Positron emission tomography with 11C-methionine and computed tomography of intracranial tumours compared with histopathologic examination of multiple biopsies

A selected group of 36 patients with suspected supratentorial gliomas were investigated with positron emission tomography (PET) using 11C-methionine and transmission computed tomography (CT) before and after intravenous injection of contrast medium. Every examination was performed with the head fixed in a plastic helmet and a baseplate to guarantee that the slice orientation was the same at examinations with the two modalities and over time. Guided by the examinations, multiple stereotactic biopsies were performed with the biopsy instrument mounted on the baseplate. Regional accumulation of methionine was compared with histology of the corresponding samples and with attenuation before and after injection of contrast medium as well as mass effect on CT. Typically, there was a low attenuating lesion with a slight mass effect on CT. There was an increased accumulation compared with normal brain tissue in 31 cases of tumours and ordinary or decreased accumulation in 3 cases of tumours. In 22 cases with increased accumulation of methionine the extension of the tumour judged by PET corresponded with that of histology. In 4 cases tumour cells were found outside the area with pathologic methionine uptake. In 5 patients there were areas with increased methionine accumulation where no tumour cells were found. In 22 cases PET using methionine was more accurate than CT in defining the tumour boundaries as determined from the histologic findings. Four groups of biopsy specimens with different amounts of methionine accumulation are described. The uptake in a single biopsy gives good but not exact information about the histology of the specimen.     

Detection of pelvic lymph node metastases in gynecologic malignancy: a comparison of CT, MR imaging, and positron emission tomography.

OBJECTIVE: Accurate assessment of lymph node status before treatment is critical in the treatment of gynecologic cancers because the 5-year survival and treatment of women is influenced by lymph node involvement. The aims of this study were to investigate the ability of X-ray CT, MR imaging, and (18)F-FDG positron emission tomography (PET) to detect pelvic lymph node metastases by comparing imaging with histopathologic findings after lymph node dissection. MATERIALS AND METHODS: Eighteen patients with gynecologic cancers were studied by all three imaging methods before surgery. The images were initially reviewed with routine diagnostic conditions and then, subsequently, by two observers who were unaware of the clinical and histopathologic findings of the patients. The nodal sites were split into upper (aortic to common iliac bifurcations) and lower (common iliac bifurcations to inguinal ligament) iliac chains. All observers' results were statistically analyzed with specificity, sensitivity, positive and negative predictive values, Fisher's exact test (individual observers) or chi-square test (combined observers), and Cohen's kappa test. RESULTS: Eight of 18 patients had lymph node metastases at histology. Findings of all three modalities agreed in full in only one patient. CT correctly revealed 10 node-negative patients, whereas MR imaging was correct in eight of these patients. (18)F-FDG PET correctly depicted one patient with lymph nodes negative for tumor. CT was the most specific imaging modality (97.0%), with MR imaging and PET rendering values of 90.7% and 77.3%, respectively, but sensitivity of all modalities was low (CT, 48.1%; MR imaging, 53.7%; PET, 24.5%). Observer agreement for each modality was good; kappa values among all observers were 0.88 for CT, 0.85 for MR imaging, and 0.72 for PET. CONCLUSION: CT is the most specific modality for detecting lymph nodes positive for tumor in gynecologic cancers, whereas MR imaging is the most sensitive. The poor results of PET in the pelvis are attributed to urinary (18)F-FDG in the ureters or bladder, which may mask or imitate lymph node metastases.     

Detection of bone metastases: assessment of integrated FDG PET/CT imaging

PURPOSE: To retrospectively evaluate the positive predictive value (PPV) of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the identification of malignant bone lesions when the PET and CT findings are discordant and concordant. MATERIALS AND METHODS: The study conformed to HIPAA standards, and the need for informed consent was waived by the institutional review board that approved the study. FDG PET/CT reports of 712 patients were reviewed to identify patients with malignant bone lesions. Fifty-nine patients (30 female and 29 male patients; age range, 10-82 years) with 113 lesions were analyzed. With use of confirmation from histopathologic examination or clinical follow-up, the PPVs of the integrated examination and of the stand-alone CT and PET components of the examination were calculated. The results were stratified according to cancer type, chemotherapy status, and number of bone lesions and were compared by using Fisher exact tests. RESULTS: Of 47 lesions with positive findings at both PET and CT, 46 were malignant and one was benign, for a PPV of 98%. Of 31 lesions with positive findings at PET and negative findings at CT, 19 were malignant and 12 were benign, for a PPV of 61%. Of 35 lesions with negative findings at PET and positive findings at CT, six were malignant and 29 were benign, for a PPV of 17%. Independently, the PPV of all lesions with positive findings at PET was significantly higher than that of all lesions with positive findings at CT. Chemotherapy status for lesions with positive findings at CT and the number of lesions per patient had a statistically significant effect on the PPV of examinations (P = .02 and P < .001, respectively). CONCLUSION: PET/CT has a very high PPV for bone metastases (98%) when the findings at PET and CT are concordant; however, in lesions with discordant PET and CT findings at the integrated examination, PPV is markedly diminished.     

Delineation of gliomas with magnetic resonance imaging using Gd-DTPA in comparison with computed tomography and positron emission tomography

Fourteen patients with cerebral gliomas were investigated by MR imaging using Gd-DTPA (Magnevist), CT with the contrast agent iohexol (Omnipaque) and, as a reference, positron emission tomography (PET) using 11C-L-methionine. Tumour areas with disruption of the blood-brain-barrier (BBB) as seen on MR and CT were compared with areas increased accumulation of methionine in PET. There were 6 patients with high-grade astrocytoma (grade III-IV), 5 with low-grade astrocytoma (grade I-II) and 3 with oligodendroglioma. In 4 high-grade tumours, PET showed a larger tumour or tumour tissue in additional areas, compared with enhancement on MR and CT, while in 2 cases the tumour extension was similar in the three modalities. In the low grade tumour group, the findings on PET differed from those on post-contrast MR or CT in 7 cases. In 3 of these cases, no disruption of the BBB was seen either on MR or on CT. In 2 of our 14 patients CT showed larger enhancement extension than MR and in 2 cases MR was superior to CT in this respect. The enhancement intensity was higher on MR in 4 patients and on CT in 2 patients. No definite difference in the delineation of tumour tissue between the T1 weighted SE sequences was found. The gradient echo sequences FLASH and FISP gave limited information that was less than that provided by the T1 weighted SE sequences. A greater increase in signal intensity in T1 weighted images was usually seen 5 min post-contrast in the high-grade tumours than in the low-grade ones.     

Stereotactic computer tomography for biopsy of gliomas.

A technique is introduced enabling automatic transfer of coordinates obtained at computer tomography into a stereotactic system previously applied in biopsies of brain lesions. Four to five biopsies from different parts of gliomas were taken to compare the structures demonstrated on computer tomography with the microscopic appearances. Of 45 biopsies in 13 patients, 36 were predicted correctly. This also served as an attempt to classify gliomas on the basis of their appearance in the CT image.     

Stereotactic brain biopsy using a narrow aperture computed tomography scanner

A technique for stereotactic brain biopsy with guidance by computed tomography (CT) has been developed and the procedure carried out on a series of 12 patients. A head fixation device, based on the Leksell method, has been designed which allows exact transfer of CT co-ordinates to a Bennett stereotactic frame for the purpose of the biopsy. The development and initial experience of this stereotactic technique in 12 cases is reported and the accuracy of the method confirmed by histological examination and post-operative CT verification of the biopsy site, by means of a small marker inserted at the time of surgery.     

线粒体脑肌病的影像诊断价值

目的探讨多种影像技术对线粒体脑肌病的诊断价值。方法回顾性分析11例线粒体脑肌病的临床资料和影像学表现。本组病例9例行MR扫描，其中2例并行MR血管成像检查和数字减影血管造影，3例行CT平扫检查，1例行正电子发射计算机体层成像。结果CT和MR显示9例脑内病变为多发性或游走性脑梗死样病灶，主要累及颞枕叶后部，病变与血管分布区无关，7例发生于颞顶枕叶，位于双侧丘脑1例，脑干、小脑、侧脑室旁1例。另外小脑萎缩1例，胸髓空洞1例。急性期PET显示病灶中葡萄糖代谢明显升高，缓解期转为低代谢。结论结合多种影像学方法检查线粒体脑肌病，可提高诊断准确性。     

CT appearance of bone metastases detected with FDG PET as part of the same PET/CT examination

PURPOSE: To retrospectively evaluate lesion findings at computed tomography (CT) performed as part of a combined positron emission tomography (PET)/CT examination in patients suspected of having metastatic bone lesions-lesions that were detected with fluorine 18 fluorodeoxyglucose (FDG) PET as part of the same examination-and to correlate the CT and FDG PET findings. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval, and the need for patient informed consent was waived. Three hundred fifty-nine consecutive patients (191 male patients, 168 female patients; mean age, 56.9 years; age range, 8-92 years) underwent PET/CT. PET images were first reviewed by nuclear medicine physicians who had no clinical information regarding the presence or absence of bone metastasis by using a five-point grading system (0, a lesion was definitely negative for metastasis; 1, a lesion was probably negative; 2, a lesion was equivocal; 3, a lesion was probably positive; and 4, a lesion was definitely positive). For lesions assigned a grade of 3 or 4 at PET, CT characteristics such as the presence or absence of morphologic changes or accompanying findings (including bone destruction) were assessed by radiologists on the CT images obtained during the same imaging session. RESULTS: One hundred seventy-nine lesions in 55 patients were considered to be probable or definite bone metastases at PET. One hundred thirty-three of these lesions in 33 patients were clinically confirmed to be bone metastases at follow-up and/or histopathologic examination. CT revealed osteolytic changes in 41 (31%) and osteoblastic changes in 21 (16%) of the 133 lesions, but no or nonspecific changes were seen at CT in 49 (37%) and 22 lesions (17%), respectively. Of the 179 lesions suspected at PET, 46 ultimately proved to be nonosseous or false-positive for bone metastasis. Of these 46 lesions, 38 were not located in the bone but in adjacent tissues such as the pleura. CONCLUSION: CT images obtained as part of PET/CT scanning were useful in yielding the precise location of bone lesions and thus helping avoid misdiagnosis of bone metastasis; however, CT revealed morphologic changes in only half of the lesions assigned a grade of 3 or 4 at PET.     

Contrast-enhanced FDG-PET/CT vs. SPIO-enhanced MRI vs. FDG-PET vs. CT in patients with liver metastases from colorectal cancer: a prospective study with intraoperative confirmation

BACKGROUND: The choice of imaging before liver surgery is debated regarding the use of magnetic resonance (MR) imaging, computed tomography (CT), and positron emission tomography (PET). No studies have compared contrast-enhanced PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging. PURPOSE: To compare PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging, PET, and CT in the detection of liver metastases (LM) and extrahepatic tumor from colorectal cancer (CRC). MATERIAL AND METHODS: Thirty-five patients with suspected LM underwent PET/CT with a contrast-enhanced CT protocol and SPIO-enhanced MR imaging. Readers independently analyzed images from MR imaging, PET/CT, and the CT part and PET part of the PET/CT study. Imaging findings were compared with surgical and histological findings. RESULTS: Lesion-by-lesion sensitivity and accuracy for liver lesions was 54% and 77% for PET alone, 66% and 83% for PET/CT, 82% and 82% for SPIO-enhanced MR imaging, and 89% and 77% for CT alone, respectively. CT and SPIO-enhanced MR imaging were less specific but significantly more sensitive than PET (P<0.0001). For extrahepatic tumor, sensitivity and specificity was 83% and 96% for PET/CT and 58% and 87% for CT, respectively. CONCLUSION: CT and SPIO-enhanced MR imaging are more sensitive but less specific than PET in the detection of LM. PET/CT can detect more patients with extrahepatic tumor than CT alone.     

Usefulness of intraoperative sonography for revealing hepatic metastases from colorectal cancer in patients selected for surgery after undergoing FDG PET.

OBJECTIVE: The purpose of this study was to compare the diagnostic performance of preoperative positron emission tomography (PET) with FDG and intraoperative sonography with the standard of histologic examination of resected liver specimens in evaluating patients for curative resection of liver metastases from colorectal cancer. MATERIALS AND METHODS: We retrospectively identified 47 patients with recurrent colorectal cancer who underwent surgical exploration for possible curative resection of hepatic metastases. All patients underwent CT or MR imaging and FDG PET preoperatively and intraoperative sonography. The performance of the imaging techniques was evaluated through review of the radiologic reports and correlation with surgical and histopathologic findings. RESULTS: Eighty-seven malignant hepatic lesions were identified by histopathologic analysis of liver specimens, and 23 benign hepatic abnormalities were documented histopathologically or by uroradiologic imaging. For hepatic sections characterized as containing metastases by radiologic imaging, the positive predictive value for FDG PET was 93% (54/58); for intraoperative sonography, 87% (52/60); and for conventional imaging, 83% (43/52). For individual lesions characterized as probably malignant, the positive predictive value for FDG PET was 93% (62/68); for intraoperative sonography, 89% (63/71); and for conventional imaging, 78% (46/59). The findings at intraoperative sonography led to a change in the clinical treatment of only one patient (2%). CONCLUSION: The results indicate that FDG PET effectively screens potential candidates for curative liver resection. Although intraoperative sonography helps to determine the anatomic location of metastases thus facilitating surgical resection, its adjunctive use in patients screened preoperatively by FDG PET has limited impact on treatment selection.     

Metachronous, multicentric giant cell tumor of the sphenoid bone with histologic, CT, MR imaging, and positron-emission tomography/CT correlation

Giant cell tumor (GCT) of the sphenoid bone is a relatively rare entity and metachronous multicentric GCT of the sphenoid is even rarer; we are aware of only 3 previous cases in the literature. We describe here a tumor of the sphenoid bone that was identified 15 years after multiple resections of a GCT of the left inferior pubic ramus. Correlation is made between the histopathologic findings, MR imaging of the brain, CT of the head, and fusion positron-emission tomography (PET)/CT scan performed with fluorine-18 fluoro-2-deoxy-D-glucose (18F-FDG). This report is the first to describe the appearance of a GCT of the sphenoid bone on a fusion PET/CT examination. High metabolic activity in the base of the skull adjacent to the middle cranial fossa was demonstrated in a fashion similar to that of the known pelvic lesion. This case also demonstrates that the increased metabolic activity seen in a GCT of the sphenoid bone may be partially obscured by the adjacent physiologic high metabolic activity of the brain.     

PET evaluation of soft-tissue masses with fluorine-18 fluoro-2-deoxy-D-glucose.

Positron emission tomography (PET) with fluorine-18 fluoro-2-deoxy-D-glucose (FDG) was performed in 19 patients referred for clinical evaluation of soft-tissue masses. These patients had 20 different lesions and had been evaluated previously with computed tomography (CT) and/or magnetic resonance (MR) imaging. The diagnoses were subsequently confirmed with open biopsy or excision (19 lesions) or by clinical and radiographic follow-up (one lesion). Semiquantitative assessment of FDG accumulation (differential uptake ratio) within the suspected tumor helped correctly separate the 10 malignant tumors from the 10 benign lesions. In contrast, a simple ratio of FDG uptake within the suspected tumor to that within comparable normal soft tissue was less successful in helping make this distinction, with overlap in 12 of the 20 cases. Careful comparison with findings from other available imaging studies is essential for accurate interpretation of PET studies of soft-tissue masses, but in many cases, PET may be a useful adjunct in the preoperative evaluation of suspected soft-tissue tumors, yielding valuable information that is not provided with CT or MR imaging.     

Liver lesions: manganese-enhanced MR and dual-phase helical CT for preoperative detection and characterization comparison with receiver operating characteristic analysis

PURPOSE: The purpose of this study was to compare, by means of receiver operating characteristic (ROC) analysis, dual-phase helical computed tomography (CT) and manganese-enhanced magnetic resonance (MR) imaging in the detection and characterization of hepatic lesions in patients prior to surgery. MATERIALS AND METHODS: Twenty-five patients known to have or suspected of having hepatic lesions who were eligible for surgery underwent dual-phase (ie, arterial and portal phase) helical CT and phased-array MR imaging (ie, unenhanced fast spin-echo T2-weighted imaging and gradient-echo T1-weighted imaging performed before and after administration of mangafodipir trisodium). All images were reviewed independently by three off-site blinded reviewers who separately reviewed the CT scans and MR images. The standard of reference was findings at surgery, intraoperative ultrasonography (US), and histopathologic examination. ROC curves were established to analyze the results for each reader and modality. RESULTS: Ninety-four lesions (77 malignant and 17 benign) were revealed at surgery, intraoperative US, and/or histopathologic examination. The overall rate of lesion detection for the three readers at CT was 81.9% +/- 7.8, 90.4% +/- 5.9, and 76.6% +/- 8.6. At MR imaging, the detection rates were 72.3% +/- 9.0, 71.3% +/- 9.1, and 69.1% +/- 9.3 (P =.001 for the difference between MR and CT). The average rate of false-positive diagnoses in patients was 14.1% at CT and 6.4% at MR imaging (P =.06 for the difference between MR and CT). The mean areas under the alternative-free-response ROC curves were 0.74 for MR and 0.72 for CT (P =.751, not significant). CONCLUSION: In detection and characterization of liver lesions, manganese-enhanced MR imaging and dual-phase helical CT were not statistically different.     

Primary dedifferentiated liposarcoma of the retroperitoneum. Prognostic significance of computed tomography and magnetic resonance imaging features

OBJECTIVES: To describe computed tomography (CT) and magnetic resonance (MR) imaging findings and to determine the prognostic significance of radiologic appearances in primary dedifferentiated liposarcoma of the retroperitoneum. METHODS: Initial CT and MR imaging studies of 20 pathologically confirmed cases of primary dedifferentiated liposarcoma of the retroperitoneum were retrospectively reviewed and assessed for correlations with the histopathologic features. CT and MR images were evaluated by 2 radiologists with agreement by consensus, and univariate analyses were conducted to evaluate survival with a mean clinical follow-up duration of 47 months (range, 5-114 months). RESULTS: Tumor invasion was more frequent in the anterior or posterior pararenal originating tumors than in pararenal tumors (P<0.05). Well-defined nonlipomatous masses juxtaposed with fatty tumors were identified in all cases. Calcification or ossification was seen in 6 patients (30%) on unenhanced CT. Imaging findings including attenuation, signal characteristics, and enhancement patterns of nonlipomatous masses were nonspecific regardless of histologic variances. Recurrent tumors (n=6) tended to invade surrounding organs. Univariate analysis revealed that calcification or ossification (P<0.05) and first recurrence with duration of a mean 13 months (P<0.05) identified by imaging studies had significant impacts on overall survival. CONCLUSIONS: Calcification or ossification and first recurrence identified by CT and MR imaging studies are significant adverse prognostic factors in primary dedifferentiated liposarcoma of the retroperitoneum.     

Stereotactic comparison among cerebral blood volume, methionine uptake, and histopathology in brain glioma

BACKGROUND AND PURPOSE: Vascularity, metabolism, and histologic grade are related in gliomas but the exact determinants of these relationships are not fully defined. We used image coregistration and stereotactic biopsies to regionally compare cerebral blood volume (CBV) and (11)C-methionine (MET) uptake measurements in brain gliomas and to assess their relationship by histopathologic examination. MATERIALS AND METHODS: Fourteen patients with brain gliomas underwent MR imaging, including dynamic susceptibility contrast-enhanced MR and positron-emission tomography (PET) using MET acquired in identical stereotactic conditions before biopsy. MR-based CBV maps were calculated and both CBV maps and PET images were coregistered to anatomic images. Sixty-five biopsy samples were obtained on trajectories targeted toward high MET uptake area. The following histopathologic features were semiquantified in each sample: mitotic activity, endothelial proliferation, cellular pleomorphism, and tumor necrosis. CBV and MET uptake values were measured in the biopsy area and normalized to contralateral white matter. CBV ratios were compared with MET uptake ratios, and both measurements were compared with histologic features of each sample. RESULTS: CBV ratios ranged from 0.08 to 10.24 (median = 1.73), and MET uptake ratios ranged from 0.30 to 4.91 (median = 1.67). There was a positive correlation between CBV ratios and MET uptake ratios (r = 0.65, P < .001). Both CBV and MET uptake ratios were found to be significantly related to endothelial proliferation and mitotic activity (P < .01). CONCLUSION: Within glial tumors, there is a local relationship between CBV and MET uptake measurements. Both provide indices of focal malignant activity.     

The blood tumour barrier in intracranial tumours studied with X-ray computed tomography and positron emission tomography using 68-Ga-EDTA

Summary Disruption of the blood brain barrier or rather blood tumour barrier in cerebral tumours was studied with CT after intravenous injection of contrast medium and with PET after intravenous administration of 68-Ga-EDTA. Histology from stereotactic biopsies or open surgery is compared with the radiologic findings and advantages of the respective methods are discussed. The material consisted of 47 patients mainly with supratentorial gliomas and a few miscellaneous tumours. Astrocytomas (Kernohan grade II) were found to have no disruption of blood tumour barrier while anaplastic astrocytomas and glioblastomas (Kernohan grade III and IV) had. PET is somewhat superior to CT in detection of disruption of the blood tumour barrier. It is concluded that the combination of CT and PET is of value in the assessment of intracranial tumours.     

颅内胚胎发育不良性神经上皮瘤影像与病理

目的探讨颅内胚胎发育不良性神经上皮瘤(DNT)的影像表现,以期提高诊断水平。方法回顾分析13例经手术和病理证实的颅内胚胎发育不良性神经上皮瘤的影像表现,并与手术病理相对照。全部病例行MRI平扫与增强扫描,其中6例行CT平扫,3例行18F-FDG正电子发射体层摄影(PET)检查。结果颞叶8例,额叶3例,顶叶及四脑室底各1例,病变位于皮层及皮层下区。MRI平扫呈均匀或不均匀长T1、长T2信号,增强扫描12例无明显强化,1例仅见结节状强化。CT平扫4例呈均匀低密度,2例呈低、等混杂密度;PET检查3例均呈低代谢改变。结论颅内胚胎发育不良性神经上皮瘤的影像表现有一定特点,综合影像学检查有助于该病的诊断。     

Comparative analysis of MR imaging, positron emission tomography, and ictal single-photon emission CT in patients with neocortical epilepsy

BACKGROUND AND PURPOSE: MR imaging, positron emission tomography (PET), and single-photon emission CT (SPECT) play important roles in presurgical localization of epileptic foci. However, comparative study of these imaging methods for cases of neocortical epilepsy has been limited. The purpose of this study was to compare the sensitivities of these three imaging methods for presurgical localization of neocortical epileptogenic foci. METHODS: We studied 117 consecutive patients who underwent surgery for intractable neocortical epilepsy. The pathologic substrates were neuronal migration disorder (n = 77), tumor (n = 15), and others (n = 25). MR imaging was compared retrospectively with (18)F-fluorodeoxyglucose PET and ictal technetium-99m hexamethylpropyleneamine oxime SPECT regarding their capability to correctly localize the epileptogenic foci. The pathologic findings were used as the standard of reference. RESULTS: Overall, MR imaging, PET, and ictal SPECT correctly localized the lesions for 59.8%, 77.7%, and 70.3% of the patients, respectively, with a 38% concordance rate among the three methods. PET was most sensitive (71-100%) in detecting all substrates. MR imaging was as sensitive (100%) as PET in detecting tumor but was least sensitive (48.1%) in detecting neuronal migration disorder. Ictal SPECT was more sensitive (75.8%) than MR imaging in detecting neuronal migration disorder. Patients with imaging abnormalities achieved good outcomes in 81.4% of the cases, in contrast to 59.5% for those without imaging abnormalities (P <.05). CONCLUSION: PET and ictal SPECT were overall more sensitive than was MR imaging, despite the low concordance rate and variable sensitivity depending on substrates. The detection of abnormalities by MR imaging was associated with good outcome. PET or ictal SPECT can be well used as complementary tools, particularly in cases of negative MR imaging findings.     

Positron emission tomography of cavernous haemangiomas of the brain

Four cases with lesions suspected to be low-grade intracerebral tumours but later proved to be cavernous haemangiomas are described. The patients were examined with contrast enhanced CT and with positron emission tomography (PET). The lesions were partly calcified with a mild or no mass effect and a slight contrast enhancement at CT. There were signs of disrupture of the blood-lesion barrier also on radionuclide studies. PET with 11C-methionine and 11C-glucose showed a normal or decreased accumulation of the tracers. This combination of findings has not been encountered in intracranial tumours. As a comparison, one case of glioblastoma is described. In this patient, the CT findings suggested a cavernous haemangioma. However, PET showed a markedly increased accumulation of 11C-methionine, which is compatible with brain tumour but not with haemangioma.     

Positron-emission tomography and computed tomography of cystic pancreatic masses

AIM: To investigate the sensitivity and specificity of computed tomography (CT), positron-emission tomography (PET), and both methods in combination, for determining whether cystic pancreatic tumours are malignant. MATERIALS AND METHODS: We retrospectively identified all patients with cystic pancreatic tumours who underwent separate PET and contrast-enhanced CT examinations within a 1-month interval. Tumours were classified as benign or malignant on CT (two radiologists, independently), PET [a reported standardized uptake value (SUV) of 2.5 was taken as the cut-off between benign and malignant], and with PET and CT images together (two radiologists, in consensus). Readers were blinded to pathological and other radiological findings. Mean patient age and lesion size were compared between benign and malignant groups using Student's t-test. For CT findings, odds ratios (OR) and confidence intervals (CI) were calculated using multivariate logistic regression models. For CT, PET, and the combined images, sensitivities and specificities were calculated, and compared between groups using Fisher's exact test. RESULTS: Thirty patients were identified. The best CT predictor of malignancy was size; mean diameter was 2.3 cm (benign) and 4.1 cm (malignant) (p<0.01); OR was 2.80 (95% CI, 1.26-6.20). Sensitivities of CT, PET and combined PET/CT images were 67-71, 57, and 86%, respectively. PET/CT was more sensitive than PET (p<0.01) or CT (p<0.01) alone. Specificities of CT, PET, and combined PET/CT images were 87-90, 65, and 91%, respectively. PET/CT was more specific than PET (p<0.01) but not CT (p>0.05). CONCLUSION: The sensitivity and specificity of combined PET and CT images is comparable with or superior to either CT or PET alone in determining malignancy in cystic pancreatic lesions.