FDG PET in the Evaluation of Treatment for Lymphoma: Clinical Usefulness and Pitfalls

Overview of F18-FDG uptake patterns in retroperitoneal pathologies: imaging findings, pitfalls, and artifacts

INTRODUCTION

Retroperitoneum can be the origin of a wide variety of pathologic conditions and potential space for disease spread to other compartments of the abdomen and pelvis. Computed tomography (CT) and magnetic resonance imaging (MRI) are often the initial imaging modalities to evaluate the retroperitoneal pathologies, however given the intrinsic limitations, F18-FDG PET/CT provides additional valuable metabolic information which can change the patient management and clinical outcomes. We highlight the features of retroperitoneal pathologies on F18-FDG PET/CT and the commonly encountered imaging artifacts and pitfalls. The aim of this review is to characterize primary and secondary retroperitoneal pathologies based on their metabolic features, and correlate PET findings with anatomic imaging.

CONCLUSION

Retroperitoneal pathologies can be complex, ranging from oncologic to a spectrum of non-oncologic disorders. While crosse-sectional imaging (CT and MRI) are often the initial imaging modalities to localize and characterize pathologies, metabolic information provided by F18-FDG PET/CT can change the management and clinical outcome in many cases.

18F-Fluorodeoxy Glucose and 11C-Methionine Accumulation in Demyelinating Lesions

Background Few studies have evaluated the accumulation of 18F-fluorodeoxyglucose (FDG), 11C-methionine (MET), and other positron emission tomography (PET) tracers in patients with demyelinating disease.

Purpose This study aimed to investigate the accumulation of FDG-PET/computed tomography (CT) and MET-PET/CT in demyelinating lesions.

Material and Methods A retrospective search of the patient database in our hospital identified five patients with demyelinating disease in whom PET studies performed in the past 10 years revealed accumulation of FDG or MET. The clinical diagnoses were multiple sclerosis (n=1), myelitis (n=1), limbic encephalitis (n=1), chronic inflammatory demyelinating polyneuropathy (CIDP; n=1), and acute demyelinating encephalomyelitis (ADEM; n=1). Two patients received FDG-PET/CT alone and three patients received both FDG-PET/CT and MET-PET/CT on the same day. Images were visually and conjointly reviewed by two radiologists. In semiquantitative evaluation, the maximum standardized uptake value (SUVmax) of the lesion was measured. The lesion-to-normal brain uptake ratio (L/N ratio) was calculated.

Results FDG and/or MET accumulated to a part of the lesions seen on MRI. SUVmax on FDG-PET/CT ranged from 3.8 to 10.3, and L/N ratio on MET-PET/CT ranged from 16.6 to 2.4.

Conclusion It has been established that neoplastic and demyelinating lesions can be differentiated on the basis of FDG or MET uptake. However, as accumulation of FDG and MET can also occur in demyelinating lesions; knowledge of this possibility is of clinical importance.

[18F]FDG-PET Evaluation of Spinal Pathology in Patients in Oncology: Pearls and Pitfalls for the Neuroradiologist

[¹⁸F]FDG-PET is a widely used technique for specific evaluation of disease and treatment response in oncology. However, the principles behind [¹⁸F]FDG-PET imaging allow a wide-ranging array of benign and malignant pathologies to be identified on both initial and routine surveillance imaging. This is important for clinicians and radiologists, alike, in that effective and accurate evaluation of malignancy and metastatic disease, specifically involving the spine and central nervous system, is crucial. In this article, we review the normal and posttherapy appearance of the spine on [¹⁸F]FDG-PET, the various types and patterns of metastatic disease that involve the spine and spinal cord, and, finally, important spinal pathologies that may mimic malignancy on [¹⁸F]FDG-PET.

In vivo quantitative assessment of therapeutic response to bortezomib therapy in disseminated animal models of multiple myeloma with [18F]FDG and [64Cu]Cu-LLP2A PET

Background

Multiple myeloma (MM) is a disease of cancerous plasma cells in the bone marrow. Imaging-based timely determination of therapeutic response is critical for improving outcomes in MM patients. Very late antigen-4 (VLA4, CD49d/CD29) is overexpressed in MM cells. Here, we evaluated [¹⁸F]FDG and VLA4 targeted [⁶⁴Cu]Cu-LLP2A for quantitative PET imaging in disseminated MM models of variable VLA4 expression, following bortezomib therapy.

Methods

In vitro and ex vivo VLA4 expression was evaluated by flow cytometry. Human MM cells, MM.1S-CG and U266-CG (C: luciferase and G: green fluorescent protein), were injected intravenously in NOD-SCID gamma mice. Tumor progression was monitored by bioluminescence imaging (BLI). Treatment group received bortezomib (1 mg/kg, twice/week) intraperitoneally. All cohorts (treated, untreated and no tumor) were longitudinally imaged with [¹⁸F]FDG (7.4–8.0 MBq) and [⁶⁴Cu]Cu-LLP2A (2–3 MBq; Molar Activity: 44.14 ± 1.40 MBq/nmol) PET, respectively.

Results

Flow cytometry confirmed high expression of CD49d in U266 cells (> 99%) and moderate expression in MM.1S cells (~ 52%). BLI showed decrease in total body flux in treated mice. In MM.1S-CG untreated versus treated mice, [⁶⁴Cu]Cu-LLP2A localized with a significantly higher SUV_mean in spine (0.58 versus 0.31, p < 0.01) and femur (0.72 versus 0.39, p < 0.05) at week 4 post-tumor inoculation. There was a four-fold higher uptake of [⁶⁴Cu]Cu-LLP2A (SUV_mean) in untreated U266-CG mice compared to treated mice at 3 weeks post-treatment. Compared to [⁶⁴Cu]Cu-LLP2A, [¹⁸F]FDG PET detected treatment-related changes at later time points.

Conclusion

[⁶⁴Cu]Cu-LLP2A is a promising tracer for timely in vivo assessment of therapeutic response in disseminated models of MM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00840-4.

Can FDG-PET replace biopsy for the evaluation of residual tumor in pediatric mature B-cell non-Hodgkin lymphoma?

INTRODUCTION

The aim of our study is to evaluate the role of ¹⁸ F-labeled fluorodeoxy glucose positron emission tomography (¹⁸ FDG-PET) scan for the detection of viable residual mass in pediatric mature B-cell non-Hodgkin lymphoma (NHL). This study also aims to detect the negative predictive value, positive predictive value (PPV), sensitivity, and specificity of ¹⁸ FDG-PET.

PATIENTS AND METHODS

A retrospective, cross-sectional nonrandomized study was carried out. We included all patients with newly diagnosed mature B-cell NHL treated at the Children Cancer Hospital Egypt during the period between July 2007 and the end of May 2018. Patients were included in the study if they (a) had a residual tumor mass, (b) underwent an ¹⁸ FDG-PET scan, and (c) had a pathologic documentation of this residual tumor. Patients were followed up till June 2019.

RESULTS

Thirty-six patients were included, for whom 39 biopsies were performed. Mean age was 7.7 years. Median follow-up period was 52.8, range 6.1 to 117 months.¹⁸ FDG-PET scan was positive (Deauville score 3, 4, or 5) in 24 of 39 patients (61.5%), while it was negative (Deauville score 1 or 2) in 15 patients (38.5%). Positive ¹⁸ FDG-PET scan and biopsy were performed in 15 of 39 samples (38.4%; true positive, TP), while they were both negative in 13 samples (33.3%; true negative). Nine patients (23%) had positive scan and a negative biopsy (false positive), while 2 patients had negative uptake and a positive biopsy (false negative, FN)). Sensitivity of the ¹⁸ FDG-PET scan was 88.2% and specificity was 59.1%. PPV was 62.5% and NPPV was 86.6%.

CONCLUSION

Changing therapy on the basis of a positive finding alone at the time of evaluation is not recommended. FN results exist, so biopsy confirmation is required to avoid the missing refractory disease. If negative, ¹⁸ FDG^- PET can replace a biopsy if the latter is inaccessible or carries an unnecessary risk.

Unexpected positron emission tomography/computed tomography uptake in benign dermal naevus

Positron emission tomography/computed tomography (PET/CT) imaging modalities are commonly utilised for investigation of known or suspected neoplastic disease. A variety of 18-F-fluorodeoxyglucose (FDG) positive cutaneous lesions have been described in the literature, including both malignant lesions and benign inflammatory conditions. We report a case of PET/CT-positive dermal naevus.

Can Positron Emission Tomography and Computed Tomography Be a Substitute for Bone Marrow Biopsy in Detection of Bone Marrow Involvement in Patients with Hodgkin's or Non-Hodgkin's Lymphoma?

Objective:

Positron emission tomography and computed tomography (PET/CT) has become an important part of staging and treatment evaluation algorithms of lymphoma. We aimed to compare the results of PET/CT with bone marrow biopsy (BMB) with respect to bone marrow involvement (BMI) in patients with Hodgkin’s lymphoma (HL) and aggressive non-Hodgkin’s lymphoma (aNHL).

Materials and Methods:

The medical files of a total of 297 patients diagnosed with HL or aNHL and followed at the hematology clinics of 3 major hospitals in İstanbul between 2008 and 2012 were screened retrospectively and 161 patients with classical HL and aNHL were included in the study. The patients were referred for PET/CT and BMB at the initial staging. BMB was performed as the reference standard for the evaluation of BMI.

Results:

There were 61 (38%) HL and 100 (62%) aNHL patients. Concordant results were revealed between PET/CT and BMB in 126 patients (78%) (52 HL, 74 aNHL), 20 with positive PET/CT and BMB results and 106 with negative PET/CT and BMB results. There were discordant results in 35 patients (9 HL, 26 aNHL), 16 of them with positive BMB and negative PET/CT results and 19 of them with negative BMB and positive PET/CT results.

Conclusion:

We observed that PET/CT is effective to detect BMI, despite it alone not being sufficient to evaluate BMI in HL and aNHL. Bone marrow trephine biopsy and PET/CT should be considered as mutually complementary methods for detection of BMI in patients with lymphoma. In suspected focal involvement, combining biopsy and PET/CT might improve staging results.

18F-FDG PET/CT for the Diagnosis of Malignant and Infectious Complications After Solid Organ Transplantation

PURPOSE

Infection and malignancy represent two common complications after solid organ transplantation, which are often characterized by poorly specific clinical symptomatology. Herein, we have evaluated the role of ¹⁸F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) in this clinical setting.

METHODS

Fifty-eight consecutive patients who underwent FDG PET/CT after kidney, lung or heart transplantation were included in this retrospective analysis. Twelve patients underwent FDG PET/CT to strengthen or confirm a diagnostic suspicion of malignancies. The remaining 46 patients presented with unexplained inflammatory syndrome, fever of unknown origin (FUO), CMV or EBV seroconversion during post-transplant follow-up without conclusive conventional imaging. FDG PET/CT results were compared to histology or to the finding obtained during a clinical/imaging follow-up period of at least 6 months after PET/CT study.

RESULTS

Positive FDG PET/CT results were obtained in 18 (31 %) patients. In the remaining 40 (69 %) cases, FDG PET/CT was negative, showing exclusively a physiological radiotracer distribution. On the basis of a patient-based analysis, FDG PET/CT's sensitivity, specificity, PPV and NPV were respectively 78 %, 90 %, 78 % and 90 %, with a global accuracy of 86 %. FDG PET/CT was true positive in 14 patients with bacterial pneumonias (n = 4), pulmonary fungal infection (n = 1), histoplasmosis (n = 1), cutaneous abscess (n = 1), inflammatory disorder (sacroiliitis) (n = 1), lymphoma (n = 3) and NSCLC (n = 3). On the other hand, FDG PET/CT failed to detect lung bronchoalveolar adenocarcinoma, septicemia, endocarditis and graft-versus-host disease (GVHD), respectively, in four patients. FDG PET/CT contributed to adjusting the patient therapeutic strategy in 40 % of cases.

CONCLUSIONS

FDG PET/CT emerges as a valuable technique to manage complications in the post-transplantation period. FDG PET/CT should be considered in patients with severe unexplained inflammatory syndrome or FUO and inconclusive conventional imaging or to discriminate active from silent lesions previously detected by conventional imaging particularly when malignancy is suspected.

Comparative Analysis between [(18)F]Fludarabine-PET and [(18)F]FDG-PET in a Murine Model of Inflammation

Lymphoma research has advanced thanks to introduction of [(18)F]fludarabine, a positron-emitting tool. This novel radiotracer has been shown to display a great specificity for lymphoid tissues. However, in a benign process such as inflammation, the uptake of this tracer has not been questioned. Indeed, in inflammatory zones, elevated glucose metabolism rate may result in false-positives with [(18)F]FDG-PET Imaging. In the present investigation, it has been argued that cells, involved in inflammation, might be less avid of [(18)F]fludarabine. To generate inflammation, Swiss mice were intramuscularly injected with 0.1 mL of turpentine oil into the right front paw. Imaging sessions with (18)F-labeled tracers named above were conducted on days 5 and 25 after inoculation. For each animal, volumes of interest (VOI), delineating the muscle of the inflamed (IP) and normal paws (NP), were determined on PET scans. For characterization of inflammation, muscle samples from IP and NP were stained with hematoxylin and eosin (H&E). In early (day 5) inflammation, [(18)F]FDG accumulation was 4.00 ± 1.65 times greater in the IP than in the contralateral NP; for [(18)F]fludarabine, this IP/NP ratio was 1.31 ± 0.28, resulting in a significant difference between radiotracer groups (p < 0.01). In late (day 25) inflammation, the IP/NP ratios were 2.07 ± 0.49 and 1.03 ± 0.07, for [(18)F]FDG and [(18)F]fludarabine, respectively (p < 0.001). [(18)F]Fludarabine showed significantly weaker uptake in inflammation when compared with [(18)F]FDG. This encouraging finding suggests that [(18)F]fludarabine-PET might well be a robust approach for distinguishing tumor from inflammatory tissue, avoiding false-positive PET results and thus enabling an accurate imaging of lymphoma.

Correlation between the Uptake of 18F-Fluorodeoxyglucose (18F-FDG) and the Expression of Proliferation-Associated Antigen Ki-67 in Cancer Patients: A Meta-Analysis

Objective

To study the correlation between ¹⁸F-FDG uptake and cell proliferation in cancer patients by meta-analysis of published articles.

Methods

We searched PubMed (MEDLINE included), EMBASE, and Cochrane Database of Systematic Review, and selected research articles on the relationship between ¹⁸F-FDG uptake and Ki-67 expression (published between August 1, 1994-August 1, 2014), according to the literature inclusion and exclusion criteria. The publishing language was limited to English. The quality of included articles was evaluated according to the Quality Assessment of Diagnosis Accuracy Studies-2 (QUADAS-2). The correlation coefficient (r) was extracted from the included articles and processed by Fisher's r-to-z transformation. The combined correlation coefficient (r) and the 95% confidence interval (CI) were calculated with STATA 11.0 software under a random-effects model. Begg's test was used to analyze the existence of publication bias and draw funnel plot, and the sources of heterogeneity were explored by sensitivity and subgroup analyses.

Results

According to the inclusion and exclusion criteria, 79 articles were finally included, including 81 studies involving a total of 3242 patients. All the studies had a combined r of 0.44 (95% CI, 0.41-0.46), but with a significant heterogeneity (I² = 80.9%, P<0.01). Subgroup analysis for different tumor types indicated that most subgroups showed a reduced heterogeneity. Malignant melanoma (n = 1) had the minimum correlation coefficient (-0.22) between ¹⁸F-FDG uptake and Ki-67 expression, while the thymic epithelial tumors (TETs; n = 2) showed the maximum correlation coefficient of 0.81. The analytical results confirmed that correlation between ¹⁸F-FDG uptake and Ki-67 expression was extremely significant in TETs, significant in gastrointestinal stromal tumors (GISTs), moderate in patients with lung, breast, bone and soft tissue, pancreatic, oral, thoracic, and uterine and ovarian cancers, average in brain, esophageal and colorectal cancers, and poor in head and neck, thyroid, gastric and malignant melanoma tumors. Subgroup analysis indicated that positron emission tomography (PET) or PET/CT imaging technology or Ki-67 and standardized uptake value (SUV) measurement technology did not significantly affect the results of r values, and Begg's test showed no significant publication bias.

Conclusion

In cancer patients, ¹⁸F-FDG uptake showed a moderate positive correlation with tumor cell proliferation. Different tumor types exhibited varied degree of correlation, and the correlation was significant in TETs and GSTs. However, our results need further validation by clinical trials with a large sample of different tumor types.

Evaluation of the specificity of [(18)F]fludarabine PET/CT in a xenograft model of follicular lymphoma: comparison with [(18)F]FDG and impact of rituximab therapy

Background

[¹⁸F]Fludarabine is a novel positron emission tomography (PET) radiotracer for imaging lymphoma. The purpose of this preclinical study was to evaluate the robustness of [¹⁸F]fludarabine during rituximab therapy. In addition, a comparison was made between [¹⁸F]fludarabine and [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) with regard to their concordance with histologically derived data.

Methods

CB17-SCID mice bearing human follicular DOHH-2 lymphoma were treated once weekly with rituximab (10 mg/kg) or physiological saline over 3 weeks. To obtain the tracer uptake in the metabolically active volume of the tumour (MAVT), a background-level threshold was applied to the volume of interest (VOI) defined on computed tomography (CT) image. The tumour uptake analysis was performed with MAVT-based segmentation for data analysis of sequential [¹⁸F]fludarabine PET/CT studies and with total tumour-based segmentation for comparison with histologically derived data.

Results

The correlation between the MAVT and [¹⁸F]fludarabine accumulation (%ID) in those viable tissues was equally significant for both vehicle- or rituximab-treated mice; for these latter, the presence of lymphoid tissues at the end of imaging sessions was confirmed histologically. A stronger correlation was demonstrated between quantitative values extracted from [¹⁸F]fludarabine-PET and histology (r² = 0.91, p < 0.001) when compared to [¹⁸F]FDG-PET (r² = 0.55, p = 0.03).

Conclusions

[¹⁸F]Fludarabine uptake in the follicular lymphoma model compared favourably with [¹⁸F]FDG in terms of specificity for PET imaging and also remained robust for persistent viable tissues following rituximab therapy. [¹⁸F]Fludarabine PET/CT may be a promising approach to evaluate lymphoma, including their surveillance during therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-015-0101-7) contains supplementary material, which is available to authorized users.

Positron emission tomographic monitoring of dual phosphatidylinositol-3-kinase and mTOR inhibition in anaplastic large cell lymphoma

Background

Dual phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibition offers an attractive therapeutic strategy in anaplastic large cell lymphoma depending on oncogenic nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) signaling. We tested the efficacy of a novel dual PI3K/mTOR inhibitor, NVP-BGT226 (BGT226), in two anaplastic large cell lymphoma cell lines in vitro and in vivo and performed an early response evaluation with positron emission tomography (PET) imaging using the standard tracer, 2-deoxy-2-[¹⁸F]fluoro-D-glucose (FDG) and the thymidine analog, 3′-deoxy-3′-[¹⁸F] fluorothymidine (FLT).

Methods

The biological effects of BGT226 were determined in vitro in the NPM-ALK positive cell lines SU-DHL-1 and Karpas299 by 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay, propidium iodide staining, and biochemical analysis of PI3K and mTOR downstream signaling. FDG-PET and FLT-PET were performed in immunodeficient mice bearing either SU-DHL-1 or Karpas299 xenografts at baseline and 7 days after initiation of treatment with BGT226. Lymphomas were removed for immunohistochemical analysis of proliferation and apoptosis to correlate PET findings with in vivo treatment effects.

Results

SU-DHL-1 cells showed sensitivity to BGT226 in vitro, with cell cycle arrest in G0/G1 phase and an IC₅₀ in the low nanomolar range, in contrast with Karpas299 cells, which were mainly resistant to BGT226. In vivo, both FDG-PET and FLT-PET discriminated sensitive from resistant lymphoma, as indicated by a significant reduction of tumor-to-background ratios on day 7 in treated SU-DHL-1 lymphoma-bearing animals compared with the control group, but not in animals with Karpas299 xenografts. Imaging results correlated with a marked decrease in the proliferation marker Ki67, and a slight increase in the apoptotic marker, cleaved caspase 3, as revealed by immunostaining of explanted lymphoma tissue.

Conclusion

Dual PI3K/mTOR inhibition using BGT226 is effective in ALK-positive anaplastic large cell lymphoma and can be monitored with both FDG-PET and FLT-PET early on in the course of therapy.

FDG PET during radiochemotherapy is predictive of outcome at 1 year in non-small-cell lung cancer patients: a prospective multicentre study (RTEP2)

PURPOSE

To assess prospectively the prognostic value of FDG PET/CT during curative-intent radiotherapy (RT) with or without concomitant chemotherapy in patients with non-small-cell lung cancer (NSCLC).

METHODS

Patients with histological proof of invasive localized NSCLC and evaluable tumour, and who were candidates for curative-intent radiochemotherapy (RCT) or RT were preincluded after providing written informed consent. Definitive inclusion was conditional upon significant FDG uptake before RT (PET₁). All included patients had a FDG PET/CT scan during RT (PET₂, mean dose 43 Gy) and were evaluated by FDG PET/CT at 3 months and 1 year after RT. The main endpoint was death (from whatever cause) or tumour progression at 1 year.

RESULTS

Of 77 patients preincluded, 52 were evaluable. Among the evaluable patients, 77% received RT with induction chemotherapy and 73% RT with concomitant chemotherapy. At 1 year, 40 patients (77 %) had died or had tumour progression. No statistically significant association was found between stage (IIIB vs. other), histology (squamous cell carcinoma vs. other), induction or concomitant chemotherapy, and death/tumour progression at 1 year. The SUVmax in the PET2 scan was the single variable predictive of death or tumour progression at 1 year (odds ratio 1.97, 95% CI 1.25 - 3.09, p = 0.003) in multivariate analysis. The area under the receiver operating characteristic curve was 0.85 (95% CI 0.73 - 0.94, p < 10(-4)). A SUVmax value of 5.3 in the PET₂ scan yielded a sensitivity of 70% and a specificity of 92% for predicting tumour progression or death at 1 year.

CONCLUSION

This prospective multicentre study demonstrated the prognostic value in terms of disease-free survival of SUVmax assessed during the 5th week of curative-intent RT or RCT in NSCLC patients (NCT01261598; RTEP2 study).

18 F-fluorothymidine uptake in follicular lymphoma and error-prone DNA repair

Background

We observed a disproportional 18 F-fluorothymidine (F-FLT) uptake in follicular lymphoma (FL) relative to its low cell proliferation. We tested the hypothesis that the ‘excess’ uptake of 18 F-FLT in FL is related to error-prone DNA repair and investigated whether this also contributes to 18 F-FLT uptake in diffuse large B cell lymphoma (DLBCL).

Methods

We performed immunohistochemical stainings to assess the pure DNA replication marker MIB-1 as well as markers of both DNA replication and repair like PCNA, TK-1 and RPA1 on lymph node biopsies of 27 FLs and 35 DLBCLs. In 7 FL and 15 DLBCL patients, 18 F-FLT-PET had been performed.

Results

18 F-FLT uptake was lower in FL than in DLBCL (median SUVmax 5.7 vs. 8.9, p = 0,004), but the ratio of 18 F-FLT-SUVmax to percentage of MIB-1 positive cells was significantly higher in FL compared with DLBCL (p = 0.001). The median percentage of MIB-1 positive cells was 10% (range, 10% to 20%) in FL and 70% (40% to 80%) in DLBCL. In contrast, the median percentages of PCNA, TK-1 and RPA1 positive cells were 90% (range, 80 to 100), 90% (80 to 100) and 100% (80 to 100) in FL versus 90% (60 to 100), 90% (60 to 100) and 100% (80 to 100) in DLBCL, respectively.

Conclusions

This is the first demonstration of a striking discordance between 18 F-FLT uptake in FL and tumour cell proliferation. High expression of DNA replication and repair markers compared with the pure proliferation marker MIB-1 in FL suggests that this discordance might be due to error-prone DNA repair. While DNA repair-related 18 F-FLT uptake considerably contributes to 18 F-FLT uptake in FL, its contribution to 18 F-FLT uptake in highly proliferative DLBCL is small. This apparently high contribution of DNA repair to the 18 F-FLT signal in FL may hamper studies where 18 F-FLT is used to assess response to cytostatic therapy or to distinguish between FL and transformed lymphoma.

Dual-time-point FDG PET/CT for the evaluation of pediatric tumors

OBJECTIVE

The utility of dual-time-point (18)F-FDG PET/CT in differentiating benign from malignant processes in pediatric patients was assessed.

SUBJECTS AND METHODS

Twenty-one patients (13 girls and eight boys; age range, 1-17 years) with suspected malignancy underwent dual-time-point FDG PET/CT. Scan 1 was performed at approximately 60 minutes after i.v. injection of 5.18 MBq/kg of FDG, and scan 2 was performed at 121 ± 43 minutes after the first scan. Regions of interest were overlaid onto each non-attenuated-corrected image, and semiquantitative analysis was performed using the standardized uptake value (SUV) obtained from early and delayed images. A retention index was calculated according to the following equation: [(delayed SUV - early SUV) / early SUV] × 100. Results were compared prospectively in relation to pathologic examination or other conventional radiologic imaging or clinical follow-up. A retention index of 10% or higher was chosen as a cutoff for differentiating malignant from benign entities.

RESULTS

For patients with malignant disease, the average SUV increased from 7.3 ± 1.2 to 10.9 ± 2.7 between the two time points, whereas the SUV changed from 4.5 ± 0.8 to 4.2 ± 1.0 for patients with benign lesions. The average retention index was 37.1% ± 10.8% for patients with malignant lesions versus -9.9% ± 7.1% for benign lesions (p < 0.01). With a cutoff value of 10% or higher for the retention index, the sensitivity and specificity of dual-time-point FDG PET/CT were 77% and 80%, respectively.

CONCLUSION

These data show that dual-time-point FDG PET/CT is useful in distinguishing malignant from benign processes in pediatric patients.

An Unusual Case of Infectious Mononucleosis Presenting with Advanced Lymphadenopathy and Ascites

We report a case of infectious mononucleosis initially presented with lymphoma-like features. Examinations revealed abdominal ascites, splenomegaly, elevated lactic dehydrogenase, extensive lymphadenopathy from neck to the mediastinum, and a high 18F-fluoro-2-deoxy-D-glucose uptake pattern on positron emission tomography scan. The impression of lymphoma could not be ruled out based on the clinical manifestations, most importantly the diffuse necrosis with focal monotonous pattern and a high Ki-67 proliferation index found on pathological examination. Our presentation emphasizes the potential challenge in misdiagnosis of advanced infectious mononucleosis. Knowledge of its unusual clinical features is therefore essential to avoid misdirected interventions when it mimics diseases like lymphoma.

Diagnostic value of software-based image fusion of computed tomography and F18-FDG PET scans in patients with malignant lymphoma

AIM

The purpose of this study was to evaluate the accuracy of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) positron emission tomography (PET), computed tomography (CT), and software-based image fusion of both modalities in the imaging of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD).

METHODS

77 patients with NHL (n = 58) or HD (n = 19) underwent a FDG PET scan, a contrast-enhanced CT, and a subsequent digital image fusion during initial staging or followup. 109 examinations of each modality were evaluated and compared to each other. Conventional staging procedures, other imaging techniques, laboratory screening, and follow-up data constituted the reference standard for comparison with image fusion. Sensitivity and specificity were calculated for CT and PET separately.

RESULTS

Sensitivity and specificity for detecting malignant lymphoma were 90% and 76% for CT and 94% and 91% for PET, respectively. A lymph node region-based analysis (comprising 14 defined anatomical regions) revealed a sensitivity of 81% and a specificity of 97% for CT and 96% and 99% for FDG PET, respectively. Only three of 109 image fusion findings needed further evaluation (false positive).

CONCLUSION

Digital fusion of PET and CT improves the accuracy of staging, restaging, and therapy monitoring in patients with malignant lymphoma and may reduce the need for invasive diagnostic procedures.

Assessment of splenic perfusion in patients with malignant hematologic diseases and spleen involvement, liver cirrhosis and controls using volume perfusion CT (VPCT): a pilot study

RATIONALE AND OBJECTIVES

The aim of this study was to assess splenic perfusion in patients with spleen involvement in malignant hematologic diseases and liver cirrhosis and in controls without hepatosplenic disease using volume perfusion computed tomography.

MATERIALS AND METHODS

Between October 2009 and December 2011, 14 hematologic patients with known spleen involvement were recruited. An additional 17 consecutive patients without known splenic or liver disease were enrolled as controls, as well as 29 patients with liver cirrhosis and portal hypertension. A 40-second volume perfusion computed tomographic scan of the upper abdomen was performed. Analysis included measurement of splenic volume, blood flow (BF), blood volume (BV), K(trans), and mean transit time (MTT).

RESULTS

In lymphoma patients, mean splenic volume and perfusion parameters were as follows: splenic volume, 1125.34 mL; BF, 61.24 mL/100 mL/min; BV, 16.53 mL/100 mL; K(trans), 37.00 mL/100 mL/min; and MTT, 12.42 seconds. All perfusion values of patients with lymphoma and cirrhosis differed significantly, except for BV, compared to controls. For patients with lymphoma, significant correlations were found between splenic volume and BF (r = -0.683, P = .000), splenic volume and BV (r = -0.525, P = .002), and splenic volume and MTT (r = 0.543, P = .001). During treatment, significant correlations between the diameters of nodular lymphoma target lesions, splenic volume, and the perfusion parameters were present for splenic volume (r = 0.601, P = .002), BF (r = -0.777, P = .000) and BV (r = -0.500, P = .011).

CONCLUSIONS

Volume perfusion computed tomography represents a novel tool for the assessment of splenic perfusion. Preliminary results in patients with spleen involvement reveal lower perfusion values compared to controls or patients with cirrhosis. Therefore, this technique might provide additional information in clinical routine.

Application of metabolic PET imaging in radiation oncology

Positron emission tomography (PET) is a noninvasive imaging technique that provides functional or metabolic assessment of normal tissue or disease conditions and is playing an increasing role in cancer radiotherapy planning. (18)F-Fluorodeoxyglucose PET imaging (FDG-PET) is widely used in the clinic for tumor imaging due to increased glucose metabolism in most types of tumors; its role in radiotherapy management of various cancers is reviewed. In addition, other metabolic PET imaging agents at various stages of preclinical and clinical development are reviewed. These agents include radiolabeled amino acids such as methionine for detecting increased protein synthesis, radiolabeled choline for detecting increased membrane lipid synthesis, and radiolabeled acetate for detecting increased cytoplasmic lipid synthesis. The amino acid analogs choline and acetate are often more specific to tumor cells than FDG, so they may play an important role in differentiating cancers from benign conditions and in the diagnosis of cancers with either low FDG uptake or high background FDG uptake. PET imaging with FDG and other metabolic PET imaging agents is playing an increasing role in complementary radiotherapy planning.

Imaging of extranodal lymphoma with PET/CT

Hodgkin disease (HD) and non-Hodgkin lymphoma (NHL) represent a spectrum of malignant neoplasms arising from the lymphoid system with an incidence of around 8% of all malignancies. Although they are generally known as tumors of lymph nodes, 25% to 40% of HD/NHL tumors, especially NHL, arise at extranodal sites along the gastrointestinal tract, head and neck, orbit, central and peripheral nervous system, thorax, bone, skin, breast, testis, thyroid, and genitourinary tract. Extranodal involvement is an important pretreatment prognostic factor for patients with lymphoma and its incidence has increased in the past 2 decades. Imaging plays an important role in the noninvasive pretreatment assessment of patients with extranodal lymphoma. This involvement can be subtle and may be overlooked during computed tomography (CT). Positron emission tomography/CT (PET/CT) has evolved into an important imaging tool for evaluation of lymphomas, facilitating the detection of affected extranodal sites even when CT shows subtle or no obvious lesions. Familiarity with extranodal manifestations and suggestive PET/CT features in different sites is important for accurate evaluation of lymphoma. This article reviews the extranodal PET/CT imaging findings regarding HD and NHL.

Synchronous second primary neoplasms detected by initial staging F-18 FDG PET/CT examination in patients with non-Hodgkin lymphoma

PURPOSE OF THE REPORT

Cases of synchronous non-Hodgkin lymphoma (NHL) and second primary carcinoma in previously untreated immunocompetent patients are relatively rare. The aim of this part of our prospective study was to a revealed 2-F-18 fluoro-2-deoxy-D-glucose (F-18 FDG) positron emission tomography (PET)-positive lesion in an extranodal organ suggestive of second primary neoplasm in newly diagnosed NHL patients.

MATERIALS AND METHODS

A total of 209 patients with NHL underwent initial staging F-18 FDG PET/computed tomography (CT). The finding was assessed by a radiologist, nuclear medicine physician, and hematologist. In 6 suspicious cases (2.9%) of second neoplasm, the decision was made to perform further investigations before lymphoma therapy.

RESULTS

Two patients were diagnosed with colorectal carcinoma, 1 with esophageal adenocarcinoma, 1 with invasive ductal breast carcinoma, 1 with medullary thyroid carcinoma, and 1 with squamous cell lung carcinoma. In 5 of the 6 patients, the second solid tumor was completely asymptomatic and revealed only by F-18 FDG PET/CT examination.

CONCLUSIONS

We conclude that in patients with NHL, appropriate imaging, clinical, and histologic analysis of organ lesions detected by F-18 FDG PET/CT will occasionally demonstrate significant synchronous neoplasms.

Causes and imaging features of false positives and false negatives on F-PET/CT in oncologic imaging

BACKGROUND: 18F-FDG is a glucose analogue that is taken up by a wide range of malignancies. 18F-FDG PET-CT is now firmly established as an accurate method for the staging and restaging of various cancers. However, 18F-FDG also accumulates in normal tissue and other non-malignant conditions, and some malignancies do not take up F18-FDG or have a low affinity for the tracer, leading to false-positive and false-negative interpretations. METHODS: PET-CT allows for the correlation of two separate imaging modalities, combining both morphological and metabolic information. We should use the CT to help interpret the PET findings. In this article we will highlight specific false-negative and false-positive findings that one should be aware of when interpreting oncology scans. RESULTS: We aim to highlight post-treatment conditions that are encountered routinely on restaging scans that can lead to false-positive interpretations. We will emphasise the importance of using the CT component to help recognise these entities to allow improved diagnostic accuracy. CONCLUSION: In light of the increased use of PET-CT, it is important that nuclear medicine physicians and radiologists be aware of these conditions and correlate the PET and CT components to avoid misdiagnosis, over staging of disease and unnecessary biopsies.

Review of Physiologic and Pathophysiologic Sources of Fluorodeoxyglucose Uptake in the Chest Wall on PET

The chest wall can be defined as the osseous and soft tissue structures that form the outer framework of the thorax and move during breathing. Topics discussed in this article include physiologic uptake of fluorodeoxyglucose, benign diseases of the chest wall, and malignant tumors of the chest wall.

Metabolic positron emission tomography imaging in cancer detection and therapy response

Positron emission tomography (PET) is a noninvasive imaging technique that provides a functional or metabolic assessment of normal tissue or disease conditions. Fluorine 18-fluorodeoxyglucose PET imaging (FDG-PET) is widely used clinically for tumor imaging due to increased glucose metabolism in most types of tumors, and has been shown to improve the diagnosis and subsequent treatment of cancers. We review its use in cancer diagnosis, staging, restaging, and assessment of response to treatment. In addition, other metabolic PET imaging agents in pre-clinical research or clinical trial stages of development are discussed, including amino acid analogs based on increased protein synthesis, and choline, which is based on increased membrane lipid synthesis. Amino acid analogs and choline are more specific to tumor cells than FDG, so they play an important role in differentiating cancers from benign conditions and in the diagnosis of cancers with low FDG uptake or high background FDG uptake. For decades, researchers have shown that tumors display altered metabolic profiles with elevated uptake of glucose, amino acids, and lipids. This can be used for cancer diagnosis and monitoring of the therapeutic response with excellent signal-to-noise ratios.

Spectrum of FDG PET/CT findings in Burkitt lymphoma

PURPOSE

F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is known to be a useful diagnostic tool for staging, restaging, and monitoring therapy for lymphoma. The purpose of this retrospective study is to present a spectrum of FDG PET findings at initial presentation of Burkitt lymphoma and subsequent findings after therapy.

METHOD AND MATERIALS

We retrospectively reviewed 48 patients with Burkitt lymphoma referred for a total of 160 FDG PET/computed tomography (CT) scans at our institution. We characterized the disease distribution of Burkitt lymphoma in all patients and measured representative FDG activity from initial staging scans. Therapeutic response and disease remission were assessed in patients with PET/CT and clinical follow-up studies.

RESULTS

Of the 48 patients diagnosed with Burkitt lymphoma, 25 patients had FDG PET/CT scans for initial staging. All untreated lesions of Burkitt lymphoma were highly FDG avid. The mean maximum standardized uptake value of 54 representative lesions is 16.5 (range: 6-54). Twelve patients were immune compromised. The majority of patients had disease localized to the abdomen and the pelvis. Extranodal involvement was identified in more than half of the patients studied.

CONCLUSION

The American (or sporadic) form of Burkitt lymphoma presented with intense hypermetabolic lesions when untreated. The information is useful in evaluating post-treatment studies in the absence of a pretreatment scan.

Endoscopic ultrasound-guided fine-needle aspiration in patients with lymphadenopathy suspected of recurrent malignancy after curative treatment

BACKGROUND

The diagnosis of lymphadenopathy after treatment of malignancy is sometimes difficult, especially in patients whose treatment was deemed curative and without local recurrence or those who have increased serum levels of related tumor markers. We aimed to evaluate the effectiveness of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) as a diagnostic tool in patients with lymphadenopathy after curative treatment of malignancy.

METHODS

Consecutive patients with mediastinal, intraabdominal, or pelvic lymphadenopathy after curative treatment of malignancy who were referred to our hospital between October 2003 and September 2007 were enrolled in this study.

RESULTS

A total of 62 patients were included. The lymph nodes were located at the mediastinum in 22 patients, intraabdomen in 38 patients, and intrapelvis in 2 patients. From the pathological findings of the FNA sample, 31 patients (50%) were confirmed to have recurrence of the prior malignancy, and 9 patients (15%) were diagnosed as having a different new malignancy. The remaining 22 patients (35%) were shown to have no recurrence or no other malignancies. However, 1 of them was later diagnosed with recurrence by open laparotomy. The overall sensitivity, specificity, accuracy, and positive and negative predictive values of the EUS-FNA were 97%, 100%, 98%, 100%, and 97%, respectively.

CONCLUSIONS

Lymphadenopathy after treatment of malignancy is not a definitive sign of recurrence. Therefore, pathological sampling and diagnosis are essential for determining the appropriate treatment. For this purpose, EUS-FNA is a safe, convenient, and minimally invasive procedure with high diagnostic value.

PET imaging in lymphoma

PET has become a cornerstone procedure in modern lymphoma management. This paper reviews, from a clinical point of view, the evidence for using PET in the different subtypes of lymphoma and the different steps of their management. The reader is given an overview of the current PET-based interventional lymphoma trials and an insight into possible future developments in the field, including new PET tracers.

Radiofrequency ablation of the spleen in patients with thalassemia intermedia: a pilot study

OBJECTIVE

We investigated the efficacy and safety of radiofrequency ablation on the hematologic parameters in patients with thalassemia intermedia (TI).

MATERIALS AND METHODS

Radiofrequency ablation of the spleen was performed in 15 children with TI under general anesthesia using a cool-tip radiofrequency probe. These patients were regarded as the radiofrequency ablation group. Nine patients with TI who underwent partial splenectomy during the past 3 years and another 14 patients with TI who underwent total splenectomy were also enrolled in this study as the first and second control groups (CG1 and CG2).

RESULTS

In the radiofrequency ablation group, two (13%) patients showed a significant increase in the mean hemoglobin level compared with the year before (1.5 and 1.8 g/dL). In addition, three (20%) other patients became transfusion-free in the year after radiofrequency ablation. In CG1, one (11%) patient showed a significant increase in hemoglobin the year after partial splenectomy, and another two (22%) patients became transfusion-free. In CG2, six (43%) patients revealed a significant increase in hemoglobin in the year after total splenectomy, and another four (29%) revealed a significant decrease in the need for transfusions. The mean increase in hemoglobin and platelet count was more significant in CG2 than in the radiofrequency ablation group and CG1. The mean hospital stay was significantly shorter in the radiofrequency ablation group (1.7 days vs 7.5 and 8.2 days in CG1 and CG2, respectively).

CONCLUSION

We believe that radiofrequency ablation of the spleen can be a safe procedure in patients with TI and is at least as effective as partial splenectomy, having only minor self-limiting complications.

Acute necrotizing pancreatitis following inadvertent extensive splenic artery embolisation for trauma

We present a case of splenic artery embolisation (SAE) after traumatic splenic injury that was complicated by acute necrotizing pancreatitis, caused by inadvertently extensive embolisation of the splenic artery. Although SAE is increasingly used for splenic preservation in trauma, there is insufficient knowledge on its efficacy and pitfalls. This report aims to draw attention to a rare but potentially serious complication of SAE.

Subcutaneous panniculitis-like T-cell lymphoma in a child: whole-body MRI in the initial and follow-up evaluations

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is classified as an unusual subtype of peripheral T-cell lymphoma that preferentially infiltrates the subcutaneous tissue without overt lymph node involvement. SPTCL is particularly rare in children, and there have been only a few case reports describing the US and CT findings of SPTCL. To our knowledge, the use of whole-body (WB) MRI as the initial and follow-up diagnostic method to assess the extent of disease and relapse of SPTCL has not been reported in children. In our case report involving one child, WB MRI was useful as both the initial and follow-up diagnostic method to assess the extent of disease and to monitor the patient's response to therapy for SPTCL.

Perspectives of molecular imaging and radioimmunotherapy in lymphoma

Successful treatment of Hodgkin lymphomas and non-Hodgkin lymphomas depends on accurate staging and prognostic estimations, as well as evaluation of response to therapy as early after initiation as possible. We focus on several aspects of molecular imaging and therapy that affect the management of patients who have lymphoma. First, we review prior use of gallium-67 citrate for evaluation of lymphoma patients, mainly from a historical perspective, since it was the mainstream lymphoma functional imaging tracer for decades. Next, we review current clinical uses of 18F Fluoro-2-Deoxyglucose (18F FDG) PET and PET/CT for evaluation of lymphoma patients and use of radioimmunotherapy in lymphoma. Finally, we discuss advances in molecular imaging that may herald the next generation of PET radiotracers after 18F FDG.