Computer-based quantification of the Achilles tendon thickness in sequential B-mode ultrasound images: a study of feasibility and reliability.

INTRODUCTION: Assessment of the Achilles tendon thickness (ATT) using B-mode ultrasound is a common technique for clinical evaluation of chronic mid-part tendinosis. Currently used image-based assessment is limited by relatively high inter- and intra-observer variability. In this study, it was tested whether a new sequence-based automated assessment of ATT provides more reliable and reproducible results than the standard image-based procedure. MATERIALS AND METHODS: A total of 118 non-operated tendons of 59 healthy subjects (44, range 28-50 years) were analysed using an automated image based as well as a newly developed automated sequence-based method. Correlation and agreement of both methods were evaluated. The root mean square deviation (RMSD) and a Bland-Altman analysis were performed to highlight observer (n = 18 tendons) as well as reader (n = 40 tendons) dependent variabilities of both methods. RESULTS: A strong correlation was found between image and sequence-based ATT assessment (p = 0.92). The Bland-Altman analysis showed a good agreement between both methods (mean difference 0.0018, 95 % CI: -0.046; 0.05). In repetitive examinations, sequence-based analysis showed a significant reduction concerning reader- and observer-dependent variability compared to image-based assessment. The RMSD for repetitive sequence-based measurements was approximately 0.3 mm (compared to 0.6 mm for image-based measurement), respectively. CONCLUSIONS: The study shows sequence-based automated assessment of ATT being clearly superior to the standard image-based procedure. The new method provides a clear reduction of reader as well as observer-dependent variability. Due to the decreased scattering of measurement data sequence-based measurement seems especially valuable for quantification of small tendon thickness changes such as exercise-induced hypertrophy.

Staging of neuroendocrine tumours: comparison of [68Ga]DOTATOC multiphase PET/CT and whole-body MRI.

PURPOSE: In patients with a neuroendocrine tumour (NET), the extent of disease strongly influences the outcome and multidisciplinary therapeutic management. Thus, systematic analysis of the diagnostic performance of the existing staging modalities is necessary. The aim of this study was to compare the diagnostic performance of 2 whole-body imaging modalities, [(68)Ga]DOTATOC positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging (MRI) in patients with NET with regard to possible impact on treatment decisions. MATERIALS AND METHODS: [(68)Ga]DOTATOC-PET/CT and whole-body magnetic resonance imaging (wbMRI) were performed on 51 patients (25 females, 26 males, mean age 57 years) with histologically proven NET and suspicion of metastatic spread within a mean interval of 2.4 days (range 0-28 days). PET/CT was performed after intravenous administration of 150 MBq [(68)Ga]DOTATOC. The CT protocol comprised multiphase contrast-enhanced imaging. The MRI protocol consisted of standard sequences before and after intravenous contrast administration at 1.5 T. Each modality (PET, CT, PET/CT, wbMRI) was evaluated independently by 2 experienced readers. Consensus decision based on correlation of all imaging data, histologic and surgical findings and clinical follow-up was established as the standard of reference. Lesion-based and patient-based analysis was performed. Detection rates and accuracy were compared using the McNemar test. P values <0.05 were considered significant. The impact of whole-body imaging on the treatment decision was evaluated by the interdisciplinary tumour board of our institution. RESULTS: 593 metastatic lesions were detected in 41 of 51 (80%) patients with NET (lung 54, liver 266, bone 131, lymph node 99, other 43). One hundred and twenty PET-negative lesions were detected by CT or MRI. Of all 593 lesions detected, PET identified 381 (64%) true-positive lesions, CT 482 (81%), PET/CT 545 (92%) and wbMRI 540 (91%). Comparison of lesion-based detection rates between PET/CT and wbMRI revealed significantly higher sensitivity of PET/CT for metastatic lymph nodes (100% vs 73%; P < 0.0001) and pulmonary lesions (100% vs 87%; P = 0.0233), whereas wbMRI had significantly higher detection rates for liver (99% vs 92%; P < 0.0001) and bone lesions (96% vs 82%; P < 0.0001). Of all 593 lesions, 22 were found only in PET, 11 only in CT and 47 only in wbMRI. The patient-based overall assessment of the metastatic status of the patient showed comparable sensitivity of PET/CT and MRI with slightly higher accuracy of PET/CT. Patient-based analysis of metastatic organ involvement revealed significantly higher accuracy of PET/CT for bone and lymph node metastases (100% vs 88%; P = 0.0412 and 98% vs 78%; P = 0.0044) and for the overall comparison (99% vs 89%; P < 0.0001). The imaging results influenced the treatment decision in 30 patients (59%) with comparable information from PET/CT and wbMRI in 30 patients, additional relevant information from PET/CT in 16 patients and from wbMRI in 7 patients. CONCLUSION: PET/CT and wbMRI showed comparable overall lesion-based detection rates for metastatic involvement in NET but significantly differed in organ-based detection rates with superiority of PET/CT for lymph node and pulmonary lesions and of wbMRI for liver and bone metastases. Patient-based analysis revealed superiority of PET/CT for NET staging. Individual treatment strategies benefit from complementary information from PET/CT and MRI.

[Application of MR/PET in oncologic imaging]. / Einsatz von MR/PET in der onkologischen Bildgebung.

The present review aims to depict the possibilities offered by hybrid imaging with magnetic resonance positron emission tomography (MR/PET). Recently, new whole-body MR/PET scanners were introduced allowing for the combination of both modalities outside the brain. This is a challenge for both modalities: For MRI, it is essential to provide anatomical images with high resolution. Additionally, diffusion-weighted imaging (DWI), proton spectroscopy, but also dynamic contrast-enhanced imaging plays an important role. With regard to PET, the technical challenge mainly consists of obtaining an appropriate MR-based attenuation correction for the PET data. Using MR/PET, it is possible to acquire morphological and functional data in one examination. In particular, children and young adults will benefit from this new hybrid technique, especially in oncologic imaging with multiple follow-up examinations. However, it is expected that PET/CT will not be replaced completely by MR/PET because PET/CT is less cost-intensive and more widely available. Moreover, in lung imaging, MRI limitations still have to be accepted. Concerning research, simultaneous MR/PET offers a variety of new possibilities, for example cardiac imaging, functional brain studies or the evaluation of new tracers in correlation with specific MR techniques.

FDG-PET/CT-guided biopsy of bone metastases sets a new course in patient management after extensive imaging and multiple futile biopsies.

A 73-year-old man with a history of prostate and bladder carcinoma and persistent back pain was diagnosed by MRI with multiple vertebral metastases including a compression fracture of T7. He received radiotherapy for pain relief and for vertebral instability with incipient spinal stenosis, but additional targeted systemic therapy was intended. Therefore, multiple attempts at minimally invasive and open biopsies for histological characterisation of the bone metastases were performed, but failed to provide a conclusive specimen, although CT, MRI and bone scintigraphy were used for biopsy planning. Only histopathological analysis of an (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET)/CT-guided additional biopsy at a site with high metabolic activity yielded the final diagnosis of bone metastases of a neuroendocrine small cell cancer of unknown origin; hence, the patient had a third malignancy requiring a different therapy regimen and diagnostic work-up.

Integrated FDG-PET/CT for detection, therapy monitoring and follow-up of granulocytic sarcoma. Initial results.

AIM: Granulocytic sarcomas (GS) are rare extramedullary manifestations of myeloid or lymphoblastic leukaemia. Laboratory examinations are of limited use for diagnosis of extramedullary disease. Radiological imaging based on morphology is challenging. To date, the possible role of FDG-PET/CT as a method for combined metabolic and morphologic imaging is unclear. We present a series of 10 patients to evaluate the potential role of FDG-PET/CT in the management of GS. PATIENTS, MATERIALS, METHODS: A retrospective evaluation of 18 FDG-PET/CT exams in 10 patients with histologically proven GS was performed. All scans included a contrast enhanced CT. The FDG uptake of GS was analyzed and the sensitivity of lesion detection was compared to PET and CT alone. The changes in FDG uptake after therapy were compared to morphological changes detected by CT and follow-up / clinical outcome. RESULTS: 52 untreated or recurrent GS lesions were detected by FDG-PET/CT and all showed an increased FDG uptake with a mean SUVmax and SUVavg of 5.1 and 3.4, respectively. GS was multifocal in 8/10 patients. Combined PET/CT avoided 5 false positive findings compared to PET alone and 13 false negative findings and 1 false positive compared to CT alone. Changes in FDG uptake after therapy correlated with clinical outcome and were more reliable than CT assessment alone. PET/CT identified recurrent GS in 3 patients. CONCLUSION: Viable GS are FDG-avid. Using this metabolic information and morphologic CT criteria, combined FDG-PET/CT was more accurate in lesion detection than FDG-PET or CT alone. Changes in FDG uptake after therapy might be a useful additional parameter for therapy monitoring. Therefore, FDG-PET/CT appears to be a promising diagnostic and monitoring tool in the management of patients with GS.

Image quality analysis to reduce dental artifacts in head and neck imaging with dual-source computed tomography.

PURPOSE: Important oropharyngeal structures can be superimposed by metallic artifacts due to dental implants. The aim of this study was to compare the image quality of multiplanar reconstructions and an angulated spiral in dual-source computed tomography (DSCT) of the neck. MATERIALS AND METHODS: Sixty-two patients were included for neck imaging with DSCT. MPRs from an axial dataset and an additional short spiral parallel to the mouth floor were acquired. Leading anatomical structures were then evaluated with respect to the extent to which they were affected by dental artifacts using a visual scale, ranging from 1 (least artifacts) to 4 (most artifacts). RESULTS: In MPR, 87.1 % of anatomical structures had significant artifacts (3.12 +/- 0.86), while in angulated slices leading anatomical structures of the oropharynx showed negligible artifacts (1.28 +/- 0.46). The diagnostic growth due to primarily angulated slices concerning artifact severity was significant (p < 0.01). CONCLUSION: MPRs are not capable of reducing dental artifacts sufficiently. In patients with dental artifacts overlying the anatomical structures of the oropharynx, an additional short angulated spiral parallel to the floor of the mouth is recommended and should be applied for daily routine. As a result of the static gantry design of DSCT, the use of a flexible head holder is essential.