Micro-computed tomography with contrast enhancement: An excellent technique for soft tissue examination in humans

Manual dissection and histologic examination are commonly used to investigate human structures, but there are limitations in the damage caused to delicate structures or the provision of limited information. Micro-computed tomography (microCT) enables a three-dimensional volume-rendered observation of the sample without destruction and deformation, but it can only visualize hard tissues in general. Therefore, contrast-enhancing agents are needed to help in visualizing soft tissue. This study aimed to introduce microCT with phosphotungstic acid preparation (PTA-microCT) by applying the method to different types of human tissue. Specimens from human cadavers were used to examine the orbicularis retaining ligament (ORL), nasolabial fold (NLF), and the calcaneal tunnel of the sole. Using PTA-microCT, relevant information of human structures was identified. In the ORL study, tiny and delicate ligamentous fibers were visualized in detail with multidirectional continuity. In the NLF study, complex structural formation consisting of various types of soft tissue were investigated comprehensively. In the calcaneal tunnel study, the space surrounded by diverse features and its inner vulnerable structures were examined without damage. Consequently, we successfully applied the PTA-microCT technique to the analysis of specific human soft tissue structures that are challenging to analyze by conventional methods.ope

Anatomy of the external branch of the superior laryngeal nerve in Asian population

Injury to the external branch of the superior laryngeal nerve (eSLN) can cause a hoarse or weak voice with dysergia of the cricothyroid. The present study provided the topographic information of the eSLN in the Asian and verified anatomical validity of the landmarks previously recruited to localize the eSLN. Thirty specimens were dissected from 16 human embalmed cadavers (12 men and four women; mean age: 80.5 years). The vertical distance between the eSLN and the apical pole of the thyroid gland (AP) was 8.2 ± 4.2 mm. It descended over the AP with 1 cm distance in 27.6% and under the AP in 20.7%. The piercing point (PP) of the eSLN to the muscles located 26.0 ± 5.5 mm posterior and 14.7 ± 5.0 mm inferior to the laryngeal prominence. Generally, the PP located superoposterior to the midpoint of the joint between the joint of inferior constrictor and cricothyroid (ICJ). The distance between the PP and the midpoint was 8.7 ± 5.1 mm. We found that 1) the Asian had the eSLN located over the AP with <1 cm distance about half cases, 2) the PP can be a consistent reference for the eSLN identification, 3) the ICJ can be a useful landmark to preserve the eSLN at the PP.ope

Heights and spatial relationships of the facial muscles acting on the nasolabial fold by dissection and three-dimensional microcomputed tomography

The aim of this study was to clarify the heights and spatial relationships of the facial muscles acting on the nasolabial fold (NLF) by dissection and three-dimensional microcomputed tomography for use in aesthetic treatments. This study used 56 specimens from 34 embalmed adult Korean. A reference line (RF) was set to imitate the NLF after removing the skin, from the superior point of the alar facial crease to the lateral point of the orbicularis oris muscle at the level of the corner of the mouth. The heights and spatial relationships of the facial muscles along the RF could be categorized into five main patterns. The dominant pattern was that the levator labii superioris alaeque nasi muscle (LLSAN), levator labii superioris muscle (LLS), zygomaticus minor muscle (Zmi), and zygomaticus major muscle (Zmj) were on the medial third, medial half, middle third, and lateral third of the RF, respectively. In micro-CT imaging, beneath the skin of the medial half of the NLF, the LLSAN and Zmi fibers inserted into the dermis of the NLF and adjacent to the NLF. Beneath the skin of the middle third of the NLF, the Zmi fibers were found before the muscle inserted into the dermis of the NLF and adjacent to the NLF. Beneath the skin of the lateral third of the NLF, the lateral margin of the orbicularis oris muscle and some Zmj fibers were found at the location of the NLF. The present study utilized dissections and micro-CT to reveal the general pattern and variations of heights and spatial relationships of the facial muscles passing beneath the NLF. These findings will be useful for understanding which muscles affect specific parts of NLFs with various contours, for reducing the NLF in aesthetic treatments, and for reconstructing the NLF in cases of facial paralysis.ope

Stereotactic topography of the greater and third occipital nerves and its clinical implication

This study aimed to provide topographic information of the greater occipital (GON) and third occipital (3ON) nerves, with the three-dimensional locations of their emerging points on the back muscles (60 sides, 30 cadavers) and their spatial relationship with muscle layers, using a 3D digitizer (Microscribe G2X, Immersion Corp, San Jose CA, USA). With reference to the external occipital protuberance (EOP), GON pierced the trapezius at a point 22.6 +/- 7.4 mm lateral and 16.3 +/- 5.9 mm inferior and the semispinalis capitis (SSC) at a point 13.1 +/- 6.0 mm lateral and 27.7 +/- 9.9 mm inferior. With the same reference, 3ON pierced, the trapezius at a point 12.9 +/- 9.3 mm lateral and 44.2 +/- 21.4 mm inferior, the splenius capitis at a point 10.0 +/- 5.3 mm lateral and 59.2 +/- 19.8 mm inferior, and SSC at a point 11.5 +/- 9.9 mm lateral and 61.4 +/- 15.3 mm inferior. Additionally, GON arose, winding up the obliquus capitis inferior, with the winding point located 52.3 +/- 11.7 mm inferior to EOP and 30.2 +/- 8.9 mm lateral to the midsagittal line. Knowing the course of GON and 3ON, from their emergence between vertebrae to the subcutaneous layer, is necessary for reliable nerve detection and precise analgesic injections. Moreover, stereotactic measurement using the 3D digitizer seems useful and accurate for neurovascular structure study.ope

Influence of injectate volume on paravertebral spread in erector spinae plane block: An endoscopic and anatomical evaluation

The paravertebral spread that occurs after erector spinae plane block may be volume-dependent. This cadaveric study was undertaken to compare the extent of paravertebral spread with erector spinae plane block using different dye volumes. After randomization, twelve erector spinae plane blocks were performed bilaterally with either 10 ml or 30 ml of dye at the level of T5 in seven unembalmed cadavers except for two cases of unexpected pleural puncture using the 10 ml injection. Direct visualization of the paravertebral space by endoscopy was performed immediately after the injections. The back regions were also dissected, and dye spread and nerve involvement were investigated. A total of five 10 ml injections and seven 30 ml injections were completed for both endoscopic and anatomical evaluations. No paravertebral spread was observed by endoscopy after any of the 10-ml injections. Dye spread to spinal nerves at the intervertebral foramen was identified by endoscopy at adjacent levels of T5 (median: three levels) in all 30 ml injections. In contrast, the cases with two, four, and three out of five were stained at only the T4, T5, and T6 levels, respectively, with the 10 ml injection. Upon anatomical dissection, all blocks were consistently associated with posterior and lateral spread to back muscles and fascial layers, especially with the 30 ml injections, which showed greater dye expansion. In one 30 ml injection, sympathetic nerve involvement and epidural spread were observed at the level of the injection site. Although paravertebral spread following erector spinae plane block increased in a volume-dependent manner, this increase was variable and not pronounced. As the injectate volume increased for the erector spinae blocks, the injectate spread to the back muscles and fascial layers seemed to be predominantly increased compared with, the extent of paravertebral spread.ope

Anatomical analysis of the distribution patterns of occipital cutaneous nerves and the clinical implications for pain management

Purpose: Establishing the distribution patterns of occipital cutaneous nerves may help us understand their contribution to various occipital pain patterns and ensure that a proper local injection method for treatment is employed. The aim of this study was to demonstrate the detailed distribution patterns of the greater occipital nerve (GON), lesser occipital nerve (LON), and third occipital nerve (TON) using the modified Sihler's staining technique. Methods: Ten human cadavers were manually dissected to determine the nerve distributions. Specimens from eight human cadavers were treated using the modified Sihler's staining. Results: In all cases, distinct GON branches proceeded laterally and were intensively distributed in the superolateral area from their emerging point. Very thin twigs were observed at the middle-trisected area, which had a fan-like shape, in the middle-upper occipital region. Conclusion: The LON and TON distribution areas were biased to the lateral side below the superior nuchal line, although these nerves exhibited multiple interconnections or overlapping areas with the GON. Furthermore, a nerve rarified zone in the shape of an inverted triangle was identified in the middle occipital area. Our findings improve our understanding of the occipital nerve anatomy and will aid in the management of occipital pain in clinical practice.ope

Three-dimensional structure of the orbicularis retaining ligament: an anatomical study using micro-computed tomography

The orbicularis retaining ligament (ORL) is an important structure for maintaining the eyelid and cheek skin and contouring the characteristic facial appearance. However, the ORL is a delicate structure that is easily damaged in manual dissection. This study aimed to comprehensively investigate the ORL using a micro-computed tomography (mCT) with phosphotungstic acid (PTA) preparation for the acquisition of its three-dimensional information non-destructively. Twenty-two specimens were obtained from non-embalmed human cadaver (mean age 73.7 years). Multidirectional images of the mCT showed that the ORL consisted of continuous tiny plates with a multilayered plexiform shape. The modified Verhoeff Van Gieson staining and immunofluorescence revealed a ligamentous tissue consisting of multiple fibroelastic bundles. The preorbicularis fibres of the ORL had more layers and a more intricate arrangement than its retro-orbicularis fibres. The number, complexity and ambiguity of the ORL fibres increased in the lateral area and their density and extent increased near the dermis. Its dermal anchorage was shown as a confluence of its fibroelastic tissue into the dermis. The ORL comprises a multilayered meshwork of very thin continuous fibroelastic plates and its related cutaneous deformities might be a complicated outcome of subcutaneous tissue shrinkage, lipid accumulation and ORL retention.ope

Comparing the injectate spread and nerve involvement between different injectate volumes for ultrasound-guided greater occipital nerve block at the C2 level: a cadaveric evaluation

Purpose: The spread patterns between different injectate volumes have not yet been investigated in ultrasound-guided greater occipital nerve (GON) block at the C2 level. This cadaveric study was undertaken to compare the spread pattern and nerve involvements of different volumes of dye using this technique. Materials and methods: After randomization, ultrasound-guided GON blocks with 1 or 5 mL dye solution were performed at the C2 level on the right or left side of five fresh cadavers. The suboccipital regions were dissected, and nerve involvement was investigated. Results: Ten injections were successfully completed. In all cases of 5 mL dye, we observed the deeply stained posterior neck muscles, including the suboccipital triangle space. The suboccipital and third occipital nerves, in addition to GONs, were consistently stained when 5-mL dye was used in all injections (100%). Although all GONs were successfully stained in the 1-mL dye cases, three of five injections (60%) concomitantly stained the third occipital nerves. Conclusion: The clinical efficacy of this technique using the 5-mL injectate seems unlikely to arise from the blockade of GON alone. Instead, its efficacy likely arises from the blockade of most nerves originating from the dorsal ramus of the upper cervical spinal nerve at the suboccipital area. Even using 1 mL of injectate may not guarantee blockade of the GON alone.ope

Optimum design of a large area, flexure based XY theta mask alignment stage for a 12-inch wafer using grey relation analysis

An optimum design methodology for a large area, flexure-based XY theta mask alignment stage, which can be applied to a 12-inch wafer photolithography process, was presented. The XY theta micropositioning stage consisted of a working plate with a 12-inch hole in the center, three piezo actuators, and three displacement amplifiers based on the bridge-type flexure mechanism. Grey relation analysis and orthogonal array were incorporated with finite element analysis to find optimum design conditions. The grey relation grade with weight factors was used to simultaneously optimize three objective characteristics of the micropositioning stage: the maximum stroke, deflection of the working plate, and first natural frequency. The optimally-designed stage was fabricated by wire electrical discharge machining and tested to investigate its performance. The proposed stage showed the first natural frequency of 57 Hz and the maximum stroke of 122.84 mu m, 108.46 mu m, 0.685 mrad in the x-, y-, and theta-direction, respectively. The resolutions in corresponding directions were 11 nm, 10 nm, and 0.5 mu rad. The performance of the stage was improved by optimum design process, and the experimental results were in good agreement with the predicted ones from the finite element analysis.This work was supported by the WC300 R&amp;D program (S2341147) funded by the Small and Medium Business Administration (SMBA, Korea). It was also partly supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted from the Ministry of Trade, Industry &amp; Energy (MOTIE) (no. 20174010201310)

Fatigue Behaviors of Resistance Spot Welds for 980 MPa Grade TRIP Steel

The fatigue life of the resistance spot weld of 980 MPa grade transformation induced plasticity (TRIP) steel was investigated and failure modes and fracture surfaces according to the fatigue load were analyzed. The fatigue life according to the nugget size was observed by using two electrodes with face diameters of 8 mm and 10 mm. When an electrode face diameter with 10 mm was used, the nugget size was large, and the fatigue life was further increased. After the fatigue test, three types of failure modes were observed, namely pull-out, plug, and heat affected zone (HAZ) failure, depending on the fatigue load. The fracture surfaces in each failure mode were analyzed. In all failure modes, a crack was initiated in the HAZ region, which is the interface between the two materials in all failure modes. In the case of pull-out failure, the crack propagates as if it surrounds the nugget at the outer edge of the nugget. In the case of HAZ failure, the crack propagates in the thickness direction of the material and outward in the nugget shell. Plug failure occurs with pull-out failure and HAZ failure mixed. The propagation patterns of cracks were different for each failure mode. The reason why the failure mode and the fracture surface are different according to the fatigue load is that the propagation speed of the fatigue crack is fast when the fatigue load is relatively large and is slow when the fatigue load is low.This research was funded by the Technology Innovation Industrial Program funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea) (Development of Car Body Modularization Technology using Advanced Cold Forming and Welding Technologies of Low Density GIGA Grade Light Steel Sheets)