Paravertebral infection (phlegmon) demonstrated by FDG dual-head coincidence imaging in a patient with multiple malignancies

A 66-year-old woman was referred for a bone scan to assess back pain on a background of breast cancer, melanoma, and rheumatic heart disease. The scan appearance was suspicious for a localized soft tissue neoplasm. An FDG coincidence positron emission tomography (PET) study demonstrated a large FDG-avid soft tissue abnormality. Staphylococcus aureus was isolated from a subsequent needle biopsy. This case illustrates the use of FDG-PET in infection imaging, as well as demonstrating the potential pitfalls in nuclear oncology. Because FDG is not tumor-specific, accumulation in benign lesions may give rise to false-positive results despite a high pretest probability for malignancy.     

F-18 FDG positron emission tomography and benign fractures

PURPOSE: F-18 2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) has been used extensively in the imaging of cancer, including metastatic skeletal disease. Although uptake into benign osseous disease has been reported, there is very limited information regarding uptake into benign fractures. This report provides additional information regarding the appearance of benign fractures on FDG-PET images. MATERIALS AND METHODS: Four case reports of FDG-PET scanning are presented in patients with proved benign fractures. RESULTS: In three of these cases, FDG uptake was noted in fractures when images were obtained 17 days to 8 weeks after injury, with the most avid uptake observed when FDG-PET imaging was performed 17 days after fracture. In the patient in whom imaging was performed 8 weeks after fracture, no uptake of FDG was seen in a benign fracture. CONCLUSIONS: Fractures may accumulate FDG to varying degrees, and false-positive findings may occur when FDG-PET imaging is performed to assess for metastases, although the different pattern of uptake and clinical correlation usually allows accurate differentiation of fracture from skeletal metastases.     

Paget disease of the humerus mimicking metastatic disease in a patient with metastatic malignant mesothelioma on whole body F-18 FDG PET/CT

A 71-year-old man with newly diagnosed malignant mesothelioma was referred for an F-18 FDG PET/CT study to evaluate the extent of disease. PET showed mild FDG uptake in the right chest, corresponding to a lobulated, mass-like right pleural effusion versus thickening involving the entire right pleural space, and some mediastinal involvement, on the accompanying CT scan. In addition, marked FDG uptake was seen in the proximal left humerus, suspicious for an osseous metastasis. The corresponding CT scan findings of cortical thickening and a "Swiss cheese" appearance were most consistent with Paget disease. The intense FDG uptake in an osseous lesion on FDG-PET in our case reminds us of the variable nature of FDG uptake in Paget disease, the possibility of false-positive findings on FDG-PET in patients with cancer, and the usefulness of the fusion techniques in the evaluation of skeletal lesions, with the potential for discriminating between benign Paget disease and other pathologic bone findings.     

Unexpected finding of elevated glucose uptake in fibrous dysplasia mimicking malignancy: contradicting metabolism and morphology in combined PET/CT

Fibrous dysplasia is a common benign disorder of bone in which fibro-osseous tissue replaces bone spongiosa. Lesions have a typical appearance on computed tomography (CT) images and regularly show a markedly increased uptake in bone scintigraphy using ^99mTc-labelled methylene diphosphonate (^99mTc-MDP) as radiotracer. The glucose avidity of these lesions depicted by positron emission tomography (PET) using the radiolabelled glucose derivative ¹⁸F-fluoro-2-deoxy-glucose (FDG) is less well known since FDG-PET does not have a role in the assessment of this disease. However, single cases have been reported in which fibrous dysplasia was present in patients undergoing FDG-PET scanning for oncological reasons, and no significant FDG uptake was observed for lesions identified as fibrous dysplasia. We report on a 24-year-old man with known fibrous dysplasia who underwent combined FDG-PET/CT scanning because of suspected recurrence of testicular cancer. In contrast to prior reports, a markedly elevated uptake of FDG was seen in numerous locations that were identified as fibrous dysplasia by CT. Based on this result, we conclude that fibrous dysplasia may mimick malignancy in FDG-PET and that coregistered CT may help to resolve these equivocal findings.     

^18FDG-PET和^99mTc-MDP骨扫描检测骨转移瘤价值的比较

目的:评价18FDG-PET恶性肿瘤骨转移的作用及与99mTc-MDP-ECT 比较.材料和方法: 经病理证实为恶性肿瘤患者51 例及非肿瘤性疾病5例在本科同时接受18F-FDG-PET和99mTc-MDP-ECT检查(时间间隔不超过2周).骨转移的诊断由病理、X线或CT/MRI、随访超过1年综合决定.结果:99mTc-MDP和18FDG-PET 对骨转移瘤诊断的灵敏度、特异性、准确率率分别为93.7%、93.7%,97.5%、50%,90.8%、62.5%.99mTc-MDP和18FDG-PET均为阳性15例,其中证实骨转移为14例,假阳性1例;均为阴性例数为20例.21例不相符的结果中20例99mTc-MDP-ECT 阳性而18F-FDG-PET 为阴性.18F-FDG-PET和99mTc-MDP-ECT假阴性各1例.均诊断为多发骨转移的12例患者中99mTc-MDP-ECT发现的骨转移病灶数多于18F-FDG-PET.结论:18F-FDG-PET 与99mTc-MDP骨扫描相比较对肿瘤骨转移的探测有较高的特异性,但敏感性较低.     

Superphysiologic FDG Uptake in the Non-Paralyzed Vocal Cord. Resolution of a False-Positive PET Result with Combined PET-CT Imaging

The application of positron emission tomography imaging with 18F-fluorodeoxyglucose (FDG) to the extracranial head and neck has been proven to be effective in the detection and staging of malignancy. The FDG uptake of normal laryngeal tissue is symmetric and low, while benign lesions typically have only slight increases in FDG uptake. We report a case of asymmetric, superphysiologic FDG uptake in the contralateral vocal cord of a patient with a unilateral vocal cord paralysis secondary to sacrifice of the recurrent laryngeal nerve during pneumonectomy for lung cancer. The FDG uptake of the non-paralyzed vocal cord was increased multiple-fold, placing it well within the range of malignancy. Use of unique, combined PET-CT imaging localized the high FDG uptake to the non-paralyzed vocal cord, and laryngoscopy confirmed no evidence of malignancy in the vocal cord. This case demonstrates that a benign cause of false-positive FDG-PET imaging may be encountered during evaluation of the extracranial head and neck for malignancy. We aim to alert the reader to this potential pitfall in the interpretation of FDG-PET imaging, which can be resolved with the use of combined PET-CT imaging and clinical correlation.     

Extensive FDG uptake and its modification with corticosteroid in a granuloma rat model: an experimental study for differentiating granuloma from tumors

Introduction Increased ¹⁸F-fluorodeoxyglucose (FDG) uptake in inflammatory lesions, particularly in granulomatous inflammation (e.g., sarcoidosis), makes it difficult to differentiate malignant tumors from benign lesions and is the main source of false-positive FDG-PET findings in oncology. Here, we developed a rat granuloma model and examined FDG uptake in the granuloma. The effects of corticosteroid on FDG uptake in the granuloma were compared with those in a malignant tumor. Methods Rats were inoculated with Mycobacterium bovis bacillus Calmette-Guérin (BCG) or allogenic hepatoma cells, and subdivided into control and pretreated (methylprednisolone acetate, 8 mg/kg i.m.) groups. Radioactivity in tissues was determined 1 h after the FDG injection. FDG-PET was performed in rats bearing BCG granulomas or tumors before and after prednisolone treatment. Results Mature epithelioid cell granuloma-formation and massive lymphocyte-infiltration were observed in the control group of granuloma, histologically similar to sarcoidosis. The mean FDG uptake in the granuloma was comparable to that in the hepatoma. Prednisolone reduced epithelioid cell granuloma-formation and lymphocyte-infiltration. Prednisolone significantly decreased the level of FDG uptake in the granuloma (52% of control), but not in the hepatoma. The FDG uptake levels in the granulomas and tumors were clearly imaged with PET. Conclusion We developed an intramuscular granuloma rat model that showed a high FDG uptake comparable to that of the tumor. The effect of prednisolone pretreatment on FDG uptake was greater in the granuloma than in the tumor. These results suggest that BCG-induced granuloma may be a valuable model and may provide a biological basis for FDG studies.     

Comparison of MET-PET and FDG-PET for differentiation between benign lesions and malignant tumors of the lung

OBJECTIVE: We retrospectively assessed and compared the usefulness of 11C-methionine (MET)-PET with that of 18F-FDG-PET for the differentiation between benign lesions and malignant tumors of the lung. METHODS: We examined 101 patients with a suspected lung tumor including 79 patients with primary lung cancer and 22 patients with benign lesions. One hundred and forty PET studies (46 studies with MET-PET and 94 studies with FDG-PET) were performed. Both MET-PET and FDG-PET were performed on 39 patients. The MET-PET was performed 15 minutes after the administration of 67-740 MBq of MET, and FDG-PET 45 minutes after the administration of 30-437 MBq of FDG. The results were then evaluated by the standardized uptake value (SUV). RESULTS: The MET uptake in lung cancer was 3.69+/-1.22 (n = 37) which was significantly higher than that in benign lesions 1.81+/-1.04 (n = 9) (p < 0.001). The sensitivity, specificity and accuracy of MET-PET were 83.8%, 88.9% and 84.8%, respectively, when 2.66 of SUV was used as the cutoff value. The FDG uptake in lung cancer was 5.94+/-2.89 (n = 75) and was also significantly larger than that in benign lesions 2.46+/-1.01 (n = 19) (p < 0.001). The sensitivity, specificity and accuracy of FDG-PET were 81.3%, 78.9% and 80.9%, respectively (cutoff = 3.20). The MET uptake in the lesions correlated significantly with FDG uptake (r = 0.71, p < 0.001). According to an ROC analysis, the area under the curve for MET-PET (area = 0. 833) was higher than that for FDG-PET (area = 0.828), but the difference was not statistically significant. Furthermore, the combined use of MET-PET and FDG-PET did not improve the diagnostic ability. CONCLUSIONS: In conclusion, both MET-PET and FDG-PET were considered to be equally useful for the differential diagnosis of lung tumors. Furthermore, MET uptake in lung lesions was found to correlate significantly with FDG uptake.     

FDG positron emission tomography in isolated limb perfusion therapy in patients with locally advanced melanoma: preliminary results

PURPOSE: Isolated limb perfusion (ILP) with high-dose chemotherapy and tumor necrosis factor is being tested in clinical trials as a treatment for locally advanced extremity melanoma. The authors investigated the ability of F-18 fluorodeoxyglucose positron emission tomography (FDG PET) to determine the true extent of disease in patients with this condition, whose distribution of lesions differs from that seen in previous studies. METHODS: Nine patients with locally advanced melanoma were selected for imaging of the entire body and extremities using FDG PET from a group of participants in a clinical trial of ILP with melphalan +/- tumor necrosis factor. Scans were obtained without attenuation correction. Post-treatment scans were obtained in three patients 1 month after ILP. The findings in the FDG-PET scans were compared with those of a standard protocol (SP) that included anatomic images and physical examinations. RESULTS: Eighty lesions (74 malignant, 6 benign) were detected with FDG PET and the SP combined. Only malignant lesions were detected by both methods in the perfused limbs. Of the malignant lesions, FDG PET detected 65 lesions (sensitivity rate, 88%). In contrast, 48 lesions were detected with the SP (sensitivity rate, 65%). Twenty-six malignant lesions were seen only with FDG PET (35%), whereas nine malignant lesions were seen only with SP (12%). The six benign lesions included three false-positive mediastinal lymph nodes in one patient. The accuracy rates of FDG PET and the SP were 83% and 65%, respectively. These results are comparable to those seen in previous studies with patients who had disease confined primarily to the torso. All post-therapy FDG-PET scans showed a reduction in the number of visualized limb lesions, and diffuse uptake throughout the perfused limbs. The diffuse uptake correlated with post-therapy limb inflammation. CONCLUSIONS: Non-attenuation-corrected FDG PET is more sensitive than the SP in detecting the extent of disease in candidates for ILP. The FDG uptake associated with post-therapy inflammation may reduce the contrast resolution of this technique and must be evaluated further.     

Fluorodeoxyglucose positron emission tomography of soft tissue tumours: is a non-invasive determination of biological activity possible?

Since musculoskeletal tumours comprise a large heterogeneous group of entities with different biological behaviour, clinical diagnosis of such lesions can be very difficult. The aim of this prospective study was to assess the usefulness of 2-[F-18]-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the non-invasive evaluation of soft tissue tumours. One hundred and two patients with suspected soft tissue neoplasms were investigated by FDG-PET. The uptake of FDG was evaluated semiquantitatively by determining the tumour to background ratio (TBR). All patients underwent biopsy, resulting in the histological detection of 39 high-grade sarcomas, 16 intermediate-grade sarcomas, 11 low-grade sarcomas, 25 benign tumours, 10 tumour-like lesions such as spontaneous myositis ossificans (n = 6) and one non-Hodgkin lymphoma. All lesions except for two lipomas disclosed an increased FDG uptake. Sarcomas showed significantly higher TBR values than latent or active benign lesions (P<0.001) and aggressive benign lesions (P<0.05). Using a TBR cut-off level of 3.0 for malignancy, sensitivity of FDG-PET was 97.0%, specificity 65.7% and accuracy 86. 3%. From our data there are three main conclusions: (1) Except for patients with pseudotumoral myositis ossificans, lesions with a TBR >3 were sarcomas (91.7%) or aggressive benign tumours (8.3%). (2) Tumours with a TBR <1.5 were latent or active benign lesions, exclusively. (3) The group with intermediate TBR values (<3 and >1. 5) comprised primarily latent or active benign lesions, but also four aggressive benign tumours and two low-grade sarcomas. Our data suggest that FDG-PET represents a useful tool for the evaluation of the biological activity of soft tissue neoplasms.     

PET imaging of musculoskeletal tumours with fluorine-18 alpha-methyltyrosine: comparison with fluorine-18 fluorodeoxyglucose PET

Fluorine-18 labelled alpha-methyltyrosine (FMT) was developed for positron emission tomography (PET) imaging, and its potential for clinical application in patients with brain tumours has been demonstrated. This is the first trial to compare FMT with 18F-fluoro-2-deoxy-D-glucose (FDG) for the evaluation of musculoskeletal tumours. Seventy-five patients were examined with both FMT- and FDG-PET within a 2-week period. Imaging findings were visually inspected in conjunction with computed tomography and/or magnetic resonance imaging, and standardized uptake values (SUVs) for both FMT and FDG in lesions were also generated and compared with histological findings. A significant correlation between FMT and FDG SUVs was found for all lesions (r=0.769, P<0.0001), and mean values for malignant tumours were significantly higher than those for benign lesions in both FMT- and FDG-PET. The diagnostic sensitivities and specificities for malignancy were 72.7% and 84.9%, respectively, using FMT with a cut-off SUV of 1.2, and 72.7% and 66.0%, respectively, using FDG with a cut-off SUV of 1.9. The resultant accuracy with FMT was 81.3%, higher than that for FDG (68.0%), and the difference with respect to specificity was significant (chi2cal=5.0625, P<0.05). On the other hand, while a significant correlation was found between malignant tumour grade and SUV with both FMT- (rho=0.656) and FDG-PET (rho=0.815), only the latter demonstrated significant differences among grades I, II and III. FMT and FDG for PET appear equally effective at detecting musculoskeletal tumours. In evaluating musculoskeletal tumours, FMT may be superior to FDG in the differentiation between benign and malignant tumours, while FDG may be the better choice for non-invasive malignancy grading.     

Utility of FDG-PET in differential diagnosis of benign and malignant fractures in acute to subacute phase

OBJECTIVE: To evaluate the usefulness of positron emission tomography with [fluorine-18] 2-deoxy-2-fluoro-D-glucose (FDG-PET) for early differential diagnosis of benign and malignant fractures. MATERIALS AND METHODS: Among 1,164 patients who had received FDG-PET between January 1999 and December 2000, 20 patients were found to have an acute fracture on review of clinical charts and/or radiologic images taken within one month before or after FDG-PET examination. The fractures were finally diagnosed by clinical follow up of at least five months duration. Standardized uptake values (SUV) for the benign and malignant bone lesions were calculated and compared. RESULTS: Ten of the 20 patients were finally diagnosed to have a benign fracture, nine patients to have a malignant fracture, and one patient to have both a benign and a malignant fracture at different locations. A statistically significant difference in the SUV was found between the benign group (SUV: 1.36 +/- 0.49) and the malignant group (SUV: 4.46 +/- 2.12) (p = 0.0006, the nonparametric Mann-Whitney U test). CONCLUSIONS: FDG-PET can be a useful method for early differentiation between acute benign and metastatic fractures. Our retrospective study indicates that an acute benign fracture itself does not show significant FDG uptake.     

Nuclear imaging of bone tumors: FDG-PET

Positron emission tomography (PET) has become a very useful adjunct to anatomic imaging techniques, because it can provide an in vivo method for quantifying functional metabolism in normal and diseased tissues. Clinical trials with [(18)F] 2-deoxy-2-fluoro-D-glucose (FDG), the most commonly used radiolabeled tracer for PET imaging, has demonstrated increased accumulation of FDG in cancer tissue. FDG-PET is now widely used for the detection, differentiation, grading, staging, and monitoring of various neoplasms. However, the significance of FDG-PET in such evaluations of primary bone tumors and tumor-like lesions has not been extensively elucidated. In this article, we present recent advances in FDG-PET studies for evaluating primary bone tumors and tumor-like lesions.     

Breast cancer with low FDG uptake: characterization by means of dual-time point FDG-PET/CT

Background

Malignant breast lesions usually are differentiated by FDG-PET with a semiquantitative FDG standardized uptake value (SUV) of 2.5. However, the frequency of breast cancer with an SUV of less than or equal to 2.5 is noteworthy, and often present diagnostic challenges. This study was undertaken to evaluate the accuracy of dual-time point FDG-PET/CT with FDG standardized uptake value (SUV) calculation in the characterization of such breast tumors.

Methods

Forty-nine female patients with newly diagnosed breast cancer were found to have primary breast cancer with minimally increased FDG uptake and met the criteria for inclusion in this study by having borderline levels of increased FDG uptake (SUVmax less than or equal to 2.5) in the initial FDG-PET/CT images. Consequently, they underwent further delayed phase FDG-PET/CT scan for better evaluation of the disease.

Results

Of the 49 cancer lesions; the majority were found to have rising or unvarying dual-time changes in SUVmax (75.5%). The median value of SUVmax increases by 25% between the early and delayed scan. The means ± S.D. of the SUVmax1, the SUVmax2, and the ΔSUVmax% were 1.2 ± 0.6%, 1.3 ± 0.9%, and 5.1 ± 22.4%, respectively. The receiver-operating-characteristic (ROC) analysis proved that the highest accuracy for characterization of malignant breast lesions was obtained when a ΔSUVmax% cut-off value 0.0% was used as criteria for malignant FDG uptake-change over time with sensitivity 75.5%, and false-positive rate 20.4%.

Conclusion

These results suggested that dual-time FDG-PET/CT imaging with standardized uptake value (SUV) estimation can improve the accuracy of the test in the evaluation of breast cancer with low FDG uptake.     

Fluorodeoxyglucose positron emission tomography of soft tissue tumours: is a non-invasive determination of biological activity possible?

Since musculoskeletal tumours comprise a large heterogeneous group of entities with different biological behaviour, clinical diagnosis of such lesions can be very difficult. The aim of this prospective study was to assess the usefulness of 2-[F-18]-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the non-invasive evaluation of soft tissue tumours. One hundred and two patients with suspected soft tissue neoplasms were investigated by FDG-PET. The uptake of FDG was evaluated semiquantitatively by determining the tumour to background ratio (TBR). All patients underwent biopsy, resulting in the histological detection of 39 high-grade sarcomas, 16 intermediate-grade sarcomas, 11 low-grade sarcomas, 25 benign tumours, 10 tumour-like lesions such as spontaneous myositis ossificans (n = 6) and one non-Hodgkin lymphoma. All lesions except for two lipomas disclosed an increased FDG uptake. Sarcomas showed significantly higher TBR values than latent or active benign lesions (P<0.001) and aggressive benign lesions (P<0.05). Using a TBR cut-off level of 3.0 for malignancy, sensitivity of FDG-PET was 97.0%, specificity 65.7% and accuracy 86.3%. From our data there are three main conclusions: (1) Except for patients with pseudotumoral myositis ossificans, lesions with a TBR >3 were sarcomas (91.7%) or aggressive benign tumours (8.3%). (2) Tumours with a TBR <1.5 were latent or active benign lesions, exclusively. (3) The group with intermediate TBR values (<3 and >1.5) comprised primarily latent or active benign lesions, but also four aggressive benign tumours and two low-grade sarcomas. Our data suggest that FDG-PET represents a useful tool for the evaluation of the biological activity of soft tissue neoplasms. Received 27 November 1998 and in revised form 20 January 1999     

The detection of local recurrent head and neck cancer with fluorine-18 fluorodeoxyglucose dual-head positron emission tomography.

Primary tumors of the larynx and hypopharynx are preferably treated with high-dose radiation therapy. In these patients, it may be difficult to distinguish recurrent disease from post-treatment reactions. The aim of the present study was to assess the value of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in the detection of local relapses of laryngeal or hypopharyngeal carcinoma after radiotherapy using a dual-head PET camera. Forty-eight patients (43 male, 5 female; mean age +/-SD, 61+/-9.5 years) with suspected recurrent laryngeal or hypopharyngeal cancer were prospectively studied. The mean interval between initial treatment and suspicion of recurrent disease was 14.6 months (range: 3-100 months). FDG dual-head PET was followed by endoscopy with or without biopsy under general anaesthesia within a period of 2 months in all patients. The mean period of follow-up after FDG dual-head PET was 13.7 months. In 19 out of 31 patients with focally increased uptake, tumour recurrence (mean diameter: 2.4 cm; range 0.4-6.5 cm) was found at initial endoscopy. In five patients recurrence was found during follow-up with a mean interval of 6.6 months. Seven patients had a false-positive study due to benign lesions or swallowing artefacts. In none of the patients with a normal PET study was tumour recurrence found during follow-up. The sensitivity and specificity of FDG dual-head PET were 100% and 71%, respectively. It is concluded that FDG dual-head PET is highly sensitive for the detection of local recurrence of laryngeal and hypopharyngeal carcinoma after radiotherapy. Some lesions were detected with a mean interval of 6.6 months before histological confirmation. In patients suspected of having recurrent laryngeal or hypopharyngeal cancer in whom FDG-PET is negative, endoscopy may be omitted for at least 6 months and possibly for up to 1 year.     

Comparison of18FDG-PET with99mTc-HMDP scntigraphy for the detection of bone metastases in patients with breast cancer

OBJECTIVE: Bone is one of the most common sites of metastasis in breast cancer patients. Although bone scintigraphy is widely used to detect metastatic breast cancer, the usefulness of 18FDG-PET for detecting bone metastasis has not been clearly evaluated. The purpose of this study was to compare the diagnostic accuracy of 18FDG-PET with bone scintigraphy in detecting bone metastasis in breast cancer patients. METHODS: Forty-four women aged 35 to 81 years (mean, 56 years) with breast cancer were examined in this study. Both 18FDG-PET and bone scintigraphy were performed for each patient with 0-69 day intervals (mean, 11.5 days). The results of each image interpretation were compared retrospectively. Whole-body bones were classified into 9 anatomical regions. Metastases were confirmed at 45/187 regions in 14 patients by bone biopsy or clinical follow-up including other imaging techniques for a period of at least 6 months afterwards. RESULTS: On a region basis, the sensitivity, specificity, and accuracy of 18FDG-PET were 84%, 99% and 95%, respectively. Although these results were comparable to those of bone scintigraphy, the combination of 18FDG-PET and bone scintigraphy improved the sensitivity (98%) and accuracy (97%) of detection. False negative lesions of bone scintigraphy were mostly bone marrow metastases and those of 18FDG-PET were mostly osteoblastic metastases. 18FDG-PET was superior to bone scintigraphy in the detection of osteolytic lesions (92% vs. 73%), but inferior in the detection of osteoblastic lesions (74% vs. 95%). CONCLUSIONS: This study shows that 18FDG-PET tends to be superior to bone scintigraphy in the detection of osteolytic lesions, but inferior in the detection of osteoblastic lesions. 18FDG-PET should play a complementary role in detecting bone metastasis with bone scintigraphy.     

Fluorine-18 2-deoxy-2-fluoro-D-glucose PET in the preoperative staging of breast cancer: comparison with the standard staging procedures

The present study compared the diagnostic accuracy of fluorine-18 2-deoxy-2-fluoro-D-glucose positron emission tomography (FDG-PET) with conventional staging techniques. The differentiation between malignant and benign lesions and the detection of multifocal disease, axillary and internal lymph node involvement, and distant metastases were evaluated. One hundred and seventeen female patients were prospectively examined using FDG-PET and conventional staging methods such as chest X-ray, ultrasonography of the breast and liver, mammography and bone scintigraphy. All patients were examined on a modern full-ring PET scanner. Histopathological analysis of resected specimens was employed as the reference method. The readers of FDG-PET were blinded to the results of the other imaging methods and to the site of the breast tumour. The sensitivity and specificity of FDG-PET in detecting malignant breast lesions were 93% and 75% respectively. FDG-PET was twofold more sensitive (sensitivity 63%, specificity 95%) in detecting multifocal lesions than the combination of mammography and ultrasonography (sensitivity 32%, specificity 93%). Sensitivity and specificity of FDG-PET in detecting axillary lymph node metastases were 79% and 92% (41% and 96% for clinical evaluation). FDG-PET correctly indicated distant metastases in seven patients. False-positive or false-negative findings were not encountered with FDG-PET. Chest X-ray was false-negative in three of five patients with lung metastases. Bone scintigraphy was false-positive in four patients. Three patients were upstaged since FDG-PET detected distant metastases missed with the standard staging procedure. It is concluded that, compared with the imaging methods currently employed for initial staging, FDG-PET is as accurate in interpreting the primary tumour and more accurate in screening for lymph node metastases and distant metastases. Due to a false-negative rate of 20% in detecting axillary lymph node metastases, FDG-PET cannot replace histological evaluation of axillary status.     

Fluorodeoxyglucose-PET in the management of malignant melanoma

FDG-PET is of limited use in patients with early-stage disease without nodal or distant metastases (stage I-II), because sentinel node biopsy is much more sensitive in detecting microscopic lymph node metastases. Because of the high tumor-to-background ratio, FDG-PET can highlight metastases at unusual sites that are easily missed with conventional imaging modalities. PET has been shown to have a strong role in detecting metastatic disease. FDG-PET is more sensitive than CT for detecting metastatic lesions in skin, lymph nodes, and abdomen, but CT is equivalent to or more sensitive than FDG-PET for detecting small pulmonary lesions. FDG-PET identifies the location and number of metastatic lesions in stage III and IV disease and therefore is important for surgical planning. Most of the false-negative FDG-PET results are caused by micrometastases and lesion smaller than 10 mm. Postsurgical inflammation, other inflammatory lesions, and some benign tumors cause some false-positive FDG-PET results.     

Sacral insufficiency fracture detected by FDG-PET/CT: Report of 2 cases

We report 2 cases of sacral insufficient fracture detected by FDG-PET/CT. In case 1, a 79-year-old female patient with malignant lymphoma, who had recent lumbago, received FDG-PET/CT examination. Vertical linear FDG uptake medial to bilateral sacro-iliac joint was observed on FDG-PET and a fracture line corresponding to FDG uptake was observed in bone window of CT images. In case 2, an 81-year-old male patient with colon cancer, who also complained of lumbago, received FDG-PET/CT examination. Vertical linear FDG uptake medial to bilateral sacro-iliac joint and horizontal uptake which connects vertical line (H-shaped) was demonstrated and CT also demonstrated a fracture line corresponding to FDG uptake. H-shaped high intensity area corresponding to FDG uptake was observed on T2-weighted image of MRI. On bone scintigraphy, H-shaped uptake was also observed. Like bone scintigraphy, typical H-shaped FDG uptake may be diagnostic in sacral insufficiency fracture. Adding CT information to FDG-PET, that is, assessing SIF with FDG-PET/CT may be useful when atypical findings are observed.