[Orbital tumors]. / Tumoren der Orbita.

Orbital tumours include a variety of orbital diseases of different origins. In the case of malignant orbital tumours, early detection is important so that treatment can be initiated promptly. Neuroradiological imaging, in particular magnetic resonance imaging (MRI), plays an important role in the diagnostic of orbital tumours. In adults, lymphoproliferative diseases, inflammations and secondary orbital tumours are most frequently found, whereas in children mostly dermoid cysts, optic gliomas and capillary haemangiomas are found. Optic glioma is a pilocytic astrocytoma and accounts for two thirds of all primary optic tumours. Optic nerve sheath meningiomas mostly affect middle-aged women. In childhood, retinoblastoma is the most common intraocular tumour. This is an aggressive malignant tumour which can occur unilaterally or bilaterally. Based on the imaging findings, differential diagnoses can usually be easily narrowed down using criteria such as age of manifestation, frequency, localisation and imaging characteristics.

Preliminary experience of CT imaging of the ischaemic brain penumbra through spectral processing of multiphasic CTA datasets.

To assess ischaemic penumbra through the post-processing of the spectral multiphasic CT Angiography (mCTA) data in acute ischaemic stroke (AIS) patients. Thirty one consecutive patients strongly suspected of severe Middle Cerebral Artery AIS presenting less than 6 h after onset of symptoms or with unknown time of onset of symptoms underwent a standardized CT protocol in spectral mode including Non Contrast CT, mCTA, and Perfusion CT (CTP) on a dual-layer MDCT system. Areas disclosing delayed enhancement on iodine density (ID) maps were highlighted by subtraction of the serial mCTA datasets. Two neuroradiologists independently rated the correspondence between delayed enhancing areas at mCTA and the penumbral/infarcted areas delineated by two validated CTP applications using a 5-levels scoring scale. Interobserver agreement between observers was evaluated by kappa statistics. Dose delivery was recorded for each acquisition. Averaged correspondence score between penumbra delineation using subtracted mCTA-derived ID maps and CTP ones was 2.76 for one application and 2.9 for the other with best interobserver agreement kappa value at 0.59. All 6 stroke mimics out of the 31 patients' cohort were correctly identified. Average dose delivery was 7.55 mSv for the whole procedure of which CTP accounted for 39.7%. Post-processing of spectral mCTA data could allow clinically relevant assessment of the presence or absence of ischaemic penumbra in AIS-suspected patients if results of this proof-of-concept study should be confirmed in larger patients'series.

Iodine uptake of adrenal glands: A novel and reliable spectral dual-layer computed tomographic-derived biomarker for acute septic shock.

OBJECTIVES: Septic shock is a potentially fatal condition. This study aims to assess whether iodine uptake and iodine density of abdominal organs on dual-layer spectral detector computed tomography (SDCT) could serve as a new imaging biomarker for patients in septic shock. METHODS: Here, 95 patients who received contrast-enhanced abdominal CT examinations were included and separated into two groups: group A - septic shock; group B - no shock condition. Preselected abdominal (right and left adrenal gland, right and left kidney, infrarenal inferior vena cava (IVC), pancreas, spleen, and liver) localizations were independently evaluated by two radiologists, who measured iodine concentrations (mg/ml) and Hounsfield units (HU). RESULTS: In all, 1520 measurements of iodine concentrations in mg/ml and HU were performed, with 27 patients in group A and 68 in group B. Iodine concentrations in mg/ml and HU correlated significantly in all organs measured. The corresponding correlation coefficient (r) ranged from 0.809 (pancreas) to 0.963 (right kidney). Inter-rater reliability (IRR) was very good for mg/ml (κ = 0.8; p < 0.01) and good for HU (κ = 0.773; p < 0.01) measurements. The mean iodine concentration and HU of the adrenal glands in septic and nonseptic patients was 4.88 ± 1.16 mg/ml/153 ± 36 HU and 2.67 ± 1.07 mg/ml/112 ± 41 HU, respectively. Iodine concentrations in the adrenal glands were significantly higher in group A than in group B patients (p < 0.01). The other organs remained unaffected and no significant difference was observed between patients in group A and B. Patients in group A presented significantly more often with an iodine uptake of >3.5 mg/ml of one adrenal gland (sensitivity = 0.926, specificity = 0.849, AUC = 0.951) or/and a combined concentration of >7 mg/ml of both adrenal glands (sensitivity = 0.889, specificity = 0.836, AUC = 0.928). CONCLUSION: SDCT-derived iodine concentration of the adrenal glands could serve as a novel imaging biomarker for patients in acute septic shock. Our data suggest that an iodine uptake of >3.5 mg/ml of at least one adrenal gland or a combined iodine uptake of >7 mg/ml in both adrenal glands identifies patients in this condition.

Individualized arterial spin labeling background suppression by rapid T1 mapping during acquisition.

OBJECTIVE: Arterial spin labeling blood perfusion signal relies on the difference between a label and a control image. Background suppression pulses are commonly used to improve the contrast, yet these are based on estimates of tissue relaxation times. The aim of this study is to improve the perfusion contrast by individualizing the timing of these background suppression pulses by means of T1 mapping. METHODS: The optimized timing of the background suppression pulses is obtained by rapid T1 mapping employing the variable flip angle technique. Ten healthy volunteers were included in this study. To compare the results, visual grading and the Wilcoxon signed-rank test was used comparing three categories of image quality. RESULTS: The readers confirmed that the images of the proposed method generally show a higher signal-to-background ratio and cortical structures are better visible. Noise was mostly comparable to the standard method. Relative blood flow was statistically significant higher in the modified method. CONCLUSION: The individually optimized background suppression pulses improve the image appearance and allow for a better visualization of cortical structures. The proposed technique however prolongs scan time, which can be seen as negative result, yet needs to be further evaluated. KEY POINTS: • Background suppression timing in ASL can vary. • Both the label and control condition can be modified for T1 mapping. • Adapting the pulse timing improves the signal-to-background ratio.