荧光素酶标的人肝癌细胞裸鼠异种移植瘤模型的生物发光成像和PET-CT成像比较

目的利用荧光素酶基因标记的人肝癌细胞株BEL-7402建立裸鼠肝原位移植模型,及小鼠肝原位移植模型的生物发光和小动物PET-CT成像的比较。方法构建表达荧光素酶基因的真核表达载体并将其转入人肝癌细胞BEL-7402,经梯度浓度G418筛选获得稳定表达荧光素酶基因的细胞克隆并扩大培养。BALB/cA-nu裸鼠肝门静脉接种5×105个发光细胞使其成瘤,活体荧光成像和小动物PET-CT成像系统观察肿瘤的生长情况。结果获得了稳定表达Luc的人肝癌细胞株,将其接种到裸鼠体内,活体荧光成像系统观察发现能够成瘤,小动物PET-CT影像观察发现小鼠肝脏边缘对18 F-FDG有高摄取区域。结论利用荧光素酶基因标记的人肝癌细胞BEL-7402成功建立了原位肝癌裸鼠模型,小动物活体成像结合小动物PET-CT技术为原位肿瘤模型的建立提供了一种新的可靠的技术,为进一步研究肝癌生长转移机制和药物开发提供了新的有用工具。     

A case of heterotopic pancreas mimicking an intestinal neuroendocrine tumor in 18F-DOPA PET-CT and a review of the literature

18-Fluoro-L-dihydroxyphenylalanine positron emission tomography/computed tomography (18F-DOPA PET-CT) is a nuclear medicine imaging modality indicated for the diagnosis and staging of neuroendocrine tumors (NETs), particularly for the midgut tumors, due to its excellent sensitivity and specificity. Its performance for the detection of foregut-derived NETs (duodenopancreas and proximal jejunum) and for the detection of hindgut-derived NETs is poor and inferior to PET somatostatin receptor imaging such as DOTATOC PET-CT and even inferior to somatostatin analog scintigraphy (octreoscan). There are few studies in the literature on heterotopic pancreas (HP) which is a rare entity, and which can be in some cases a false positive in 18F-DOPA PET-CT. We report a case of HP showing focal uptake on 18F-DOPA PET-CT mimicking an intestinal NET. This case suggests that HP should be included as a possible false positive on 18F-DOPA PET-CT.     

A Monte Carlo investigation of the spatial resolution performance of a small-animal PET scanner designed for mouse brain imaging studies

Our laboratory has developed PET detectors with depth-encoding accuracy of ∼2 mm based on finely pixelated crystals with a tapered geometry, readout at both ends with position-sensitive avalanche photodiodes (PSAPDs). These detectors are currently being used in our laboratory to build a one-ring high resolution PET scanner for mouse brain imaging studies. Due to the inactive areas around the PSAPDs, large gaps exist between the detector modules which can degrade the image spatial resolution obtained using analytical reconstruction with filtered backprojection (FBP). In this work, the Geant4-based GATE Monte Carlo package was used to assist in determining whether gantry rotation was necessary and to assess the expected spatial resolution of the system. The following factors were investigated: rotating vs. static gantry modes with and without compensation of missing data using the discrete cosine transform (DCT) method, two levels of depth-encoding, and positron annihilation effects for ¹⁸F. Our results indicate that while the static scanner produces poor quality FBP images with streak and ring artifacts, the image quality was greatly improved after compensation of missing data. The simulation indicates that the expected FWHM system spatial resolution is 0.70 ± 0.05 mm, which approaches the predicted limit of 0.5 mm FWHM due to positron range, photon non-colinearity and physical detector element size effects. We conclude that excellent reconstructed resolution without gantry rotation is possible even using FBP if the gaps are appropriately handled and that this design can approach the resolution limits set by positron annihilation physics.     

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.     

Hyperfixations costales bifocales découvertes à la TEP au fluorure (18F) de sodium lors de la stadification d’un cancer de la prostate

A prostate biopsy screening (PSA = 2 ng/mL) evidenced a prostate adenocarcinoma featuring a Gleason score of 8 (4 + 4) in a 62-year-old patient incurring an increased familial risk of prostate cancer. In order to stage the prostate adenocarcinoma, 2 PET scans were ordered. A PET/CT examination with FNa disclosed two hot spots on distinct ribs matching with heterogeneous sclerotic areas on low dose CT. A PET/CT examination with FDG disclosed a hypermetabolic focus of prostate left lobe and a weak intensity hypermetabolic focus of left ilio-obturator node but no bone metabolic abnormality. Staging was categorized distant (bone) metastatic disease upon FNa PET/CT findings. The patient benefited from pelvic external beam radiation therapy and hormone therapy. One year later, a PET/CT examination with FCH while patient was still on hormone therapy depicted a photopaenic area of prostate left lobe and a questionable hypermetabolic focus of right lobe but no bone metabolic abnormality. Retrospectively, bone lesions visible on PET with FNa were already conspicuous on plain X-rays and a CT examination performed a decade before. A new advice in a center specialized in bone and joint imaging suggested a benign condition for these protracted rib lesions even if the exact benign condition was elusive (fibrous dysplasia, aneurysmal bone cyst…). Two years later, the patient is symptom-free and his PSA level is 0.03 ng/mL.     

FDG-PET-CT in pyrexia of unknown origin and inflammatory diseases

FDG-PET has been used successfully over the last decade for imaging patients with fever of unknown origin. Nowadays, PET-CT has become the standard in many centres although a limited number of prospective studies is available. This article summarizes the experience in the field and the potential use of FDG-PET in other inflammatory or immune diseases, such as sarcoidosis or rheumatoid arthritis.     

荧光素酶标记人胃癌细胞裸鼠原位移植模型的建立

目的建立荧光素酶标记人胃癌原位异种移植模型。方法将萤火虫荧光素酶作为标记基因导入人胃癌MGC803细胞,建立稳定表达荧光素酶的细胞,将其接种裸鼠胃壁浆膜下,建立胃癌裸鼠原位肿瘤模型。用活体荧光成像系统检测肿瘤的发生发展,并进行小动物超声影像和病理学分析。结果裸鼠原位成瘤率为100%,活体荧光成像观察发现在接种第7天,就可以观察到肿瘤发光。21 d后肿瘤进入对数生长期,28 d后肿瘤出现明显坏死,平均荧光光子数呈现下降趋势。超声成像发现小鼠胃部有直径为8.39 mm,面积为28.92 mm2瘤块。结论荧光素酶标记可以实时监测原位异种移植人胃癌生长状况。     

Intérêt pronostique et prédictif de la TEP-TDM au 18F-FDG chez les patients atteints de léiomyosarcomes de stades avancés

PurposeAssessment of early therapeutic response is essential to guide therapeutic management in patients with advanced leiomyosarcoma (LMS). We compared the predictive values of various 18F-FDG PET-CT-derived metabolic parameters, SUVmax, SUVpeak, metabolic tumor volume (MTV) and total lesion glycolysis (TLG).MethodsA total of 64 patients with LMS who underwent FDG PET/CT before and 6 weeks after the initiation of treatment were retrospectively analyzed. We determined SUVmax, SUVpeak, MTV, and TLG by segmentation to compare their predictive value for 9-month progression-free survival and overall survival. These parameters were dichotomized using the optimal threshold according to the area under the ROC (Receiver Operation Characteristic) curve and evaluated using a Cox model. Overall and progression-free survival analyses were performed using the Kaplan Meier model.ResultsSUVmax showed greater accuracy than TLG or MTV in ROC analysis (area under the curve, AUC, 0.680, 0.677, and 0.675, respectively). The cutoff values derived from the AUC data were SUVmax 4.7, TLG 37.46, and MTV 25 cm³. After dichotomization by threshold values, MTV was the most significant predictor compared with SUVmax and TLG (P = 0.000165, P = 0.007, and P = 0.001, respectively). In early therapeutic evaluation at 6 weeks, delta SUVpeak and PERCIST metabolic response were significantly correlated with progression-free survival (P = 0.008 and 0.035, respectively).ConclusionBaseline SUVmax, MTV and TGL were predictive of overall survival, delta SUVpeak and PERCIST response obtained by functional imaging in early therapeutic evaluation were significantly correlated with progression-free survival in advanced leiomyosarcoma patients.     

188Re image performance assessment using small animal multi-pinhole SPECT/PET/CT system

PurposeThe goal of this study was to investigate the performance of a pre-clinical SPECT/PET/CT system for ¹⁸⁸Re imaging.MethodsPhantom experiments were performed aiming to assess the characteristics of two multi-pinhole collimators: ultra-high resolution collimator (UHRC) and high-energy ultra high resolution collimator (HE-URHC) for imaging ¹⁸⁸Re. The spatial resolution, image contrast and contrast-to-noise ratio (CNR) were investigated using micro-Jaszczak phantoms. Additionally, the quantification accuracy of ¹⁸⁸Re images was evaluated using two custom-designed phantoms. The ¹⁸⁸Re images were compared to those obtained with ^99mTc (gold standard); the acquired energy spectra were analyzed and Monte-Carlo simulations of the UHRC were performed. To verify our findings, a C57BL/6-mouse was injected with ¹⁸⁸Re-microspheres and scanned with both collimators.ResultsThe spatial resolution achieved in ¹⁸⁸Re images was comparable to that of ^99mTc. Acquisitions using HE-UHRC yielded ¹⁸⁸Re images with higher contrast and CNR than UHRC. Studies of quantitative accuracy of ¹⁸⁸Re images resulted in <10% errors for both collimators when the activity was calculated within a small VOI around the object of interest. Similar quantification accuracy was achieved for ^99mTc. However, ¹⁸⁸Re images showed much higher levels of noise in the background. Monte-Carlo simulations showed that ¹⁸⁸Re imaging with UHRC is severely affected by down-scattered photons from high-energy emissions. The mouse images showed similar biodistribution of ¹⁸⁸Re-microspheres for both collimators.ConclusionsVECTor/CT provided ¹⁸⁸Re images quantitatively accurate and with quality comparable to ^99mTc. However, due to large penetration of UHRC by high-energy photons, the use of the HE-UHRC for imaging ¹⁸⁸Re in VECTor/CT is recommended.     

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.