Improved in vivo optical coherence tomography imaging of animal peripheral nerves using a prism nerve holder

Significance

Modern optical volumetric imaging modalities, such as optical coherence tomography (OCT), provide enormous information about the structure, function, and physiology of living tissue. Although optical imaging achieves lateral resolution on the order of the wavelength of light used, and OCT achieves axial resolution on a similar micron scale, tissue optical properties, particularly high scattering and absorption, limit light penetration to only a few millimeters. In addition, in vivo imaging modalities are susceptible to significant motion artifacts due to cardiac and respiratory function. These effects limit access to artifact-free optical measurements during peripheral neurosurgery to only a portion of the exposed nerve without further modification to the procedure.

Aim

We aim to improve in vivo OCT imaging during peripheral neurosurgery in small and large animals by increasing the amount of visualized nerve volume as well as suppressing motion of the imaged area.

Approach

We designed a nerve holder with embedded mirror prisms for peripheral nerve volumetric imaging as well as a specific beam steering strategy to acquire prism and direct view volumes in one session with minimal motion artifacts.

Results

The axially imaged volumes from mirror prisms increased the OCT signal intensity by > 22    dB over a 1.25-mm imaging depth in tissue-mimicking phantoms. We then demonstrated the new imaging capabilities in visualizing peripheral nerves from direct and side views in living rats and minipigs using a polarization-sensitive OCT system. Prism views have shown nerve fascicles and vasculature from the bottom half of the imaged nerve which was not visible in direct view.

Conclusions

We demonstrated improved OCT imaging during neurosurgery in small and large animals by combining the use of a prism nerve holder with a specifically designed beam scanning protocol. Our strategy can be applied to existing OCT imaging systems with minimal hardware modification, increasing the nerve tissue volume visualized. Enhanced imaging depth techniques may lead to a greater adoption of structural and functional optical biomarkers in preclinical and clinical medicine.

Multiparametric approach with diffusion-weighted imaging and dynamic contrast-enhanced MRI: a comparison study for differentiating between benign and malignant bone lesions in adults

AIM

To evaluate and compare the diagnostic performance of quantitative parameters derived from diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in differentiating benign and malignant bone tumours.

MATERIALS AND METHODS

Fifty-five patients (age range, 21-82 years; mean age, 55 years) underwent pretreatment MRI. Apparent diffusion coefficient (ADC) values were calculated by DWI. The DCE-MRI data were analysed for the volume transfer constant (K^trans), extravascular extracellular volume fraction (V_e), and volume rate constant (K_ep), and K^trans/ADC ratio. Each parameter's performance was evaluated using the area under the receiver operating characteristic (ROC) curv (AUC), and their AUCs were compared. ROC curves were analysed and each parameter's optimal cut-off value was determined, from which each parameter was evaluated for sensitivity, specificity, accuracy, and positive and negative predictive values. The odds ratio (OR) with 95% confidence interval for detecting malignant bone lesions after adjusting the age factor of each parameter was estimated.

RESULTS

All parameter values (except V_e) were significantly different between benign and malignant bone tumours (p<0.05). The K^trans had a significantly greater AUC than V_e (p=0.03). The K^trans/ADC and K_ep had the best sensitivity (0.917) and specificity (0.632), respectively. The K_ep and K^trans/ADC had the best positive (0.811) and negative (0.769) predictive values, respectively. The OR was highest for K^trans/ADC (17.38; p=0.0013).

CONCLUSION

The K^trans, K_ep, ADC, and K^trans/ADC could help to detect malignant lesions from bone tumours and K^trans/ADC appears to be the superior variable among them.

Diagnostic performance of conventional MRI parameters and apparent diffusion coefficient values in differentiating between benign and malignant soft-tissue tumours

AIM

To compare the abilities of conventional magnetic resonance imaging (MRI) and apparent diffusion coefficient (ADC) in differentiating between benign and malignant soft-tissue tumours (STT).

MATERIAL AND METHODS

A total of 123 patients with STT who underwent 3 T MRI, including diffusion-weighted imaging (DWI), were retrospectively analysed using variate conventional MRI parameters, ADC_mean and ADC_min.

RESULTS

For the all-STT group, the correlation between the malignant STT conventional MRI parameters, except deep compartment involvement, compared to those of benign STT were statistically significant with univariate analysis. Maximum diameter of the tumour (p=0.001; odds ratio [OR], 8.97) and ADC_mean (p=0.020; OR, 4.30) were independent factors with multivariate analysis. For the non-myxoid non-haemosiderin STT group, signal heterogeneity on axial T1-weighted imaging (T1WI; p=0.017), ADC_mean, and ADC_min (p=0.001, p=0.001), showed significant differences with univariate analysis between malignancy and benignity. Signal heterogeneity in axial T1WI (p=0.025; OR, 12.64) and ADC_mean (p=0.004; OR, 33.15) were independent factors with multivariate analysis.

CONCLUSION

ADC values as well as conventional MRI parameters were useful in differentiating between benign and malignant STT. The ADC_mean was the most powerful diagnostic parameter in non-myxoid non-haemosiderin STT.

Reuse of a previously transplanted kidney from a deceased donor using Luminex virtual crossmatching: a case report

Kidney transplantation is the most desired modality of renal replacement therapy for patients with end-stage renal disease (ESRD). We have attempted to expand the organ donor pool through several methods, including the use of expanded donor criteria. Although previously transplanted kidneys are rarely reused, they can be suitable for transplantation into patients in need. We report a case of successful reuse of a previously transplanted kidney from a deceased donor by means of Luminex virtual crossmatching with the first donor and actual crossmatching with the second donor.

Clinical relevance of the apparent diffusion coefficient value of metastatic bone tumours on diffusion-weighted MRI images: differences according to the types of primary tumour, the affected bones, and clinical factors

AIM

To evaluate whether the apparent diffusion coefficient (ADC) of metastatic bone tumours on diffusion-weighted magnetic resonance imaging (MRI) images differs according to the type of primary cancer, the affected bone, and clinical factors.

MATERIALS AND METHODS

For this retrospective study, two radiologists reviewed MRI images, including ADC maps, of 67 patients (M:F=38:29; median age, 48 years) who were diagnosed with bone metastasis by means of histological or clinical confirmation. The primary tumours included 29 lung adenocarcinomas, 15 invasive ductal adenocarcinomas of the breast, 13 hepatocellular carcinomas, six prostatic carcinomas, and four renal cell carcinomas. ADC values of the metastatic tumour were compared according to the type of primary malignancy, the affected bone, and the age and sex of the patient using Kruskal-Wallis and Mann-Whitney U-tests with Bonferroni correction. In addition, pre-contrast CT images were available in 38 of 67 patients; a subanalysis of the CT radiodensity and ADC values were performed with Spearman correlation.

RESULTS

The mean, standard deviation, and minimum and maximum values of the ADC of metastatic bone tumours did not differ significantly according to type of primary malignancy, the affected bone, or clinical variables (p>0.1). The ADC value was not significantly correlated with CT radiodensity (p=0.24). Intra- and interobserver agreements for the mean ADC values were excellent (intra-observer: p=0.98; interobserver: p=0.98).

CONCLUSIONS

Assessment of the ADC value of metastatic bone tumours is not reliable for differentiation of the type of primary cancer.

Clinical anatomy of vertebrae in scoliosis: global analysis in four different diseases by multiplanar reconstructive computed tomography

BACKGROUND CONTEXT

Few accurate analyses of clinically useful vertebral anatomy have been conducted, and most have focused on thoracic idiopathic scoliosis.

PURPOSE

To evaluate the different anatomic characteristics in scoliosis by disease type and level.

STUDY DESIGN

Observational cohort study.

PATIENT SAMPLE

Forty-eight patients with scoliosis were included in this study.

OUTCOME MEASURES

Subjects underwent computed tomography (CT) of the whole spine.

METHODS

Forty-eight patients with scoliosis were included in this study: 15 adolescent idiopathic, 11 cerebral palsy (CP), 10 muscular dystrophy (MD), and 12 congenital (CG) scoliosis patients with similar demographics. Subjects underwent CT of the whole spine, preoperatively. Eight anatomic parameters were measured in multiplanar reconstructive CT images, and statistical analysis was performed to investigate differences.

RESULTS

In general, values in the anatomic parameters were similar for the four diseases. Each parameter showed the unique change pattern according to the spinal level regardless of curvature shape, direction, or magnitude. In particular, chord length (CL) in MD and CG scoliosis was lower than in adolescent idiopathic scoliosis (AIS) and CP, and pedicle rib unit length was lower in CG scoliosis than in the other diseases (p<.05). Comparisons of convex and concave anatomies in AIS showed that inner pedicle width (PWI) and outer pedicle width (PWO) were wider for convex side, CL, pedicle width, and transverse pedicle angle were greater for concave side (p<.05), and differences were more significant at apices. However, in CP, PWI and PWO were similar between convex and concaves sides (p>.05). Although PWI and PWO were wider for convex sides and CL and pedicle length were greater for concave sides in MD (p<.05), differences were less significant at apices. Particularly, CG scoliosis showed severely deformed anatomy, with differences of seven parameters at apical vertebrae (p<.05).

CONCLUSION

Clinical anatomies of vertebrae in scoliosis were found to differ significantly at different levels and in terms of convexity and disease type.

Reducing metallic artefacts in post-operative spinal imaging: slice encoding for metal artefact correction with dual-source parallel radiofrequency excitation MRI at 3.0 T

OBJECTIVE

To compare the effects of metal artefacts and acquisition time among slice encoding for metal artefact correction (SEMAC), SEMAC with dual-source parallel radiofrequency (SEMAC-DSPRF) transmission and fast spin echo (FSE) images using 3.0-T MRI.

METHODS

The signal-to-noise ratio (SNR) was calculated in a phantom study using a pedicle screw. A total of 16 patients who underwent spinal surgery using pedicle screws were included in the clinical study. T1 weighted FSE, SEMAC and SEMAC-DSPRF images were obtained. Four imaging findings (visibility of the dural sac, neural foramens, bone-implant interface and overall artefacts) were evaluated by using five-point scales independently by two observers. The mean scan time was recorded.

RESULTS

The mean SNR was 71.2, 25.7 and 28.4 for FSE, SEMAC and SEMAC-DSPRF images, respectively. FSE images were ranked lower than SEMAC and SEMAC-DSPRF images, and ranking of SEMAC and SEMAC-DSPRF images did not differ statistically for all four imaging findings. The mean scan time was 9 min 51 s and 6 min 31 s for SEMAC and SEMAC-DSPRF images, respectively.

CONCLUSION

SEMAC can reduce metallic artefacts and improve the visualisation of anatomical structures around metal implants. An additional DSPRF technique can reduce the acquisition time of SEMAC images without the loss of SNR and image quality.

ADVANCES IN KNOWLEDGE

This study demonstrates that the use of the DSPRF transmission technique can reduce the acquisition time of SEMAC images without loss of image quality in patients with metal implants.

T2 mapping of the articular cartilage in the ankle: correlation to the status of anterior talofibular ligament

AIM

To evaluate differences in T2 relaxation time of ankle cartilage using magnetic resonance imaging (MRI) according to the status of the anterior talofibular ligament (ATFL).

MATERIALS AND METHODS

The talar trochlear cartilage (TTC) was evaluated in 52 patients with ankle pain that were categorized according to the status of ATFL; normal (NL; n = 23, mean age 40 years); partial tear (PT; n = 21, mean age 39 years); or complete tear (CT; n = 8, mean age 33 years). The TTC was divided into six compartments (medial anterior, medial centre, medial posterior, lateral anterior, lateral centre, and lateral posterior). The mean T2 value of each compartment was obtained using the multi-echo sequence. Data were analysed with parametric and non-parametric statistical tests.

RESULTS

The mean T2 values of the TTC showed significant differences between the three groups; NL, PT, and CT (p < 0.001). The T2 value between the three ligamentous groups were significantly different in the medial anterior, lateral anterior, and lateral centre compartments (p = 0.003, 0.002, 0.002, respectively). T2 values of the PT and CT groups were significantly higher than those of the NL group in the medial anterior compartment (p = 0.015, 0.002) and lateral anterior compartment (p = 0.026, <0.001). The T2 value of the CT group was significantly higher than that of NL and PT groups in the lateral centre compartment (p < 0.001, 0.031).

CONCLUSION

The T2 value of the TTC in patients with ATFL injury increased at the medial anterior, lateral anterior, and lateral centre compartments.

Blind oral endotracheal intubation of rats using a ventilator to verify correct placement

Endotracheal intubation in rats is challenging due to difficulties visualizing the epiglottis and vocal cords. No visualization of these structures results in repeated intubation attempts which can cause trauma to the oral cavity and/or oesophagus, and death of the animal due to respiratory failure. Here, we describe a simple blind oral tracheal intubation technique in the rat that decreases the frequency of repeated intubations using an intubation device that comprises a 16 G intravenous catheter and a modified 18 G epidural needle, and a rodent ventilator. The epidural needle is bent in such a way that it curves in conformity with the rat's oral airway in order to direct the catheter into the larynx, and the rodent ventilator is used to verify its correct placement. The first attempt success rate of endotracheal intubation using the blind oral tracheal intubation technique with a rodent ventilator was greater than the first attempt success rate using the blind oral tracheal intubation technique without using a rodent ventilator. Although this method is a simple modification of a previously described method of blind oral endotracheal intubation, our method is easy to learn, inexpensive and does not require specialized equipment.

Which oblique plane is more helpful in diagnosing an anterior cruciate ligament tear?

AIM

To evaluate the diagnostic role of additional oblique coronal and oblique sagittal magnetic resonance imaging (MRI) for an anterior cruciate ligament (ACL) tear.

MATERIALS AND METHODS

A total of 101 patients who had undergone preoperative knee MRI examinations with orthogonal and two sets of oblique images were enrolled in the study. Two radiologists evaluated the MRI images by the use of four methods: orthogonal images only (method A); orthogonal and additional oblique coronal images (method B); orthogonal and oblique sagittal images (method C); and orthogonal images with oblique coronal and sagittal images (method D). The status of the ACL (normal or tear) was determined by consensus. The sensitivity, specificity, and accuracy for an ACL tear with the use of each method were calculated in comparison with arthroscopy as the reference standard, and values were statistically analysed using the McNemar test. The diagnostic accuracies were compared using receiver operating characteristic (ROC) analysis.

RESULTS

Arthroscopy identified 10 partial ACL tears and 30 complete ACL tears. The specificities and accuracies for methods B, C, and D were significantly higher than the specificities and accuracies for method A (p<0.05). There was no significant difference in the sensitivity, specificity, and accuracy for methods B, C, and D. Diagnostic ability was not significantly different for each method, as determined by ROC analysis (p>0.05).

CONCLUSIONS

Additional oblique imaging for an ACL tear improved the specificity. Either of the oblique imaging methods is sufficient, and no further improvement in the diagnostic efficacy was achieved by simultaneous use.

A case of disseminated Nocardia farcinica diagnosed through DNA sequencing in a kidney transplantation patient

Nocardia is a rare gram-positive bacteria causing opportunistic infection, and belongs to the aerobic Actinomycetes group. As the mortality in the immunocompromised patients with nocardiosis is high, early diagnosis and treatment is very important. However, clinical manifestations of infection caused by Nocardia are very variable and early diagnosis is limited by the difficulty in obtaining specimens and its isolation. Rapid diagnosis of Nocardia infection may allow for earlier effective therapy, thus improving patient outcome. We report a case of Nocardia farcinica diagnosed by DNA sequencing through blood culture in a renal transplant recipient with severe pneumonia and multiple brain abscesses.

Association of MCP-1 and CCR2 polymorphisms with the risk of late acute rejection after renal transplantation in Korean patients

Among the factors modulating transplant rejection, chemokines and their respective receptors deserve special attention. Increased expression of monocyte chemoattractant protein-1 (MCP-1) and its corresponding receptor (chemokine receptor-2, CCR2) has been implicated in renal transplant rejection. To determine the impact of the MCP-1-2518G and CCR2-64I genotypes on renal allograft function, 167 Korean patients who underwent transplantation over a 25-year period were evaluated. Genomic DNA was genotyped using polymerase chain reaction followed by restriction fragment length polymorphism analysis. Fifty-five (32.9%) patients were homozygous for the MCP-1-2518G polymorphism. Nine (5.4%) patients were homozygous for the CCR2-64I polymorphism. None of the investigated polymorphism showed a significant shift in long-term allograft survival. However, a significant increase was noted for the risk of late acute rejection in recipients who were homozygous for the MCP-1-2518G polymorphism (OR, 2.600; 95% CI, 1.125–6.012; P = 0.022). There was also an association between the MCP-1-2518G/G genotype and the number of late acute rejection episodes (P = 0.024). Although there was no difference in the incidence of rejection among recipients stratified by the CCR2-V64I genotype, recipients with the CCR2-V64I GG genotype in combination with the MCP-1-2518G/G genotype had a significantly higher risk of acute or late acute rejection among the receptor-ligand combinations (P = 0.006, P = 0.008, respectively). The MCP-1 variant may be a marker for risk of late acute rejection in Korean patients.

Microscopic origin of surface-plasmon radiation in plasmonic band-gap nanostructures

We report spatial domain measurements of the damping of surface-plasmon excitations in metal films with periodic nanohole arrays. The measurements reveal a short coherent propagation length of a few microm inside nanohole arrays, consistent with delays of about 10 fs in ultrafast transmission experiments. This implies that the transmission spectra of the entire plasmonic band-gap structure are homogeneously broadened by radiative damping of surface-plasmon excitations. We show that a Rayleigh-like scattering of surface plasmons by the periodic hole array is the microscopic origin of this damping, allowing the reradiation rate to be controlled.

Effect of iron and ascorbate on cyclosporine-induced oxidative damage of kidney mitochondria and microsomes

The stimulatory effect of iron and ascorbate on the damaging action of cyclosporine in kidney mitochondria, microsomes and epithelial cells was examined. Cyclosporine induced malondialdehyde formation and hydrogen peroxide production in mitochondria and attenuated the activity of MnSOD and glutathione peroxidase. The damaging effect of cyclosporine (50 microM) plus Fe2+(20 microM) on mitochondrial and microsomal lipids and proteins as well as mitochondrial thiols was greater than the summation of the oxidizing action of cyclosporine alone and Fe2+ alone. As for tissue components, iron enhanced cyclosporine-induced viability loss in kidney epithelial cells. Fe2+, EDTA and H2O2- induced 2-alpha deoxyribose degradation was attenuated by 10 mM DMSO and 200 microM DTPA but not affected by 200 microM cyclosporine. The addition of Fe2+ caused a change in the absorbance spectrum of cyclosporine in the wavelength range 230-350 nm. The simultaneous addition of cyclosporine (50 microM) and ascorbate (100 microM) showed the enhanced peroxidative effect on mitochondrial and microsomal lipids, which was inhibited by DTPA and EDTA (1 mM). Similar to iron, ascorbate enhanced cyclosporine-induced cell viability loss. The results show that iron and ascorbate promote the damaging action of cyclosporine in kidney cortex mitochondria and microsomes and in kidney epithelial cells, which may contribute to the enhancement of cyclosporine-induced nephrotoxicity.