Next generation coronary CT angiography: in vitro evaluation of 27 coronary stents

Objectives

To evaluate in-stent lumen visibility of 27 modern and commonly used coronary stents (16 individual stent types, two stents at six different sizes each) utilising a third-generation dual-source CT system.

Methods

Stents were implanted in a plastic tube filled with contrast. Examinations were performed parallel to the system's z-axis for all stents (i.e. 0°) and in an orientation of 90° for stents with a diameter of 3.0 mm. Two stents were evaluated in different diameters (2.25 to 4.0 mm). Examinations were acquired with a collimation of 96?×?0.6 mm, tube voltage of 120 kVp with 340 mAs tube current. Evaluation was performed using a medium-soft (Bv40), a medium-sharp (Bv49) and a sharp (Bv59) convolution kernel optimised for vascular imaging.

Results

Mean visible stent lumen of stents with 3.0 mm diameter ranged from 53.3 % (IQR 48.9???56.7 %) to 73.9 % (66.7???76.7 %), depending on the kernel used at 0°, and was highest at an orientation of 90° with 80.0 % (75.6???82.8 %) using the Bv59 kernel, strength 4. Visible stent lumen declined with decreasing stent size.

Conclusions

Use of third-generation dual-source CT enables stent lumen visibility of up to 80 % in metal stents and 100 % in bioresorbable stents.

Key Points

? Blooming artefacts impair in–stent lumen visibility of coronary stents in CT angiography. ? CT enables stent lumen visibility of up to 80 % in metal stents. ? Stent lumen visibility varies with stent orientation and size. ? CT angiography may be a valid alternative for detecting in-stent restenosis.     

Automatic detection of osteoporotic vertebral fractures in routine thoracic and abdominal MDCT

Objectives

To develop a prototype algorithm for automatic spine segmentation in MDCT images and use it to automatically detect osteoporotic vertebral fractures.

Methods

Cross-sectional routine thoracic and abdominal MDCT images of 71 patients including 8 males and 9 females with 25 osteoporotic vertebral fractures and longitudinal MDCT images of 9 patients with 18 incidental fractures in the follow-up MDCT were retrospectively selected. The spine segmentation algorithm localised and identified the vertebrae T5-L5. Each vertebra was automatically segmented by using corresponding vertebra surface shape models that were adapted to the original images. Anterior, middle, and posterior height of each vertebra was automatically determined; the anterior-posterior ratio (APR) and middle-posterior ratio (MPR) were computed. As the gold standard, radiologists graded vertebral fractures from T5 to L5 according to the Genant classification in consensus.

Results

Using ROC analysis to differentiate vertebrae without versus with prevalent fracture, AUC values of 0.84 and 0.83 were obtained for APR and MPR, respectively (p?<?0.001). Longitudinal changes in APR and MPR were significantly different between vertebrae without versus with incidental fracture (ΔAPR: -8.5 %?±?8.6 % versus -1.6 %?±?4.2 %, p?=?0.002; ΔMPR: -11.4 %?±?7.7 % versus -1.2 %?±?1.6 %, p?<?0.001).

Conclusions

This prototype algorithm may support radiologists in reporting currently underdiagnosed osteoporotic vertebral fractures so that appropriate therapy can be initiated.

Key points

? This spine segmentation algorithm automatically localised, identified, and segmented the vertebrae in MDCT images. ? Osteoporotic vertebral fractures could be automatically detected using this prototype algorithm. ? The prototype algorithm helps radiologists to report underdiagnosed osteoporotic vertebral fractures.     

Detection of acute pulmonary embolism: feasibility of diagnostic accuracy of MRI using a stepwise protocol

Multidetector computed tomography (MDCT) has become the imaging method of choice in patients suspected of having pulmonary embolism (PE) but has the inherent limitation of radiation dose and the side effects of contrast agents. The purpose of the study was to assess the feasibility of a stepwise MRI protocol in the clinical setting of acute PE. The stepwise approach should make it possible to diagnose acute PE in critically ill patients using fast MR sequences and included the option to add comprehensive sequences when patients were stable. Forty-five patients with acute PE (26 men, 19 women; 41?±?16 years) were included in this prospective study. The diagnosis was initially confirmed by MDCT as gold standard. MRI at 1.5 T was subsequently performed without any delay in medical treatment. The MRI protocol proceeded stepwise from robust to detailed imaging techniques (i.e., from TrueFISP and single shot HASTE sequence to MR perfusion and 3D-MR angiography) if the patient was able to tolerate additional imaging time. Diagnostic accuracy was evaluated on the central (lobar) and peripheral (segmental) levels. The complete MR protocol was applied in 40 of the 45 patients (88 %). In the remaining five patients with severe dyspnea the diagnosis of acute PE was established by using fast TrueFISP sequences that were insensitive to respiratory movement. All five patients suffered from a major central PE. Highest sensitivity was achieved by MR perfusion (lobar, 98 %; segmental, 95 %). Real-time TrueFISP and MR angiography showed the highest specificity (lobar, 90–100 %; segmental, 95–97 %). The combination of all MR sequences matched closely the results of MDCT (lobar: sensitivity 98 %, specificity 100 %; segmental: sensitivity 95 %, specificity 97 %). MRI using a stepwise protocol is a promising approach for diagnosing acute PE. The protocol can be tailored for dyspneic patients with central PE using real-time MRI sequences. The diagnostic accuracy for peripheral PE can be improved by using combined MR techniques, achieving comparable results to MDCT.     

End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers

Purpose

Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images.

Methods

Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3 mm, matrix: 256 × 384, FOV: 150 × 150 mm. Two observers independently measured the TTTG at all positions.

Results

Mean TTTG for observer 1 was 15.1 ± 3.2 mm at full extension, 10.0 ± 3.5 mm at 15° flexion and 8.1 ± 3.4 mm at 30° flexion. Mean TTTG for observer 2: 14.8 ± 3.3 mm at full extension, 9.4 ± 3.0 mm at 15° flexion, 8.6 ± 3.4 mm at 30° flexion. Mean values were significantly different (p < 0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p < 0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87–0.88; p < 0.001).

Conclusions

The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited.

Level of evidence

Development of diagnostic criteria in a consecutive series of patients and a universally applied ‘gold’ standard, Level II.     

Apnea following spinal anaesthesia in two former pre-term infants

Purpose

To report the occurrence of apnea and bradycardia in two former pre-term infants who received spinal anaesthesia without inhalational or intravenous anaesthetic agents during inguinal hemiorrhaphy.

Clinical features

Two former pre-term infants who had no recent history of apnea or bradycardia and who had been discharged from the hospital presented for anaesthetic care during inguinal hemiorrhaphy. Spinal anaesthesia using 1 mg·kg^?1 tetracaine in dextrose 10% was performed. A sensory level of T_4–6 was obtained in both infants. Neither infant received intravenous, oral, or inhalational agents for sedation. Five to ten minutes after placement of the spinal block, the two infants had frequent episodes of apnea and bradycardia. No change in the sensory level of spinal anaesthesia was noted. The apnea and bradycardia continued for a variable time into the postoperative period. Caffeine benzoate 10 mg·kg^?1 was administered to one infant. Other than the apnea and bradycardia, both infants had uncomplicated postoperative courses.

Conclusion

Apnea can occur when spinal anaesthesia is used as the sole anaesthetic technique in the former pre-term infant. Appropriate monitoring for such problems based on the infant’s post-conceptual age is suggested.     

Rotational instability of the knee: internal tibial rotation under a simulated pivot shift test

Introduction  Recently, several publications investigated the rotational instability of the human knee joint under pivot shift examinations and reported the internal tibial rotation as measurement for instrumented knee laxity measurements. We hypothesize that ACL deficiency leads to increased internal tibial rotation under a simulated pivot shift test. Furthermore, it was hypothesized that anatomic single bundle ACL reconstruction significantly reduces the internal tibial rotation under a simulated pivot shift test when compared to the ACL-deficient knee. Methods  In seven human cadaveric knees, the kinematics of the intact knee, ACL-deficient knee, and anatomic single bundle ACL reconstructed knee were determined in response to a 134 N anterior tibial load and a combined rotatory load of 10 N m valgus and 4 N m internal tibial rotation using a robotic/UFS testing system. Statistical analyses were performed using a two-way ANOVA test. Results  Single bundle ACL reconstruction reduced the anterior tibial translation under a simulated KT-1000 test significantly compared to the ACL-deficient knee (P < 0.05). After reconstruction, there was a statistical significant difference to the intact knee at 30° of knee flexion. Under a simulated pivot shift test, anatomic single bundle ACL reconstruction could restore the intact knee kinematics. Internal tibial rotation under a simulated pivot shift showed no significant difference in the ACL-intact, ACL-deficient and ACL-reconstructed knee. Conclusion  In conclusion, ACL deficiency does not increase the internal tibial rotation under a simulated pivot shift test. For objective measurements of the rotational instability of the knee using instrumented knee laxity devices under pivot shift mechanisms, the anterior tibial translation should be rather evaluated than the internal tibial rotation. This study was supported in part by a grant of the German Speaking Association of Arthroscopy (AGA).     

The Lymph Node Ratio is the Strongest Prognostic Factor after Resection of Pancreatic Cancer

Introduction  Survival after surgery of pancreatic cancer is still poor, even after curative resection. Some prognostic factors like the status of the resection margin, lymph node (LN) status, or tumor grading have been identified. However, only few data have been published regarding the prognostic influence of the LN ratio (number of LN involved to number of examined LN). We, therefore, evaluated potential prognostic factors in 182 patients after resection of pancreatic cancer including assessment of LN ratio. Methods  Since 1994, 204 patients underwent pancreatic resection for ductal pancreatic adenocarcinoma. Survival was evaluated in 182 patients with complete follow-up evaluations. Of those 182 patients, 88% had cancer of the pancreatic head, 5% of the body, and 7% of the pancreatic tail. Patients underwent pancreatoduodenectomy (85%), distal resection (12%), or total pancreatectomy (3%). Survival was analyzed by the Kaplan–Meier and Cox methods. Results  In all 204 resected patients, operative mortality was 3.9% (n = 8). In the 182 patients with follow-up, 70% had free resection margins, 62% had G1- or G2-classified tumors, and 70% positive LN. Median tumor size was 30 (7–80) mm. The median number of examined LN was 16 and median number of involved LN 1 (range 0–22). Median LN ratio was 0.1 (0–0.79). Cumulative 5-year survival (5-year SV) in all patients was 15%. In univariate analysis, a LN ratio ≥ 0.2 (5-year SV 6% vs. 19% with LN ratio < 0.2; p = 0.003), LN ratio ≥ 0.3 (5-year SV 0% vs. 18% with LN ratio < 0.3; p < 0.001), a positive resection margin (p < 0.01) and poor differentiation (G3/G4; p < 0.03) were associated with poorer survival. In multivariate analysis, a LN ratio ≥ 0.2 (p < 0.02; relative risk RR 1.6), LN ratio ≥ 0.3 (p < 0.001; RR 2.2), positive margins (p < 0.02; RR 1.7), and poor differentiation (p < 0.03; RR 1.5) were independent factors predicting a poorer outcome. The conventional nodal status or the number of examined nodes (in all patients and in the subgroups of node positive or negative patients) had no significant influence on survival. Patients with one metastatic LN had the same outcome as patients with negative nodes, but prognosis decreased significantly in patients with two or more LN involved. Conclusions  Not the lymph node involvement per se but especially the LN ratio is an independent prognostic factor after resection of pancreatic cancers. In our series, the LN ratio was even the strongest predictor of survival. The routine estimation of the LN ratio may be helpful not only for the individual prediction of prognosis but also for the indication of adjuvant therapy and herein related outcome and therapy studies. Presented in part at the 49th Annual Meeting of the Society for Surgery of the Alimentary Tract, May 2008 in San Diego and at the Annual Meeting of the German Cancer Society, February 2008 in Berlin, Germany     

Preliminary experience with oral dexmedetomidine for procedural and anesthetic premedication

BACKGROUND: Oral premedication is often required in children to provide anxiolysis and lessen the psychological impact of hospitalization and/or procedures. We present our experience with dexmedetomidine as an oral premedicant prior to procedural sedation or anesthetic induction. METHODS: We undertook a retrospective review of the anesthesia or sedation service records of patients who received oral dexmedetomidine. RESULTS: The cohort for the study included 13 patients ranging in age from 4 to 14 years. Oral dexmedetomidine (mean dose: 2.6 +/- 0.83 microg.kg(-1); range 1.0-4.2 microg.kg(-1)) was used as premedication prior to anesthesia induction in four patients and prior to intravenous (IV) cannula placement for procedural sedation in nine patients with neurobehavioral problems. Effective sedation was achieved in 11 of 13 patients. The one patient in whom anxiolysis was not achieved received the lowest dose of dexmedetomidine (1 microg.kg(-1)) prior to anesthesia induction. In the other three patients, parental separation and acceptance of the mask was achieved at 20-30 min with a dose of 2.5 microg.kg(-1). When used for procedural sedation, placement of an IV cannula was accomplished without difficulty in seven of eight patients with neurobehavioral disorders and with only mild resistance in the other. No complications were noted and parental satisfaction with the sedation experience was high. CONCLUSIONS: These preliminary data suggest that dexmedetomidine may be an effective oral premedicant prior to anesthesia induction or procedural sedation. We found that it was effective even in patients with neurobehavioral disorders in whom previous attempts at sedation had failed.     

Conversion to sirolimus of patients with chronic allograft nephropathy—a retrospective analysis of outcome and influencing factors

Purpose

The purpose of this study was to analyse the outcome and its influencing factors in patients whose therapy was converted from calcineurin inhibitors (CNI) to sirolimus (SRL) due to chronic allograft nephropathy (CAN).

Materials and methods

Therapies of 78 patients (44 men) with CAN from three European transplant centres were converted from CNI therapy to SRL and followed 24 months. Slopes for creatinine clearance before and after conversion were calculated. Influencing factors were analysed by a multivariance analysis.

Results

The slope of the creatinine clearance improved significantly (?0.90 vs. ?0.34 ml min^?1 month^?1; p?<?0.01). In patients whose therapy was converted from cyclosporine A (CyA) to SRL, the slope improved significantly, whereas conversion from Tacrolimus (Tac) to SRL did not affect the slope. The benefit was more pronounced in (1) patients with low or moderate baseline creatinine clearance, (2) patients receiving SRL after conversion without additional mycophenolate mofetil and (3) patients with low or moderate proteinuria.

Conclusion

Conversion from CyA to SRL but not from Tac to CRL is associated with a reduced loss of renal allograft function in patients with CAN.