Impact of dose reduction and the use of an advanced model-based iterative reconstruction algorithm on spectral performance of a dual-source CT system: A task-based image quality assessment

PurposeTo assess the impact of dose reduction and the use of an advanced modeled iterative reconstruction algorithm (ADMIRE) on image quality in low-energy monochromatic images from a dual-source dual energy computed tomography CT (DSCT) platform.Materials and methodsAcquisitions on an image-quality phantom were performed using DSCT equipment with 100/Sn150 kVp for four dose levels (CTDI_vol: 20/11/8/5mGy). Raw data were reconstructed for six energy levels (40/50/60/70/80/100 keV) using filtered back projection and two levels of ADMIRE (A3/A5). Noise power spectrum (NPS) and task-based transfer function (TTF) were calculated on virtual monoenergetic images (VMIs). Detectability index (d′) was computed to model the detection task of two enhanced iodine lesions as function of keV.ResultsNoise-magnitude was significantly reduced between 40 to 70 keV by ?56 ± 0% (SD) (range: ?56%–?55%) with FBP; ?56 ± 0% (SD) (?56%–?56%) with A3; and ?57 ± 1% (SD) (range: ?57%–?56%) with A5. The average spatial frequency of the NPS peaked at 70 keV and decreased as ADMIRE level increased. TTF values at 50% were greatest at 40 keV and shifted towards lower frequencies as the keV increased. The detectability of both lesions increased with increasing dose level and ADMIRE level. For the simulated lesion with iodine at 2 mg/mL, d’ values peaked at 70 keV for all reconstruction types, except for A3 at 20 mGy and A5 at 11 and 20 mGy, where d’ peaked at 60 keV. For the other simulated lesion, d’ values were highest at 40 keV and decreased beyond.ConclusionAt low keV on VMIs, this study confirms that iterative reconstruction reduces the noise magnitude, improves the spatial resolution and increases the detectability of enhanced iodine lesions.     

Ventricular arrhythmias after left ventricular assist device implantation

Background: Left ventricular assist devices (LVADs) have been used as a bridge to cardiac transplantation and as destination therapy in patients with advanced heart failure. The period after LVAD support is associated with ventricular arrhythmias (VAs) despite ventricular unloading and such VAs can have a detrimental effect on survival. Despite the increasing use of LVAD, little is known regarding post‐LVAD VAs at the molecular level and in vivo. Methods: Forty‐two patients who received LVAD over a 24‐month period were evaluated and grouped on the basis of the presence or absence of VAs during LVAD support. We completed a comparative microarray analyses between six patients who developed ventricular tachycardia (VT) or ventricular fibrillation (VF) after LVAD support and six patients who did not develop VAs after LVAD. Results: VAs occurred in 15 patients (35.7%) during LVAD support at a median post‐LVAD day of 25.2. VAs were strongly associated with nonusage of a β‐blocker post‐LVAD (odds ratio of 7.04, P‐value = 0.001). Analysis of a subset of patients who had VT or VF after LVAD placement showed a decrease in the expression of connexin 43 (0.48 ± 0.07), Na+/K+–ATPase (0.60 ± 0.05), and voltage‐gated K+ channel Kv4.3 (0.42 ± 0.04), and an increase in Na+/Ca2+ exchanger (2.2 ± 0.4) and the structural genes: Titin (2.1 ± 0.2), laminin (1.7 ± 0.4), calsequestrin (1.8 ± 0.5), skeletal muscle isoform of troponin T (5.1 ± 0.9), and skeletal muscle isoform of troponin I (3.9 ± 0.7). Conclusion: After LVAD, the increased risk of VAs is strongly associated with nonusage of β‐blocker postoperatively.     

Brady-tachy syndrome: rapid atrial pacing efficacy in preventing atrial fibrillation recurrence assessed by reliable electrograms: the prefib pilot study.

AIMS: Recent studies have tested different atrial pacing rates, modes, and sites for preventing atrial fibrillation (AF) recurrence. Present generation pacemakers offer reliable electrograms (EGMs) storage for optimizing the arrhythmia diagnosis. Based on these EGMs, the study objective was to assess the rate of AF recurrence at two different pacing rates. METHODS: Thirty patients suffering exclusively from symptomatic brady-tachy syndrome (BTS) resistant to > or =2 drugs, were implanted with a DDDR pacemaker. After a 5-days observation period, the DDD pacing rate was randomly programmed at 60 bpm (-15 bpm hysteresis) or at 80 bpm for 12 weeks. The two sequences were crossed over at the end of this fixed period or when earlier symptomatic AF recurred. Antiarrhythmics were maintained. Stored EGMs of > or =4 s duration identified all AF recurrence. RESULTS: Thirty patients (17 males, 77.2 +/- 8.1 years old) were included. One patient withdrew prematurely for severe heart failure associated with AF recurrence and rapid ventricular response. For the remainder of the 29 patients, fast atrial pacing neither provoked symptoms nor haemodynamic change. AF recurred in 16 patients paced at 60 (-15) bpm (mean time: 29 days; range 1-61) and in 9 patients paced at 80 bpm (mean time: 55 days; range 5-83) (P < 0.05). AF recurrence was asymptomatic in 50% of patients. CONCLUSIONS: These results confirm that rapid atrial pacing is 1) significantly effective for preventing AF recurrence in symptomatic BTS patients, and 2) haemodynamically well tolerated.     

Occurrence of Adverse Events in Long-Term Intrathecal Baclofen Infusion: A 1-Year Follow-Up Study of 158 Adults

Objective

To assess the frequency and types of adverse events (AEs) related to intrathecal baclofen (ITB) therapy in adults, and associated risk factors.

Design

A prospective, observational cohort study of adults followed up from January 1 to December 31, 2010.

Setting

A neurologic rehabilitation department in a university hospital.

Participants

All consecutive adult subjects (N=158) receiving ITB via a pump, either implanted or followed up during the study period.

Intervention

Not applicable.

Main Outcome Measures

Frequency and type of AEs.

Results

In 2010, 158 subjects were followed up for ITB therapy, of whom 128 were implanted before 2010 (nonsurgical subjects), and 30 underwent implantation in 2010 (surgical subjects). Of these 30 subjects, 20 were “newly implanted” and 10 were “replacements.” The most frequent pathologic disorders were spinal cord injury (42%) and multiple sclerosis (28%). Twenty-eight subjects (18%) experienced a total of 38 AEs. The rate of AEs was .023 per month of ITB treatment. AEs were related to the surgical procedure in 53% of cases, to the device in 29% (predominantly catheter dysfunctions), and to adverse effects of baclofen in 18%. AEs related to the surgical incision (scar complications and collections) were more frequent in replacement than newly implanted subjects (P=.009). No significant association between occurrence of an AE and subject characteristics (age, gait capacity, spinal vs cerebral spasticity, duration of ITB therapy follow-up) was found. Nearly half of the AEs were serious, extending admission time by a mean of 16 days. No AE induced long-term morbidity or death.

Conclusions

The AE rate was relatively low in this cohort. This has to be balanced against the clinical, functional, and quality-of-life improvements, which are expected from ITB therapy.     

Total posterior condylar separation in a juvenile knee: open fixation through a posterior arthrotomy

The authors report a case of separation involving the posterior aspect of the lateral femoral condyle in a 13-year-old boy. The patient presented with a 2-year history of vague knee discomfort and recurrent knee effusions in the absence of a single acute traumatic event. A large mobile osteochondral fragment involving most of the posterior aspect of the lateral condyle was refixed surgically with two screws via a posterolateral arthrotomy. The knee has recovered full function and the lesion is radiologically stable.     

Crohn’s disease: multi-detector row CT-enteroclysis appearance of the appendix

The objective of our retrospective study was to determine the MDCT-enteroclysis appearance of the appendix in patients with Crohn’s disease and to correlate this appearance with the status of the disease. We reviewed the MDCT-enteroclysis examinations of 76 patients with Crohn’s disease. Images were analyzed for visualization of the appendix, largest axial diameter of the appendix and degrees of enhancement. Findings were correlated with the status of the disease (active vs. nonactive) and compared with those observed in a control group. Among the various variables, hyperenhancement of the appendiceal wall was found in 18.9% of patients with active disease and in no patients with inactive disease nor in the control group (P = 0.0023). This sign had a specificity of 100% for differentiating between active and inactive Crohn’s disease. We conclude that increased appendiceal wall enhancement is, at a statistically significant level, more frequently observed in patients with active Crohn’s disease by comparison with patients with inactive disease and control subjects. This result suggests that this finding may be used as an additional MDCT-enteroclysis finding to determine the activity of the disease.     

Fatal hemorrhage due to an isolated dissection of the superior mesenteric artery

Intensive Care Medicine -     

Finite element analysis to determine stress fields at the apex of V-Y flaps

After performing a V-Y advancement flap, we observed an unusually shaped necrosis, resembling a keyhole at the apex of the flap. As high closing tensions are an accepted cause of skin necrosis, we developed a mathematical model based on the finite element analysis in order to determine the stress field by simulating the mechanical behavior of human skin during suture and to explain this particular shape of necrosis. For the modeling, a planar nonlinear two-dimensional finite element model was used. The numerical simulation was carried out with Ansys® v12 software. Results are expressed in numerical and graphic form. The shape of the vertical iso-stress line for a stress equal to 18.8 kPa was similar to the necrosis observed in our clinical case. Similarities between the shape of necrosis and the calculated stress field at the apex of the V-Y advancement flap indicate the major role of skin tension in this necrosis. Finite element analysis is an original approach for describing the particular shape of a necrosis. Although many factors can be implicated in skin necrosis, the modeling confirms the role of tension in the necrosis of this particular case. Level of Evidence: Level V, risk/prognostic study