Angeliki Ailianou

FDG-PET/CT pitfalls in oncological head and neck imaging

ObjectivesPositron emission tomography-computed tomography (PET/CT) with fluorine-18-fluorodeoxy-D-glucose (FDG) has evolved from a research modality to an invaluable tool in head and neck cancer imaging. However, interpretation of FDG PET/CT studies may be difficult due to the inherently complex anatomical landmarks, certain physiological variants and unusual patterns of high FDG uptake in the head and neck. The purpose of this article is to provide a comprehensive approach to key imaging features and interpretation pitfalls of FDG-PET/CT of the head and neck and how to avoid them.MethodsWe review the pathophysiological mechanisms leading to potentially false-positive and false-negative assessments, and we discuss the complementary use of high-resolution contrast-enhanced head and neck PET/CT (HR HN PET/CT) and additional cross-sectional imaging techniques, including ultrasound (US) and magnetic resonance imaging (MRI).ResultsThe commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery. False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours.ConclusionsThe interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology.Teaching points• Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies.• Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation.• Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.

Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors.

Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

Orbital tumours and tumour-like lesions: exploring the armamentarium of multiparametric imaging

AbstractAlthough the orbit is a small anatomical space, the wide range of structures present within it are often the site of origin of various tumours and tumour-like conditions, both in adults and children. Cross-sectional imaging is mandatory for the detection, characterization, and mapping of these lesions. This review focuses on multiparametric imaging of orbital tumours. Each tumour is reviewed in relation to its clinical presentation, compartmental location, imaging characteristics, and its histological features. We herein describe orbital tumours as lesions of the globe (retinoblastoma, uveal melanoma), optic nerve sheath complex (meningioma, optic nerve glioma), conal-intraconal compartment (hemangioma), extraconal compartment (dermoid/epidermoid, lacrimal gland tumours, lymphoma, rhabdomysarcoma), and bone and sinus compartment (fibrous dysplasia). Lesions without any typical compartmental localization and those with multi-compartment involvement (veno-lymphatic malformation, plexiform neurofibroma, idiopathic orbital pseudotumour, IgG4 related disease, metastases) are also reviewed. We discuss the role of advanced imaging techniques, such as MR diffusion-weighted imaging (DWI), diffusion tensor imaging, fluoro-2-deoxy-D-glucose positron emission tomography CT (FDG-PET CT), and positron emission tomography MRI (MRI PET) as problem-solving tools in the evaluation of those orbital masses that present with non-specific morphologic imaging findings. Main messages/Teaching points • A compartment-based approach is essential for the diagnosis of orbital tumours. • CT and MRI play a key role in the work-up of orbital tumours. • DWI, PET CT, and MRI PET are complementary tools to solve diagnostic dilemmas. • Awareness of salient imaging pearls and diagnostic pitfalls avoids interpretation errors.

Assessment of metal artifact reduction methods in pelvic CT

PURPOSE Metal artifact reduction (MAR) produces images with improved quality potentially leading to confident and reliable clinical diagnosis and therapy planning. In this work, the authors evaluate the performance of five MAR techniques for the assessment of computed tomography images of patients with hip prostheses. METHODS Five MAR algorithms were evaluated using simulation and clinical studies. The algorithms included one-dimensional linear interpolation (LI) of the corrupted projection bins in the sinogram, two-dimensional interpolation (2D), a normalized metal artifact reduction (NMAR) technique, a metal deletion technique, and a maximum a posteriori completion (MAPC) approach. The algorithms were applied to ten simulated datasets as well as 30 clinical studies of patients with metallic hip implants. Qualitative evaluations were performed by two blinded experienced radiologists who ranked overall artifact severity and pelvic organ recognition for each algorithm by assigning scores from zero to five (zero indicating totally obscured organs with no structures identifiable and five indicating recognition with high confidence). RESULTS Simulation studies revealed that 2D, NMAR, and MAPC techniques performed almost equally well in all regions. LI falls behind the other approaches in terms of reducing dark streaking artifacts as well as preserving unaffected regions (p < 0.05). Visual assessment of clinical datasets revealed the superiority of NMAR and MAPC in the evaluated pelvic organs and in terms of overall image quality. CONCLUSIONS Overall, all methods, except LI, performed equally well in artifact-free regions. Considering both clinical and simulation studies, 2D, NMAR, and MAPC seem to outperform the other techniques.

Malformations of cortical development of the human brain: A pictorial essay

During development in utero of the human brain, an error in one or more of the orderly processes of neuroblast proliferation and differentiation, neuroblast migration and cortical organization may result in disordered neocortical development. Nowadays, the consequent malformations of the cerebral cortex and associated structures are detectable on pre- and postnatal examination with growing frequency, thanks to the evolution of modern imaging modalities. In particular, magnetic resonance imaging (MRI), due to its excellent contrast differentiation and multiplanar capabilities as well as the development of even newer techniques, such as diffusion tensor imaging and spectroscopy, has surpassed all other forms of imaging for the thorough exploration and analysis of congenital anomalies of the central nervous system. These malformations comprise a heterogeneous group of conditions in terms of both the timing and etiology of the developmental aberration as well as the resulting morphological phenotype, including epilepsy, developmental delay/intellectual disability and focal neurological deficits. This study briefly presents some typical examples of congenital malformations of cortical development of the human brain that are encountered in practice. It is our belief that familiarity with the MRI presentations of these conditions can be of considerable value for adequate disease management and genetic counseling.

Warthin’s tumor of the larynx: a very rare case and systematic review of the literature

BackgroundWarthin’s tumor or cystadenolymphoma (CAL) is a benign salivary gland tumor occurring almost exclusively in the parotid gland. CALs of other locations are rare.Case presentationWe report a laryngeal CAL detected in a positron emission tomography/computed tomography (PET/CT) performed for breast cancer follow-up. The tumor was successfully treated by transoral surgery.DiscussionOnly 14 cases of laryngeal CAL are reported worldwide. These cases confirmed our experience of an uncomplicated and mostly successful transoral resection.ConclusionCALs of the larynx are very rare. They are characterized by hypermetabolism in PET/CT. The increasing use of PET/CT investigations in cancer patients could give rise to more incidental findings of CALs at unusual locations such as the larynx.

Magnetic resonance imaging of infections of the white matter

Infections of the nervous system are a common and serious occurrence. Neuroimaging has allowed to improve early detection and thus to initiate treatment earlier. Magnetic resonance (MR) imaging has become the method of choice in investigating a patient with suspicion of an infection of the central nervous system. Newer modalities such as MR spectroscopy and MR diffusion and perfusion will further help to improve diagnostic accuracy of the technique. For the investigation of infections of white matter, techniques such as diffusion imaging are essential.

Utility of MRI with morphologic and diffusion weighted imaging in the detection of post-treatment nodal disease in head and neck squamous cell carcinoma

PURPOSE To determine the diagnostic performance of morphologic MRI with diffusion weighted imaging (DWIMRI) for the detection of post-treatment lymph node (LN) recurrence of head and neck squamous cell carcinoma (HNSCC). METHODS This retrospective study is based on 33 HNSCC patients who underwent DWIMRI with apparent diffusion coefficient (ADC) measurements for suspected post-treatment loco-regional failure. Two radiologists, blinded to clinical/histopathological data, analyzed MR images according to established morphologic criteria and measured ADC values by drawing regions of interest on each normal/abnormal looking lymph node (LN). Histopathological findings in 40 neck dissections, 133 LN-levels and 755 LNs served as gold standard. RESULTS Malignant LNs had lower ADCmean values than benign LNs (1.15 ± 0.35 × 10-3 mm2/s versus 1.28 ± 0.28 × 10-3 mm2/s, p = .028). The optimal ADCmean threshold to differentiate malignant from benign LNs was 1.1695 × 10-3 mm2/s. Sensitivity, specificity, positive (PPV) and negative (NPV) predictive values (95%CI in parentheses) of DWIMRI with morphologic criteria and ADCmean <1.1695 × 10-3 mm2/s were: (a) 100%(86.2;100), 44.4%(15.3;77.3), 86.1%(69.7;94.7), and 100%(39.5;100) per neck dissection; (b) 83.6%(69.7;92.2), 91.6%(83.0;96.2), 85.4%(71.6;93.4), and 90.5%(81.7;95.5) per LN-level; (c) 53.1%(43.5;62.4), 95.5%(93.5;96.9), 67.4%(56.6;76.7), and 92.0%(89.6;93.9) per LN, respectively. CONCLUSION The high NPV of DWIMRI irrespective of analysis type (per neck dissection/per neck level/per lymph node) make it a useful follow-up tool after treatment.

DWI und PET/MRT nach Strahlentherapie bei malignen Kopf-Hals-Tumoren

Die Interpretation von Bildgebungsbefunden des bestrahlten Halses stellt wegen der durch die Strahlentherapie induzierten (radiogenen) Gewebeveranderungen, des variablen Erscheinungsbilds von Tumorrezidiven sowie funktions- und stoffwechselbezogener Phanomene, die dem Erscheinungsbild einer Krankheit zum Verwechseln ahnlich sind, eine Herausforderung dar. Zur Erleichterung der Diagnose werden daher in der klinischen Praxis immer haufiger folgende Verfahren angewendet: die morphologisch orientierte MRT (Magnetresonanztomografie), die DWI (diffusionsgewichtete Bildgebung), die PET/CT (Positronenemissionstomografie mit Computertomografie) sowie die Fusion von PET- und MRT-Befunden mithilfe einer entsprechenden Software. Da MRT und PET in vielen Fallen komplementare Informationen liefern, lasst die kombinierte PET/MRT-Bildgebung auf eine Erleichterung der Unterscheidung zwischen Tumorrezidiven, radiogenen Veranderungen und Komplikationen hoffen. Im Mittelpunkt dieses Review stehen die klinischen Anwendungen von DWI und PET/MRT am bestrahlten Hals und die Erorterung des Zugewinns bei der Losung diagnostischer Probleme durch die multiparametrische Bildgebung. Radiologen sollten wissen, welche DWI- und PET/MRT-Befunde kennzeichnend fur die wichtigsten strahlentherapieinduzierten Gewebeveranderungen und die potenziellen Komplikationen sind: fur Odeme, Fibrosen, Vernarbungen, Weichgewebenekrosen, Knochen- und Knorpelnekrosen, Hirnnervenlahmungen und radiogene Arteriosklerose, Hirnnekrosen und Schilddrusenerkrankungen. DWI und PET/MRT erganzen sich auch bei der Fahndung nach residualem Tumorgewebe und Rezidiven. Mogliche technik-, funktions- oder stoffwechselbedingte Fehlerquellen bei der Interpretation sollten erkannt und vermieden werden. Vertrautheit mit den Charakteristika der zu erwartenden DWI- und PET/MRT-Befunde, mit potenziellen Komplikationen und Therapieversagen nach Strahlentherapie erhoht die diagnostische Sicherheit bei der Interpretation von Aufnahmen des bestrahlten Halses.

Comparative methods for metal artifact reduction in x-ray CT

To assess the performance of five metal artefact reduction (MAR) techniques for the assessment of computed tomography (CT) images of patients with hip prostheses. Five MAR algorithms were evaluated using simulation and clinical studies. The algorithms included one-dimensional linear interpolation (LI) of the corrupted projections in the sinogram, two-dimensional interpolation (2D), a normalized metal artefact reduction (NMAR) technique, a metal deletion technique (MDT), and a 3D prior image constrained projection completion approach (MAPC). The algorithms were applied to 10 simulated datasets as well as30 clinical studies of patients with metallic hip implants. Qualitative evaluations were performed by two blinded, experienced radiologists, who ranked overall artefact severity, as well as pelvic organ recognition for each algorithm, respectively. The simulated studies revealed that 2D, NMAR and MAPC techniques performed almost equally well in regions with dark streaking artefacts. However, in regions with bright streaking artefacts, LI outperformed the other techniques (p<;0.05). Visual assessment of clinical datasets confirmed the superiority of NMAR and MAPC in the evaluated pelvic organs and in terms of overall image quality. Overall, all methods performed equally well in artefact-free regions. However, NMAR and MAPC outperformed the other techniques in regions affected by artefacts.