Role of 18F-FDG PET/CT in differentiation of a benign lesion and metastasis on the ribs of cancer patients

ObjectiveIncidental 18-Fluoro-2-deoxyglucose positron emission tomography (¹⁸F-FDG) uptake in the ribs is a relatively common finding on positron emission tomography/computed tomography (PET/CT) images of cancer patients. This study examined the role of ¹⁸F-FDG PET/CT in differentiating between benign lesions and metastases on the ribs.MethodsThis study included 264 lesions in 172 PET/CT cases with underlying malignancy showing newly developed indeterminate ¹⁸F-FDG rib uptake between June 2009 and May 2010. Patients with more than five FDG rib uptakes or hematologic malignancy were excluded. Malignancy was confirmed either histologically or by imaging studies, and clinical follow-up with serial images was at least 6 months. The maximum standardized uptake value (SUVmax) of the rib lesion was recorded. The FDG uptake patterns (focal or segmental; discrete or non-discrete) and CT findings (evidence of fracture, soft tissue lesions, osteoblastic and/or osteolytic lesions) were recorded.ResultsThere were 206 benign lesions and 58 metastases. The SUVmax was significantly higher in the metastatic group (3.0±1.8) than in the benign group (2.5±1.1), (P= .014). For the differential diagnosis between benign and metastatic lesions, the best SUVmax cut-off was determined to be 2.4. Significant indicators for metastasis were a segmental FDG uptake pattern (OR=10.262, 95% CI 4.151–25.371), presence of an osteoblastic/-lytic lesion (OR=22.903, 95% CI 10.468 to 50.108) and the absence of fractures on CT (OR=291.629, 95% CI 39.09–2175.666).ConclusionSUVmax alone is not sufficient to differentiate benign and metastatic rib lesions in cancer patients. The diagnostic accuracy can be further increased when findings of the CT part of PET/CT are considered.     

Development and Validation of 18F-FDG PET/CT-Based Multivariable Clinical Prediction Models for the Identification of Malignancy-Associated Hemophagocytic Lymphohistiocytosis

Objective¹⁸F-fluorodeoxyglucose (FDG) PET/CT is often used for detecting malignancy in patients with newly diagnosed hemophagocytic lymphohistiocytosis (HLH), with acceptable sensitivity but relatively low specificity. The aim of this study was to improve the diagnostic ability of ¹⁸F-FDG PET/CT in identifying malignancy in patients with HLH by combining ¹⁸F-FDG PET/CT and clinical parameters.Materials and MethodsNinety-seven patients (age ≥ 14 years) with secondary HLH were retrospectively reviewed and divided into the derivation (n = 71) and validation (n = 26) cohorts according to admission time. In the derivation cohort, 22 patients had malignancy-associated HLH (M-HLH) and 49 patients had non-malignancy-associated HLH (NM-HLH). Data on pretreatment ¹⁸F-FDG PET/CT and laboratory results were collected. The variables were analyzed using the Mann-Whitney U test or Pearson’s chi-square test, and a nomogram for predicting M-HLH was constructed using multivariable binary logistic regression. The predictors were also ranked using decision-tree analysis. The nomogram and decision tree were validated in the validation cohort (10 patients with M-HLH and 16 patients with NM-HLH).ResultsThe ratio of the maximal standardized uptake value (SUVmax) of the lymph nodes to that of the mediastinum, the ratio of the SUVmax of bone lesions or bone marrow to that of the mediastinum, and age were selected for constructing the model. The nomogram showed good performance in predicting M-HLH in the validation cohort, with an area under the receiver operating characteristic curve of 0.875 (95% confidence interval, 0.686–0.971). At an appropriate cutoff value, the sensitivity and specificity for identifying M-HLH were 90% (9/10) and 68.8% (11/16), respectively. The decision tree integrating the same variables showed 70% (7/10) sensitivity and 93.8% (15/16) specificity for identifying M-HLH. In comparison, visual analysis of ¹⁸F-FDG PET/CT images demonstrated 100% (10/10) sensitivity and 12.5% (2/16) specificity.Conclusion¹⁸F-FDG PET/CT may be a practical technique for identifying M-HLH. The model constructed using ¹⁸F-FDG PET/CT features and age was able to detect malignancy with better accuracy than visual analysis of ¹⁸F-FDG PET/CT images.     

Feasible Method to enable clear visualization of suspected bladder cancer with 18F-FDG PET/CT

PurposeTo evaluate value of a new method in detecting bladder lesion with ¹⁸F-FDG PET/CT.MethodsRoutine and delayed scans of 14 patients were retrospectively studied. All these bladder lesions were confirmed by pathology. By increasing display threshold of SUVmax, routine images were analyzed for the second time.ResultsOf 12 ¹⁸F-FDG-avid cases, 10 cases were confirmed to be primary bladder carcinoma, 2 false-positive cases were inflammation. There were 25% positive cases on routine display and 50% on display with increased SUVmax threshold.ConclusionThe method can effectively increase the sensitivity and accuracy in detecting bladder cancer with ¹⁸F-FDG PET/CT.     

F18-fluorodeoxyglucose positron emission tomography/computed tomography in the evaluation of vertebral vascular tumors

PurposeThe uptake of ¹⁸F-FDG is higher in most malignancies than in benign tumors. This study aimed to investigate the diagnostic value of ¹⁸F-FDG PET/CT in vertebral vascular tumors.Materials and methodsWe retrospectively collected PET/CT and clinical data of patients with vertebral vascular tumors and analyzed the location, number, and bone destruction and FDG uptake features of the lesion. We measured SUVmax and maximum diameter and analyzed the correlations between SUVmax and the pathological results, size, and CT features.ResultsTwenty-one pathology-proven vertebral vascular tumors were included: 2 angiosarcomas (SUVmax, 11.6 and 32.3), 1 epithelioid hemangioendothelioma (SUVmax, 5.7), 1 epithelioid hemangioma (SUVmax, 8.5), and 17 aggressive hemangiomas. Twelve cases of typical hemangiomas were included as controls. The SUVmax and diameter of the aggressive hemangiomas were higher than those of the typical hemangiomas. The mean SUVmax of aggressive hemangiomas with cortical destruction was higher than that of those without cortical destruction (t = −2.566, P = 0.022). Radioactive distribution in aggressive hemangiomas was homogeneous and heterogeneous in nine and eight cases, respectively. In six aggressive hemangiomas, the FDG uptake of residual and marginal sclerosing bone was higher than that of the osteolytic destruction area and/or paravertebral soft tissue. Six aggressive hemangiomas involved the spinal canal, without clear visualization on PET/CT.Conclusion¹⁸F-FDG uptake of vertebral malignant vascular tumors is higher than that of hemangiomas. The FDG uptake of hemangiomas varies and may be related to concurrent cortical destruction. ¹⁸F-FDG PET/CT shows limitations in evaluating the spinal canal involvement of aggressive hemangioma.     

Multifocal Colonic Lesions Detected by 18F-FDG PET/CT: Correlation with Histopathology and Gross Specimen

A 73-year-old man underwent ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for the staging of colon cancer. The ¹⁸F-FDG PET/CT revealed three colonic lesions. The histopathologic examination of the postoperative gross specimen revealed a tubular adenoma, a tubulovillous adenoma and an adenocarinoma. The maximal standardized uptake value (SUVmax) of a tubulovillous adenoma was much higher than that of adenocarcinoma. This patient could be considered as a representative case highlighting that SUVmax is not a reliable indicator for discriminating colon cancer from colonic adenomas.     

The value of 18F-FDG PET/CT in the assessment of active idiopathic retroperitoneal fibrosis

Purpose

The different stages in idiopathic retroperitoneal fibrosis (IRF) are generally assessed by assay of inflammatory markers and analysis of contrast-enhanced CT images of the retroperitoneal mass. We investigated the potential role of ¹⁸F-FDG PET/CT in this clinical setting.

Methods

¹⁸F-FDG uptake was assessed visually and semiquantitatively (using maximum standardized uptake values, SUVmax) in images of the abdominal mass in 22 patients prospectively enrolled from June 2008 to December 2010 who underwent a total of 33 PET/CT studies. The accuracy in discriminating active from inactive disease was calculated assuming as reference a biochemical instrumental evaluation of patients with IRF mostly based on the level of inflammatory indices and contrast enhancement (CE) of the mass at the time of each PET study. In particular, the relationship between SUVmax and CE, the latter calculated from the change in radiodensity (Hounsfield units) between the basal and postcontrast venous portal phases, was evaluated on a three-point scale (0 <20?HU, 1 20–30?HU, 2 ≥30?HU). SUVmax and CE scores were correlated with the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels. The value of PET/CT in assessing the variation of disease activity over time was also investigated by analysing the changes in metabolic volume (MV) of the retroperitoneal lesion between repeat patient studies.

Results

PET/CT accurately discriminated (93.9?%) active from inactive disease. Significant agreement (p?<?0.01) was observed between visual and semiquantitative analysis of ¹⁸F-FDG uptake, and CE score. A significant correlation (p?<?0.01) was found among SUVmax, CRP levels (rho?=?0.54) and ESR (rho?=?0.55). Corresponding variations in MV and CE score were observed in patients with multiple studies (p?<?0.01; rho?=?0.68).

Conclusion

¹⁸F-FDG PET/CT may be considered an alternative imaging method for the assessment of different stages of IRF.     

Differentiation and diagnosis of benign and malignant testicular lesions using 18F-FDG PET/CT

ObjectivesThe purpose of this study was to evaluate the differential diagnostic value of ¹⁸F-fluorodeoxy glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for benign and malignant testicular lesions.MethodsThe PET/CT scans of 53 patients with testicular lesions confirmed by biopsy or surgical pathology were retrospectively analyzed. There were 32 cases of malignant tumors and 21 cases of benign lesions. Differences in the maximum standardized uptake value (SUVmax) measurements and the SUVmax lesion/background ratios between benign and malignant lesions were analyzed. The diagnostic value of this PET/CT modality for the differential diagnosis of benign versus malignant testicular lesions was calculated.ResultsThe differences in the SUVmax measurements and the SUVmax lesion/background ratios between benign and malignant lesions were statistically significant (SUVmax: Z = −4.295, p = 0.000; SUVmax lesion/background ratio: Z = −5.219, p = 0.000); specifically, both of these indicators were higher in malignant lesions compared to benign lesions. An SUVmax of 3.75 was the optimal cutoff value to differentiate between benign and malignant testicular lesions. The diagnostic sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of this PET/CT modality in the differential diagnosis of benign versus malignant testicular lesions were 90.6%, 80.9%, 86.8%, 87.9%, and 85.0%, respectively.Conclusions¹⁸F-FDG PET/CT can accurately identify benign and malignant testicular lesions.     

Clinical correlation of metabolic parameters on <Superscript>18</Superscript>F-FDG PET/CT in idiopathic frozen shoulder

Objective

Because positron emission tomography/computed tomography (PET/CT) using fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) can be used to visualize inflammation of the musculoskeletal system, it may help elucidate the pathophysiology of frozen shoulder (FS). The purpose of this study was to characterize the uptake pattern on ¹⁸F-FDG PET/CT in patients with idiopathic FS and to determine if there is a correlation between its metabolic parameters and clinical findings.

Methods

¹⁸F-FDG PET/CT was conducted to 35 patients with unilateral idiopathic FS. Clinical data including pain, functional scores, and passive range of motion (ROM) were collected. Maximum standardized uptake values (SUVmax) were measured at the four regions of interest (ROIs): rotator interval (RI), anterior joint capsule (AJC), axillary recess (AR), and posterior joint capsule (PJC) from the attenuation-corrected axial images.

Results

Mean SUVmax values for four ROIs of the affected shoulder were significantly higher than those of the unaffected shoulder. Mean SUVmax values of RI and AR were significantly higher than those of AJC and PJC and mean SUVmax of AJC was significantly higher than that of PJC in the affected side. Three recognizable patterns of increased uptake were noted: (1) AR dominant type (15 patients); (2) RI dominant type (9 patients); (3) both RI and AR dominant type (11 patients). The SUVmax of AR showed negative correlation with abduction and forward flexion. The SUVmax of RI showed negative correlation with external rotation and internal rotation. The SUVmax of AJC showed negative correlation with all ROMs. However, there was no significant correlation between the SUVmax of PJC and any ROM.

Conclusion

Our study demonstrates that the anterior–inferior capsular portion, including RI and AR, is the main pathologic site of idiopathic FS and reveals significant correlations between ROM and metabolic parameters on ¹⁸F-FDG PET/CT. These results imply that AR and RI lesions are related to elevational limitations and rotational limitations, respectively.

     

Assessment of the diagnostic accuracy of <Superscript>18</Superscript>F-FDG PET/CT in prosthetic infective endocarditis and cardiac implantable electronic device infection: comparison of different interpretation criteria

Purpose

The diagnosis of prosthetic valve (PV) infective endocarditis (IE) and infection of cardiac implantable electronic devices (CIEDs) remains challenging. The aim of this study was to assess the usefulness of ¹⁸F-FDG PET/CT in these patients and analyse the interpretation criteria.

Methods

We included 41 patients suspected of having IE by the Duke criteria who underwent ¹⁸F-FDG PET/CT. The criteria applied for classifying the findings as positive/negative for IE were: (a) visual analysis of only PET images with attenuation-correction (AC PET images); (b) visual analysis of both AC PET images and PET images without AC (NAC PET images); (c) qualitative analysis of NAC PET images; and (d) semiquantitative analysis of AC PET images. ¹⁸F-FDG PET/CT was considered positive for IE independently of the intensity and distribution of FDG uptake. The gold standard was the Duke pathological criteria (if tissue was available) or the decision of an endocarditis expert team after a minimum 4 months follow-up.

Results

We studied 62 areas with suspicion of IE, 28 areas (45 %) showing definite IE and 34 (55 %) showing possible IE. Visual analysis of only AC PET images showed poor diagnostic accuracy (sensitivity 20 %, specificity 57 %). Visual analysis of both AC PET and NAC PET images showed excellent sensitivity (100 %) and intermediate specificity (73 %), focal uptake being more frequently associated with IE. The accuracy of qualitative analysis of NAC PET images depended on the threshold: the maximum sensitivity, specificity and accuracy achieved were 88 %, 80 %, 84 %, respectively. In the semiquantitative analysis of AC PET images, SUVmax was higher in areas of confirmed IE than in those without IE (?SUVmax 2.2, p?<?0.001). When FDG uptake was twice that in the liver, IE was always confirmed, and SUVmax 5.5 was the optimal threshold for IE diagnosis using ROC curve analysis (area under the curve 0.71).

Conclusion

The value of ¹⁸F-FDG PET/CT in the diagnosis of suspected IE of PVs and CIEDs is highly dependent on patient preparation and the method used for image interpretation. Based on our results, the best method is to consider a study positive for IE when FDG uptake is present in both AC PET and NAC PET images.

     

Usefulness of Respiratory-Gated <Superscript>18</Superscript>F-FDG PET/CT in Detecting Upper Abdominal Fever Focus

Respiratory-gated ¹⁸F-fluorodeoxygluocse (¹⁸F-FDG) PET/CT has been successfully used to better localize malignancies in the lung or upper abdominal organs. However, clinical usefulness of respiratory-gated ¹⁸F-FDG PET/CT in detection of fever focus has not been reported yet. A 68-year-old male patient with a history of living donor liver transplantation and biliary stenting was referred for ¹⁸F-FDG PET/CT due to fever of unknown origin (FUO). To find the accurate fever focus, respiratory-gated and non-gated ¹⁸F-FDG PET/CT was performed. Respiratory-gated PET/CT readily revealed prominent hypermetabolic lesion in the distal common bile duct (CBD) area where previous surgical graft was in situ. Maximum standardized uptake value (SUVmax) and SUV ratio (SUR) were greater in the gated PET/CT (SUVmax 5.4 and SUR 3.5) than in the non-gated PET/CT (SUVmax 4.6 and SUR 3.0). Fever dramatically subsided after removal of the graft in the CBD. This case report implies that respiratory-gated ¹⁸F-FDG PET/CT can visualize upper abdominal fever focus with better contrast than the conventional non-gated method.     

Pitfalls and Misinterpretations of Cardiac Findings on PET/CT Imaging: A Careful Look at the Heart in Oncology Patients

Positron emission tomography (PET) computed tomography (CT) with 2-[fluorine-18] fluoro-2-deoxy-d-glucose (FDG) has been established as an effective modality for evaluation of cancer. Interpretations of patterns of physiologic ¹⁸F-FDG uptake by the heart is particularly difficult given the wide normal variations of ¹⁸F-FDG metabolic activity observed. Atypical patterns of focal or diffuse physiologic cardiac ¹⁸F-FDG uptake and post-therapeutic effects after radiation therapy, systemic diseases, or cardiomyopathy may also be confused with malignant disease on ¹⁸F-FDG PET/CT. In this article, we review the variations of normal cardiac ¹⁸F-FDG uptake observed in oncology patients and the appearances of other patterns of pathologic metabolic activity, related or not related to the malignancy being investigated, that may lead to false-negative and false-positive results.     

18F-FDG-PET/CT predicts survival in hypopharyngeal squamous cell carcinoma

Objectives

We investigated the relationship between overall survival of patients and pretreatment [¹⁸F]-2-fluorodeoxyglucose (¹⁸F-FDG) uptake, assessed by positron emission tomography combined with computed tomography (PET/CT) in hypopharyngeal squamous cell carcinoma.

Methods

Thirty-one patients who were newly diagnosed as resectable hypopharyngeal squamous cell carcinoma underwent pretreatment ¹⁸F-FDG-PET/CT. We used the maximum standardized uptake value (SUVmax) as ¹⁸F-FDG uptake. Overall survival rate was calculated by the Kaplan–Meier method.

Results

The median SUVmax was 11.53 (range 2.49–22.33). Patients with SUVmax ≥ 13 significantly exhibited shorter overall survival in univariate analysis (p < 0.01). Moreover, by Cox proportional hazards model of multivariate analysis, SUVmax ≥ 13 was a significant prognostic factor independent of clinical T and N classification, and treatment group (p < 0.02).

Conclusions

These results suggested that SUVmax obtained by pretreatment ¹⁸F-FDG PET/CT assessment is an important prognostic factor in patients with hypopharyngeal squamous cell carcinoma.     

Comparison of diagnostic ability between 99mTc-MDP bone scan and 18F-FDG PET/CT for bone metastasis in patients with small cell lung cancer

Objective

The aim of this study was to compare the diagnostic ability of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) with that of ^99mTc-methylene diphosphonate (^99mTc-MDP) bone scan for bone metastasis in staging patients with small cell lung cancer (SCLC).

Methods

Ninety-five patients with SCLC who underwent both ¹⁸F-FDG PET/CT and ^99mTc-MDP bone scan for initial staging work-up were retrospectively enrolled. All ¹⁸F-FDG PET/CT and bone scan images were visually assessed. Bone metastasis was confirmed by histopathological results and all available clinical information.

Results

Of 95 patients with SCLC, metastatic bone lesions were found in 30 patients, and 84 metastatic lesions were evaluated on a lesion-basis analysis. The sensitivity of ¹⁸F-FDG PET/CT was 100?% on a per-patient basis and 87?% on a per-lesion basis, and there was no false-positive lesion on PET/CT images. In contrast, the sensitivity of the bone scan was 37?% on a per-patient basis and 29?% on a per-lesion basis. The bone scan showed 11 false-positive lesions. The bone scan detected two metastatic lesions that were not detected by PET/CT, which were outside the region scanned by PET/CT. On follow-up bone scan, 21 lesions that were not detected by the initial bone scan but were detected by PET/CT were newly detected.

Conclusions

In patients with SCLC, ¹⁸F-FDG PET/CT showed higher detection rate of bone metastasis than ^99mTc-MDP bone scan. Thus, ¹⁸F-FDG PET/CT can replace bone scan in staging patients with SCLC.     

18F-FDG PET/CT in HIV-related central nervous system pathology

Purpose

To evaluate the utility of ¹⁸F-FDG PET/CT in suspected cerebral pathology in HIV-infected individuals.

Methods

¹⁸F-FDG PET/CT scans from 29 HIV-infected individuals (29 brain scans, 22 whole-body scans) who presented with neurological symptoms and signs were retrospectively reviewed and compared with subsequent clinical investigations.

Results

The majority of patients (n?=?25) were referred to differentiate infection from malignant causes of cerebral pathology. Ten of the 11 patients with an eventual diagnosis of toxoplasmosis infection were correctly diagnosed by ¹⁸F-FDG PET/CT showing lesional uptake less than that of normal brain cortex (mean SUVmax 3.5, range 1.9 – 5.8). All five patients with a final diagnosis of primary central nervous system lymphoma (PCNSL) were correctly diagnosed by ¹⁸F-FDG PET/CT showing lesional uptake greater than that of normal brain cortex (mean SUVmax 18.8, range 12.4 – 29.9). Four of the five patients with ¹⁸F-FDG PET/CT features suggesting a vasculitic process had vasculitis confirmed as the final diagnosis. Three patients showed variable uptake in multiple cerebral lesions (including final diagnoses of tuberculosis and metastases from lung cancer in two patients) and there were four other miscellaneous diagnoses. In 12 patients biopsies were performed at sites guided by PET abnormality (7 brain, 5 lymph nodes) confirming or excluding significant disease in 11.

Conclusion

¹⁸F-FDG PET/CT is particularly useful for differentiating between infection and PCNSL in HIV-infected patients with a cerebral lesion on MRI or CT. ¹⁸F-FDG PET/CT was also a helpful tool in the diagnostic work-up of patients with other HIV-related cerebral pathology. Additional advantages of ¹⁸F-FDG PET/CT are the abilities to assess abnormally increased glucose metabolism in the body and to identify potential sites for biopsy.     

The Clinical Role of Dual-Time-Point 18F-FDG PET/CT in Differential Diagnosis of the Thyroid Incidentaloma

Thyroid incidentalomas are common findings during imaging studies including ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) for cancer evaluation. Although the overall incidence of incidental thyroid uptake detected on PET imaging is low, clinical attention should be warranted owing to the high incidence of harboring primary thyroid malignancy. We retrospectively reviewed 2,368 dual-time-point ¹⁸F-FDG PET/CT cases that were undertaken for cancer evaluation from November 2007 to February 2009, to determine the clinical impact of dual-time-point imaging in the differential diagnosis of thyroid incidentalomas. Focal thyroid uptake was identified in 64 PET cases and final diagnosis was clarified with cytology/histology in a total of 27 patients with ¹⁸F-FDG-avid incidental thyroid lesion. The maximum standardized uptake value (SUVmax) of the initial image (SUV1) and SUVmax of the delayed image (SUV2) were determined, and the retention index (RI) was calculated by dividing the difference between SUV2 and SUV1 by SUV1 (i.e., RI = [SUV2 - SUV1]/SUV1 × 100). These indices were compared between patient groups that were proven to have pathologically benign or malignant thyroid lesions. There was no statistically significant difference in SUV1 between benign and malignant lesions. SUV2 and RI of the malignant lesions were significantly higher than the benign lesions. The areas under the ROC curves showed that SUV2 and RI have the ability to discriminate between benign and malignant thyroid lesions. The predictability of dual-time-point PET parameters for thyroid malignancy was assessed by ROC curve analyses. When SUV2 of 3.9 was used as cut-off threshold, malignancy on the pathology could be predicted with a sensitivity of 87.5 % and specificity of 75 %. A thyroid lesion that shows RI greater than 12.5 % could be expected to be malignant (sensitivity 88.9 %, specificity 66.3 %). All malignant lesions showed an increase in SUVmax on the delayed images compared with the initial images. But in the group of benign lesions, 37.5 % (6/16) showed a decrease or no change in SUVmax. Dual-time-point ¹⁸F-FDG PET/CT, obtaining additional images 2 h after injection, seems to be a complementary method for the differentiation between malignancy and benignity of incidental thyroid lesions.     

Detection of Richter's transformation of chronic lymphocytic leukemia by PET/CT.

Our objective was to evaluate the accuracy of PET/CT for the diagnosis of Richter's transformation of chronic lymphocytic leukemia (CLL) to diffuse large cell lymphoma. METHODS: A retrospective study was performed of 37 patients with CLL who underwent 18F-FDG PET/CT at our institution between March 2003 and July 2005. All PET/CT scans were reviewed in consensus by 2 diagnostic radiologists. Sites of abnormal 18F-FDG uptake with a maximum standardized uptake value (SUVmax) of greater than 5 were considered highly suggestive of Richter's transformation. The PET/CT findings were correlated with histologic findings from bone marrow or lymph node biopsy performed within 6 wk of PET/CT and with clinical follow-up. RESULTS: The 37 patients (26 men and 11 women; mean age, 61 y, range, 40-82 y) underwent 57 PET/CT scans. In 10 (91%) of 11 patients with Richter's transformation, PET/CT detected sites of abnormal 18F-FDG uptake having an SUVmax of greater than 5. Richter's transformation was missed in 1 patient who had only low-grade 18F-FDG uptake (SUVmax < 5). Nine patients had false-positive PET/CT findings; in 3 of these patients, alternative malignancies were diagnosed (Hodgkin's disease; metastatic neuroendocrine carcinoma; non-small cell lung cancer). In all remaining patients, PET/CT correctly excluded Richter's transformation. For the specific diagnosis of Richter's transformation of CLL to diffuse large B-cell lymphoma, PET/CT had overall sensitivity, specificity, and positive and negative predictive values of 91%, 80%, and 53% and 97%, respectively. CONCLUSION: PET/CT can detect Richter's transformation of CLL to diffuse large B-cell lymphoma with a high sensitivity and a high negative predictive value.     

18F-FDG PET/CT with Contrast Enhancement for Evaluation of Axillary Lymph Node Involvement in T1 Breast Cancer

Background

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography ((PET) safely predicts axillary status in patients with breast cancer, but is not sufficiently accurate in early breast cancer patients. This study analyzed the value of ¹⁸F-FDG PET/computed tomography (CT) with contrast enhancement in detecting axillary lymph node involvement in T1 breast cancer patients.

Methods

Contrast-enhanced ¹⁸F-FDG PET/CT was performed within 20 days of surgery in 143 breast cancer patients with tumors ≤2 cm in size. The patients underwent either axillary lymph node dissection (ALND) or sentinel lymph node biopsy (SLNB), and histopathology reports were used to provide the definitive diagnosis against which the contrast-enhanced ¹⁸F-FDG PET/CT study results were compared.

Results

The sensitivity, specificity, and negative and positive predictive values of contrast-enhanced ¹⁸F-FDG PET/CT in detecting axillary involvement were 70.0%, 92.2%, 88.8%, and 77.8%, respectively, in the entire series of 143 patients, with eight false-positive and 12 false negative results. The false-negative results were associated with the number of metastatic lymph nodes and the rate of FDG uptake.

Conclusion

Contrast-enhanced ¹⁸F-FDG PET/CT cannot replace histologic staging using SLNB in patients with breast cancer, but ¹⁸F-FDG PET/CT increases the sensitivity for predicting axillary node metastasis, and allows for a selective approach to either ALND or SLNB, even in patients with T1 breast cancer.     

Heterogeneity Analysis of 18F-FDG Uptake in Differentiating Between Metastatic and Inflammatory Lymph Nodes in Adenocarcinoma of the Lung: Comparison with Other Parameters and its Application in a Clinical Setting

Purpose

Lymph node (LN) characterization is crucial in determining the stage and treatment decisions in patient with lung cancer. Although ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) has a higher diagnostic accuracy in LN characterization than anatomical imaging, differentiating between metastatic and inflammatory LNs is still challenging because both could show high ¹⁸F-FDG uptake. The purpose of this study was to assess if the heterogeneity of the ¹⁸F-FDG uptake could help in differentiating between inflammatory and metastatic LNs in lung cancer, and to compare with other parameters.

Methods

A total of 44 patients with adenocarcinoma of the lung, who underwent preoperative ¹⁸F-FDG PET/CT without having any previous treatments and were revealed to have ¹⁸F-FDG-avid LNs, were enrolled. There were 52 pathology-proven metastatic lymph nodes in 26 subjects. The pathology-proven metastatic LNs were compared with 42 pathology-proven inflammatory/benign LNs in 18 subjects. The coefficient of variation (CV) was used to assess the heterogeneity of ¹⁸F-FDG uptake by dividing the standard deviation of standardized uptake value (SUV) by mean SUV. The volume of interest was manually drawn based on the combined CT images of ¹⁸F-FDG PET/CT (no threshold is used). Comparisons were made with the maximum standardized uptake values (SUVmax), visual assessment of ¹⁸F-FDG uptake, longest diameter, and maximum Hounsfield units (HUmax).

Results

Metastatic lymph nodes tended to have higher CVs than the inflammatory LNs. The mean CV of metastatic LNs (0.30 ± 0.08; range: 0.08–0.55) was higher than that of inflammatory LNs (0.17 + 0.06; range, 0.07–0.32; P < 0.0001). On receiver operating characteristic (ROC) curve analysis, the area under curve was 0.901, and using 0.20 as cut-off value, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 88.5 %, 76.2 %, 82.2 %, 84.3, and 83.0 % respectively. Accuracy of CV was slightly higher than SUVmax and diameter, but significantly higher than visual assessment and HUmax.

Conclusions

In patients with adenocarcinoma of the lung having no prior treatments, metastatic LNs showed more heterogeneous ¹⁸F-FDG uptake than inflammatory LNs. Measuring the CV of the SUV derived from a manual volume of interest (VOI) can be helpful in determining metastatic LN of adenocarcinoma of the lung. Including diagnostic criteria of CV into the diagnostic approach can increase the accuracy of mediastinal node status.     

Imaging spectrum and pitfalls of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in patients with tuberculosis

Mycobacterium tuberculosis (TB) is one of the most prominant diseases frequently causing false positive lesions in oncologic surveys using ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT), since TB granulomas are composed of activated macrophages and lymphocytes with high affinity for glucose. These pitfalls of ¹⁸F-FDG PET/CT are important for radiologists. Being familiar with ¹⁸F-FDG images of TB could assist in preventing unfavorable clinical results based on misdiagnoses. In addition, ¹⁸F-FDG PET/CT has the advantage of being able to screen the whole body, and can clearly detect harboring TB lesions as high uptake foci. This article details the spectrum and pitfalls of ¹⁸F-FDG PET/CT imaging in TB.     

18F-FDG PET/CT Findings in a Breast Cancer Patient with Concomitant Tuberculous Axillary Lymphadenitis

Although ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) is a sensitive modality for detecting a malignant lesion, increased ¹⁸F-FDG uptake is also seen in infected or inflammatory processes. Here, we report the case of a breast cancer patient with concomitant tuberculous axillary lymphadenitis that showed increased ¹⁸F-FDG uptake. A 39-year-old woman underwent preoperative ¹⁸F-FDG PET/computed tomography (CT) as a part of the work-up for right breast cancer. ¹⁸F-FDG PET/CT images showed a malignant lesion in the right breast with moderate ¹⁸F-FDG uptake, and multiple enlarged right axillary lymph nodes with intense ¹⁸F-FDG uptake. Subsequently, the patient underwent right mastectomy and right axillary lymph node dissection. Histopathological examination confirmed breast cancer and tuberculous lymphadenitis, and the patient was treated concomitantly with anti-tuberculous therapy.