Computed Tomography Assessment of Response to Therapy: Tumor Volume Change Measurement,Truth Data,and Error

RATIONALE AND OBJECTIVES: This article describes issues and methods that are specific to the measurement of change in tumor volume as measured from computed tomographic (CT) images and how these would relate to the establishment of CT tumor volumetrics as a biomarker of patient response to therapy. The primary focus is on the measurement of lung tumors, but the approach should be generalizable to other anatomic regions. MATERIALS AND METHODS: The first issues addressed are the various sources of bias and variance in the measurement of tumor volumes, which are discussed in the context of measurement variation and its impact on the early detection of response to therapy. RESULTS AND RESOURCES: Research that seeks to identify the magnitude of some of these sources of error is ongoing, and several of these efforts are described herein. In addition, several resources for these investigations are being made available through the National Institutes of Health-funded Reference Image Database to Evaluate Response to therapy in cancer project, and these are described as well. Other measures derived from CT image data that might be predictive of patient response are described briefly, as well as the additional issues that each of these metrics may encounter in real-life applications. CONCLUSIONS: The article concludes with a brief discussion of moving from the assessment of measurement variation to the steps necessary to establish the efficacy of a metric as a biomarker for response.     

Metformin May Be Associated with False-Negative Cancer Detection in the Gastrointestinal Tract on Pet/Ct

ObjectiveConcurrent therapy with the antihyperglycemic drug metformin can hinder the detection of malignancy in the abdominal and pelvic portions of ¹⁸F-fluordeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging performed for the diagnosis or staging of malignancy, as well as for treatment response and radiation therapy planning. This is due to the metformin-induced increase in intestinal FDG radiotracer uptake. We aim to bring this potentially important interaction to the attention of clinicians who care for cancer patients with diabetes.MethodsWe searched MEDLINE (from 1970 to January 2014)and Google Scholar for relevant English-language articles using the following search terms: “metformin and FDG/PET, metformin and bowel uptake, metformin, and cancer, metformin and the intestine, metformin pharmacokinetics, hyperglycemia and FDG/PET.” We reviewed the reference lists of pertinent articles with respect to metformin gut physiology, impact on FDG uptake and the effect on diagnostic accuracy of abdominal-pelvic PET/CT scans with concurrent metformin therapy.ResultsWe reviewed the action of metformin in the intestine, with particular emphasis on the role of metformin in PET/CT imaging and include a discussion of clinical studies on the topic to help refine knowledge and inform practice. Finally, we discuss aspects pertinent to the management of type 2 diabetes (T2D) patients on metformin undergoing PET/CT.ConclusionsMetformin leads to intense, diffusely increased FDG uptake in the colon, and to a lesser degree, the small intestine, which limits the diagnostic capabilities of FDG PET/CT scanning and may mask gastrointestinal malignancies. We suggest that metformin be discontinued 48 hours before FDG PET/CT scanning is performed in oncology patients. More rigorous data are needed to support the widespread generalizability of this recommendation. (Endocr Pract. 2014;20:1079-1083)     

18F-FDG PET/CT in lymphomas: assessment difficulties due to illness characteristics, and comparison with literature data

Fluor-18-deoxy-glucose (18F-FDG or FDG) positron emission tomography - computer tomography (PET/CT) has recently become integrated into the clinical routine of patients with lymphoma in Hungary. The basic condition of risk-adapted treatment of these patients is the exact staging and early objective evaluation of the effectiveness of therapy. Between 1 May 2007 and 31 October 2010, 1862 18F-FDG PET/CT examinations were conducted for lymphoma patients at the PET/CT Center in Debrecen. This is more than 15% of the total examined patient population, and this rate shows a slight increase with each year. Based on the experience obtained from lymphoma patients by routine metabolic PET/CT scans we analyzed the difficulties of the evaluation in different time frames of patients' management. It is well known that FDG uptake of lymphomas depends on multiple factors. Although most histological subtypes are associated with uptake of FDG, the intensity of the tracer uptake is different. Different intensity of FDG uptake of the same type of lymphoma following therapeutic procedures might cause difficulties in the evaluation of the scans ensuring that primary staging by PET/CT is highly required for precise measurement and reliable comparison of data. Extranodal involvement was detected in ~40% of the patients with variable rate of prevalence. Extranodal involvement is associated with great diversity and in most cases it is not characteristic of the illness and might appear in different forms and in any organs. Additionally, because accompanying disease may produce false positive results, detailed clinical data and precise case history is highly required.     

Apport de la TEP/TDM au 18FDG dans la stadification initiale et l’évaluation précoce de la réponse thérapeutique des rhabdomyosarcomes pédiatriques

PurposeThe objective of this study was to retrospectively evaluate the impact of positron emission tomography/computed tomography (PET/CT) using fluorine-18-fluorodeoxyglucose (FDG), in comparison with conventional imaging modalities (CIM), for initial staging and early therapy assessment in paediatric rhabdomyosarcoma.Patients and methodsPrior to treatment, 18 patients (age range, 9 months to 18 years) with histologically proven rhabdomyosarcoma underwent FDG PET/CT in addition to CIM (magnetic resonance imaging of primary site, whole body CT and bone scintigraphy). After three courses of chemotherapy, 12 patients underwent FDG PET/CT in addition to CIM. RECIST criteria and visual analysis of FDG uptake were used for assessment of response. The standard of reference was determined by an interdisciplinary tumor board based on imaging material, histopathology and follow-up data (median = 5 years).ResultsPET/CT sensitivity was superior to CIM's concerning lymph node involvement (100% versus 83%, respectively) and metastases detection (100% versus 50%, respectively). PET/CT results changed therapeutic management in 11% of cases. After three courses of chemotherapy, the rate of complete response was 66% with PET/CT versus 8% with CIM. Five percent of patients relapsed during follow-up (median = 5 years).ConclusionThis study confirms that PET/CT depicts important additional information in initial staging of paediatric rhabdomyosarcomas and suggests a superior prognostic value of PET/CT in early response to chemotherapy assessment.     

Comparative Oncology: Evaluation of 2-Deoxy-2-[18F]fluoro-D-glucose (FDG) Positron Emission Tomography/Computed Tomography (PET/CT) for the Staging of Dogs with Malignant Tumors

Introduction

2-Deoxy-2-[18F]fluoro-D-glucose PET/CT is a well-established imaging method for staging, restaging and therapy-control in human medicine. In veterinary medicine, this imaging method could prove to be an attractive and innovative alternative to conventional imaging in order to improve staging and restaging. The aim of this study was both to evaluate the effectiveness of this image-guided method in canine patients with spontaneously occurring cancer as well as to illustrate the dog as a well-suited animal model for comparative oncology.

Methods

Ten dogs with various malignant tumors were included in the study and underwent a whole body FDG PET/CT. One patient has a second PET-CT 5 months after the first study. Patients were diagnosed with histiocytic sarcoma (n = 1), malignant lymphoma (n = 2), mammary carcinoma (n = 4), sertoli cell tumor (n = 1), gastrointestinal stromal tumor (GIST) (n = 1) and lung tumor (n = 1). PET/CT data were analyzed with the help of a 5-point scale in consideration of the patients’ medical histories.

Results

In seven of the ten dogs, the treatment protocol and prognosis were significantly changed due to the results of FDG PET/CT. In the patients with lymphoma (n = 2) tumor extent could be defined on PET/CT because of increased FDG uptake in multiple lymph nodes. This led to the recommendation for a therapeutic polychemotherapy as a treatment. In one of the dogs with mammary carcinoma (n = 4) and in the patient with the lung tumor (n = 1), surgery was cancelled due to the discovery of multiple metastasis. Consequently no treatment was recommended.

Conclusion

FDG PET/CT offers additional information in canine patients with malignant disease with a potential improvement of staging and restaging. The encouraging data of this clinical study highlights the possibility to further improve innovative diagnostic and staging methods with regard to comparative oncology. In the future, performing PET/CT not only for staging but also in therapy control could offer a significant improvement in the management of dogs with malignant tumors.     

Despite the increase of serum CA 19-9, complete metabolic response and tumoral calcifications in PET/CT: Could it be a tumor stunning after chemotherapy?

A 74-year-old male patient with a history of nausea, vomiting, and loss of appetite revealed thickening of the antrum and pylorus in gastroscopy and non-mucinous adenocarcinoma was diagnosed in the biopsy. The patient underwent 18F-FDG PET/CT for staging. PET/CT showed intense FDG uptakes in the primary lesion, locoregional lymph nodes and liver metastases. After 5-fluorouracil based chemotherapy, a complete metabolic response in metastatic liver lesions, lymph nodes, and the primary tumor was detected. Furthermore, tumor calcifications were observed in the liver and locoregional lymph node metastases. Although a complete response, there was a 40 percent serum CA 19-9 level increase. During the follow-up, intense FDG uptake was observed in the calcified metastatic liver lesions and some lymph nodes, similar to the continuous increase in serum CA 19-9 levels. Ascites, multiple metastatic lung nodules and metabolic progression in liver lesions were observed on PET/CT in the patient who continued to receive chemotherapy.     

Cancer de la prostate : utilité de la TEP-TDM à la F-fluorocholine

In oncology, positron emission computed tomography (PET/CT) has become an essential tool for initial staging, response evaluation and follow-up of cancer patients. Most of the frequent tumors (lung, breast, esophagus, and lymphomas) are highly avid for ¹⁸F-fluorodeoxyglucose (¹⁸FDG), but prostate cancer has not demonstrated significant uptake of FDG. The development of new tracers labeled with ¹⁸F such as choline analogs allowed already to obtain interesting results particularly in patients with biological relapse and inconclusive conventional imaging work-up. The impact of ¹⁸F-flurocholine PET/CT on patient management needs to be validated in large studies, but many centers use already this examination in order to guide further management, including radiotherapy planning.     

Early positron emission tomography/computed tomography as a predictor of response after CTL019 chimeric antigen receptor –T-cell therapy in B-cell non-Hodgkin lymphomas

Molecular imaging with ¹⁸F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is an established modality for response assessment in patients with lymphoma undergoing treatment. However, patients treated with novel immunotherapies may have false-positive PET/CT findings due to tumor site and systemic inflammation. In particular, treatment with autologous chimeric antigen receptor modified T-cells redirected at CD19 (CTL019 CAR-T cells) is often complicated by “cytokine release syndrome” (CRS) due to a severe systemic inflammatory reaction. Infiltration of tumors by activated CTL019 cells may impact radiographic and functional imaging findings. The role of PET/CT in patients treated with CTL019 has not previously been described. We performed a pilot, single-arm, prospective study to explore the utility of early PET/CT in patients with diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) undergoing treatment with CTL019 CAR-T cells. Patients had PET/CT prior to CTL019 infusion and then early PET/CT at 1 month after treatment. The primary outcome was the amount/change in metabolically active tumor volume (MTV) and FDG uptake. We enrolled seven patients (DLBCL, three; FL, four). Six of 7 had baseline PET/CT with active disease. On post-treatment PET/CT, three patients had no residual MTV, two patients had a decrease in MTV and two patients had an increase in MTV. The three patients with no residual MTV all remain in remission >2 years post-treatment. The patients with less than complete response all subsequently relapsed. Development of CRS did not confound PET/CT findings. In patients with DLBCL and FL receiving CTL019 CAR-T cells, early PET/CT may predict response to this novel immunotherapy.     

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.     

Thromboses néoplasiques et thromboses cruoriques mécaniques compliquant un cancer du testicule gauche en TEP/TDM au 18FDG

We report the case of a 46-year-old patient with pulmonary embolism complicating thrombosis of the left renal vein and inferior vena cava, which came from a malignant tumor of the left testicle. The case has been elucidated by positron emission tomography with ¹⁸FDG coupled to the CT-scan (PET/CT), performed as part of the etiological assessment of this pulmonary embolism, and anatomical and physiological considerations. The examination revealed ¹⁸FDG uptake in thrombus of the left kidney vein and the inferior vena cava. In view of the anatomy of the left spermatic vein, this finding led to the left testicle, which shows no nuclide uptake but was bathed in a large hydrocele visible on CT images. If several cases of pulmonary embolism or thrombosis of the inferior vena cava revealing a testicular cancer have been described in the literature, there has been no report including ¹⁸FDG PET/CT to the best of our knowledge. This case illustrates the imaging differences between bland and malignant thrombus as a consequence of their pathophysiology. It highlights the contribution of CT images from the PET/CT for the diagnosis.     

La fluorocholine(18F) a une utilité clinique dans le cancer de la prostate et le carcinome hépatocellulaire… parfois chez le même malade

Case reportIn order to stage hepatocellular carcinoma (HCC), a patient was referred to PET/CT using fluorodeoxyglucose(18F) (FDG) and, if necessary, fluorocholine(18F) (FCH). HCC was proven by biopsy of a hepatic mass discovered on CT performed for a biological recurrence of prostate cancer.ResultFDG PET/CT did not show any anomaly. FCH PET/CT was thus performed and showed various foci: the hepatic mass, a large abdominal adenopathy and an unexpected subcentimetre lung nodule. The diagnostic uncertainty mostly concerned this lung nodule which was biopsied and consisted of a metastasis of the prostate cancer. Due to the presence of two metastatic cancers, the patient's management was altered, with chemotherapy for the HCC and hormone therapy for the prostate cancer.ConclusionSeveral types of cancer take-up fluorocholine(18F), which is a powerful tool to detect metastases, in particular in case of rising levels of marker with a negative FDG PET/CT. Even when FDG PET/CT is positive, FCH may reveal unexpected foci with other metabolic characteristics, although it is not specific of a given primary cancer, as well as FDG. For staging of HCC, we thus recommend to perform PET/CT with both tracers.     

Comparison of the Prognostic Value of F-18 Pet Metabolic Parameters of Primary Tumors and Regional Lymph Nodes in Patients with Locally Advanced Cervical Cancer Who Are Treated with Concurrent Chemoradiotherapy

Objective

This study investigated the metabolic parameters of primary tumors and regional lymph nodes, as measured by pre-treatment F-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) to compare the prognostic value for the prediction of tumor recurrence. This study also identified the most powerful parameter in patients with locally advanced cervical cancer treated with concurrent chemoradiotherapy.

Methods

Fifty-six patients who were diagnosed with cervical cancer with pelvic and/or paraaortic lymph node metastasis were enrolled in this study. Metabolic parameters including the maximum standardized uptake value (SUVmax), the metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary tumors and lymph nodes were measured by pre-treatment F-18 FDG PET/CT. Univariate and multivariate analyses for disease-free survival (DFS) were performed using the clinical and metabolic parameters.

Results

The metabolic parameters of the primary tumors were not associated with DFS. However, DFS was significantly longer in patients with low values of nodal metabolic parameters than in those with high values of nodal metabolic parameters. A univariate analysis revealed that nodal metabolic parameters (SUVmax, MTV and TLG), paraaortic lymph node metastasis, and post-treatment response correlated significantly with DFS. Among these parameters, nodal SUVmax (hazard ratio [HR], 4.158; 95% confidence interval [CI], 1.1–22.7; p = 0.041) and post-treatment response (HR, 7.162; 95% CI, 1.5–11.3; p = 0.007) were found to be determinants of DFS according to a multivariate analysis. Only nodal SUVmax was an independent pre-treatment prognostic factor for DFS, and the optimal cutoff for nodal SUVmax to predict progression was 4.7.

Conclusion

Nodal SUVmax according to pre-treatment F-18 FDG PET/CT may be a prognostic biomarker for the prediction of disease recurrence in patients with locally advanced cervical cancer.     

PET/CT helps to determine treatment duration in patients with resected as well as inoperable alveolar echinococcosis

PurposeThe aim of the study was to determine the role of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) at the end of benzimidazole therapy in alveolar echinococcosis.MethodsA total of 22 patients undergoing PET/CT at the end of benzimidazole therapy were retrospectively registered. Maximum standardized uptake values (SUV_max) were measured in remaining echinococcus manifestations and compared to normal liver tissue. Long-term clinical follow-up was performed, and recorded data included laboratory parameters, clinical information and imaging.ResultsAll patients had no detectable levels of Em-18 antibodies and all echinococcus manifestations were negative on PET/CT, i.e. without focally increased FDG uptake or uptake higher than normal/non-infected liver tissue. All manifestations displayed significantly less FDG-uptake than normal liver tissue, i.e. SUVmax 1.8 (interquartile range (IQR) 1.5–3.5) vs. 3.0 (IQR 2.6–5.7), (p < 0.001). Patients were clinically followed for a median of 9.5 years (IQR 6.5–32.0 years) after their initial diagnosis and for 4.5 years (IQR 3.0–14.0 years) after discontinuation of benzimidazole therapy. No patient showed signs of recurrent infection at the last clinical visit. The 10-year and 20-year freedom from all-cause mortality was 95.0% (95% confidence interval 69.5% - 99.3%), for both. Two events occurred in 292 patient years of follow-up; i.e. two patients (9%) died, one because of pancreatic cancer, the other one because of unknown reasons with no detectable antibody levels.ConclusionsNegative FDG-PET/CT results combined with no detectable levels of Em-18 antibodies may allow for the safe discontinuation of benzimidazole therapy in patients with alveolar echinococcosis.     

A case of metastatic leptomeningeal carcinomatosis from early gastric carcinoma

Intramuscular myxoma is a rare benign soft tissue tumor which may be mistaken for other benign and low-grade malignant myxoid neoplasms. We present the case of a 63-year-old woman with an asymptomatic intramuscular myxoma discovered incidentally on a whole-body F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography. PET images showed a mild FDG uptake (maximum standardized uptake value, 1.78) in the left gluteus maximus. Subsequent magnetic resonance (MR) imaging revealed a well-defined ovoid mass with homogenous low signal intensity on T1-weighted sequences and markedly high signal intensity on T2-weighted sequences. Contrast-enhanced MR images showed heterogeneous enhancement throughout the mass. The diagnosis of intramuscular myxoma was confirmed on histopathology after surgical excision of the tumor. The patient had no local recurrence at one year follow-up. Our case suggests that intramuscular myxoma should be considered in the differential diagnosis of an oval-shaped intramuscular soft tissue mass with a mild FDG uptake.     

Anti-Angiogenic/Vascular Effects of the mTOR Inhibitor Everolimus Are Not Detectable by FDG/FLT-PET

Noninvasive functional imaging of tumors can provide valuable early-response biomarkers, in particular, for targeted chemotherapy. Using various experimental tumor models, we have investigated the ability of positron emission tomography (PET) measurements of 2-deoxy-2-[¹⁸F]fluoro-glucose (FDG) and 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT) to detect response to the allosteric mammalian target of rapamycin (mTOR) inhibitor everolimus. Tumor models were declared sensitive (murine melanoma B16/BL6 and human lung H596) or relatively insensitive (human colon HCT116 and cervical KB31), according to the IC₅₀ values (concentration inhibiting cell growth by 50%) for inhibition of proliferation in vitro (<10 nM and >1 µM, respectively). Everolimus strongly inhibited growth of the sensitive models in vivo but also significantly inhibited growth of the insensitive models, an effect attributable to its known anti-angiogenic/vascular properties. However, although tumor FDG and FLT uptake was significantly reduced in the sensitive models, it was not affected in the insensitive models, suggesting that endothelial-directed effects could not be detected by these PET tracers. Consistent with this hypothesis, in a well-vascularized orthotopic rat mammary tumor model, other antiangiogenic agents also failed to affect FDG uptake, despite inhibiting tumor growth. In contrast, the cytotoxic patupilone, a microtubule stabilizer, blocked tumor growth, and markedly reduced FDG uptake. These results suggest that FDG/FLT-PET may not be a suitable method for early markers of response to antiangiogenic agents and mTOR inhibitors in which anti-angiogenic/vascular effects predominate because the method could provide false-negative responses. These conclusions warrant clinical testing.     

A Comparison of Positron Emission Tomography and Colonoscopy for the Detection of Advanced Colorectal Neoplasms in Subjects Undergoing a Health Check-Up

Background & Aims

There is no agreement as to whether F-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) screening for advanced colorectal neoplasms is meaningful. This retrospective study was undertaken to determine whether FDG PET/CT may be a valuable screening tool for the detection of advanced colorectal neoplasms.

Methods

A retrospective review of the records of 1,109 FDG PET/CT scans acquired from January 2007 to December 2011 was performed. Colonoscopy and FDG PET/CT imaging were performed within two days of each other. The results of colonoscopy were taken as the gold standard, either with or without the results of the histopathological examination. An advanced neoplasm was defined as the presence of a malignant tumor, an adenoma ≥1 cm, or histological evidence of high-grade dysplasia or significant villous components.

Results

A total of 36 subjects had advanced colorectal neoplasms detected by colonoscopy (totaling 38 neoplasms). Six of the 38 neoplasms were also detected by FDG PET/CT. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of FDG PET/CT in the detection of advanced colorectal neoplasms were 15.8% (6/38), 99.1% (1063/1073), 37.5% (6/16), 97.1% (1063/1095), and 96.2% (1069/1111) respectively. The presence of lesions with an endoscopic size ≤1.5 cm (P<0.001) and low-grade dysplasia (P<0.001) were the main predictors of false-negative FDG PET/CT findings.

Conclusions

We conclude that FDG PET/CT screening of advanced colorectal neoplasms is unwarranted, especially in the presence of lesions with an endoscopic size ≤1.5 cm or low-grade dysplasia.     

Magnetic Resonance Assessment of Response to Therapy: Tumor Change Measurement,Truth Data and Error Sources

This article describes methods and issues that are specific to the assessment of change in tumor characteristics as measured using quantitative magnetic resonance (MR) techniques and how this relates to the establishment of quantitative MR imaging (MRI) biomarkers of patient response to therapy. The initial focus is on the various sources of bias and variance in the measurement of microvascular parameters and diffusion parameters as such parameters are being used relatively commonly as secondary or exploratory end points in current phase 1/2 clinical trails of conventional and targeted therapies. Several ongoing initiatives that seek to identify the magnitude of some of the sources of measurement variations are then discussed. Finally, resources being made available through the National Cancer Institute Reference Image Database to Evaluate Response (RIDER) project that might be of use in investigations of quantitative MRI biomarker change analysis are described. These resources include 1) data from phantom-based assessment of system response, including short-term (1 hour) and moderate-term (1 week) contrast response and relaxation time measurement, 2) data obtained from repeated dynamic contrast agent-enhanced MRI studies in intracranial tumors, and 3) data obtained from repeated diffusion MRI studies in both breast and brain. A concluding section briefly discusses issues that must be addressed to allow the transition of MR-based imaging biomarker measures from their current role as secondary/exploratory end points in clinical trials to primary/surrogate markers of response and, ultimately, in clinical application.     

Automated Movement Correction for Dynamic PET/CT Images: Evaluation with Phantom and Patient Data

Head movement during a dynamic brain PET/CT imaging results in mismatch between CT and dynamic PET images. It can cause artifacts in CT-based attenuation corrected PET images, thus affecting both the qualitative and quantitative aspects of the dynamic PET images and the derived parametric images. In this study, we developed an automated retrospective image-based movement correction (MC) procedure. The MC method first registered the CT image to each dynamic PET frames, then re-reconstructed the PET frames with CT-based attenuation correction, and finally re-aligned all the PET frames to the same position. We evaluated the MC method''s performance on the Hoffman phantom and dynamic FDDNP and FDG PET/CT images of patients with neurodegenerative disease or with poor compliance. Dynamic FDDNP PET/CT images (65 min) were obtained from 12 patients and dynamic FDG PET/CT images (60 min) were obtained from 6 patients. Logan analysis with cerebellum as the reference region was used to generate regional distribution volume ratio (DVR) for FDDNP scan before and after MC. For FDG studies, the image derived input function was used to generate parametric image of FDG uptake constant (K_i) before and after MC. Phantom study showed high accuracy of registration between PET and CT and improved PET images after MC. In patient study, head movement was observed in all subjects, especially in late PET frames with an average displacement of 6.92 mm. The z-direction translation (average maximum = 5.32 mm) and x-axis rotation (average maximum = 5.19 degrees) occurred most frequently. Image artifacts were significantly diminished after MC. There were significant differences (P<0.05) in the FDDNP DVR and FDG Ki values in the parietal and temporal regions after MC. In conclusion, MC applied to dynamic brain FDDNP and FDG PET/CT scans could improve the qualitative and quantitative aspects of images of both tracers.     

Positron emission tomography (18FDG-PET) in the detection of medullary thyroid carcinoma metastases

INTRODUCTION: Medullary thyroid carcinoma (MTC) is usually more advanced at presentation than differentiated thyroid cancers and often has distant metastases. The primary treatment of MTC is total thyroidectomy and regional lymph node dissection. The efficacy of these procedures has been limited by the aggressiveness of the disease and metastatic spread at the time of surgery. Persistently elevated levels of calcitonin (CT) and carcinoembryonic antigen (CEA) or their increase postoperatively are indicative for residual or recurrent disease. Conventional imaging methods such as ultrasonography, computed tomography, magnetic resonance imaging and MIBI scintigraphy usually fail to find the source of calcitonin. Better imaging properties have been shown by DMSA scintigraphy, somatostatin receptor scintigraphy or by positron emission tomography (PET). The aim of the study was to evaluate the diagnostic accuracy of PET for the localisation of occult MTC in patients after surgery with increased concentrations of CT, in whom conventional imaging procedures have not been successful. MATERIAL AND METHODS: The PET investigation using (18)F-fluoro- 2-deoxy-D-glucose combined with computed tomography ((18)FDG-PET/CT) was performed at the Department of Nuclear Medicine (Oncology Centre in Bydgoszcz) between January and October 2004. In five patients with postoperative calcitonin ranging from 164 to > 2000 ng/l (normal < 10 ng/l) no tumour lesions were found using other imaging methods. RESULTS: In four of five cases, responsible lesions with a higher metabolism of FDG, indicating MTC tissue (remnants or metastases), were localised. In one patient no focus of FDG accumulation was found despite high CT concentration. PET detected tumour manifestations in the neck and the mediastinum in two patients, in the lung and the left adrenal gland in one case and in the neck and the liver in another patient. As a result of surgery for the removal of a residual tumour or metastases the accuracy of diagnosis was confirmed by histopathology in all four cases and a decrease in CT and CEA levels was observed in 3/4 cases. The metabolic imaging findings by PET/CT ensured that the surgery on these patients was successful. CONCLUSIONS: For the detection of occult residual or metastatic MTC lesions, (18)FDG-PET is a valuable procedure in imaging diagnostics.     

La fixation vasculaire du 18FDG est reliée au risque d’événements récents ou futurs chez les patients à haut risque cardiovasculaire

With this study, we sought to identify plaque inflammation as assessed by ¹⁸FDG uptake on positron emission tomography (PET)/computed tomography (CT) as an independent cardiovascular risk factor in patients at high risk for cardiovascular events. We compared 31 consecutive cancer patients presenting with visually enhanced ¹⁸FDG uptake in arterial walls on PET/CT (Group 1) to a selection of 34 matched cancer patients not showing arterial uptake (Group 2). All patients were followed for two years before and six months after PET/CT… Cardiovascular events were classified as older (>6 months before PET/CT) or recent (<6 months before or after PET/CT). ¹⁸FDG uptake was computed on non-attenuation corrected data by a AW/L ratio: mean Arterial Wall uptake/Lung uptake in a normal area, and by SUV on corrected data. A calcium score (CS) was also calculated. ¹⁸FDG uptake and CS were higher in Group 1 than Group 2 (both p = 0.02), and older and recent cardiovascular events were significantly more frequent in Group 1 than Group 2 (p = 0.001 and p = 0.03, respectively). Among the following parameters: number of conventional risk factor, calcium score and presence of ¹⁸FDG uptake, only the latter was significantly related to the occurrence of a recent event by multivariate analysis (p = 0.02). Patients with elevated arterial ¹⁸FDG uptake have a high risk of immediate or future cardiovascular events. Arterial ¹⁸FDG uptake is an indicator of evolving atherosclerotic process and can indicate future cardiovascular events.