Morphological Imaging Procedures Research Articles

68Ga-Somatostatin Analogue PET/CT in Neuroendocrine Tumors

Neuroendocrine tumors (NETs) include a spectrum of neoplasms characterized by histologic heterogeneity with significant clinical differences. Generally are well differentiated tumors but often present metastases at diagnosis. Conventional imaging techniques result insufficient in early diagnosis and therapy monitoring. Standardized morphological criteria to assess treatment response are inadequate in NETs, because of their biologic evolution and the cytostatic nature of new oncologic treatments. Functional imaging modalities have improved the understanding and diagnosis of NETs by the use of somatostatin analogue tracers labelled with radioisotopes. 111 In-Octreotide scintigraphy was considered the gold standard imaging modalities for NET detection with a diagnostic accuracy approximately of 90%. Actually 68 Ga-Dota-SST radiotracers (SSTRTs) PET/CT represent a superior imaging procedure with higher accuracy in detection of NET lesions as compared to morphological imaging procedures and somatostatin receptor scintigraphy. Additionally, the use of somatostatin analogue radiolabelled tracers offers the possibility to non-invasively evaluate the presence of somatostatin receptor expression on NET cells, with direct therapeutic implications. However, in the management of patients with NETs and in the evaluation of response to therapy the specialists

Nuclear imaging of amyloidosis.

SummaryAmyloidosis is a clinical condition caused by deposition of various protein fibrills in extracellular space. The presented symptoms depend on the type of deposits and the organ or organs involved. The correct diagnosis is often difficult, due to lack of nonivasive imaging techniques and insufficiency of morphological imaging procedures delievered by radiology. We presented a list of potential radiopharmaceuticals that can be used in detecting various types of amyloidoses. 123I-SAP proved to have high sensitivity in imaging of AA and AL amyloidosis in visceral organs. 99mTc-Aprotinin was found to be useful in detecting cardiac amyloidosis. A couple of classical radiotracers, such as 201Tl, 123I-mIBG, together with 111In-antimyosin were also tested for accuracy in cardiac imaging, however the main problem was low specificity. Potential applicability was also found in case of some bone-seeking agents and other radiotracers, e.g. 67Ga-citrate and 99mTc-penta-DMSA. High sensitivity and specificity was achieved with β2-microglobulin labeled with 131I or 111In. Among PET tracers, 11C-PIB deserves more attention, because it may have an important role in diagnosing of AD in the near future. Further clinical studies are expected to take place, because noninvasive diagnosing and monitoring of amyloidosis is still a challenge.

68Ga-labelled peptides for diagnosis of neuroendocrine tumours

On the basis of available literature, the aim of this paper is to describe the advantages and limitations of 68Ga-DOTA peptide PET/CT imaging for the assessment of neuroendocrine tumours (NET) and to examine potential future perspectives. The introduction of new PET tracers labelled with 68Ga has changed the diagnostic approach to NET. While in the past decades the gold standard imaging modality for NET detection was the somatostatin analogue tracers labelled with 111In, several advantages now emerge by using both labelled somatostatin analogues with 68Ga and PET/CT tomography for image acquisition, leading to a larger use of these tracers in clinical practice. There is an increasing number of reports showing the higher accuracy of 68Ga-DOTA peptide PET/CT for the detection of NET lesions as compared to morphological imaging procedures and somatostatin receptor scintigraphy. The use of 68Ga-DOTA peptides offers the possibility to non-invasively evaluate NET cells for the presence of somatostatin receptor expression, with direct therapeutic implications. Last but not least, the use of 68Ga-DOTA peptides also leads to several practical advantages including the relatively easy and economic synthesis process and the fact that 68Ga labelling can be performed in centres without an on-site cyclotron.

68Ga-labelled peptides for diagnosis of gastroenteropancreatic NET

In the past few years, the introduction of novel PET tracers labelled with (68)Ga has changed the diagnostic approach to neuroendocrine tumours (NET) in specialized centres. Although somatostatin analogue tracers labelled with (111)In have represented the gold standard imaging modality for NET detection in past decades, the advantages offered by both labelling somatostatin analogues with (68)Ga and using PET/CT tomography for image acquisition, account for the increasing use of these tracers in clinical practice. There are an increasing number of reports of the higher accuracy of (68)Ga-DOTA peptide PET/CT for the detection of NET lesions as compared to morphological imaging procedures and somatostatin receptor scintigraphy. Moreover, the use of (68)Ga-DOTA peptides offers the possibility to noninvasively evaluate NET cells for the presence of somatostatin receptor expression, with direct therapeutic implications. Several practical advantages also favour the use of (68)Ga-DOTA peptides including the relatively easy and economic synthesis process and the fact that (68)Ga labelling can be performed in centres without an on-site cyclotron. We describe the advantages and limitations of (68)Ga-DOTA peptide PET/CT imaging for the assessment of gastroenteropancreatic NET referring to the available literature as well as to our experience, and finally highlight potential future perspectives.

La TEP-TDM à la 18F-Dopa aurait-elle un rôle dans le suivi postopératoire des patients atteints de carcinome médullaire de la thyroïde ? Résultats préliminaires de l’expérience strasbourgeoise et revue de la littérature

Aim Retrospective study to assess the value of fluorine-18 dihydroxyphenylalanine ( 18F-Dopa) positron emission tomography (PET)/computed tomography (CT) in the post-surgical follow-up of patients with history of medullary thyroid carcinoma (MTC) and biological suspicion of disease relapse. A review of the literature was also performed. Patients and methods Ten patients (23–71 years) with MTC previously treated by surgery were examined by at least one 18F-Dopa PET/CT. All patients presented with elevated serum calcitonin (130–9076 ng/l) and/or CEA (1.2–518 ng/ml) levels. 3D whole body PET/CT was performed 45 and 120 minutes after intravenous injection of 4 MBq/kg of 18F-Dopa. Scintigraphic images were visually interpreted. For quantitative analysis, maximum standardized uptake value (SUV max) per focus was employed. PET results were compared with histological findings and/or with the results of all other imaging procedures. Results Seven patients (70%) had a positive 18F-Dopa PET/CT. Twenty-five focal tracer accumulations were described. Histopathological confirmation of metastatic disease was obtained in four of the seven patients with pathologic 18F-Dopa PET/CT. No scintigraphic abnormalities were evidenced in the three other patients, whose conventional morphological imaging procedures were also negatives. Delayed PET/CT examinations didn’t increase sensitivity. No correlation between 18F-Dopa PET/CT results and both serum calcitonin and CEA levels was achieved. Conclusion Our results are in accordance with the existing literature, showing the potential role of 18F-Dopa PET/CT in the clinical management of patients with history of MTC and biological suspicion of relapse during post-surgical follow-up. Prospective studies including larger patient series are necessary to confirm the future place of 18F-Dopa PET/CT in follow-up of MTC.

Imaging procedures for gastrointestinal stromal tumors

Morphological and functional imaging methods are used for staging of gastrointestinal stromal tumors (GIST) and to follow-up GIST patients undergoing therapy. Computed tomography is the most frequently used morphological imaging procedure and has been recommended as the imaging method of choice according to current GIST guidelines. However, positron emission tomography using [(18)F]-2-fluoro-2-deoxy-D-glucose (FDG-PET) as the radiotracer has shown to be advantageous over morphological imaging procedures when assessing therapy response at an early time point. While tumor size reduction in morphological imaging typically requires time to develop, a decrease in FDG uptake can be detected as early as 24 h following therapy initiation. To overcome the limitations of size-based therapy response assessment on morphological imaging procedures, new density-based therapy response criteria have been developed and implemented for GIST. This review addresses both indications and accuracy of morphological and functional imaging modalities for GIST.

Lymph node staging with dual-modality PET/CT: enhancing the diagnostic accuracy in oncology

Lymph node staging according to the TNM criteria is an essential part of tumor evaluation. Several morphological and functional imaging procedures are used complementarily in this setting. Dual-modality PET/CT scanners are able to provide anatomical and functional data sets in a single session with accurate image coregistration. Comparative studies between morphological imaging procedures, such as MRI and CT, with coregistered PET/CT demonstrated significantly better lymph node staging with PET/CT than with anatomical procedures alone, regardless of the staged body compartment (head and neck, thorax, or abdominal area).

Lymph node staging with dual-modality PET/CT: Enhancing the diagnostic accuracy in oncology

Lymph node staging according to the TNM criteria is an essential part of tumor evaluation. Several morphological and functional imaging procedures are used complementarily in this setting. Dual-modality PET/CT scanners are able to provide anatomical and functional data sets in a single session with accurate image co-registration. Comparative studies between morphological imaging procedures, such as MRI and CT, with co-registered PET/CT demonstrated significantly better lymph node staging with PET/CT than with anatomical procedures alone, regardless of the staged body compartment (head and neck, thorax or abdominal area). Based on more accurate staging results, PET/CT was able to alter the patients’ therapy in a significant number of studies. Functional imaging with FDG–PET ([ 18F]-2-fluoro-2-desoxy- d-glucose–positron emission tomography) demonstrated outstanding results in lymph node staging of different tumor diseases. By adding anatomical information to PET, PET/CT outperforms PET alone when assessing the TNM-stage of different malignant diseases. This paper provides an overview concerning the performance of PET/CT in staging lymph nodes for malignant spread and points out benefits and limitations of this new imaging modality.

From Genomics to Clinical Molecular Imaging

Molecular imaging, as applied to clinical practice today, is in its early stages. Encouraging advances achieved in clinical positron emission tomography (PET) and small-animal imaging indicate that this technique is evolving into an indispensable diagnostic tool. When employed with complementary morphological imaging procedures, molecular imaging results in substantial diagnostic capability. It will enable the physician to unveil topographic biochemistry in situ and reduce invasive testing. While this is at least in part futuristic, it is clear already today that a comprehensive set of imaging modalities will be required. Imaging modalities most appropriate for molecular imaging are PET, single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), optical imaging, and ultrasound. The foundation for advances in molecular imaging, however, is not primarily imaging hardware development but scientific advancements in molecular biology and progress in probe development. Other factors to consider are postprocessing software and, inevitably, market dynamics. Thus. it implies efficient collaborations across disciplines, agencies, and industries to develop molecular imaging tools for the clinic.