PET/CT and MRI of intra-osseous haemangioma of the tibia

Intra-osseous haemangioma is a rare, benign neoplasm that usually involves the vertebrae and craniofacial bones. Furthermore, its occurrence in the long bones is extremely rare. We report the findings of fluorine-18-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT and MRI in a patient with intra-osseous haemangioma in the proximal tibia, who was initially misdiagnosed as having a malignancy based on (18)F-FDG PET/CT. (18)F-FDG PET/CT showed a well-marginated osteolytic lesion with abnormal FDG uptake. The mass demonstrated low signal intensity on T(1) weighted MRI. On T(2) weighted images, the lesion appeared as a cluster of high signal intensity lobules and showed strong enhancement on contrast-enhanced T(1) weighted images. Surgical curettage was performed and histopathological examination of the excised tissue confirmed a cavernous haemangioma.     

骨上皮样血管内皮瘤的CT、MRI及18 F-FDG PET/CT表现(附2例报道)

目的探讨骨上皮样血管内皮瘤(EHE)的CT、MRI及18 F-FDG PET/CT表现,以提高对该病的影像学认识。方法回顾性分析2例经病理证实的骨上皮样血管内皮瘤患者的CT、MRI及18 F-FDG PET/CT检查图像资料,总结其影像特点。结果2例骨EHE中,1例为全身多发骨骼病变,1例仅为胸11椎体病变。CT表现病灶为边缘清晰,轻度硬化并呈分叶状改变的膨胀性溶骨性骨质破坏,病灶内见散在斑点状高密度影,周边软组织及椎间盘未见明显受累。MRI病灶呈稍长T 1、长T 2信号,其内可见散在斑点状低信号影,增强扫描病灶呈明显不均匀强化。病灶外周可见增强无强化的低信号环。18 F-FDG PET/CT主要表现为病灶部位的溶骨性骨质破坏伴SUV摄取值的升高。结论CT、MRI及18 F-FDG PET/CT检查能帮助评估骨上皮样血管内皮瘤的病灶性质及范围,协助下一步诊疗方案的确定。     

18F-FDG PET/CT结合MRI在癫（癎）外科治疗中的应用

目的 探讨18F-脱氧葡萄糖（FDG）PET/CT结合MRI定位致（癎）灶,指导癫（癎）外科治疗的意义.方法 67例癫（癎）外科治疗患者术前均行18F-FDG PET/CT和MRI检查,根据术前评估以及术中皮质脑电图监测结果进行致（癎）灶切除术.术后长期随访,根据Engel分级将患者分为癫（癎）发作完全控制组（Engel Ⅰ）和癫（癎）发作未完全控制组（Engel Ⅱ～Ⅳ）,采用x2检验或Fisher精确检验对数据进行分析.结果 67例中48例患者术后癫（癎）发作完全控制（Engel Ⅰ,71.6%）,11例Engel Ⅱ,5例Engel Ⅲ,3例Engel Ⅳ.18F-FDG PET/CT定位定侧结果与MRI检查结果一致或基本一致者63例,其中71.4%（45/63）术后癫（癎）发作完全控制;18F-FDG PET/CT与MRI检查结果不一致者4例,其中3例术后癫（癎）发作完全控制,2组差异无统计学意义（Fisher精确检验,P＞0.05）.63例中MRI与18F-FDG PET/CT均发现局限性异常者为41例,其中80.5%（33/41）术后癫（癎）发作完全控制;MRI发现局限性病变,但18F-FDG PET/CT呈更广泛性代谢异常者20例,其中55.0%（11/20）术后癫（癎）发作完全控制,2组差异有统计学意义（x2=4.34,P＜0.05）.结论 18F-FDG PET/CT结合MRI可为致（癎）灶定位及预后评估提供重要信息.     

18F-FDG PET/CT与3.0T MRI联合显像在乳腺癌原发病灶诊断中的价值

目的 探讨18F-FDG PET/CT与3.0T MRI联合显像在乳腺癌原发病灶诊断中的价值。 方法 对38例临床怀疑为乳腺癌的女性患者于一周内分别行18F-FDG PET/CT、3.0T MRI和病理学检查。 结果 组织病理学检查结果证实,全部患者中,24例为乳腺癌患者,14例为乳腺良性肿瘤患者。3.0T MRI诊断乳腺癌的灵敏度、特异度、准确率分别为91.7%、78.6%、86.8%;PET/CT诊断乳腺癌的灵敏度、特异度、准确率分别为87.5%、92.9%、89.5%;PET/CT和3.0T MR联合显像诊断乳腺癌的灵敏度、特异度、准确率分别为100.0%、92.9%、97.4%;3种显像方法间灵敏度、特异度、准确率差异无统计学意义（χ2=2.987、1.612和2.955,P均＞0.05）。 结论 18F-FDG PET/CT和3.0T MRI联合显像在乳腺癌原发病灶诊断中具有重要价值;但与单独18F-FDG PET/CT和3.0T MRI显像比较,3种显像方法在乳腺癌原发病灶的诊断效能上差异无统计学意义。     

Retrospective review: usefulness of a number of imaging modalities including CT, MRI, technetium-99m pertechnetate scintigraphy, gallium-67 scintigraphy and F-18-FDG PET in the differentiation of benign from malignant parotid masses

Objective The aim of this study is to evaluate an imaging approach using computed tomography (CT), magnetic resonance imaging (MRI), technetium-99m pertechnetate scintigraphy (^99mTc pertechnetate scintigraphy), gallium-67 scintigraphy (⁶⁷Ga scintigraphy) and fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET). Material and Methods We reviewed retrospectively 59 patients with parotid masses. CT, MRI,⁶⁷Ga scintigraphy,^99mTc pertechnetate scintigraphy, and¹⁸F-FDG PET were performed. Results All of the benign tumors had smooth margins on CT and MRI. Patients with inflammatory lesions and malignant lesions showed well-defined margins or ill-defined margins. All Warthin's tumors showed high technetium accumulation. Many of malignant tumors showed high FDG accumulation. Both pleomorphic adenomas and Warthin's tumors showed high accumulation in some cases on¹⁸F-FDG PET. Among 15 patients with pleomorphic adenoma, 14 patients showed marked hyperintensity relative to CSF on T2-weighted images and partial enhancement on contrast-enhanced T1-weighted images. Combination of several imaging modarity offered usefulness of differential diagnosis for parotid masses. Conclusion An efficient combination of imaging methods may be helpul for achieve the correct diagnosis.     

Clinical significance of MRI/18F-FDG PET fusion imaging of the spinal cord in patients with cervical compressive myelopathy

Purpose

¹⁸F-FDG PET is used to investigate the metabolic activity of neural tissue. MRI is used to visualize morphological changes, but the relationship between intramedullary signal changes and clinical outcome remains controversial. The present study was designed to evaluate the use of 3-D MRI/¹⁸F-FDG PET fusion imaging for defining intramedullary signal changes on MRI scans and local glucose metabolic rate measured on ¹⁸F-FDG PET scans in relation to clinical outcome and prognosis.

Methods

We studied 24 patients undergoing decompressive surgery for cervical compressive myelopathy. All patients underwent 3-D MRI and ¹⁸F-FDG PET before surgery. Quantitative analysis of intramedullary signal changes on MRI scans included calculation of the signal intensity ratio (SIR) as the ratio between the increased lesional signal intensity and the signal intensity at the level of the C7/T1 disc. Using an Advantage workstation, the same slices of cervical 3-D MRI and ¹⁸F-FDG PET images were fused. On the fused images, the maximal count of the lesion was adopted as the standardized uptake value (SUV_max). In a similar manner to SIR, the SUV ratio (SUVR) was also calculated. Neurological assessment was conducted using the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy.

Results

The SIR on T1-weighted (T1-W) images, but not SIR on T2-W images, was significantly correlated with preoperative JOA score and postoperative neurological improvement. Lesion SUV_max was significantly correlated with SIR on T1-W images, but not with SIR on T2-W images, and also with postoperative neurological outcome. The SUVR correlated better than SIR on T1-W images and lesion SUV_max with neurological improvement. Longer symptom duration was correlated negatively with SIR on T1-W images, positively with SIR on T2-W images, and negatively with SUV_max.

Conclusion

Our results suggest that low-intensity signal on T1-W images, but not on T2-W images, is correlated with a poor postoperative neurological outcome. SUV_max of lesions showing increased signal intensity and SUVR measured on fusion MRI/PET scans are more sensitive parameters for predicting clinical outcome than signal intensity on the MRI scan.     

Morphologic and functional changes in nontumorous liver tissue after radiofrequency ablation in an in vivo model: comparison of 18F-FDG PET/CT, MRI, ultrasound, and CT.

Rimlike contrast enhancement on morphologic imaging and increased tracer uptake on (18)F-FDG PET in the periphery of the necrosis can hamper differentiation of residual tumor from regenerative tissue after radiofrequency ablation of liver lesions. This study used MRI, CT, ultrasound, and (18)F-FDG PET/CT to assess the typical appearance of lesions in nontumorous animal liver tissue after radiofrequency ablation. METHODS: Lesions were created by radiofrequency ablation of normal liver parenchyma in 21 minipigs. Follow-up was performed by 3 contrast-enhanced morphologic modalities-MRI, CT, and ultrasound-and by (18)F-FDG PET/CT immediately, 3 and 10 d, and 1, 2, 3, and 6 mo after radiofrequency ablation. Images were evaluated qualitatively for areas of increased enhancement and regions of elevated tracer uptake. Furthermore, all images were assessed quantitatively by determination of ratios comparing enhancement/tracer uptake in the periphery of the necrosis with enhancement/tracer uptake in normal liver parenchyma. Imaging findings were compared with histopathology findings. RESULTS: Immediately after radiofrequency ablation, no increase in (18)F-FDG uptake was visible, whereas elevated enhancement was noticed in the periphery of the necrosis on all morphologic imaging procedures. At further follow-up, an area of rimlike increase in (18)F-FDG uptake surrounding the necrosis was detected on PET/CT. The rimlike pattern of increased enhancement in the arterial phase was present for all liver lesions on CT, MRI, and ultrasound, especially between day 3 and month 1 after the radiofrequency ablation. Both elevated glucose metabolism and enhancement persisted for 6 mo postinterventionally. Histologic examination showed a hemorrhagic border converting into a regeneration capsule. CONCLUSION: If performed immediately after radiofrequency ablation, (18)F-FDG PET/CT probably has benefits over those of morphologic imaging procedures when assessing liver tissue for residual tumor. Later follow-up may be hampered by visualization of peripheral hyperperfusion and tissue regeneration. Further studies on a patient population are essential.     

18F-FDG PET/CT delayed images after diuretic for restaging invasive bladder cancer.

PET with (18)F-FDG has been considered of limited value for detection of bladder cancer because of the urinary excretion of the tracer. The purpose of this study was to investigate the role of PET/CT in the detection and restaging of bladder cancer using furosemide and oral hydration to remove the excreted (18)F-FDG from the bladder. METHODS: Seventeen patients with bladder cancer (11 without cystectomy, 6 with total cystectomy and urinary diversion) underwent (18)F-FDG PET/CT from head to the upper thighs 60 min after the intravenous injection of 370 MBq of (18)F-FDG. Additional pelvic images were acquired 1 h after the intravenous injection of furosemide and oral hydration. PET/CT findings were confirmed by MRI, cystoscopy, or biopsy. RESULTS: PET/CT was able to detect bladder lesions in 6 of 11 patients who had not undergone cystectomy. These images changed the PET/CT final reading in 7 patients: Recurrent bladder lesions were detected in 6 patients, pelvic lymph node metastases in 2 patients, and prostate metastasis in 1. This technique overcame the difficulties posed by the urinary excretion of (18)F-FDG. Hypermetabolic lesions could be easily detected by PET and precisely localized in the bladder wall, pelvic lymph nodes, or prostate by CT. Seven of 17 patients (41%) were upstaged only after delayed pelvic images. CONCLUSION: Detection of locally recurrent or residual bladder tumors can be dramatically improved using (18)F-FDG PET/CT with delayed images after a diuretic and oral hydration.     

Combined functional and structural evaluation of cancer patients with a hybrid camera-based PET/CT system using (18)F-FDG.

Correct diagnosis and definition of the functional and anatomic status of lesions in cancer patients are of clinical importance. The value of hybrid imaging using a gamma camera-based PET/CT and (18)F-FDG in determining the relationship between mass and cancer was assessed. METHODS: Hybrid imaging was performed using a device combining low-dose CT and gamma camera-based PET. Ninety-one patients with histologically proven malignancy and 190 suspected sites of disease were evaluated. Camera-based PET was performed after the injection of 296-370 MBq (18)F-FDG. The presence of organomegaly or an abnormal mass on CT and of abnormal uptake of (18)F-FDG was assessed for each suspected lesion. The presence of malignancy at each site was determined by biopsy, imaging follow-up, or clinical outcome. RESULTS: Five imaging patterns were found. Pattern 1 showed congruent abnormal (18)F-FDG uptake and a mass on CT in 110 of the lesions. One hundred two sites (93%) had active cancer. Pattern 2 showed a mass on CT, larger than the area of abnormal (18)F-FDG uptake, and was found in 5 lesions. Active malignancy was proven in 3 sites (60%). Pattern 3 showed an abnormal mass on CT with no (18)F-FDG uptake and was found in 52 lesions. Thirteen of these lesions (25%) had active tumor. Pattern 4 showing abnormal (18)F-FDG uptake with no mass on CT was found in 23 lesions. Sixteen of these sites (70%) were malignant. Pattern 5 showed normal CT findings and no abnormal (18)F-FDG uptake in 11 patients. Two of these patients (18%) had active disease. Hybrid imaging was of value in establishing the correct relationship between CT and (18)F-FDG findings in 98 of the 190 lesions (52%). CONCLUSION: A range of patterns presenting with or without abnormal (18)F-FDG uptake on camera-based PET and a mass on CT may occur in suspected cancer sites. Both structural changes on CT and increased cell metabolism expressed by abnormal (18)F-FDG uptake should be considered in oncologic imaging. Hybrid imaging, a combined physiologic and anatomic modality, appears to provide new diagnostic opportunities in characterizing function and morphology in malignancies.     

Breast cancer staging in a single session: whole-body PET/CT mammography

Our objective was to compare the diagnostic accuracy of an all-in-one protocol of whole-body 18F-FDG PET/CT and integrated 18F-FDG PET/CT mammography with the diagnostic accuracy of a multimodality algorithm for initial breast cancer staging. METHODS: Forty women (mean age, 58.3 y; range, 30.8-78.4 y; SD, 12 y) with suspected breast cancer were included. For the primary tumor, we compared 18F-FDG PET/CT mammography versus MRI mammography; for axillary lymph node status, 18F-FDG PET/CT versus clinical investigation and ultrasound; and for distant metastases, 18F-FDG PET/CT versus a multimodality staging algorithm. Histopathology and clinical follow-up served as the standard of reference. The Fisher exact test evaluated the significance of differences (P < 0.05). Alterations in patient management caused by 18F-FDG PET/CT were documented. RESULTS: No significant differences were found in the detection rate of breast cancer lesions (18F-FDG PET/CT, 95%; MRI, 100%; P = 1). 18F-FDG PET/CT correctly classified lesion focality significantly more often than did MRI (18F-FDG PET/CT, 79%; MRI, 73%; P < 0.001). MRI correctly defined the T stage significantly more often than did 18F-FDG PET/CT (MRI, 77%; 18F-FDG PET/CT, 54%; P = 0.001). 18F-FDG PET/CT detected axillary lymph node metastases in 80% of cases; clinical investigation/ultrasound, in 70%. This difference was not statistically significant (P = 0.067). Distant metastases were detected with 18F-FDG PET/CT in 100% of cases, and the multimodality algorithm identified distant metastases in 70%. This difference was not statistically significant (P = 1). Three patients had extraaxillary lymph node metastases that were detected only by PET/CT (cervical, retroperitoneal, mediastinal/internal mammary group). 18F-FDG PET/CT changed patient management in 12.5% of cases. CONCLUSION: Our data suggest that a whole-body 18F-FDG PET/CT mammography protocol may be used for staging breast cancer in a single session. This initial assessment of the 18F-FDG PET/CT protocol indicates similar accuracy to MRI for the detection of breast cancer lesions. Although MRI seems to be more accurate when assessing the T stage of the tumor, 18F-FDG PET/CT seems able to more accurately define lesion focality. Although 18F-FDG PET/CT mammography was able to detect axillary lymph node metastases with a high sensitivity, this method cannot soon be expected to replace the combination of clinical examination, ultrasound, and sentinel lymph node biopsy for axillary assessment.     

Aortic wall inflammation due to Takayasu arteritis imaged with 18F-FDG PET coregistered with enhanced CT.

The purpose of this study was to evaluate the ability of (18)F-FDG PET to identify aortitis and to localize and follow disease activity in patients with Takayasu arteritis. The value of using (18)F-FDG PET coregistered with enhanced CT in determining vascular lesion sites and inflammatory activity was assessed. METHODS: Takayasu arteritis was diagnosed according to the predefined criteria. Eleven patients with Takayasu arteritis in the active stage, 3 patients with Takayasu arteritis in the inactive stage, and 6 healthy subjects underwent (18)F-FDG PET coregistered with enhanced CT and the inflammatory vascular lesion was evaluated by using the standardized uptake value (SUV) of (18)F-FDG accumulation as an index. Two patients with active disease were analyzed by sequential (18)F-FDG PET scans during treatment. RESULTS: The (18)F-FDG PET revealed intense (18)F-FDG accumulation (SUV > or = 2.7) in the vasculature of 2 of the 11 cases in the active stage of Takayasu arteritis. The other 9 patients in the active stage revealed weak (18)F-FDG accumulation (2.3 > or = SUV > or = 1.2). No significant (18)F-FDG accumulation was observed in the patients with inactive disease (SUV < or = 1.2) and 6 control healthy subjects (SUV < 1.3). Given the cutoff SUV is 1.3, the sensitivity of (18)F-FDG PET analysis of Takayasu arteritis is 90.9% and the specificity is 88.8%. (18)F-FDG PET coregistered with enhanced CT localized (18)F-FDG accumulation in the aortic wall in the patients with Takayasu arteritis who had weak (18)F-FDG accumulation that could not otherwise be identified anatomically. Finally, (18)F-FDG accumulation resolved with therapy in 2 active cases. The disappearance of (18)F-FDG accumulation did not coincide with the level of general inflammatory markers. CONCLUSION: The (18)F-FDG PET images coregistered with enhanced CT images showed the distribution and inflammatory activity in the aorta, its branches, and the pulmonary artery in patients with active Takayasu arteritis, even those who had weak (18)F-FDG accumulation. The intensity of accumulation decreased in response to therapy.     

18F-FDG PET and CT/MRI in oral cavity squamous cell carcinoma: a prospective study of 124 patients with histologic correlation.

Accurate evaluation of primary tumors and cervical lymph node status of squamous cell carcinoma (SCC) of the oral cavity is important to treatment planning and prognosis prediction. In this prospective study, we evaluated the use of 18F-FDG PET, CT/MRI, and their visual correlation for the identification of primary tumors and cervical nodal metastases of SCC of the oral cavity with histologic correlation. METHODS: One hundred twenty-four patients with pathologically proven diagnoses of oral cavity SCC underwent 18F-FDG PET and CT/MRI within 2 wk before surgery. We interpreted 18F-FDG PET, CT/MRI, and visually correlated 18F-FDG PET and CT/MRI separately to assess the primary tumors and their regional lymph node status. We recorded lymph node metastases according to the neck level system of imaging-based nodal classification. Histopathologic analysis was used as the gold standard for assessment of the primary tumors and lymph node involvement. We analyzed differences in sensitivity and specificity among the imaging modalities using the McNemar test. The receiver-operating-characteristic (ROC) curve and calculation of the area under the curve were used to evaluate their discriminative power. RESULTS: The accuracy of 18F-FDG PET, CT/MRI, and their visual correlation for the identification of primary tumors was 98.4%, 87.1%, and 99.2%, respectively. The sensitivity of 18F-FDG PET for the identification of nodal metastases on a level-by-level basis was 22.1% higher than that of CT/MRI (74.7% vs. 52.6%, P < 0.001), whereas the specificity of 18F-FDG PET was 1.5% lower than that of CT/MRI (93.0% vs. 94.5%, P = 0.345). The sensitivity and specificity of the visual correlation of 18F-FDG PET and CT/MRI were 3.2% and 1.5% higher than those of 18F-FDG PET alone (77.9% vs. 74.7%, P = 0.25; 94.5% vs. 93.0%, P = 0.18, respectively). The area under the curve obtained from the ROC curve showed that 18F-FDG PET was significantly superior to CT/MRI for total nodal detection (0.896 vs. 0.801, P = 0.002), whereas the visual correlation of 18F-FDG PET and CT/MRI was modestly superior to 18F-FDG PET alone (0.913 vs. 0.896, P = 0.28). CONCLUSION: 18F-FDG PET is superior to CT/MRI in the detection of cervical status of oral cavity SCC. The sensitivity of 18F-FDG PET for the detection of cervical nodal metastasis on a level-by-level basis was significantly higher than that of CT/MRI, whereas their specificities appeared to be similar. Visual correlation of 18F-FDG PET and CT/MRI showed a trend of increased diagnostic accuracy over 18F-FDG PET alone but without a statistically significant difference, and its sensitivity was still not high enough to replace pathologic lymph node staging based on neck dissection.     

Patients with partial seizures: evaluation by MR, CT, and PET imaging

Fifty patients who experienced partial seizures were imaged with computed tomography (CT) and magnetic resonance imaging (MR); 14 of these also had imaging studies of local cerebral glucose metabolism with positron emission tomography (PET). Thirteen patients with attenuation abnormalities on CT scans also had abnormal signals on MR images; ten other patients had MR-image signal abnormalities but normal CT scans. In all seven patients undergoing PET who had MR-signal and sometimes also CT-attenuation abnormalities, areas of metabolic asymmetry were present. Positive PET scans were also seen in three patients with no evidence of abnormality on CT and MR studies. Focal cerebral substance loss on CT and MR studies, present in 21 patients, did not correlate well with electroencephalographic findings. MR is utilized as the initial imaging procedure in patients with partial seizures because it is more readily available and less invasive than PET and more sensitive than CT scanning.     

Increased 18F-FDG uptake in degenerative disease of the spine: Characterization with 18F-FDG PET/CT.

We determined the prevalence of abnormal spinal 18F-FDG uptake and assessed the relationship between the severity of findings on 18F-FDG PET and the severity of degenerative spinal disease (DSD) on CT. METHODS: PET/CT scans of 150 patients >18 y old, referred for whole-body 18F-FDG PET/CT for evaluation of known or suspected malignancy from June to July 2002, were analyzed retrospectively for the presence of increased 18F-FDG uptake in the spine and for anatomic correlates. Initially, PET images were examined and foci of 18F-FDG uptake in the spine were graded on a 0-4 scale based on intensity of 18F-FDG uptake (0 = definitely normal, 1 = probably normal, 2 = equivocal, 3 = probably abnormal, 4 = definitely abnormal). From PET alone, an impression as to whether lesions were most likely metastases or degenerative, as well the level of the spine involved, was also recorded. CT images of all 150 patients were reviewed independently by a musculoskeletal radiologist, who was unaware of patient identification, history, and findings of other imaging modalities, with the location recorded and severity graded on a 4-point-scale (0 = normal, 1 = mild, 2 = moderate, 3 = severe for both degenerative disk and facet disease). The relationship between PET and CT findings was then determined. RESULTS: Of the 150 patients, 63 (42.0%) had no abnormal findings in the spine on PET (grade 0), 27 (18.0%) had grade 1, 25 (16.7%) had grade 2, 17 (11.3%) had grade 3, and 16 patients (10.7%) had grade 4 18F-FDG uptake for DSD. Two additional patients had apparent spinal metastases with no degenerative changes. Five patients had metastases and DSD (included above). Of the patients who had abnormal spinal findings graded as probable or definite for DSD on CT (grades 3-4), 11 had abnormal findings in the cervical spine, 16 in the thoracic spine, and 23 patients in the lumbosacral spine. Seven patients (4.7%) had PET findings suggestive of spinal metastases. For patients with a maximum regional DSD score of 3, the mean 18F-FDG uptake for that spinal level was 1.4 +/- 1.5, whereas for patients with a maximum regional DSD score of 0, the mean PET grade was significantly lower at 0.4 +/- 0.9 (P = 0.0001). CONCLUSION: Incidental findings on PET suggestive of DSD are common (22% of patients), most common in the lumbosacral spine, and can be recognized on CT. The severity of PET findings correlates with the severity of degenerative disk and facet disease as graded by CT, likely due to the fact that the inflammatory process that accompanies DSD is evident on PET. Increased 18F-FDG uptake in DSD should not be confused with metastatic disease.     

Experimental study on “ischemic memory” of myocardium with different ischemic degrees by 18 F-FDG PET/CT

Glucose metabolism and ranges of ischemic cardiomyocytes in model rats under fasting or feeding were compared by 18F-FDG PET/CT, respectively, to investigate the changes of glucose metabolism after myocardial reperfusion, and to determine time window of myocardial “ischemic memory” under feeding. The ischemic–reperfusion model rats were established by ligating the left anterior descending coronary artery of rats. In fasting–feeding experiment, long-ischemia rats (n = 10) under fasting or feeding were subjected to 18F-FDG PET/CT at 24 h after modeling. Ischemic myocardium range and glucose metabolism were compared by calculating volume of interest (VOI), and mean standard uptake value (SUVmean). Under feeding, model rats in short, intermediate and long-ischemia groups were subjected to 18F-FDG PET/CT at 24, 48, and 72 h and long-ischemia rats were also subjected to 18F-FDG PET/CT at 96 h, and VOI and SUVmean were calculated and compared. (1) Under fasting, myocardial ischemic area of model rats showed “focal” 18F-FDG uptake, while “focal” 18F-FDG uptake defect appeared in the same area of myocardium under feeding and the difference was not statistically significant (P > 0.05). (2) Under feeding, PET myocardial images of model rats in three groups at 24 h and 48 h showed that there was an 18F-FDG uptake defect area near the apex of left ventricular wall. The images at 72 h showed that there was no abnormal 18F-FDG uptake defect area in short and intermediate-ischemia groups, while 18F-FDG uptake defect area in long-ischemia group disappeared at 96 h. Variance analysis of repeated measures was performed for data of three groups, which showed there was statistical significance between myocardial ischemia degree and “ischemic memory” time window (P < 0.05), and also between myocardial ischemia degree and difference of myocardial defect volume (P < 0.05). Under feeding, recent myocardial ischemia could be diagnosed by 18F-FDG PET/CT. Under feeding, “ischemic memory” time window for short and intermediate-myocardial ischemia was at least 48 h and for long ischemia was at least 72 h. This study suggested that as the degree of myocardial ischemia increased, “ischemic memory” time window also extended.     

PET/CT in malignant bone disease

The most commonly used positron emission tomography (PET) tracer in clinical practice, fluorine-18 fluorodeoxyglucose ( (18)F-FDG) is a glucose analogue that directly gains entry in excess into tumor cells. It is therefore sensitive for the detection of early bone marrow involvement prior to any identifiable bone changes. The introduction of (18)F-FDG-PET in the imaging algorithms of various malignant diseases often obviates the need to perform a separate assessment of malignant bone involvement with conventional bone scintigraphy. After therapy, disappearance of (18)F-FDG accumulation indicates success even when the bone remains morphologically abnormal. Novel hybrid systems composed of PET and computed tomography (CT) allow for acquisition of both modalities in the same clinical setting and the generation of fused functional-anatomical images. This technique has been found to improve the diagnostic accuracy of PET in detecting malignant bone involvement. This article discusses the role of PET/CT, primarily (18)F-FDG PET/CT, in the assessment of malignant bone involvement in patients with primary bone sarcomas, common solid malignancies, lymphoma, and multiple myeloma.     

Discrimination and anatomical mapping of PET-positive lesions: comparison of CT attenuation-corrected PET images with coregistered MR and CT images in the abdomen

Purpose

PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions.

Methods

A total of 100 oncological patients underwent sequential whole-body ¹⁸F-FDG PET with CT-based attenuation correction (AC), 40?mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization.

Results

From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p?<?0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40?% of lesions, equal to CT in 49?%, and inferior to CT in 11?%.

Conclusion

Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robust.     

^11C—MET和^18F—FDG PET／CT诊断胶质瘤术后残余或复发的比较

目的探讨^11C甲基蛋氨酸（MET）PET／CT对胶质瘤术后残余或复发病灶的诊断价值,并与^18F-FDG进行比较。方法46例胶质瘤术后患者均行^11C—MET和^18F-FDGPET／CT颅脑显像,2次显像间隔时间在5d内。采用ROI技术计算肿瘤与对侧灰质和白质比值。胶质瘤残余或复发病灶的诊断根据手术或立体定向活组织病理学检查、MRI、CT等影像学检查及临床随访,随访时间〉6个月。统计学比较采用z。检验或独立样本t检验。结果46例胶质瘤术后患者中残余或复发者36例。^11C-MET、^18F-FDGPET／CT显像对残余或复发病灶诊断的灵敏度分别为94．4％（34／36）、47．2％（17／36）,χ2=19．429,P〈0．001;特异性分别为90．0％（9／10）、100％（10／10）,χ2＝1．053,P〉0．05;准确性分别为93．5％（43／46）、58．7％（27／46）,χ2=15．294,P〈0．001。半定量分析：^11C—MET肿瘤／灰质比值为1．68±0．23,明显高于^18F—FDG的1．13±0．51（t=5．877,P〈0．001）,^11C—MET肿瘤／白质比值为2．52±0．28,明显高于^18F—FDG的1．42±0．57（t=10．470,P〈0．001）。结论^11C-METPET／CT显像对胶质瘤术后残余或复发病灶的诊断具有一定的临床价值,并优于^18F—FDGPET／CT显像。     

Standardized uptake values of uterine leiomyoma with <Superscript>18</Superscript>F-FDG PET/CT: variation with age,size, degeneration,and contrast enhancement on MRI

OBJECTIVE: To assess the effect of age, size, the degree of degeneration, and contrast enhancement on magnetic resonance imaging (MRI) on 18F-fluoro-2-deoxyglucose (18F-FDG) uptake in uterine leiomyomas using quantitative standardized uptake values (SUVs). METHODS: A total of 61 leiomyomas of 41 patients, who underwent combined positron emission tomography/computed tomography (PET/CT) using 18F-FDG and contrast-enhanced MRI were included in this study. Sixty-one leiomyomas were divided into two groups: "non-degenerated" leiomyomas showing distinct low signal intensity on T2-weighted images and intermediate signal intensity on T1-weighted images, and "degenerated" leiomyomas showing other types of signal intensity. Sixty-one leiomyomas were also divided into two groups of "strongly enhancing" leiomyomas and "weakly enhancing" leiomyomas in terms of their degree of contrast enhancement on MRI. RESULTS: The mean values of the maximum and average SUVs for the total of 61 leiomyomas were 2.34 +/- 0.75 (range 1.59-5.15) and 1.74 +/- 0.50 (0.66-3.95), respectively. There was a moderate negative correlation between the maximum and average SUVs and age (r = -0.43 and P = 0.00016, r = -0.31 and P = 0.029, respectively). Although there was a mild positive correlation between maximum SUV and size (r = 0.35 and P = 0.011), there was no significant difference between average SUV and size. Although there was no significant difference in average SUV between "degenerated" and "non-degenerated" leiomyomas, the maximum SUV of "degenerated" leiomyomas was significantly higher than that of "non-degenerated" leiomyomas (P = 0.0012). The degree of contrast enhancement on MRI was not significantly correlated with 18F-FDG uptake. CONCLUSIONS: Mild or moderate uptake of 18F-FDG is often observed in uterine leiomyoma and declines with age, and should not be confused with malignant accumulation.     

18F-FDG PET detection of lymph node metastases in medullary thyroid carcinoma.

Postsurgically elevated or increasing serum calcitonin levels strongly suggest the presence of residual or recurrent medullary thyroid carcinoma (MTC). Several imaging modalities (sonography, MRI, CT, scintigraphy with different types of radiolabeled ligands, etc.) are routinely used in an attempt to localize tumorous tissue, but such efforts often fail. In the search for a more reliable method, 18F-FDG PET was applied to detect tumor tissue of residual or recurrent MTC. METHODS: Forty patients with a postoperatively elevated plasma calcitonin level were included. These patients underwent routine diagnostic imaging procedures (CT, MRI, and 131I-metaiodobenzylguanidine [MIBG] whole-body planar scintigraphy or SPECT) and 18F-FDG PET examinations. Two independent experts visually analyzed the images provided by each method to detect pathologic lesions. Lymph nodes of > or = 1 cm in short diameter that were detected by radiologic methods were considered to be pathologic. 18F-FDG accumulation with a sharp contour reported by both independent observers was similarly regarded as pathologic. RESULTS: PET detected 270 foci with a high tracer accumulation, whereas only 116 lesions were detected by MRI and 141 by CT. The numbers of such foci determined by PET, MRI, and CT were 98, 34, and 34, respectively, in the neck; 25, 5, and 6, respectively, in the supraclavicular regions; and 117, 35, and 39, respectively, in the mediastinum. 131I-MIBG scintigraphy findings were positive for only 3 patients. CONCLUSION: For MTC patients with a postoperatively elevated plasma tumor marker level, PET was more sensitive and superior in localizing tumorous lymph node involvement than were the other imaging modalities, especially in the cervical, supraclavicular, and mediastinal lymphatic regions.