False-positive PET Scans Research Articles

Management and Outcomes for Primary Mediastinal B-Cell Lymphoma Patients with Partial Metabolic Response

Background: The optimal management of patients with primary mediastinal B-cell lymphoma (PMBCL) who experience a partial metabolic response (PMR) on FDG-PET after initial systemic therapy is unclear. This study aimed to investigate different management strategies and outcomes for PMBCL patients who achieved PMR following primary systemic therapy, utilizing a single-center retrospective design. Methods: We reviewed the electronic medical records of 121 PMBCL patients who underwent post-chemotherapy PET scans at the Princess Margaret Cancer Center, Toronto, from January 2009 to September 2021. Using Modified Lugano criteria (2014), post-chemotherapy PET scan results were evaluated, with Deauville score (DS) 0-3 considered a complete metabolic response. Demographic, clinical, and imaging characteristics of the PMBCL population were analyzed. The Kaplan-Meier method was used to estimate progression-free survival (PFS), measured from the time of the post-systemic therapy PET. Results: A total of 121 patients with PMBCL underwent post-chemotherapy PET scans. Among them, 49 patients (40%) demonstrated incomplete metabolic response (DS4-5) Among these 49 patients, 12 showed primary refractory disease, while 37 demonstrated a partial metabolic response (PMR, DS4). The median age at diagnosis of the 37 patients with PMR was 30.8 years (range:18.4 - 52.8 years), and 20 (54%) were female. The median length of follow-up for these patients was 3.7 years (range: 0.4 to 9.2 years). Most PMR patients were stage I/II (26 patients, 70.3%), while the remaining were stage III (2 patients, 5.4%), or stage IV (8 patients, 21.6%), and 26 (70.3%) had a large mediastinal mass (maximum diameter exceeding 10cm). Initial systemic treatment was R-CHOP-21 (34 patients, 91.9%), R-CHOP combined with dose-adjusted R-EPOCH (2 patients, 5.4%), and dose-adjusted EPOCH (1 patient, 2.7%). Thirty one patients (83.8%) received 6 cycles. Following treatment strategies were employed to manage PMR: 1) radiation therapy (RT) only with or without biopsy in 30 patients (80.1%); 2) an observational approach (repeating PET scans without immediate treatment) in 3 patients (8.1%); 3) salvage chemotherapy in 3 patients (8.1%) and other approach in 1(2.7%) patient. The 2-year progression-free survival (PFS) rate for all patients with incomplete metabolic response (n=49) was 74.5% (95% CI = 62.5% to 88.9%). For patients with primary progression on post-chemotherapy PET scans the 2-year PFS (ie free of 2nd progression) was 40% (18.7% to 85.5%), while the 2-year PFS for patients with PMR was 85.4% (74.3% to 98.1%). PMR patients who underwent radiotherapy (RT) had the 2-year PFS rate of 92.7% (95% CI: 83.5% to 100.0%). No progression or relapsed occurred among the 3 patients with PMR who were managed with repeating PET scans without immediate further treatment. Conclusion: This study replicates prior work demonstrating a higher rate of incomplete metabolic response for PMBCL patients following R-CHOP-21 than typically reported for DLBCL. RT to persistent PET-avid sites is associated with excellent PFS. The favorable outcome of PMR patients without any additional treatment illustrates the non-trivial risk of false-positive PET scans following systemic therapy, and the need to identify criteria that can distinguish those who need additional treatment from those who can be safely observed.

False positive PET scan in patients with treated malignancy following COVID-19 vaccination.

e18698 Background: The COVID-19 pandemic led to mass vaccination across the globe and resulted in several unintended consequences, one of which being reactive lymphadenopathy mimicking malignancy. A large study reported hypermetabolic lymphadenopathy (HLN) in over 45% of patients after receiving at least one dose of COVID-19 vaccine. A study on breast cancer patients noted a near-400% increase in lymphadenopathy on MRI and ultrasonography over the two years prior to mass vaccination. These findings present a dilemma in patients with treated malignancy while under surveillance. As vaccination became more commonplace, a case series reported on patients with PET-detected lymphadenopathy, with biopsies confirming VRLN. These investigations contributed to general recommendations on the importance of clinical context in patient care after COVID-19 vaccination. We present a unique study that evaluates patients with treated solid and hematological malignancies that presented with HLN after COVID-19 vaccination which emphasizes the importance of clinical acumen in the management of oncological patients in the pandemic era. Methods: We identified 6 patients aged 39-95 with prior malignancy. 5 were diagnosed with metastatic melanoma, and one had a diagnosis of high-grade B-cell lymphoma. Patients were managed with chemotherapy, immunotherapy, surgery, radiotherapy, or a combination of modalities, and were in complete radiological remission. All patients received at least two doses of a COVID-19 vaccine, with one dose at least three weeks prior to a routine surveillance PET-CT. Each patient exhibited HLN. Results: Of six patients, three underwent biopsy. There was no evidence of malignancy in any biopsy, and VRLN was confirmed. The remaining patients were followed with surveillance, and all had resolution of HLN without intervention. Time between COVID-19 vaccination and PET evidence of HLN ranged from 19 to 232 days. Time between first positive and first resolved PET ranged from 92 to 463 days. All patients were alive at the time of abstract submission. Conclusions: Our study emphasizes the importance of a focused history when suspecting recurrent malignancy, especially after sustained remission in our vulnerable populations. Acknowledging that COVID-19 vaccination can lead to HLN is becoming more common, and we show that this can occur, persist, and resolve even months after vaccination. While high suspicion for recurrence should be maintained, all efforts should be taken to protect patients and prevent unnecessary procedures. Records of recent vaccinations should be available and reviewed prior to radiological studies and clinical decisions, which can reduce avoidable interventions and harm. Surveillance of our patients proved to be an appropriate approach, and our study shows that similar patient presentations can have different paths of care depending on the awareness of treating physicians.

Allogeneic and Alloplastic Augmentation Grafts in Nipple-Areola Complex Reconstruction: A Systematic Review and Pooled Outcomes Analysis of Complications and Aesthetic Outcomes.

With advancements in materials engineering, many plastic surgeons have looked to allogeneic tissue and alloplastic materials as a possible source of structure for long-lasting nipple-areola complex reconstruction. Furthermore, in light of the recent mandate from the Food and Drug Administration restricting the marketing and direct indication of acellular dermal matrices (ADMs) in breast reconstruction, we sought to highlight the overall safety and efficacy demonstrated in the existing literature surrounding all alloplastic materials in nipple-areola complex reconstruction. In this study, the authors conduct a systematic review and pooled outcomes analysis on allogenic and alloplastic implant materials utilized to achieve long-lasting nipple projection stratified by specific material used and respective outcomes. A comprehensive systematic review on allogenic and synthetic materials data utilized in nipple reconstruction was conducted utilizing Medline/PubMed database. Articles were stratified by (1) alloplastic material, as well as (2) objective and patient-reported outcomes. A total of 592 nipple-areola complexes on 482 patients were featured in 15 case series. In all studies, alloplastic or allograft material was utilized to achieve and maintain nipple projection. Subjective measurements revealed a patient satisfaction rate of 93.3% or higher with the majority of patients being very satisfied with their reconstruction. The alloplastic and allograft implants analyzed had an overall complication rate of 5.3% across all materials used. The most common complication reported was flap or graft necrosis with a pooled rate of 2.5%. Overall, the Ceratite implant presented with the highest complication rate (18%) including flap/graft necrosis (13%) and extrusion of the artificial bone (5%). Other rigid implants such as the biodesign nipple reconstruction cylinder reported complications of extrusion (3.6%), projection loss requiring revision (2.5%), wound dehiscence/drainage (1.5%), flap or graft necrosis (1.0%) and excessive bleeding (0.5%). ADM implants had reported complications of both insufficient projection (0.8%) and excessive projection (1.6%), which required surgical revision. Injectable materials had minimal reported complications of pain during injection (0.8%) with Radiesse and a false-positive PET scan result (0.8%) with DermaLive. Allogeneic and alloplastic grafts are a reliable means of achieving satisfactory nipple projection, with a relatively low overall complication profile. The use of Ceratite (artificial bone) led to the highest complication rates. Further clinical studies are necessary to better understand the feasibility and longer-term outcomes of the use of allogeneic and synthetic augmentation grafts to improve nipple projection. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Assessment of Fluorodeoxyglucose F18–Labeled Positron Emission Tomography for Diagnosis of High-Risk Lung Nodules

Clinicians rely heavily on fluorodeoxyglucose F18-labeled positron emission tomography (FDG-PET) imaging to evaluate lung nodules suspicious for cancer. We evaluated the performance of FDG-PET for the diagnosis of malignancy in differing populations with varying cancer prevalence. To determine the performance of FDG-PET/computed tomography (CT) in diagnosing lung malignancy across different populations with varying cancer prevalence. Multicenter retrospective cohort study at 6 academic medical centers and 1 Veterans Affairs facility that comprised a total of 1188 patients with known or suspected lung cancer from 7 different cohorts from 2005 to 2015. 18F fluorodeoxyglucose PET/CT imaging. Final diagnosis of cancer or benign disease was determined by pathological tissue diagnosis or at least 18 months of stable radiographic follow-up. Most patients were male smokers older than 60 years. Overall cancer prevalence was 81% (range by cohort, 50%-95%). The median nodule size was 22 mm (interquartile range, 15-33 mm). Positron emission tomography/CT sensitivity and specificity were 90.1% (95% CI, 88.1%-91.9%) and 39.8% (95% CI, 33.4%-46.5%), respectively. False-positive PET scans occurred in 136 of 1188 patients. Positive predictive value and negative predictive value were 86.4% (95% CI, 84.2%-88.5%) and 48.7% (95% CI, 41.3%-56.1%), respectively. On logistic regression, larger nodule size and higher population cancer prevalence were both significantly associated with PET accuracy (odds ratio, 1.027; 95% CI, 1.015-1.040 and odds ratio, 1.030; 95% CI, 1.021-1.040, respectively). As the Mayo Clinic model-predicted probability of cancer increased, the sensitivity and positive predictive value of PET/CT imaging increased, whereas the specificity and negative predictive value dropped. High false-positive rates were observed across a range of cancer prevalence. Normal PET/CT scans were not found to be reliable indicators of the absence of disease in patients with a high probability of lung cancer. In this population, aggressive tissue acquisition should be prioritized using a comprehensive lung nodule program that emphasizes advanced tissue acquisition techniques such as CT-guided fine-needle aspiration, navigational bronchoscopy, and endobronchial ultrasonography.

Increased x-ray attenuation in malignant vs. benign mediastinal nodes in an orthotopic model of lung cancer.

Staging of lung cancer is typically performed with fluorodeoxyglucose-positron emission tomography-computed tomography (FDG-PET/CT); however, false positive PET scans can occur due to inflammatory disease. The CT scan is used for anatomic registration and attenuation correction. Herein, we evaluated x-ray attenuation (XRA) within nodes on CT and correlated this with the presence of malignancy in an orthotopic lung cancer model in rats. 1×10⁶ NCI-H460 cells were injected transthoracically in six National Institutes of Health nude rats and six animals served as controls. After two weeks, animals were sacrificed; lymph nodes were extracted and scanned with a micro-CT to determine their XRA prior to histologic analysis. Median CT density in malignant lymph nodes (n=20) was significantly higher than benign lymph nodes (n=12; P = 0.018). Short-axis diameter of metastatic lymph nodes was significantly different than benign nodes (3.4 mm vs. 2.4 mm; P = 0.025). Area under the curve for malignancy was higher for density-based lymph node analysis compared with size measurements (0.87 vs. 0.7). XRA of metastatic mediastinal lymph nodes is significantly higher than benign nodes in this lung cancer model. This suggests that information on nodal density may be useful when used in combination with the results of FDG-PET in determining the likelihood of malignant adenopathy.

Tissue Is the Issue: Accuracy of PET Imaging to Detect Bone Marrow Clearance in Patients with Peripheral T-Cell Lymphoma

INTRODUCTION:Adult mature T- and NK-cell neoplasms are a heterogeneous group of aggressive lymphomas comprising approximately 10% to 20% of all non-Hodgkin lymphomas (NHL) with an estimated 5-year overall survival of 40%. Staging and treatment strategies are guided by malignant involvement on PET/CT scan and bone marrow (BM) biopsy. The Lugano Criteria, established in 2014, suggested that focal FDG uptake within the bone marrow was highly sensitive for both Hodgkin (HL) and diffuse large B-cell lymphoma (DLBCL) potentially obviating the need for a bone marrow biopsy if no lesions were seen. Limited data exist regarding the sensitivity of PET for BM involvement in T-cell lymphoma. This study compares PET/CT scans and repeat BM biopsy in patients who have undergone treatment for peripheral T-cell lymphomas (PTCL) by evaluating BM avidity on PET scans.METHODS:This is a single institution study using the Mayo Clinic Lymphoma Database between January 1, 2001 and January 1, 2015. We retrospectively identified all patients with a diagnosis of PTCL, biopsy proven BM involvement at diagnosis, and a concomitant PET for staging. Patients were then reviewed to assess completion of induction therapy and availability of both PET/CT and bone marrow results post-therapy. Evaluation for concordance and discordant BM involvement were then determined using BM biopsy as the gold standard.RESULTS:Sixteen patients had both PET/CT and BM biopsy after completing induction therapy. Median age at diagnosis was 63 years (range 34-72) and 69% were male. PTCL subtype was peripheral T-cell lymphoma, not otherwise specified in seven patients; ALK negative anaplastic large cell lymphoma in one patient; and angioimmunoblastic in 8 patients. Pre-treatment PET/CT scans demonstrated eight patients (50%) with false negative scans. Post-treatment biopsy results demonstrated that ten (62.5%) had biopsy proven residual bone marrow involvement after induction. Eight patients (50%) were found to have BM biopsy proven disease with a negative PET scan. Two patients (12.5%) had both positive BM biopsy and PET scans; 5 patients (31.3%) had negative BM biopsies and PET scans. One patient (6.25%) had a negative BM biopsy, but had a PET scan that revealed positive disease. This patient was considered to have had a false positive PET scan and indeed has remained in remission since April 2009 without any further relapse or treatment. Sensitivity of PET for BM involvement was very poor at 20% (2/10) with a specificity of 50% (2/4) (Table 1 and 2).CONCLUSIONS:This study in PTCL indicates that PET scans at the completion of therapy have a 50% false negative rate. These patients should not be assumed to have negative bone marrow involvement based solely on PET/CT scans. A bone marrow biopsy at the end of therapy is necessary in PTCL patients to confirm complete response.Table 1Bone Marrow InvolvementPre-Therapy PET Scan ImagingPET NegativePET PositiveTotal PatientsBone Marrow NegativeNANANABone Marrow Positive8816Total Patients8 (50%)8 (50%)16Abbreviations: NA, not applicable. The study defined that all patients had to have a positive bone marrow at baseline to be eligible for the study.Table 2Bone Marrow InvolvementPET NegativePET PositiveTotal PatientsBone Marrow Negative426 (37.5%)Bone Marrow Positive8210 (62.5%)Total Patients12 (75%)4 (25%)16Table 1 and 2. Involvement of bone marrow with peripheral T-cell lymphoma based on evaluation by PET scans versus bone marrow biopsy. DisclosuresMaurer:Kite Pharma: Research Funding.

The Role of Functional Imaging in Lymphoma: Current Controversies and Future Directions

Fluorodeoxyglucose positron emission tomography (FDG-PET)/computerized tomography (CT) has revolutionized the management of several lymphoma subtypes, yet controversy remains regarding its cost-effectiveness and the appropriate interpretation of equivocal or false-positive PET scans. In this review, we examine the current evidence base informing the management of these controversial aspects of PET, and look ahead to the emerging uses of PET imaging and the application of novel tracers and quantification tools.

PWE-038 Significance Of Incidental Gastrointestinal Lesion On Pet Scan

IntroductionCT PET scan with fluorine-18 (F-18) fluorodeoxyglucose (FDG), is a increasingly common investigation in the evaluation and management of several malignant and non-malignant conditions. (1–3). The usefulness of this technique...

Mycobacterial Infection of the Gallbladder Masquerading as Gallbladder Cancer with a False Positive Pet Scan

Isolated mycobacterial infection of gall bladder is an extremely rare entity. Only anecdotal reports are evident in the literature. A preoperative diagnosis of mycobacterial infection of gallbladder is therefore very difficult. The case of a 72-year-old male who underwent surgery for suspected gallbladder cancer is presented. The diagnosis of cancer was based on radiological findings and an abnormal uptake of fluorine-18-fluoro-2-deoxy-D-glucose (FDG) on positron emission tomography (PET) scan whilst being followed up for colorectal cancer. He underwent cholecystectomy and gallbladder bed resection. Histopathology was consistent with mycobacterial infection of the gallbladder.

Day 100 PET Scan Positivity Predicts for Worse Survival in Lymphoma Patients Given Allogeneic Peripheral Blood Stem Cells After Non-Myeloablative Conditioning,

Abstract 4155 BackgroundPET scan is increasingly used in the follow-up of lymphoma patients given allogeneic hematopoietic cell transplantation (Allo-HCT). However, whereas several studies addressed the question of the impact of PET positivity after autologous transplantation on transplantation outcomes, very few have been performed after allo-HCT. This is the aim of the current retrospective study. MethodsWe retrospectively analyzed data from 50 lymphoma patients who underwent an allo-HSCT after non-myeloablative conditioning between March 2000 and March 2009. The diagnoses were Hodgkin's lymphoma (n=8) and non-Hodgkin's lymphoma (n=42; 14 follicular, 11 mantle cell, 9 diffuse large B cell, 2 MALT, 1 Burkitt, 1 lymphocytic and 4 T-cell lymphomas). Patients were scheduled to benefit from a follow-up by PET scan on days 100, 180 and 365 and then yearly for a total of five years. ResultsDay 100 PET scans were not performed in 5/50 patients (4 patients died before day 100, while another onewas in intensive care unit at that time).Among the remaining 45 patients, 20 (44.4%) presented hypermetabolic lesions, including 9 patients(20%) who had hypermetabolic lesions evocative of lymphoma.One-year OS (Figure 1) was higher in patients whose PET scan was negative or positivefor infectious/inflammatory reasons than for those with typical lymphoma lesions (85% vs 44%, p=0.0013). Among patients with day-100 PET positivity evocative of lymphoma, 7 patients died, 5 of them of their lymphoma, while 2 patients remained alive. [Display omitted] During further follow-up, twenty patients (44.4%) never presented hypermetabolic lesions after transplantation and 25 (55.6%) had at least one abnormal PET scan.Among the 25 patients, only 11 (24.5%) had probable/proven neoplasia: 1 died with residual disease, 2 had residual lymphoma that went into remission after GVHR, 5 had biopsy-proven relapse, 1 had non-biopsy proven progression, 1 had lung cancer and 1 lung PTLD. The other 14 patients (31.1%) had suspicious lesions at one of the follow-up PET scans, but after further work-up, none of these lesions proved to be a relapse, and all disappeared afterwards. Biopsies were performed in 6 of these cases, including 2 lymph node (1 normal and 1 lymphoid hyperplasia), 2 lung (1 normal and 1 aspergillosis) and 2 GI (1 normal and 1GVHD) biopsies. For 6 patients, imaging studies (CT scan, MRI or echography) were normal or demonstrated infectious or inflammatory (including gut GVHD) disorders. The last 2 patients were thought to relapse based on both PET and CT scans, but refused biopsies, but their lesions regressed spontaneously. ConclusionIn our study, a positive PET scan at day 100 after transplant is predictive of poorer OS. However, there is a noteworthyincidence of false-positive PET scans after non-myeloablativeallo-HCT. We therefore recommend that every suspicious lesion,and particularly in areas not previously involved by lymphoma, should be explored at least by CT scan and/or biopsy, before initiating any new treatment. Disclosures:No relevant conflicts of interest to declare.

False Positive PET Scan Due to Vocal Cord Paralysi

INTRODUCTION: PET-CT scans are used to clinically stage cancers; however clinicians must know the causes of false positive and negative results to fully interpret the test results. We report a case of synchronous head and neck and lung cancer in a patient with a false positive PET scan in the larynx due to excessive muscle activity of the right vocal cord as it compensates for the paralyzed left vocal cord.

Cost and Outcomes of Patients With Solitary Pulmonary Nodules Managed With PET Scans

No prior study to our knowledge has observed the cost of managing solitary pulmonary nodules of patient groups defined by PET scan results. We combined study and administrative data over 2 years of follow-up. Of 375 individuals with a definitive diagnosis, 54.4% had a malignant nodule and 62.1% had positive PET scan results. Mortality risk was 5.0 times higher (CI, 3.1-8.2) and cost was greater (50,233 dollars vs 22,461 dollars, P<.0001) among patients with malignant nodule. Mortality risk was 4.1 times higher (CI, 2.4-7.0) and cost was greater (47,823 dollars vs 20,744 dollars, P<.0001) among patients with a positive PET scan result. Among patients with a malignant nodule, 4.9% had a false-negative PET scan, but cost and survival were not different from true positives. Among patients with a benign nodule, 22.8% had a false-positive PET scan. These patients had greater cost (33,783 dollars vs 19,115 dollars, P<.01), more surgeries and biopsies, and 3.8 times the mortality risk (CI, 1.6-9.2) of true negatives. Just over one-half (54.5%) of individuals with positive PET scans received surgery. Most individuals with negative PET scans (85.2%) were managed by watchful waiting. They incurred fewer costs than patients with negative PET scans who were managed more aggressively (19,378 dollars vs 28,611 dollars, P<.01). Management of solitary pulmonary nodules is expensive, especially if the nodule is malignant or if the PET scan result is false positive. Among patients with malignant nodules, 2-year survival is poor. Compared with true-positive PET scan results, false-negative results are not associated with lower costs or better outcomes.

High incidence of false-positive PET scans in patients with aggressive non-Hodgkin’s lymphoma treated with rituximab-containing regimens

BackgroundPositron emission tomography (PET) is a powerful predictor of relapse and survival in non-Hodgkin’s lymphomas (NHLs) based on studies carried out in the prerituximab era. Little is known about the predictive power of PET in rituximab-treated patients. Patients and methodsPatients with aggressive B-cell NHL with baseline and follow-up PET studies were included. Clinical characteristics, PET and computed tomography scans, biopsy results, and outcomes were reviewed. PET was defined as positive if higher than mediastinal or background activity was observed. ResultsIn all, 51 patients (diffuse large B cell—38; mantle cell lymphoma—13) treated with rituximab-containing regimens were included. For 13 of 40 patients (32.5%), mid-therapy PET studies were positive and 9 of 48 patients (18.7%) had positive posttherapy PET. The positive predictive value (PPV), negative predictive value (NPV), sensitivity (Se), and specificity (Sp) of the mid-therapy PET for predicting relapse were 33% [95% confidence interval (CI) 19% to 49%], 68% (95% CI 51% to 81%), 33% (95% CI 6% to 76%), and 68% (95% CI 49% to 82%), respectively. For posttherapy PET, the relapse PPV, NPV, Se and Sp were 19% (95% CI 9% to 33%), 81% (95% CI 67% to 91%), 13% (95% CI 0.6% to 53%), and 80%(95% CI 64% to 90%), respectively. ConclusionsCompared with previous reports in prerituximab era, addition of rituximab resulted in reduced PPV and sensitivity of mid- and posttherapy PET in patients with aggressive B-cell NHL.

18F‐fluorodeoxyglucose positron emission tomography imaging in brain tumours: The Western Australia positron emission tomography/cyclotron service experience

(18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) scans in the first 49 patients referred with either possible brain tumour or brain tumour recurrence were reviewed. FDG-PET imaging was reported with reference to anatomical imaging. Based on the report the FDG study was classified as either positive or negative for the presence of tumour. Thirty-eight cases were included in the analysis, 21 having pathological data and 17 with diagnostic clinical follow up. Eleven were excluded, as they had inadequate follow-up data. Of the 21 cases with pathology, 18 were shown to have tumour. In this group there were five false-negative scans and two false-positive PET scans. Seventeen cases were assessed by clinical follow up, nine were considered to have been tumour. There were two false negatives with one false positive. The overall sensitivity, specificity and positive and negative predictive values were 74, 73, 87 and 53% respectively. This is similar to figures previously quoted in published work. Despite relatively limited numbers, the utility of FDG PET imaging in our hands is similar to published reports. With a positive predictive value of 87%, a positive FDG study indicates a high likelihood that there is brain tumour present. A negative study does not exclude the presence of tumour.

FDG PET in the Staging and Management of Cutaneous T Cell Lymphoma

We aimed to assess the usefulness of 18F-FDG PET in siting lymphoma involvement for CTCL patients. We retrospectively analyzed CTCL patients who had received a lymph node biopsy within approximately one month of a PET scan. Between 2003 and 2007, 19 CTCL patients (7 males, 12 females, age range: 4 – 70, median: 55) underwent a combined 56 PET scans. All studies were performed on GE Discovery LS 8 slice MDCT PET CT scanner or GE Discovery DST 16 slice MDCT PET CT scanner (Milwaukee, WI) and the images were interpreted on a GE AW or Xeleris workstation. The patients underwent whole body imaging from the head to foot at 4 minutes per bed position. Of these 19 patients, eight patients (four men, four women, mean age: 56.6, range: 49 – 70) received a lymph node biopsy following a PET scan that demonstrated elevated focal uptake (SUVs ranging from 2.2 to 9.9) in at least one lymph node. In four of the cases, the biopsied lymph node directly confirmed CTCL involvement sited in that node by PET scan (SUV 2.2 to 6.1). Three cases represented false-positive PET scans which were attributed to category 1 dermatopic lymphadenopathy and post radiation change. Despite these lack in correlations, in one case, PET sited adenopathy (SUV 9.9) in an inguinal node that biopsy pronounced benign. Further studies proved that a sampling error produced a false-negative biopsy. Despite the small sample, the study demonstrates the importance of PET imaging in staging patients with CTCL. Findings suggest that lymph node SUV values ranging from 2.2 – 9.9 often correlate with definite involvement of the nodes, and consequentially progression of the disease. It was found that false-positive PET scans may result from post radiation change or dermatopathic lymphadenopathy, category 1. The sample size was too small to detect differences in SUV and correlation in lymph node involvement. Our study demonstrates the need for improvement in the specificity of FDG-PET scans possibly by two point imaging and accurate localization of lymph nodes by use of an intraoperative probe to further enhance its usefulness in the staging of CTCL. Further prospective study is needed to determine correlation with SUV and lymph node involvement.

Preliminary PET/CT study of 18F-FDG uptake in cervical and supraclavicular brown adipose tissue

OBJECTIVE The clinical use of PET/CT in oncology has led to the realization that 18F-FDG uptake in brown adipose tissue (BAT) can be a common cause of potentially misleading false-positive PET scans. The goal of this study was to study 18F-FDG uptake in cervical and supraclavicular regions and its characteristics with PET/CT. METHODS All the PET/CT scans obtained at our institution from July 2007 to January 2008 were retrospectively reviewed for increased 18F-FDG uptake in BAT. The cases in which increased 18F-FDG in cervical and supraclavicular regions was not localized to a soĞ -tissue mass or lymph node or muscle on the CT images, were included in this study. The following features were recorded: body weight, body mass index (BMI) and maximal standardized uptake value (SUVmax). In these selected patients, the BAT uptake in other area of UIF body was also recorded. RESULTS PET/CT scans were obtained in 457 patients (259 males and 198 females). In all of the scans, cervical and supraclavicular BAT uptake was observed in 12 patients (2 males and 10 females) and was typically bilateral, symmetric and intense. The range of the SUVmax was 3.6~12.82 (mean 6.9 ± 2.6). BAT uptake was more common in females than in males, showing a significant difference ( P = 0.004). Although 18F-FDG uptake in BAT occurred more often in underweight patients with low BMI, there was no di ff erence in the body weight ( P = 0.607) or BMI ( P = 0.491) of these patients with hypermetabolic BAT compared with controls. CONCLUSION Hypermetabolic BAT uptake can be localized in cervical and supraclavicular regions with it occurring more commonly in females compared to males. Knowledge of this potential pitfall with PET/CT is important in improving diagnostic interpretation and accurate staging.

Primary Pulmonary Meningioma Manifesting as a Solitary Pulmonary Nodule With a False-positive PET Scan

Primary pulmonary meningioma is very rare, with about 30 cases reported in the English literature. These lesions are usually benign, grow slowly, and have an excellent prognosis. However, they can mimic any other pulmonary tumor, as the most common presentation is as a solitary pulmonary nodule. We report a case of a primary pulmonary meningioma manifesting as a solitary lung nodule with a very high metabolic activity on the positron emission tomography, mimicking a primary lung cancer.

PET scan–CT correlation: what the chest radiologist needs to know

The purpose of this article is to familiarize the chest radiologist with the basics of PET scanning in the chest and to correlate PET findings with thoracic CT findings. After completing this article, the reader should know the following: (a) how PET scanning is performed; (b) the indications for PET scanning in the chest; (c) the significance of SUV and a positive test; (c) the causes of false-positive and false-negative PET scans; and (d) the importance of correlating PET findings with Chest CT findings. The authors conclude that PET and chest CT studies should be read in conjunction to optimize diagnostic accuracy. Interpreting either study alone is fraught with errors, while combined interpretations yield information on both functional activity and anatomic localization. PET–CT hybrid devices that fuse PET and CT data simplify this task and fusion imaging is rapidly becoming the test of choice for evaluating thoracic malignancies.

How to optimize staging in early non-small cell lung cancer

The topic was discussed by Dr Johan Vansteenkiste, Leuven Belgium. PET is an exciting new imaging modality that has rapidly acquired a prominent position in evaluation of solitary pulmonary nodules (SPN) and staging of lung cancer. It is based on the principle that cancer cells have a higher rate of glycolysis and an increased cellular uptake of glucose due to increased number of transport proteins than non-neoplastic cells. The PET tracer, 18 fluoro-deoxyglucose (18 FDG) is taken up into cells and metabolically trapped and accumulates. 18 FDG is a positron emitter, and therefore, can be measured. Thus, PET provides evidence of metabolic activity of tumor cells and has opened up the relative new field of ‘molecular imaging’. PET has a sensitivity of approximately 90% and a specificity of 85 /90% for evaluating SPN, but the data available is based on nodules ]/1 cm in size [1]. The resolution limit of PET is thought to be 7 /8 mm. For nodules smaller than 1 cm, the sensitivity and specificity is unknown. The sensitivity and specificity of the CT scan for evaluating mediastinal lymph nodes for metastasis is 60 /70% each [2,3]. This means that 30 /40% of lymph nodes one cm or smaller will have microscopic metastasis (sensitivity) and 30 /40% of lymph nodes /1 cm in size will not contain metastases, but will only be reactive (specificity). In contrast, data presented and a published meta-analysis documents a sensitivity of 89% and specificity of 92% for PET evaluation of mediastinal nodes in patients with NSCLC [4]. A limitation of PET is that it lacks precise anatomic details. Studies have shown that the sensitivity and accuracy of PET is significantly improved when it is correlated with the CT scan. New scanners are just coming on the market that fuse the CT and PET images, thus giving better anatomic detail. It is likely that these new CT/PET scanners may replace the current PET scanners. They decrease the PET scan time from 60 to 30 min. False positive PET scans can occur in patients with tuberculosis, other granulomatous disease, sarcoidosis, and anthrasilicosis. Care must be taken to distinguish a malignancy adjacent to mediastinum from adjacent mediastinal nodal metastasis with the current scanners. False negative PET scans may occur in patients with carcinoid tumors and bronchoalveolar cell carcinoma because of the low metabolic activity. PET will also miss microscopic lymph node metastases (resolution size limitation). Dr Vansteenkiste recommended that PET evaluation of mediastinum be used as follows:

FDG-PET, 99mtc-HMPAO white blood cell SPET and bone scintigraphy in the evaluation of painful total knee arthroplasties.

Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), technetium-99m hexamethylpropylene amine oxime (HMPAO)-labelled white blood cell (WBC) scintigraphy and bone scintigraphy were used in the evaluation of total knee arthroplasties (TKAs). We prospectively included 21 patients who had a three-phase bone scan for exclusion of infection of TKAs. Four hours after injection of 185 MBq 99mTc-HMPAO-labelled WBCs, planar and single-photon emission tomographic (SPET) imaging was performed. Planar imaging was repeated at 24 h p.i. Consecutively images of the knees were obtained with a dedicated PET system 60 min following the injection of 370 MBq of FDG. Focal tracer uptake was scored on SPET and PET visually (0=no uptake, 4=intense uptake). In addition, SUV (standardised uptake value) per voxel was calculated from attenuation-corrected PET images using the MLAA algorithm. Focal uptake at the bone-prosthesis interface was used as the criterion for infection before and after correlation with the third phase of the bone scan. Final diagnosis was based on operative findings, culture and clinical outcome. In the infected TKAs, the WBC scan showed focal activity of grade 2 (n=2), 3 (n=l) or 4 (n=2). PET scan revealed focal activity of grade 4 (n=5) or 3 (n=1). WBC scan alone had a specificity for infection of 53% [positive predictive value (PPV) 42%, sensitivity 100%], compared with 73% for PET scan (PPV 60%, sensitivity 100%). Considering only lesions at the bone-prosthesis interface that were also present on the third phase of the bone scan, we found a specificity of 93% (PPV 83%) for WBC scan. Using these criteria, a specificity of 80% (PPV 67%) was obtained for PET scan. Two out of three false-positive PET scans were due to loosening of the TKA. It is concluded that WBC scintigraphy in combination with bone scintigraphy has a high specificity in the detection of infected TKAs. FDG-PET seems to offer no additional benefit.