Pheochromocytomas: detection with 11C hydroxyephedrine PET

PURPOSE: To evaluate the accuracy of carbon 11 (11C) hydroxyephedrine (HED) positron emission tomography (PET) in the detection of pheochromocytomas. MATERIALS AND METHODS: Nineteen patients (12 women, seven men; mean age, 53 years) suspected of having pheochromocytoma were evaluated. Patients had enlarged adrenal glands at computed tomography and either increased urinary catecholamine levels (n = 18) or normal biochemistry (n = 1). Dynamic PET examination in the adrenal region was performed after injection of 800 MBq 11C HED. PET data were analyzed visually and semiquantitatively. Time-activity curves were generated for different organs. PET results were validated with histologic evaluation (n = 16) or clinical follow-up (n = 3). The diagnostic value of HED PET was evaluated by calculating the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy. RESULTS: In 12 patients, 13 pheochromocytomas were verified at surgery and histologic evaluation. All but one of the pheochromocytomas were detected with HED PET, which demonstrated elevated uptake. The rest of the patients (n = 7) did not have pheochromocytomas. In these patients, HED PET did not show any abnormal uptake in the suspicious tumors (confirmed at surgery in four patients and at clinical follow-up in three). Mean standardized uptake value of the tumors was 21.4 (range, 11.1-40.9). The time-activity curves for pheochromocytomas showed early uptake after injection, and the activity increased with the time of examination. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of HED PET in the detection of pheochromocytomas were 92% (12 of 13), 100% (seven of seven), 100% (12 of 12), 87.5% (seven of eight), and 95% (19 of 20), respectively. CONCLUSION: HED PET is useful in the detection of pheochromocytomas, providing a high level of accuracy.     

硝酸甘油介入99Tcm-tetrofosmin SPECT与18F-FDG PET显像评估心肌活力比较

目的 比较硝酸甘油介入^99Tc^m-tetrofosmin SPECT心肌血流灌注显像与^18F-FDG PET心肌代谢显像评估心肌活力的价值。方法 既往有心肌梗死史伴左心功能不全经冠状动脉造影确诊为冠心病的患者36例，行二日法静息和硝酸甘油介入^99Tc^m-tetrofosmin SPECT显像，并在1周内再行^18F-FDG PET心肌代谢显像及静息超声心动图检查。将左心室分成13个节段，分析超声心动图室壁运动，并分析相同节段^99Tc^m-tetrofosmin与^18F-FDG的相对摄取比值，以^18Tc^m-tetrofosmin摄取比值55％，^18F—FDG摄取比值50％为判断心肌活力有无的阈值。以k统计比较3种方法的一致性。结果 超声心动图示131个节段呈无运动或反向运动。^99Tc^m-tetrofosmin静息显像示其中78个节段（60％）心肌有活力，53个节段（40％）无活力。该53个节段中14个（26％）在硝酸甘油介入后可见再填充，余39个节段无改变。在^18F—FDGPET显像中，硝酸甘油介入显像再填充节段的心肌放射性摄取明显增高。再填充节段与无填充节段比较，心肌FDG摄取分别为（76±15）％和（58±17）％，差异有统计学意义（P〈0．01）。硝酸甘油介入显像中，92个心肌节段（70％）有活力，39个无活力。tetrofosmin静息显像评估心肌活力与FDG PET显像比较，k值为0．35，而硝酸甘油介入^99Tc^m-tetrofosmin SPECT与^18F—FDGPET显像结果比较，k值为0．53。结论 硝酸甘油介入^99Tc^m-tetrofosmin SPECT显像可提高对心肌活力的检测能力，与^18F—FDG PET心肌代谢显像有很好的一致性。     

Metastatic medullary thyroid cancer: localization with iodine-131 metaiodobenzylguanidine

A patient in whom metastatic medullary thyroid cancer was diagnosed underwent a scintigraphic examination using [131I]MIBG. Multiple hot lesions and diffuse hepatic uptake were noted corresponding to bone and liver metastases. Iodine-131 MIBG may prove to be useful for scintigraphic localization and for the treatment of medullary thyroid cancer as in pheochromocytoma and neuroblastoma.     

FDG PET evaluation of mucinous neoplasms: correlation of FDG uptake with histopathologic features

OBJECTIVE: Our goal was to assess the sensitivity of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) for the detection of mucinous carcinoma and to determine the histologic features of these tumors that may affect lesion detectability. MATERIALS AND METHODS: A retrospective review of all patients with mucinous carcinoma who had undergone FDG PET at our institution from 1995 through 1998 identified 25 patients with new or recurrent mucinous carcinoma at the time of PET. In 22 of these patients, tissue specimens available from either core biopsy or surgical resection allowed detailed histologic analysis. RESULTS: FDG PET revealed mucinous carcinoma in only 13 (59%) of 22 patients, resulting in an unusually high percentage (41%) of false-negative results. Two histologic features were found to be predictive of FDG PET results: tumor cellularity (p = 0.011) and the amount of mucin within the tumor mass (p = 0.009). There was a positive correlation between tumor FDG uptake and cellularity but a negative correlation with the amount of mucin. CONCLUSION: FDG PET is limited in the evaluation of mucinous tumors, particularly in hypocellular lesions with abundant mucin.     

^18F—FDG PET脑显像在癫痫图型，病灶定位及预后预测中的价值

目的 分析各种癫痫患者的^18F－脱氧葡萄糖（FDG）PET图像与致痫灶的关系,以期术前较准确地定位,选择手术适应证和预测疗效。方法 73例癫痫患者（男51例,女22例,平均年龄23．3岁）行FDG PET脑显像,并与同期脑电图和MRI结果进行比较,40例进行了手术疗效随访,其中8例术后复查了FDG PET,并比较FDG PET,视频脑电图（VEEG）,MRI对致痫灶术前定位的准确性及脑代谢改变的不同图型与手术疗效的关系,结果（1）72 例癫痫患者发作间期皮层局灶为低代谢表现,仅1例部分癫痫持续状态者表现出发作期的高代谢。（2）FDG PET病变定侧率高于VEEG,低代谢灶检出率高于MRI,（3）40例手术患者中,属于Engels疗效分级I,II级的30例手术切除部位应为确定的致痫灶,FDG PET＜VEEG与MRI定侧定位准确性分别为93．3％,73．3％,53．3％,经X2检验,差异有显著性（P＜0．05）,（4）单侧颞叶低代谢手术效果好;对部分双侧颞叶低代谢者,切除其代谢减低更严重的一侧,发作也会改善,颞叶外癫痫手术效果不如颞叶癫痫好,病灶局限者,手术效果优于伴有其他部位皮层代谢改变者：单侧多脑叶代谢改变者,半大脑切除术效果好;双侧大脑多脑叶弥漫性病变者,手术效果差。结论 FDG PET对癫痫灶定位的灵敏度和准确性优于VEEG和形态学影像技术。FDG PET的代谢图形可帮助临床医生确定病灶部位,选择手术适应证和预测疗效。     

对胸部病变的定位价值对胸部病变的定位价值

目的　探讨18F 脱氧葡萄糖 (FDG)PET发射和透射扫描图像融合对胸部病变的定位价值。方法　对 2 1例胸部肿瘤患者进行18F FDGPET肿瘤显像 ,图像重建后获得透射扫描和衰减校正后发射扫描各断面断层图像。计算机自动生成发射和透射扫描各断面断层图像双肺胸膜轮廓 ,采用表面轮廓匹配法进行图像融合。结果　在PET胸部透射扫描断层图像上可分辨出主动脉弓、气管、肺门大血管、心脏、肺组织、纵隔、胸壁等解剖结构。 2 1例患者在PET和CT图像上均检出的病灶共6 1个 ,与CT图像病灶位置对比 ,除后纵隔近脊柱旁 1个病灶在融合图像上难以定位外 ,余病灶均能正确定位。CT和融合图像相应横断面图像上病变中心点离胸壁前、后径和左、右径距离的平均差值分别为 (2 7± 0 8)、(2 4± 0 9)、(2 9± 0 5 )和 (2 1± 0 4)mm。结论　PET胸部发射和透射扫描图像融合对胸部病变可作出正确定位。PET透射扫描不仅可用于衰减校正 ,还可用于图像融合 ,提供胸部解剖结构信息。     

Standardized perfusion value: universal CT contrast enhancement scale that correlates with FDG PET in lung nodules

The standardized enhancement value and standardized perfusion value allow comparison between different methods for quantification of contrast enhancement during computed tomography (CT). Standard perfusion values calculated from CT measurements of perfusion within pulmonary nodules compared favorably with those derived from previously reported enhancement data and correlated with standardized uptake values obtained from positron emission tomographic images (r = 0.8, P <.01).     

Present status of PET images: clinical FDG PET in oncology

The clinical application of positron emission tomography with fluorodeoxyglucose (FDG PET) in the field of cancer diagnosis is expanding rapidly. FDG PET has been proven to be a clinically useful tool for the detection and staging of malignant tumors, differentiation of mass lesions, and follow-up and monitoring of malignant diseases after treatment. Several factors relating to the clinical spread of FDG PET, including the simplification of FDG production, establishment of an FDG delivery system, shortening of the data acquisition time for whole body imaging, development of a coincidence gamma camera, and reimbursement from medical insurance, are reviewed and discussed in this article. PET oncology currently has greater potential as a result of the development of new radiopharmaceuticals based on the tumor characteristics of biochemical and genetic processes. The recent development of clinical FDG PET might be simply a stepping stone for the development of more advanced PET oncology in the near future.     

Measurements of glucose phosphorylation with FDG and PET are not reduced by dephosphorylation of FDG-6-phosphate

To improve the measurements of glucose metabolism in the human brain, we imposed biologic constraints on the deoxyglucose model with and without dephosphorylation of FDG-6-phosphate (the k4*- and k3*-models). The constraints included constant transport and phosphorylation ratios (tau and phi) and a common partition volume (K1/k2) for tracer [18F]FDG and glucose. In the presence of significant dephosphorylation, the k3*-model yielded time-dependent estimates of the phosphorylation coefficient (k3*), while the K4*-model yielded time-independent estimates. However, the two models yielded practically identical measurements of regional cerebral glucose metabolism in PET studies of six normal volunteers when the phosphorylation affinity ratio (the k3*/k3 ratio of FDG and glucose) and tracer circulation time were 0.30 and 20 min for the k3*-model and 0.33 and 45 min for the k4*-model.     

Pheochromocytomas: imaging with 2-[fluorine-18]fluoro-2-deoxy-D-glucose PET.

PURPOSE: To assess the sensitivity of positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) in pheochromocytomas and, secondarily, to compare images obtained with FDG PET to those obtained with metaiodobenzylguanidine (MIBG) scintigraphy. MATERIALS AND METHODS: Twenty-nine patients with one or more known or subsequently proved pheochromocytomas underwent FDG PET (35 scans) and MIBG scintigraphy (35 scans). Tumor uptake of FDG was quantified on positive PET scans. RESULTS: Tumor uptake of FDG was detected in 22 of 29 patients. Most benign (seven of 12 patients) and most malignant (15 of 17 patients) pheochromocytomas and their metastases avidly concentrated FDG. In four patients whose pheochromocytomas failed to accumulate MIBG, uptake of FDG in the tumors was intense. For the majority of the 16 patients whose tumors concentrated both agents, however, ratings for MIBG images compared to FDG PET images for delineation of the tumor in comparison to background and normal organ accumulation were superior for nine patients (56%) and as good or better for 14 (88%). CONCLUSION: Most pheochromocytomas accumulate FDG. Uptake is found in a greater percentage of malignant than benign pheochromocytomas. FDG PET is especially useful in defining the distribution of those pheochromocytomas that fail to concentrate MIBG.