Uptake of iodine-123-α-methyl tyrosine by gliomas and non-neoplastic brain lesions

Using single-photon emission tomography (SPET), the radiopharmaceuticall,-3-iodine-123--methyl tyrosine (IMT) has been applied to the imaging of amino acid transport into brain tumours. It was the aim of this study to investigate whether IMT SPET is capable of differentiating between high-grade gliomas, low-grade gliomas and non-neoplastic brain lesions. To this end, IMT uptake was determined in 53 patients using the triple-headed SPET camera MULTISPECT 3. Twenty-eight of these subjects suffered from high-grade gliomas (WHO grade III or IV), 12 from low-grade gliomas (WHO grade II), and 13 from non-neoplastic brain lesions, including lesions after effective therapy of a glioma (five cases), infarctions (four cases), inflammatory lesions (three cases) and traumatic haematoma (one case). IMT uptake was significantly higher in high-grade gliomas than in low-grade gliomas and non-neoplastic lesions. IMT uptake by low-grade gliomas was not significantly different from that by non-neoplastic lesions. Diagnostic sensitivity and specificity were 71% and 83% for differentiating high-grade from low-grade gliomas, 82% and 100% for distinguishing high-grade gliomas from non-neoplastic lesions, and 50% and 100% for discriminating low-grade gliomas from non-neoplastic lesions. Analogously to positron emission tomography with radioactively labelled amino acids and fluorine-18 deoxyglucose, IMT SPET may aid in differentiating high-grade gliomas from histologically benign brain tumours and non-neoplastic brain lesions; it is of only limited value in differentiating between non-neoplastic lesions and histologically benign brain tumours.     

SPECT、SPECT-CT与MRI对新鲜骨质疏松性椎体压缩骨折的诊断价值

目的:比较分析单光子发射计算机断层摄影术(SPECT)、单光子发射计算机断层摄影术联合同机CT扫描图像融合技术(SPECT-CT)与磁共振成像(MRI)对新鲜骨质疏松性椎体压缩骨折(OVCF)的诊断价值.方法:对201 1年10月～2012年4月因OVCF就诊而又同时接受了胸腰椎MRI、SPECT及SPECT-CT检查的20例老年患者进行回顾性分析,其中女12例,男8例,年龄60～80岁,平均73.5岁,平均病程21d.根据MRI表现确定最终诊断,MRI上出现骨髓水肿像的椎体定义为新鲜骨折椎体,椎体形态有压缩改变但MRI信号无异常者定义为陈旧骨折.由2位核医学医师分别评估SPECT及SPECT-CT检查,记录出现核素浓集的椎体,并给出疾病诊断意见.采用Kappa检验对比MRI与SPECT-CT判断新鲜骨折及陈旧骨折的一致性以及定性诊断能力.参考MRI发现,采用卡方检验分析SPECT与SPECT-CT定位病椎能力的异同.结果:根据MRI或SPECT-CT,20例患者均确诊为新鲜OVCF,其中MRI发现32个椎体存在新鲜OVCF,SPECT-CT发现34个椎体存在新鲜OVCF;根据SPECT诊断新鲜OVCF 12例,疑似新鲜OVCF但难以与肿瘤、感染相鉴别8例,共发现34个椎体存在核素浓集.MRI发现新鲜OVCF 32个椎体、陈旧OVCF 10个椎体,SPECT-CT发现新鲜OVCF 34个椎体、陈旧OVCF 8个椎体,两者之问具有良好的一致性(Kappa=0.0577,P＜0.05).在对病椎定位的准确性上,以MRI定位的病椎节段为参考,SPECT与MRI定位相同24个椎体,SPECT-CT与MRI定位相同30个椎体,SPECT-CT定位准确性优于SPECT(P＜0.05).SPECT-CT检查还发现了MRI未能显示的骨骼病损,其中骶尾椎骨折1例,肋骨骨折2例,骶髂关节炎1例,胸锁关节良性病变1例.结论:SPECT-CT在OVCF的定位、定性诊断上与MRI的价值相似,其准确定位病椎的性能优于传统SPECT检查;SPECT-CT还可以发现一些MRI未能显示的合并骨骼病损.SPECT-CT是患者不能接受MRI时的可靠选择.     

FDG双探头符合成像与X线断层图像同机融合在胸腹部肿瘤病变诊断中的价值

目的 :初步评价FDG双探头符合成像与X线断层图像同机融合在胸腹部肿瘤病变诊断中的价值。材料和方法 :回顾性分析 2 2例疑为胸腹部肿瘤或肿瘤术后复发而行18F -FDG双探头符合成像与X线断层联合扫描同机图像融合患者的资料。结果 :14例肿瘤或肿瘤术后复发的患者FDG显像 ,在 34个病灶中共检出 33个病灶 ( 97.1% )。融合影像可更加直观清晰地显示占位性病变或肿大淋巴结的代谢活性。其中 4例 ( 4 /14 )患者位于邻近膈肌上下及胸椎体、前列腺的 6个病灶 ( 6 /34)必须借助融合图像才能精确定位。结论 :FDG双探头符合成像与X线断层图像同机融合可明显提高符合显像定位诊断的准确性。     

Correction of nonuniform attenuation and image fusion in SPECT imaging by means of separate X-ray CT

Improvements in image quality and quantitation measurement, and the addition of detailed anatomical structures are important topics for single-photon emission tomography (SPECT). The goal of this study was to develop a practical system enabling both nonuniform attenuation correction and image fusion of SPECT images by means of high-performance X-ray computed tomography (CT). A SPECT system and a helical X-ray CT system were placed next to each other and linked with Ethernet. To avoid positional differences between the SPECT and X-ray CT studies, identical flat patient tables were used for both scans; body distortion was minimized with laser beams from the upper and lateral directions to detect the position of the skin surface. For the raw projection data of SPECT, a scatter correction was performed with the triple energy window method. Image fusion of the X-ray CT and SPECT images was performed automatically by auto-registration of fiducial markers attached to the skin surface. After registration of the X-ray CT and SPECT images, an X-ray CT-derived attenuation map was created with the calibration curve for 99mTc. The SPECT images were then reconstructed with scatter and attenuation correction by means of a maximum likelihood expectation maximization algorithm. This system was evaluated in torso and cylindlical phantoms and in 4 patients referred for myocardial SPECT imaging with Tc-99m tetrofosmin. In the torso phantom study, the SPECT and X-ray CT images overlapped exactly on the computer display. After scatter and attenuation correction, the artifactual activity reduction in the inferior wall of the myocardium improved. Conversely, the incresed activity around the torso surface and the lungs was reduced. In the abdomen, the liver activity, which was originally uniform, had recovered after scatter and attenuation correction processing. The clinical study also showed good overlapping of cardiac and skin surface outlines on the fused SPECT and X-ray CT images. The effectiveness of the scatter and attenuation correction process was similar to that observed in the phantom study. Because the total time required for computer processing was less than 10 minutes, this method of attenuation correction and image fusion for SPECT images is expected to become popular in clinical practice.     

Variation in FDG uptakes in different regions in normal human brain as a function of the time (30 and 60 minutes) after injection of FDG

OBJECTIVE: The authors' goal was to determine whether FDG uptakes in various regions of the brain are different for early and late scanning time in positron emission tomography (PET). METHOD: F-18 fluorodeoxyglucose (FDG) PET was performed on 15 healthy normal subjects to obtain early and late acquisition glucose metabolic images (30 and 60 min after FDG injection), respectively. The two sets of images were compared in a voxel-by-voxel analysis. RESULTS: In the bilateral posterior cingulate gyrus, parietal and frontal association cortices, and subcallosal cortices, the FDG uptakes were larger on the late scan image than on the early scan image, and the FDG uptakes were larger in the cerebellar hemisphere, vermis and frontal basis on the early scan image than on the late scan image. CONCLUSIONS: These results suggest that there are different regional FDG uptakes depending on the scanning time after FDG injection and we must be careful in replacing conventional FDG PET scanning with early scanning in FDG PET study.     

焦虑症患者平静及紧张状态局部脑血流灌注改变

目的：探讨焦虑症患者平静及紧张状态局部脑血流（rCBF)灌注特点。方法：对20例未经治疗的焦虑症患者和20例健康志愿者用双日法进行平静及紧张状态下SPECT显像，以瑞文推理测试为模拟应激工具诱发受检者紧张情绪。结果：（1）平静状态患者桥脑、大部分额叶、部分颞叶、丘脑和基底节的rCBF明显低于对照组（P均＜0．05和0．01）。（2）紧张状态患者桥脑、大部分额叶和颞叶、部分枕叶和顶叶、丘脑和基底节的rCBF明显低于对照组（P＜0．05和0．01）。（3）经协方差分析，模拟应激前后大部分脑区rCBF变化与对照组相比差异均有显著性，且与平静状态相比，紧张状态下rCBF灌注普遍降低，与对照组相反。结论：焦虑症患者可能存在额叶、颞叶、丘脑和基底节的功能低下，焦虑反应时rCBF灌注异常下降可能是焦虑症的特征性改变之一。     

Risk stratification in patients with remote prior myocardial infarction using rest-stress myocardial perfusion spect: prognostic value and impact on referral to early catheterization

BACKGROUND: Little is known about the prognostic value of myocardial perfusion single photon emission computed tomography (SPECT) in patients with remote prior myocardial infarction (MI). METHODS AND RESULTS: We identified 1413 consecutive patients with remote prior MI who underwent rest-stress myocardial perfusion SPECT. Semiquantitative visual analysis of 20 SPECT segments was used to define the summed stress, rest, and difference scores. The number of non-reversible segments was used as an index of infarct size. During follow-up (>or=1 year), 118 hard events occurred: 64 cardiac deaths (CDs) and 54 recurrent MIs. Annual CD and hard event rates increased significantly as a function of SPECT abnormality. For summed stress scores less than 4, 4 to 8, 9 to 13, and more than 13, the annual CD rates were 0.4%, 0.9%, 1.7%, and 3.5%, respectively (P =.002). Patients with small MI (<4 non-reversible segments) and no or mild ischemia (summed difference score or=4 non-reversible segments) had moderate to high annual CD rates (3.7%-6.6%) regardless of the extent of ischemia. Nuclear testing added incremental prognostic information to pre-scan information. Compared with a strategy in which all patients are referred to catheterization, a strategy that referred only those patients with a risk for CD of greater than 1% by myocardial perfusion SPECT resulted in a 41.6% cost savings. CONCLUSIONS: Myocardial perfusion SPECT adds incremental value to pre-scan information and is highly predictive and cost-efficient in the risk stratification of patients with remote prior MI. Patients with normal or mildly abnormal scan results or small MI in combination with absent or mild ischemia have a low risk for CD.     

Discordance between dipyridamole stress Tc-99m sestamibi SPECT and coronary angiography in patients with Kawasaki disease

BACKGROUND: Kawasaki disease is an acute vasculitis syndrome of unknown etiology that mainly affects the coronary arteries. The purpose of this study was to assess the agreement between dipyridamole stress technetium 99m sestamibi single photon emission computed tomography (SPECT) and coronary angiography in these patients. METHODS AND RESULTS: Forty-one consecutive patients (29 boys and 12 girls) who underwent coronary angiography were studied prospectively. Their ages at onset of the disease ranged from 2 months to 4.8 years (mean +/- SD, 1.9 +/- 1.3 years). Their ages at the time of the study ranged from 8 months to 15.3 years (6.2 +/- 4.4 years). The duration between symptom onset and the study ranged from 2 months to 12 years (4.3 +/- 4.0 years). All patients underwent dipyridamole stress Tc-99m sestamibi SPECT within 1 month of their angiographic studies. They were divided into 3 groups according to coronary angiography findings. Group A consisted of 2 patients (1 boy and 1 girl, aged 10.3 and 1.9 years, respectively) with coronary stenoses who also had aneurysms. Group B consisted of 10 patients (8 boys and 2 girls, aged 0.7-15.3 years [mean, 3.8 years]) with coronary aneurysms. Group C consisted of 29 patients (20 boys and 9 girls, aged 1.2-13.8 years [mean, 7 years]) with normal coronary angiograms. Two patients in group A (100%), 3 of 10 patients in group B (30%), and 19 of 29 patients in group C (65.5%) had myocardial perfusion defects. There was poor agreement between Tc-99m sestamibi SPECT and coronary angiography for detecting coronary stenoses (kappa = 0.07; P =.222) and aneurysms (kappa = -0.184; P =.158). CONCLUSION: Significant discordance exists between Tc-99m sestamibi SPECT and coronary angiography in patients with Kawasaki disease.     

Utility of positron emission tomography in schwannomatosis

Schwannomatosis is characterized by multiple non-intradermal schwannomas with patients often presenting with a painful mass in their extremities. In this syndrome malignant transformation of schwannomas is rare in spite of their large size at presentation. Non-invasive measures of assessing the biological behavior of plexiform neurofibromas in neurofibromatosis type 1 such as positron emission tomography (PET), CT scanning and MRI are well characterized but little information has been published on the use of PET imaging in schwannomatosis. We report a unique clinical presentation portraying the use of PET imaging in schwannomatosis. A 27-year-old woman presented with multiple, rapidly growing, large and painful schwannomas confirmed to be related to a constitutional mutation in the SMARCB1 complex. Whole body PET/MRI revealed numerous PET-avid tumors suggestive of malignant peripheral nerve sheath tumors. Surgery was performed on multiple tumors and none of them had histologic evidence of malignant transformation. Overall, PET imaging may not be a reliable predictor of malignant transformation in schwannomatosis, tempering enthusiasm for surgical interventions for tumors not producing significant clinical signs or symptoms.