The road to optimal acceleration of Dixon imaging and quantitative T2-mapping in the ankle using compressed sensing and parallel imaging.

OBJECTIVE: This study aimed to find the optimal acceleration factor achievable with CS-SENSE for a clinical ankle protocol while maintaining comparable image quality. METHODS: We explored the optimal acceleration achievable with factor CS-SENSE, for an ankle protocol with T2-weighted, PD-weighted TSE-Dixon (coronal, axial and sagittal) and T2-mapping (sagittal) sequences, on a 3 T MRI-scanner. This study contained three steps: (1) phantom test, (2) pilot test on healthy volunteers, (3) anatomical assessment on a cohort of healthy volunteers and a quantitative analysis. CS-SENSE images (acceleration factors between 2.0× and 12.0×) were compared to reference SENSE images (acceleration factor 2.0×). Three blinded radiologists evaluated the image quality and provided an anatomical assessment using a five-point Likert scale of 25 anatomical regions. RESULTS: The total acquisition time of the TSE-Dixon sequence was reduced by 45 % from 13'38″ to 7'37″ (acceleration factor between 3.6× and 4.0×), the T2-mapping scan time was reduced by 31 % from 5'28″ to 3'47″ (acceleration factor of 3.0×), while maintaining comparable image quality. The results from the anatomical assessment of SENSE 2.0× versus CS-SENSE 3.6× were comparable in 88.7 % as shown by the 5-point Likert scale measurements. The T2-relaxation measurements had a good correlation of ρ = 0.7 between SENSE and CS-SENSE. CONCLUSION: We found an optimum acceleration factor with CS-SENSE between 3.6× and 4.0× for TSE-Dixon and 3.0× for T2-mapping sequences in a clinical MR imaging protocol of the ankle. The total scan time was reduced by 41 % while maintaining adequate image quality.

[Postoperative analgesia with thoracic peridural morphine in pulmonary surgery. 117 cases]. / Analgésie postopératoire par la morphine péridurale thoracique en chirurgie pulmonaire. Cent dix-sept observations.

Post-operative analgesia by peridural injection of morphine in the thoracic spine was evaluated in a series of 117 successive patients with pulmonary pathology operated upon by the same surgeon. The catheters were introduced, either on the day preceding the operation or at the end of it, above or below T6-T7, after localization of the peridural space by the hanging drop technique or by loss of resistance to a liquid mandrel; 5 mg of preservative-free morphine diluted in 3 ml isotonic saline were injected. The catheter was left in situ for 3 days, then systematically removed and cultivated. Analgesia was considered excellent in 66.7% of the cases, good in 26.5% and insufficient or non-existent in 6.8%. Each dose was effective for 15 hours on average. The mean total dose administered was 18.2 mg and did not exceed 40 mg during the first three post-operative days. There was no respiratory depression requiring naloxone or mechanical ventilation. Urinary retention occurred in 62% of the patients and troublesome pruritus in 0.3%. No death attributable to the method and no neurological or infectious complication was noted. There was no problem in removing the catheter, and no redness, pain or haematoma was observed at the site of injection. In view of the potential risk of insidious and delayed respiratory depression, the patients must be closely supervised specialized by staff. This technique must not be used unless the conditions required are fulfilled.