, whose undoubted advantages are valuable in clinical oncology as well as in all fields of diagnosis, staging, and treatment. The hardware combination of anatomy and function has been the true evolution in imaging. PET using 18F-fluorodeoxyglucose (FDG) is increasingly used for the staging of solid malignancies, including colon, lung, etc., but anatomic information is limited. Integrated PET/CT enables optimal anatomic delineation of PET findings and identification of FDG-negative lesions on computed tomography (CT) images and might improve preoperative staging. However, controversy still exists in relation to the application of PET/CT in clinical practice, mainly because of its high cost. It is evident that apart from additional costs, potential savings also are associated with PET/CT as a result of avoiding additional imaging examinations or invasive procedures and by helping clinicians make the optimum treatment decisions. The authors review the literature on the role of PET/CT in management of various tumors and discuss the medicoeconomic usefulness.     

Metformin May Be Associated with False-Negative Cancer Detection in the Gastrointestinal Tract on Pet/Ct

ObjectiveConcurrent therapy with the antihyperglycemic drug metformin can hinder the detection of malignancy in the abdominal and pelvic portions of ¹⁸F-fluordeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging performed for the diagnosis or staging of malignancy, as well as for treatment response and radiation therapy planning. This is due to the metformin-induced increase in intestinal FDG radiotracer uptake. We aim to bring this potentially important interaction to the attention of clinicians who care for cancer patients with diabetes.MethodsWe searched MEDLINE (from 1970 to January 2014)and Google Scholar for relevant English-language articles using the following search terms: “metformin and FDG/PET, metformin and bowel uptake, metformin, and cancer, metformin and the intestine, metformin pharmacokinetics, hyperglycemia and FDG/PET.” We reviewed the reference lists of pertinent articles with respect to metformin gut physiology, impact on FDG uptake and the effect on diagnostic accuracy of abdominal-pelvic PET/CT scans with concurrent metformin therapy.ResultsWe reviewed the action of metformin in the intestine, with particular emphasis on the role of metformin in PET/CT imaging and include a discussion of clinical studies on the topic to help refine knowledge and inform practice. Finally, we discuss aspects pertinent to the management of type 2 diabetes (T2D) patients on metformin undergoing PET/CT.ConclusionsMetformin leads to intense, diffusely increased FDG uptake in the colon, and to a lesser degree, the small intestine, which limits the diagnostic capabilities of FDG PET/CT scanning and may mask gastrointestinal malignancies. We suggest that metformin be discontinued 48 hours before FDG PET/CT scanning is performed in oncology patients. More rigorous data are needed to support the widespread generalizability of this recommendation. (Endocr Pract. 2014;20:1079-1083)     

<Superscript>18</Superscript>F-labeled tyrosine derivatives: Synthesis and experimental studies on accumulation in tumors and abscesses

Tyrosine derivatives labeled with a short-lived fluorine-18 isotope (T _1/2 110 min), namely 2-[¹⁸F]fluoro-L-tyrosine (FTYR) and O-(2′-[¹⁸F]fluoroethyl)-L-tyrosine (FET), promising radiopharmaceuticals (RPs) for positron emission tomography (PET), were obtained by asymmetric syntheses. Accumulation of FTYR and FET in the rat tumor “Glioma 35 rats tumor” and in abscesses induced in Wistar rats muscles was studied and compared with that of a well-known glycolysis radiotracer 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG). It was shown that the relative accumulation indices of amino acid RPs were considerably lower than those of FDG. At the same time, tumor/muscle ratios were high enough (2.9 for FET and 3.9 for FTYR 120 min after injection) for reliable tumor visualization. The data obtained indicated a possibility in principle to use FTYR and FET for differentiated PET diagnostics of brain tumors and inflammation lesions. Of the tyrosine derivatives studied, FET seems to be the most promising agent due to a simple and easily automated method of preparation based on direct nucleophilic substitution of the leaving tosyloxy group of an enantiomerically pure Ni-(S)-BPS-(S)-Tyr(CH₂CH₂OTs) precursor by an activated [¹⁸F]fluoride.     

Thromboses néoplasiques et thromboses cruoriques mécaniques compliquant un cancer du testicule gauche en TEP/TDM au 18FDG

We report the case of a 46-year-old patient with pulmonary embolism complicating thrombosis of the left renal vein and inferior vena cava, which came from a malignant tumor of the left testicle. The case has been elucidated by positron emission tomography with ¹⁸FDG coupled to the CT-scan (PET/CT), performed as part of the etiological assessment of this pulmonary embolism, and anatomical and physiological considerations. The examination revealed ¹⁸FDG uptake in thrombus of the left kidney vein and the inferior vena cava. In view of the anatomy of the left spermatic vein, this finding led to the left testicle, which shows no nuclide uptake but was bathed in a large hydrocele visible on CT images. If several cases of pulmonary embolism or thrombosis of the inferior vena cava revealing a testicular cancer have been described in the literature, there has been no report including ¹⁸FDG PET/CT to the best of our knowledge. This case illustrates the imaging differences between bland and malignant thrombus as a consequence of their pathophysiology. It highlights the contribution of CT images from the PET/CT for the diagnosis.     

No diagnostic impact of routinely use of respiratory gating to characterize lung nodules with 18F-FDG PET/CT

Purpose

To evaluate diagnostic impact of routinely use of respiratory gated (RG) ¹⁸FDG PET/CT to distinguish benign and malignant lung nodules.

TEP-TDM au FNa et IRM avec séquences de diffusion dans la détection des métastases osseuses : étude comparative prospective par lésion

IntroductionThe development of technologies aimed to detect bone metastases in nuclear medicine and radiology prompts us to compare their performance in their most effective form: positron emission tomography (PET) with NaF combined with computed tomography (CT) and magnetic resonance imaging (MRI) using anatomical and diffusion weighted sequences (T1-STIR, and DWI MRI), as well as to study several factors involved in the visualization of these lesions (anatomo-functional correlation, nature, size and localization).Materials and methodsThirteen patients underwent NaF PET-CT and T1-STIR-DWI MRI in a prospective study. One hundred and sixty-four lesions were found. For each, a malignancy score of 1 to 5 was assigned. Expert consensus and follow-up data for each patient, available in their medical records, determined the final diagnosis as gold standard.ResultsThe sensitivities, specificities, precision and AUC of the lesion-based analysis were respectively 78.3%, 93.8%, 89.3% and 0.85 for NaF PET-CT and 60.9%, 97.4%, 86.7% and 0.81 for T1-STIR-DWI MRI. Results were independent on the nature, size or location of the metastases. A significant change in AUC when CT was combined with PET, and when DWI was combined with T1-STIR was found for one of the two observers in both fields.ConclusionThe performance of PET-CT at NaF and T1-STIR-DWI MRI appeared equivalent. The combination of functional and morphological images is beneficial in both fields (nuclear and magnetic resonance) but its contribution varies depending on the observer.     

TEP-FDG et pathologies infectieuses

Interests of ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET/CT) have been demonstrated since many years. FDG physiopathology explains its use for infectious diseases, especially in infective endocarditis, cardiac electronic device infection, and in vascular graft infection, as well as in fever of unknown origin. FDG PET is very interesting to make the diagnostic and for the extension of these infectious diseases, thanks to the whole body acquisition. This synthesis article identifies and illustrates principal indications in this field of this imagery modality.     

La TEP/TDM au FDG a-t-elle un impact dans la prise en charge des patients atteints d’un cancer du canal anal ?

PurposeTo evaluate the impact of FDG PET/CT on the management of patients referred for the staging and/or the follow-up of anal carcinoma, and PET/CT on patient management.Patients and methodsWe included patients referred to our department for anal carcinoma whose therapeutic management was evaluable thanks to follow-up data during at least 6 months.ResultsData of 44 patients were analysed: 22 had PET/CT for initial staging and 36 during follow-up. PET/CT had impact in nine patients out of 44 (20%) and it was relevant in eight of them.ConclusionFDG PET/CT is an accurate imaging modality in anal cancer, its impact on patient management is more obvious when persistence or recurrence of disease is suspected.     

Cancer de la prostate : utilité de la TEP-TDM à la F-fluorocholine

In oncology, positron emission computed tomography (PET/CT) has become an essential tool for initial staging, response evaluation and follow-up of cancer patients. Most of the frequent tumors (lung, breast, esophagus, and lymphomas) are highly avid for ¹⁸F-fluorodeoxyglucose (¹⁸FDG), but prostate cancer has not demonstrated significant uptake of FDG. The development of new tracers labeled with ¹⁸F such as choline analogs allowed already to obtain interesting results particularly in patients with biological relapse and inconclusive conventional imaging work-up. The impact of ¹⁸F-flurocholine PET/CT on patient management needs to be validated in large studies, but many centers use already this examination in order to guide further management, including radiotherapy planning.     

Intérêt de la tomographie par émission de positons (TEP) au 18FDG dans le suivi des patients traités pour carcinome épidermoïde des voies aérodigestives supérieures (VADS) en rémission clinique

IntroductionPosttreatment follow-up of head and neck squamous cell carcinoma (HNSCC) recurrence is a diagnostic challenge. Tissue distortions from radiation and surgery can obscure early detection of recurrence by conventional follow-up approaches such as physical examination (PE), computed tomography, and magnetic resonance imaging. A number of studies have shown that ¹⁸Fluoro-fluorodeoxyglucose (¹⁸FDG) Positron emission tomography (PET) may be an effective technique for the detection of persistent, recurrent, and distant metastatic HNSCC after treatment. The aim of this prospective study was to determine the benefits (sensitivity, specificity, predictive values, and accuracy) of ¹⁸FDG PET using hybrid PET–Computed tomography system (PET/CT) in the detection of HNSCC subclinical locoregional recurrence and distant metastases, in patients 12 months after curative treatment with a negative conventional follow up.Materials and MethodsNinety-one patients cured from head and neck squamous cell carcinoma (HNSCC) without any clinical element for recurrence were included. Whole-body ¹⁸FDG PET/CT examination was performed 11.6 ± 4.4 months after the end of the treatment. The gold standard was histopathology or 6 months imaging follow-up.ResultsThe whole-body ¹⁸FDG PET/CT of the 91 patients in this study consisted of 52 negative and 39 positive results. Nine of these patients who exhibited abnormal ¹⁸FDG uptake in head and neck area did not have subsequently proven recurrent HNSCC (false positive). Thirty had proven recurrence (true positive). All 52 patients with negative readings of ¹⁸FDG PET/CT remained free of disease at 6 months (true negative). The sensitivity and specificity of ¹⁸FDG PET/CT in this study for the diagnosis of HNSCC recurrence were 100% (30/30) and 85% (52/61) respectively. The positive predictive value was 77% (30/39). The negative predictive value was 100% (52/52). The overall accuracy was 90% (82/91).ConclusionThe results of our study confirm the high effectiveness of ¹⁸FDG PET/CT in assessment of HNSCC recurrence. It suggests that this modality is more accurate than conventional follow-up PE alone in the assessment of patient recurrence after previous curative treatment for HNSCC. Therefore, a PET study could be systematically proposed at 12 months after the end of the treatment.