M. Ohana

Current and future imaging of the peripheral nervous system

Peripheral nervous system (PNS) imaging is usually carried out by ultrasound and MRI. Thanks to its wide availability and excellent spatial resolution, ultrasound is a mature investigation with clearly established indications, particularly in entrapment syndromes and tumors. MRI is generally a second-line examination, which provides decisive additional information thanks to its excellent contrast resolution and its multiplanar abilities. This review describes the current methods for imaging the PNS, concentrating on acquisition techniques, normal results and basic pathological semiology. Ongoing and future developments are described in order to underline the forthcoming changes in this very dynamic field of musculoskeletal radiology.

Thoracic dual energy CT: Acquisition protocols, current applications and future developments

Thanks to a simultaneous acquisition at high and low kilovoltage, dual energy computed tomography (DECT) can achieve material-based decomposition (iodine, water, calcium, etc.) and reconstruct images at different energy levels (40 to 140keV). Post-processing uses this potential to maximise iodine detection, which elicits demonstrated added value for chest imaging in acute and chronic embolic diseases (increases the quality of the examination and identifies perfusion defects), follow-up of aortic endografts and detection of contrast uptake in oncology. In CT angiography, these unique features are taken advantage of to reduce the iodine load by more than half. This review article aims to set out the physical basis for the technology, the acquisition and post-processing protocols used, its proven advantages in chest pathologies, and to present future developments.

Longitudinal 2D strain can help diagnose coronary artery disease in patients with suspected non-ST-elevation acute coronary syndrome but apparent normal global and segmental systolic function

BACKGROUND The clinical work-up of patients presenting with chest pain is a diagnostic challenge. We investigated the diagnostic performance of global (GLS) and territorial (TLS) longitudinal strain to predict coronary artery disease (CAD) in patients presenting with suspected non-ST-segment elevation acute coronary syndrome (NSTE-ACS) but apparent normal global and regional systolic function. METHODS 150 consecutive suspected NSTE-ACS patients were initially screened for inclusion ; 58 patients with normal LVEF (≥55%) and WMSI (=1) were prospectively enrolled. Speckle-tracking echocardiography was performed on admission and all the patients underwent coronary angiography. CAD was defined as the presence of stenosis of >50%. RESULTS CAD was present in 33 patients (57%). LVEF was 60.7±4.6% in group 1 (CAD) and 61.1±5.0% in group 2 (no CAD). Global longitudinal strain (GLS) was altered in group 1 (-16.7±3.4%) as compared to group 2 (-22.4±2.9%, p<0.001). ROC curve analysis showed a high diagnostic value of GLS for the prediction of CAD (AUC=0.92 [0.84-1.00], p=0.0001). TLS was able to discriminate between coronary stenosis in the LAD, LCX or RCA. CONCLUSIONS Longitudinal 2D strain has a good diagnostic value and can efficiently localize the culprit lesion in patients presenting with NSTE-ACS but apparent normal global and regional systolic function.

Iterative reconstruction in single source dual-energy CT pulmonary angiography: Is it sufficient to achieve a radiation dose as low as state-of-the-art single-energy CTPA?

OBJECTIVE Dual-energy (DE) brings numerous significant improvements in pulmonary CT angiography (CTPA), but is associated with a 15-50% increase in radiation dose that prevents its widespread use. We hypothesize that thanks to iterative reconstruction (IR), single source DE-CTPA acquired at the same radiation dose that a single-energy examination will maintain an equivalent quantitative and qualitative image quality, allowing a more extensive use of the DE technique in the clinical routine. MATERIAL AND METHODS Fifty patients (58% men, mean age 64.8yo ± 16.2, mean BMI 25.6 ± 4.5) were prospectively included and underwent single source DE-CTPA with acquisition parameters (275 mA fixed tube current, 50% IR) tweaked to target a radiation dose similar to a 100 kV single-energy CTPA (SE-CTPA), i.e., a DLP of 260 mGy cm. Thirty patients (47% men, 64.4yo ± 18.6, BMI 26.2 ± 4.6) from a previous prospective study on DE-CTPA (375 mA fixed tube current, reconstruction with filtered-back projection) were used as the reference group. Thirty-five consecutive patients (57% men, 65.8yo ± 15.5, BMI 25.7 ± 4.4) who underwent SE-CTPA on the same scanner (automated tube current modulation, 50% IR) served as a comparison. Subjective image quality was scored by two radiologists using a 5-level scale and compared with a Kruskal-Wallis nonparametric test. Density measurements on the 65 keV monochromatic reconstructions were used to calculate signal-to-noise (SNR) and contrast-to-noise (CNR) ratios that were compared using a Students t test. Correlations between image quality, SNR, CNR and BMI were sought using a Pearsons test. p<0.05 was considered significant. RESULTS All examinations were of diagnostic quality (score ≥ 3). In comparison with the reference DE-CTPA and the SE-CTPA protocols, the DE-IR group exhibited a non-inferior image quality (p=0.95 and p=0.21, respectively) and a significantly lower mean image noise (p<0.01 and p=0.01) thus slightly improving the SNR (p=0.09 and p=0.47) and the CNR (p=0.12 and p=0.51). There was a strong negative relationship between BMI and SNR/CNR (ρ=-0.59 and -0.55 respectively), but only a moderate negative relationship between BMI and image quality (ρ=-0.27). CONCLUSION With iterative reconstruction, objective and subjective image quality of single source DE-CTPA are preserved even though the radiation dose is lowered to that of a single-energy examination, overcoming a major limitation of the DE technique and allowing a widespread use in the clinical routine.

Imaging of lung transplant complications

Since the late 1980s, lung transplantation has emerged as a valid treatment option for some patients with advanced non-neoplastic lung disease. Long-term survival of lung transplant recipients, however, is lower than that of patients with other types of transplantation, because of numerous specific postoperative complications. Thanks to X-ray and CT, radiologists can guide clinicians, helped in this diagnostic approach by the time between the date of injury and date of transplantation. We will detail in this pictorial review the immediate and late surgical complications, the immunological complications, the infectious complications and other late complications.

Midterm failure after endovascular treatment of a persistent sciatic artery aneurysm.

Persistent sciatic artery (PSA) is a rare arterial embryologic malformation that tends to present early atherosclerotic degeneration such as aneurysmal formation. Open surgical treatment of PSA aneurysms has been considered as the gold standard but endovascular techniques have been recently proposed in the literature. We report the case of a 65-year-old man, diagnosed with a PSA aneurysm on peripheral thromboembolic complications. We achieved an endovascular repair with a covered stent. Despite an uneventful postoperative course, the covered stent demonstrated fracture and thrombosis 6 months after implantation without any symptoms.

Late Detection of Left Ventricular Dysfunction Using Two-Dimensional and Three-Dimensional Speckle-Tracking Echocardiography in Patients with History of Nonsevere Acute Myocarditis

Background: Acute myocarditis (AM) often involves the left ventricular (LV) subepicardium that might be displayed by cardiac magnetic resonance even late after the acute phase. In the absence of global or regional LV dysfunction, conventional transthoracic echocardiography (TTE) does not accurately identify tissue sequelae of AM. We sought to evaluate the diagnostic value of two‐dimensional (2D) and three‐dimensional (3D) speckle‐tracking echocardiography to identify patients with a history of AM with preserved LV ejection fraction (LVEF). Methods: Fifty patients (group 1: age, 31.4 ± 10.5 years; 76% males) with a history of cardiac magnetic resonance–confirmed diagnosis of AM (according to the Lake Louise criteria) were retrospectively identified and then (21.7 ± 23.4 months later) evaluated by complete echocardiography including 2D and 3D speckle‐tracking analysis, as well as 50 age‐ and gender‐matched healthy controls (group 2: age, 31.2 ± 9.5 years: 76% males). Patients with a history of severe clinical presentation of AM (sudden death, ventricular arrhythmia, heart failure, alteration of LVEF) were excluded. Results: At diagnosis, peak troponin and C‐reactive protein were 11.97 (interquartile range, 4.52‐25.92) &mgr;g/L and 32.3 (interquartile range, 14.85‐70.45) mg/L, respectively. Mean delay between acute phase and follow‐up study TTE was 21.7 ± 23.4 months. LVEF was not statistically different between groups (62.1% vs 63.5%, P = .099). Two‐dimensional global longitudinal strain (GLS) was lower in magnitude in group 1 (−17.8% vs −22.1%, P < .0001) as were 2D layer‐specific subepicardial GLS (−15.4% vs −19.7%, P < .0001) and subendocardial GLS (−20.71% vs −25.08%, P < .0001). Three‐dimensional global longitudinal, circumferential, area, and radial strains were lower in magnitude in group 1 (−11.80% vs −14.98%, P < .0001; −12.57% vs −15.12%, P < .0001; −22.28% vs −25.87%, P < .0001; 31.47% vs 38.06%, P < .0001, respectively). Receiver operating characteristic curve analysis showed that subepicardial GLS displayed a better diagnostic performance to detect sequelae of AM as compared with GLS (area under the curve = 0.97 vs 0.93, P = .045). Conclusions: In patients with a history of AM, a subtle LV dysfunction can be detected by 2D and 3D speckle‐tracking echocardiography, even though LVEF is conserved, adding incremental information over conventional TTE. HighlightsIn patients with a history of AM, a subtle myocardial dysfunction can be detected even late after the episode.Both LV and right ventricular strain parameters are altered compared with healthy controls.Layer‐specific 2DSTE is useful to detect subepicardial alteration of LV longitudinal function.These tools represent a potential novel approach for noninvasive multimodality evaluation of AM patients.

DWI in the Etiologic Diagnosis of Excretory Upper Urinary Tract Lesions: Can It Help in Differentiating Benign From Malignant Tumors? A Retrospective Study of 98 Patients

OBJECTIVE The objective of this study was to evaluate the diagnostic performance of high-field DWI in distinguishing benign from malignant lesions of the upper urinary tract (UUT). MATERIALS AND METHODS Ninety-eight patients who underwent 3-T DWI (b = 1000 s/mm(2)) for assessment of a UUT lesion were retrospectively included in the study. Data on the size, location, and mean apparent diffusion coefficient (ADC) value of the lesions were collected and correlated with the final diagnosis. ROC curve analysis was used to determine the best threshold value of the mean ADC for characterization of the lesions. RESULTS A total of 66 carcinomas and 33 benign lesions were identified. The mean (± SD) ADC value was statistically significantly lower for the malignant lesions than for the benign lesions (0.984 ± 0.048 vs 1.536 ± 0.067 × 10(-3) mm(2)/s; p = 0.000007). For characterization of malignant lesions, the best cutoff ADC value on the ROC curve was found to be less than or equal to 0.996 10(-3) mm(2)/s. On the basis of this value, the sensitivity and specificity of 3-T DWI for the identification of malignant UUT lesions were 78.3% and 95.5%, respectively, with a positive predictive value of 94.7% and a negative predictive value of 80.8% (p = 0.0001). The thickness of the smallest lesion was 3 mm. The mean ADC value of high-grade tumors was not statistically significantly lower than that of low-grade tumors. The best cutoff value for predicting benignancy was greater than or equal to 1.100 × 10(-3) mm(2)/s with sensitivity of 90.9%, specificity of 82.6%, positive predictive value of 83.3%, and negative predictive value of 90.5%. CONCLUSION The ADC measurement is a useful additional parameter in the differentiation of benign from malignant UUT lesions.

Treatment of Aneurysmal Aberrant Right Subclavian Artery with Triple-Barrel Stent Graft

Aneurysmal evolution of an aberrant right subclavian artery (ARSA) is an operative indication. Endovascular treatment is a minimally invasive procedure, which offers good short-term and midterm results. We describe a case of a 9-cm diameter ARSA aneurysm in a symptomatic man, treated with the triple-barrel technique using a thoracic aortic stent graft combined with surgical and endovascular revascularization of the supra-aortic trunks. Postoperatively, the patient developed a type III endoleak which was covered. The triple-barrel technique has been a proposed treatment approach for complex aortic arch pathologies and remains a less invasive option when compared with open surgery.

Axonotmesis of the sciatic nerve.

We report the case of an eight-year old girl who was admitted for aftercare and rehabilitation one month after a serious head injury that required a four-day stay in intensive care. Initial investigations did not show any evidence of post-traumatic injury. During her admission, she developed significant pain in the left buttock radiating to the lower limb associated with a sensorimotor deficit. These disabling pains persisted at rest. The clinical examination revealed that the patient had great difficulty walking, presenting a limp, a tender point on palpation of the left buttock radiating to the thigh and the leg along a posterolateral course, with hyperaesthesia in the whole area. Extension of the leg and both flexion and extension of the foot were impossible; hip flexion was normal. Hypoaesthesia was noted on the inside of the left leg and foot. The left patellar and Achilles reflexes were absent. Vital signs were normal. First-line magnetic resonance imaging (MRI) of the lumbar spine did not reveal any abnormalities. An MRI of the pelvis and lower limbs was then carried out and this highlighted involvement of the sciatic nerve along its whole extra-perineal course (Fig. 1a), with an overall increase in its calibre (Fig. 1b), a clear and homogenous high T2 signal intensity and a loss of its fascicular structure compared to the contralateral side (Fig. 1c). The nerve remained uninterrupted along its whole course.