Dimitri Papathanassiou

Impact on Overall Survival of Radioactive Iodine in Low-Risk Differentiated Thyroid Cancer Patients

CONTEXT American Thyroid Association and European Thyroid Association guidelines cannot recommend for or against radioactive iodine (RAI) ablation after surgery in low-risk differentiated thyroid cancer (DTC) patients. OBJECTIVES The objective of the study was to assess the survival benefit of RAI for these patients. DESIGN We identified 1298 DTC patients at low risk treated between 1975 and 2005. Logistic regressions were used to identify variables associated to RAI and to calculate the propensity score to receive RAI after surgery. We compared overall survival (OS) and disease-free survival (DFS) according to RAI with the log-rank tests and univariate and multivariate Cox analyses. Analyses stratified on propensity score were also performed. RESULTS Median follow-up was 10.3 yr. Nine hundred eleven patients received RAI after surgery vs. 387 patients without RAI after surgery. Using univariate analysis, 10-yr OS was found to be 95.8% in patients without RAI after surgery vs. 94.6% in RAI after surgery (P = 0.006), and 10-yr DFS was found to be 93.1% vs. 88.7% (P = 0.001). All clinical factors except sex were significantly associated with RAI. Using multivariate Cox analyses, RAI was neither significantly nor independently associated with OS (P = 0.243) and DFS (P = 0.2659). After stratification on propensity score, Cox univariate analyses showed that OS did not differ according to RAI (P = 0.3524), with a hazard ratio for RAI of 0.75 (95% confidence interval 0.40-1.38). Similarly, DFS did not differ (P = 0.48) with a stratified univariate hazard ratio of 1.11 (95% confidence interval 0.73-1.70). CONCLUSION With a long-term follow-up of 10.3 yr, we failed to prove any survival benefit of RAI after surgery in a large cohort of low-risk DTC patients.

Single-photon emission computed tomography combined with computed tomography (SPECT/CT) in bone diseases

Radionuclide bone scanning was proven effective many years ago. Its main advantages are good sensitivity, limited radiation exposure, and noninvasiveness. However, increased radionuclide uptake by a lesion is not specific, and differentiating malignant from nonmalignant disorders may therefore be difficult. An additional structural imaging study is often needed to establish the final diagnosis. Furthermore, the limited resolution of radionuclide bone scanning images does not allow accurate localization of the lesions. Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) provides both structural and functional information. SPECT/CT has been proven useful for interpreting radionuclide bone scan results in patients with bone malignancies, showing far better specificity than planar imaging or SPECT alone, most notably in the evaluation of spinal abnormalities. SPECT/CT provides an accurate evaluation of the site of the lesions and also supplies other information that can be useful in nonmalignant conditions such as injuries, infections, and degenerative disease. Nevertheless, there are only a few published studies on the usefulness of SPECT/CT in nonmalignant conditions. However, SPECT/CT is only starting to become available and may become a routine investigation for a number of rheumatic disorders.

Positron Emission Tomography in oncology: present and future of PET and PET/CT.

PET is a crucial technique in molecular imaging, allowing in vivo assessment and localization of pathological processes, thanks to its ability to detect very small amounts of radioactive molecules. This is of particular interest in oncology where abnormal metabolism or synthesis in tumor cells but also various tumor characteristics can be studied using this nuclear medicine technique. FDG is currently the most widely used tracer, nowadays essential in the management of various malignancies, with large applications in diagnosis, initial assessment, therapy monitoring, and recurrence detection. The combination of anatomical information provided by PET/CT further increased its interest. Beyond its spread use in daily practice, future applications of PET will involve other tracers than FDG and develop research applications in humans as well as in small animals.

SPECT/CT in localization of parathyroid adenoma or hyperplasia in patients with previous neck surgery.

Purpose: Single photon emission computed tomography/computed tomography (SPECT/CT) now makes it possible to use combined morphologic CT and functional scintigraphy information. It has proved useful for localization of abnormal parathyroid glands, especially in the case of an ectopic gland. We experienced that it was also beneficial for patients with a history of previous neck surgery, and we report 4 cases in this entity. Materials and Methods: Four patients with prior neck surgery and hyperparathyroidism underwent parathyroid Tc-99m MIBI scintigraphy with SPECT/CT. Two patients had undergone surgery for hyperparathyroidism and 2 had undergone thyroidectomy, 1 for thyroid cancer and 1 for multinodular goiter. Parathyroid hormone levels were assessed during surgery, and patients were followed several months after treatment. Results: SPECT/CT successfully localized the abnormal gland, including an uncommon anterior situation for which previous surgery guided by planar imagery failed to cure the hyperparathyroidism. It allowed efficient surgical treatment, as confirmed by parathyroid hormone level normalization, without complications and with a relatively short operation time in those challenging cases. Conclusions: SPECT/CT seems to be a useful tool for presurgical assessment in hyperparathyroidism, not only for ectopic glands but also for patients with previous neck surgery.

The growing development of multimodality imaging in oncology.

The first decade of the century has been the beginning of an era of new practice in daily medical imaging, that is the multimodality involving functional or metabolic imaging brought by nuclear medicine techniques directly associated with anatomical information brought by CT (Computed X-Ray Tomography) devices combined with nuclear medicine detectors. PET (Positron Emission Tomography)/CT and SPECT (Single Photon Emission Computed Tomography)/CT are now established to further increase the interest of PET and SPECT, thanks to improved localization of the pathologic processes, and in many instances thanks to a gain in specificity. An even better use of the combined information will necessitate redefining some protocols and indications, and the future will probably see the continued development of multimodality imaging in practice. Besides the combination with CT, another modality is expected in the future: PET/MRI (Magnetic Resonance Imaging).

Cesium attenuation correction of the liver dome revealing hepatic lesion missed with computed tomography attenuation correction because of the respiratory motion artifact.

Abstract Computed tomography (CT) attenuation-corrected FDG images are known to have particular artifacts, especially the respiratory artifact. The respiratory artifact may decrease the diagnostic value of the study around the diaphragm. Malpositioning of lesions, mismatches in location or size of organs, and constitution of an artifactual curvilinear cold area in the liver dome (the so-called “banana artifact”) or spleen have been reported. We report the case of a small liver metastasis in the hepatic dome, which was absolutely not seen on CT attenuation-corrected FDG images, but was clearly demonstrated on cesium transmission attenuation-corrected images. This case emphasizes the risk of the false-negative diagnosis of a liver metastasis in relation to a respiratory artifact and illustrates the usefulness of completing, if technically possible, the positron emission tomography (PET)/CT examination with a short conventional transmission acquisition centered on the diaphragm.

Prognostic value of (18)F-FDG PET/CT metabolic parameters in metastatic differentiated thyroid cancers.

Purpose To evaluate the prognostic value of 18F-fluorodeoxyglucose positron emission tomography (FDG PET) with quantitative analysis using metabolic parameters in metastatic differentiated thyroid cancer (DTC). Materials and Methods The FDG-PET scans of 37 patients with metastatic DTC were studied retrospectively. The number of FDG-avid lesions, the SUVmax, the SULpeak of the lesion with the highest FDG uptake, the overall metabolic tumor volume (MTV), and the total lesion glycolysis (TLG) were measured. Curves of progression-free survival (Kaplan-Meier) and Cox univariate and multivariate analyses determined the prognostic factors for survival. Results Progression-free survival was better in patients with less than 10 FDG-avid lesions (P = 0.0089), the SUVmax less than 10 (P = 0.0026), the SULpeak less than 5 (P = 0.0004), and the TLG less than 154 (P = 0.0110). Cox analyses showed that only the result of the PET scan was predictive of survival (age, TNM stage, histology, and the 131I whole body radioiodine scan were not associated with prognosis). In the univariate analysis, prognostic factors for progression-free survival and overall survival were the SUVmax (P = 0.004; P = 0.018), the SULpeak (P = 0.001; P = 0.017), and the TLG (P = 0.014; P = 0.012). The number of FDG-avid lesions was significantly associated with progression-free survival (P = 0.012), but not the MTV. In the multivariate analysis, the number of FDG-avid lesions and the SULpeak were independent prognostic factors. Conclusions FDG PET using metabolic parameters is a prognostic factor in metastatic DTC. It could improve the therapeutic management and follow-up of patients.

Incidental finding of F-18 FDG skin uptake in a patient with psoriasis during the evaluation of a recurrent papillary thyroid carcinoma.

We report the case of a patient, referred in our institution for a PET/CT for a suspected recurrence of papillary thyroid carcinoma. An intense cutaneous uptake of FDG was seen in the upper neck region. The clinical examination showed an indurate and thickened red descamative plaque evocative of psoriasis, and the patient reported a long history of psoriatic lesions of the skin, evolving for many years. This case illustrates an incidental finding which must be recognized, and not confounded with other causes of skin uptake. The FDG image is not surprising, as FDG uptake is expected in active inflammatory disease.

Multicriteria 3D PET image segmentation

The analysis of images acquired with Positron Emission Tomography (PET) is challenging. In particular, there is no consensus on the best criterion to quantify the metabolic activity for lesion detection and segmentation purposes. Based on this consideration, we propose a versatile knowledge-based segmentation methodology for 3D PET imaging. In contrast to previous methods, an arbitrary number of quantitative criteria can be involved and the experts behaviour learned and reproduced in order to guide the segmentation process. The classification part of the scheme relies on example-based learning strategies, allowing interactive example definition and more generally incremental refinement. The image processing part relies on hierarchical segmentation, allowing vectorial attribute handling. Preliminary results on synthetic and real images confirm the relevance of this methodology, both as a segmentation approach and as an experimental framework for criteria evaluation.

Hierarchical forest attributes for multimodal tumor segmentation on FDG-PET/contrast-enhanced CT

Accurate tumor volume delineation is a crucial step for disease assessment, treatment planning and monitoring of several kinds of cancers. However, this process is complex due to variations in tumors properties. Recently, some methods have been proposed for taking advantage of the spatial and spectral information carried by coupled modalities (e.g., PET-CT, MRI-PET). Simultaneously, the development of attributebased approaches has contributed to improve PET image analysis. In this work, we aim at developing a coupled multimodal / attribute-based approach for image segmentation. Our proposal is to take advantage of hierarchical image models for determining relevant and specific attribute from each modality. These attributes then allow us to define a unique, semantic vectorial image. Sequentially, this image can be processed by a standard segmentation method, in our case a random-walker approach, for segmenting tumors based on their intrinsic attribute-based properties. Experimental results emphasize the relevance of computing region-based attributes from both modalities.