Surface Landmarks Research Articles

Regularized Surface and Point Landmarks Based Efficient Non-Rigid Medical Image Registration

Medical image registration is one of the fundamental tasks in medical image processing. It has various applications in field of image guided surgery (IGS) and computer assisted diagnosis (CAD). A set of non-linear methods have been already developed for inter-subject and intra-subject 3D medical image registration. However, efficient registration in terms of accuracy and speed is one of the most demanded of today surgical navigation (SN) systems. This paper is a result of a series of experiments which utilizes Fast Radial Basis Function (RBF) technique to register one or more medical images non-rigidly. Initially, a set of curves are extracted using a combined watershed and active contours algorithm and then tiled and converted to a regular surface using a global parameterization algorithm. It is shown that the registration accuracy improves when higher number of salient features (i.e. anatomical point landmarks and surfaces) are used and it also has no impact on the speed of the algorithm. The results show that the target registration error is less than 2 mm and has sub-second performance on intra-subject registration of MR image real datasets. It is observed that the Fast RBF algorithm is relatively insensitive to the increasing number of point landmarks used as compared with the competing feature based algorithms.

An estimation of right and left sided central venous catheter insertion depth using measurement of surface landmarks along the course of central veins -a descriptive observational study

Aim and Objectives: To determine whether the measurement of surface landmarks along the course of central veins can estimate the approximate insertion depths of both right and left sided C.V.C. via the internal jugular veins (I.J.V.) and subclavian veins (S.C.V.). Methods: Total 150 central venous catheterizations were performed using a triple lumen C.V.C. with Seldinger technique. The anterior approach, using the sternocleidomastoid muscle as a landmark was used for I.J.V. insertion and infraclavicular approach for S.C.V. insertion. Topographical measurement was done by placing the catheter naturally with its own curvature over the draped skin, starting from the insertion point of the needle through ipsilateral clavicular notch and to the insertion point of second right coastal cartilage to the manubriosternal joint. The C.V.C. was then inserted and secured to a depth determined topographically. The position of C.V.C. tip, in relation to the carina, was confirmed and measured on a post procedural full inspiration chest X ray. Results: The mean (SD) depth of insertion of Right I.J.V., Right S.C.V., Left I.J.V. and Left S.C.V were 12.26 (0.30) cm, 12.86 (0.36) cm, 16.27 (0.22) cm and 16.30 (0.23) cm respectively. The mean (SD) value for vertical distance between C.V.C. tip and carina of Right I.J.V, Right S.C.V., Left I.J.V. and Left S.C.V were 0.38 (0.26) cm, 0.43 (0.27) cm, 0.41 (0.23) cm and 0.55 (0.29) cm respectively. We found no statistically significant difference in incidence of complications and type of C.V.C inserted but statistical significant difference found between incidence of complications and Position of CVC Tip on Post-procedure Chest X-ray. Conclusion: The approximate insertion depth of a CVC can be estimated using measurement of surface landmarks along the pathway of central veins.

Can thyromental distance be measured accurately?

Using the thyromental distance (TMD) measured based on the ultrasonographic location of the thyroid cartilage prominence as the criterion, we investigated the accuracy of TMD measurement by surface landmark identification of the thyroid cartilage prominence. Twenty-nine anesthetist resident volunteers were recruited, including 10 first-year residents, 9 second-year residents and 10 third-year residents. Each volunteer measured the other 28 volunteers’ TMD. Then, the thyroid cartilage prominence of each volunteer was identified by ultrasonography of the junction of the vocal cord and thyroid cartilage, and the TMD was measured precisely. The error of the TMD measurement was determined by the minimal detectable difference (MDD) compared to the ultrasound measurement. A difference of greater than 5.4 mm between the TMD measured by volunteers and that based on ultrasound localization was defined as a measurement error. The measurement error rate of females’ TMD was significantly higher than that of males’ (50 vs 10%, P < 0.001). The error rates of anesthetist residents of first-year, second-year and third-year were 34, 27, and 31%, respectively, and were not significantly different. The error of TMD measurement by surface landmark identification is often, especially for women. More clinic experience don’t improve it.

A Noninvasive Body Setup Method for Radiotherapy by Using a Multimodal Image Fusion Technique.

Purpose:To minimize the mismatch error between patient surface and immobilization system for tumor location by a noninvasive patient setup method.Materials and Methods:The method, based on a point set registration, proposes a shift for patient positioning by integrating information of the computed tomography scans and that of optical surface landmarks. An evaluation of the method included 3 areas: (1) a validation on a phantom by estimating 100 known mismatch errors between patient surface and immobilization system. (2) Five patients with pelvic tumors were considered. The tumor location errors of the method were measured using the difference between the proposal shift of cone-beam computed tomography and that of our method. (3) The collected setup data from the evaluation of patients were compared with the published performance data of other 2 similar systems.Results:The phantom verification results showed that the method was capable of estimating mismatch error between patient surface and immobilization system in a precision of <0.22 mm. For the pelvic tumor, the method had an average tumor location error of 1.303, 2.602, and 1.684 mm in left–right, anterior–posterior, and superior–inferior directions, respectively. The performance comparison with other 2 similar systems suggested that the method had a better positioning accuracy for pelvic tumor location.Conclusion:By effectively decreasing an interfraction uncertainty source (mismatch error between patient surface and immobilization system) in radiotherapy, the method can improve patient positioning precision for pelvic tumor.

Effectiveness of Intracavitary Electrocardiogram Guidance in Peripherally Inserted Central Catheter Tip Placement in Neonates.

Correct tip location is crucial for a peripherally inserted central catheter (PICC) to maximize the effects of central venous infusion. However, it is difficult to place the tip in a correct location in neonates because of the unreliable estimated length by surface landmark. Therefore, we evaluated the feasibility and safety of an improved intracavitary electrocardiogram (IC-ECG) technique in guiding PICC placement in neonates based on the ratios of P/R wave amplitudes on IC-ECG. The results showed that all of the 32 neonates whose PICCs had been successfully placed and correct tip position verified by chest radiography acquired qualified P wave on IC-ECG. The average ratio of P/R wave amplitude was 0.6 ± 0.1, with a range of 0.4 to 0.8. The 49 neonates who received IC-ECG-guided PICC catheterization showed higher success rates of correct PICC tip position on the first attempt than traditional, predetermined length estimation on surface landmark (93.9% vs 62.5%, χ = 18.01, P < .001). No significant complications occurred in the studied neonates. Based on these findings, IC-ECG-guided tip placement appears to be a promising approach in improving the success rate of tip location when placing a PICC in neonates.

Anatomical Relationship of the Middle Cranial Fossa Dura to Surface Landmarks of the Temporal Bone.

The suprameatal crest and temporal line provides a reliable landmark to the middle fossa dura. Surface anatomy of the temporal bone is used to guide mastoid surgery, but studies investigating these landmarks are limited. The aim of this study was to examine the anatomical relationship of the middle fossa dura to the temporal line. Thirty-two fresh hemicephalic temporal bones were prepared by drawing four lines along the mastoid including the suprameatal crest and temporal line (line 2), one line 5 mm superior to line 2 (line 1), and one 5 mm inferior to line 2 (line 3), and at Reid's base line (line 4). Four points were marked along these lines anterior to posterior 3 mm apart. A 1 mm bur was used to drill perpendicular to these points to examine the relationship to the middle fossa dura. The dura was found inferior to line 2 in 6.3% at point 1, 6.3% at point 2, 9.4% at point 3, and 18.8% at point 4. The dura in line 1 was found inferior to point 1 in 52.1%, point 2 in 46.9%, point 3 in 56.3%, and point 4 in 62.5%. Only one specimen (3.1%) had dura lying inferior to line 3. No specimens were inferior line 4 at any point. The dura of the middle fossa lies superior the temporal line in >80% of specimens and at least 5 mm superior in nearly half. This indicates the temporal line or a line slightly inferior to this is reliably inferior the middle fossa dura.

A method for going from 2D laparoscope to 3D acquisition of surface landmarks by a novel computer vision approach.

This paper presents a method to use the Smart Trocars-our new surgical instrument recognition system-or any accurate localization system of surgical instrument for acquiring intraoperative surface data. Complex laparoscopic surgeries need a proper guidance system which requires registering the preoperative data from a CT or MRI scan to the intraoperative patient state. The Smart Trocar can be used to localize the instruments when it comes to contact with the soft tissue surface. Two successive views through the laparoscope at different angles with the 3D localization of a fixed tool at one single location using the Smart Trocars can point out visible features during the surgery and acquire their location in 3D to provide a depth map in the region of interest. In other words, our method transforms a standard laparoscope system into a system with three-dimensional registration capability. This method was initially tested on a simulation for uncertainty assessment and then on a rigid model for verification with an accuracy within 2mm distance. In addition, an in vivo experiment on pig model was also conducted to investigate how the method might be used during a physiologic respiratory cycle. This method can be applied in a large number of surgical applications as a guidance system on its own or in conjunction with other navigation techniques. Our work encourages further testing with realistic surgical applications in the near future.

The fulcrum axis: an accurate measure of glenoid version on radiographs and computed tomography.

Proper glenoid position in total shoulder arthroplasty (TSA) is important. However, traditional glenoid version (GV) measurements overestimate retroversion on radiographs (XR) and computed tomography (CT).The fulcrum axis (FA) uses palpable surface landmarks and may be useful as an intra-operative guide. Also, the FA has not yet been validated on XR or CT in an arthritic population. Four observers measured FA and GV on the XR, CT and three-dimensional CT (3DCT) of 40 patients who underwent TSA at a single institution from 2009 to 2015. Reliability and accuracy of FA and GV were calculated for XR and CT, using 3DCT as the gold standard. The mean FA and GV were 7.768° and 18.910° on XR; 6.23° and 12.920° on CT; and 8.100° and 7.740° on 3DCT, respectively. FA and GV were significantly different for XR and CT (p < 0.001) but not for 3DCT (p = 0.725). The inter-rater reliability, intra-rater reliability and accuracy of FA were not significantly different from GV and were 0.929 to 0.948, 0.779 to 0.974 and 0.674 to 0.705, respectively. However, the absolute difference of FA was closer to the gold standard (3DCT) than GV for XR (0.330° versus 11.172°) and CT (1.871° versus 5.178°) (p < 0.001). FA showed comparable reliability and accuracy to GV. However, FA more accurately reflected the gold standard.

Safe Zone Technique Improves Suture Placement During Remplissage

Objectives:Recent studies have raised concern over the accuracy of suture passage into the infraspinatus tendon during remplissage. Our purpose was to evaluate the accuracy of suture passage during remplissage and identify surface landmarks to improve accuracy. Our secondary purpose was to validate the use of these identified landmarks to improve accuracy of suture passage through the infraspinatus tendon.Methods:12 cadaveric specimens were used. In the first 6 specimens (control group), standard arthroscopic remplissage was performed. Specimens were dissected to quantify the location of suture passage in reference to the posterolateral acromion (PLA) and to identify the location of posterior cuff penetration. After analyzing the control group specimens a “safe zone” (SZ) was identified to improve accuracy of passage and increase infraspinatus tendon penetration. For final 6 specimens, the safe zone technique was utilized for suture passage during arthroscopic remplissage. Specimens were again dissected to analyze the accuracy of suture passage and location of penetration. Results were compared to the control group.Results:For the control group, 24 sutures were passed. 25.0% (6/24) were passed through the infraspinatus tendon, and 75%(18/75) were through the teres or infraspinatus muscle or MTJ. Sutures passage through the infraspinatus were an average of 25±5.4 mm distal to the PLA, while teres minor sutures were an average of 35.8±5.7mm distal to the PLA. If passes were less than 3 cm distal to the PLA, there was a significantly higher rate of infraspinatus tendon penetration (odds ratio[OR]=25 ,p<0.01). Sutures passing through muscle and MTJ were significantly more medial than those passing through tendon, at an average 8.1±5.1mm lateral to the PLA compared to 14.5±5.5mm (p<0.02). Passes were more likely to be in tendon, rather than muscle or MTJ if greater than 1 cm lateral to the PLA (p=0.013). The safe zone was defined as passing all tenodesis sutures greater than 1 cm lateral and less then 3cm distal to the PLA. Utilizing this technique, 24 sutures were also passed arthroscopically in the remaining 6 specimens. 83.3% (20/24) were in the infraspinatus tendon, which was significantly improved from the control group (p<0.01). Only, 4.2% (1/24) of attempted passes in the SZ group passed through the muscle or MTJ which was also significantly improved from the control group (p<0.01). Prevention of over-medialization significantly improved using the SZ as represented by both anchors having suture passage significantly more lateral (6-10mm) than the control group (p<0.01). There was also an improvement in the precision of suture passes with utilization of the SZ, as overall precision (SD) improved in 75% of sutures passes.Conclusion:We found standard remplissage suture passage was inaccurate with only 25% of sutures penetrating the infraspinatus tendon. We recommend utilization of the “safe zone” technique, which consists of passing sutures 1 cm lateral and within 3 cm distal of the PLA. Furthermore this study validates that the “safe zone” technique, demonstrating significant improvement in accuracy of suture passage into the infraspinatus tendon and prevented over-medialization with muscle penetration. The safe zone technique provides a reproducible method that may prove useful to prevent previously reported complications associated with arthroscopic remplissage.

A reappraisal of pediatric thoracic surface anatomy.

Accurate knowledge of surface anatomy is fundamental to safe clinical practice. A paucity of evidence in the literature regarding thoracic surface anatomy in children was identified. The associations between surface landmarks and internal structures were meticulously analyzed by reviewing high quality computed tomography (CT) images of 77 children aged from four days to 12 years. The results confirmed that the sternal angle is an accurate surface landmark for the azygos-superior vena cava junction in a plane through to the level of upper T4 from birth to age four, and to lower T4 in older children. The concavity of the aortic arch was slightly below this plane and the tracheal and pulmonary artery bifurcations were even lower. The cardiac apex was typically at the 5th intercostal space (ICS) from birth to age four, at the 4th ICS and 5th rib in 4-12 year olds, and close to the midclavicular line at all ages. The lower border of the diaphragm was at the level of the 6th or 7th rib at the midclavicular line, the 7th ICS and 8th rib at the midaxillary line, and the 11th thoracic vertebra posteriorly. The domes of the diaphragm were generally flatter and lower in children, typically only one rib level higher than its anterior level at the midclavicular line. Diaphragm apertures were most commonly around the level of T9, T10, and T11 for the IVC, esophagus and aorta, respectively. This is the first study to provide an evidence-base for thoracic surface anatomy in children. Clin. Anat. 30:788-794, 2017. © 2017Wiley Periodicals, Inc.

Analysis of Finger Motion Coordination during Packaging Interactions

Packaging accessibility is a significant problem for many older people. Whilst the majority of studies have focused on issues surrounding strength, work has shown that dexterity required to open a pack is also a major issue for many older people.Hence, the work undertaken here reports a quantitative study that aimed to analyse motion coordination patterns across digits 2–5 (index to little finger) during interactions with three of the most common types of packaging: plastic bottles, jars and crisps packets, and comparing those interactions with a common measure of dexterity, the Perdue Pegboard. Ten subjects (six male participants and four female participants) were examined whilst reaching forward to grasp and open a 300 ml plastic bottle and a 500 g jar. A 10‐camera optoelectronic motion capture system measured trajectories of 25 miniature reflective markers placed on the dorsal surface landmarks of the hand. Joint angular profiles for 12 involved flexion–extension movements were derived from the measured coordinates of surface markers.The results showed that finger correlations vary widely across the differing pack formats with the crisps having the lowest finger movement correlation and the jar having the highest. Speed and jerk metrics were also seen to vary across the various pack formats.However, finger correlations were seen to be more relevant to perceive dexterity of pack opening than finger speeds and jerk motions. Copyright © 2017 John Wiley &amp; Sons, Ltd.

The Relationships Between Surface Measurements and Underlying Tendon Autograft Length for Upper Extremity Reconstructive Surgery

The availability of tendon grafts is an important consideration for successful upper extremity reconstructive surgery, including flexor or extensor tendon reconstructions, tendon transfers, and ligament reconstructions. Graft selection is based on availability, expendability, ease of harvest, and length. Given variations in patient height and extremity length, existing average values may provide suboptimal insight into actual tendon lengths available. The purpose of this study is, therefore, to pursue a method of estimating available donor tendon lengths based on easily measured anatomical surface landmarks. Thirty cadaveric upper and lower extremity limbs were dissected and the length of commonly harvested tendon grafts including the palmaris longus, extensor indicis proprius, extensor digiti minimi, plantaris, and second long toe extensor was measured. Surface forearm length (from finger tip to cubital fossa) and surface fibular length (from lateral malleolus to fibular head) were also measured. Correlations between surface measurements and underlying tendon lengths were analyzed, and linear models were generated that predicted tendon length as a function of surface measurements. Surface measurements were correlated with underlying tendon length (R= 0.46 - 0.66). Linear models could predict tendon lengths based on surface measurements. A ratio of donor tendon length compared with the limb segment measured was established for each tendon and can be applied to estimate donor tendon length. For the upper extremity tendons, the multipliers for the palmaris longus, extensor indicis proprius, and extensor digiti minimi were 0.51, 0.20, and 0.18, respectively. Lower extremity tendon ratios for the plantaris and extensor digitorum longus were 0.69 and 0.60, respectively. Although length of available donor tendon can be a limiting variable at the time of surgery, surgeons may be better able to estimate underlying tendon lengths using easily obtained superficial measurements. Information obtained from these cadaveric measurements may aid in preoperative planning in hand and upper extremity surgery.

Improved visual odometry method for simultaneous unmanned aerial vehicle navigation and earth surface mapping

The paper deals with application possibility of visual odometry algorithm for sparse three-dimensional reconstruction and earth surface mapping. Photography is taken by camera mounted on unmanned aerial vehicle during its flying along the specified trajectory. The sparse three-dimensional reconstruction and mapping are based on ability of visual odometry algorithm that retrieves information about geometry of specially selected landmarks on the basis of data received from inertial navigation system, and information retrieved from earth surface photographs. Simultaneously with earth surface reconstruction we define more precisely spatial position and orientation of aircraft that is important for acquisition of qualitative earth surface reconstruction with high resolution by means of stereophotogrammetry methods or by means of points clouds alignment methods in case of laser scanner usage. We have also proposed a method for quality improvement of visual odometry algorithm for precision increase of aircraft spatial position and orientation estimation, and also for earth surface reconstruction quality improvement. For visual odometry algorithm quality improvement we have proposed an original algorithm for detection of earth surface landmarks. Proposed modified visual odometry algorithm can find wide application for different autonomous vehicle navigation, and also as a part of informational system proposed for the Earth remote sensing data processing.

Imaging of human vertebral surface using ultrasound RF data received at each element of probe for thoracic anesthesia

Epidural anesthesia is a common technique for perioperative analgesia and chronic pain treatment. Since ultrasonography is insufficient for depicting the human vertebral surface, most examiners apply epidural puncture by body surface landmarks on the back such as the spinous process and scapulae without any imaging, including ultrasonography. The puncture route to the epidural space at thoracic vertebrae is much narrower than that at lumber vertebrae, and therefore, epidural anesthesia at thoracic vertebrae is difficult, especially for a beginner. Herein, a novel imaging method is proposed based on a bi-static imaging technique by making use of the transmit beam width and direction. In an in vivo experimental study on human thoracic vertebrae, the proposed method succeeded in depicting the vertebral surface clearly as compared with conventional B-mode imaging and the conventional envelope method. This indicates the potential of the proposed method in visualizing the vertebral surface for the proper and safe execution of epidural anesthesia.

New Insights into the Anatomy of the Midface Musculature and its Implications on the Nasolabial Fold.

The prominent nasolabial fold is a distinct feature of the aging midface. As minimally invasive procedures have become mainstream, chemodenervation is a preferred method for treating dynamic facial rhytids. We therefore sought to identify relevant nasolabial fold and midfacial muscular anatomy to determine the ideal location of neuromodulation to improve the aesthetics of the midface and nasolabial fold without altering the upper lip and smile. Twelve hemifacial cadaveric dissections were performed to identify midface muscle origin, insertion, width, vector of pull, and neighboring structures. Attention was focused on the levator labii superioris alaeque nasi (LLSAN), levator labii superioris (LLS), nasalis, and orbicularis oculi. Measurements were obtained based on surface landmarks including the medial canthus for future neurotoxin injection. The LLSAN inserts into the medial nasolabial fold and alar base, while the LLS inserts into the middle third of the nasolabial fold. The broadest portion of the superior LLSAN was on average 8.4mm inferior and 4.6mm medial to the medial canthus. A separate muscle obliquely oriented between the orbicularis oculi and LLSAN was identified and found to insert into the malar fat pad. This "malar levator" was present in all specimens and has implications on medial periorbital rhytids and the tear trough deformity. This study further defines midfacial and nasolabial fold muscular anatomy and provides new insights into the use of neuromodulators for these areas without affecting upper lip position. The malar levator muscle appears to be a separate midfacial muscle with independent action. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Maxillary nerve blocks in horses: an experimental comparison of surface landmark and ultrasound-guided techniques

ObjectiveThe aim of this preliminary proof-of-concept study was to evaluate and compare the success and complication rate of infiltration of the maxillary nerve of cadaver heads using previously described surface landmarks, standard ultrasound and a novel needle guidance positioning ultrasound system (SonixGPS). Study designProspective, anatomical, method-comparison study. AnimalsThirty-eight equine cadaver heads. MethodsTwenty-six veterinary students performed the three methods consecutively on cadaver heads using an 18 gauge, 8.9 cm spinal needle and 0.5 mL iodinated contrast medium. Computed tomography was used to quantify success (deposition of contrast in contact with the maxillary nerve) and complication rate (contrast identified within surrounding vasculature or periorbital structures) associated with each method. ResultsPerineural injection of the maxillary nerve was attempted 76 times, with an overall success rate of 65.8% (50/76) and complication rate of 53.9% (41/76). Success rates were 50% (13/26) with surface landmark, 65.4% (17/26) with standard ultrasound guidance and 83.3% (20/24) with SonixGPS guidance approaches (Fisher's exact test, p=0.046). No significant difference in complication rate was found between the three methods. ConclusionsUltrasound-guided maxillary nerve blocks were significantly more successful than surface landmark approaches when performed by inexperienced operators, and the highest success rate was achieved with guidance positioning system (GPS) needle guidance. Clinical relevanceLocal anaesthesia of the equine maxillary nerve in the fossa pterygopalatina is frequently used for diagnostic and surgical procedures in the standing sedated horse. Due to vague superficial landmarks with various approaches and the need for experience via ultrasound guidance, this block remains challenging. GPS guidance may improve reliability of maxillary and other nerve blocks, and allow a smaller volume of local anaesthetic solution to be used, thereby improving specificity and reducing the potential for side effects.

Radiographic Evaluation of the Reliability of Neck Anatomic Structures as Anterior Cervical Surgical Landmarks.

Accurate location of the skin incision is helpful to decrease the technical difficulty and save the operative time in anterior cervical spine surgery. Spine surgeons usually use the traditional neck anatomic structures (the hyoid bone, thyroid cartilage, and cricoid cartilage) as landmarks during the surgery. However, the reliability of these landmarks has not been validated in actual practice. To find out which landmark is the most accurate for identifying the cervical levels in anterior cervical spine surgery. The lateral flexion and extension radiographs of cervical spine in standing position from 30consecutive patients from January 2015 to February 2015 were obtained. The cervical vertebral bodies from C2 to C7 were divided equally into 2 segments. The cervical segments corresponding to each of the surface landmarks were recorded on the flexion and extension radiographs, respectively, and the displacement of corresponding cervical segments from the flexion to extension radiographs for each landmark was calculated. Based on the measurements, the main corresponding cervical levels for the mandibular angle were C2 on both of the flexion and extension films, for the hyoid bone were the C3-C4 interspace on flexion film and C3 on extension film, for the thyroid cartilage C5 on both of flexion and extension films, and for the cricoid cartilage C6 on flexion film and C5-C6 interspace on extension film, respectively. The ratios of displacement within 2 segments from flexion to extension were 83.3% (25/30) for mandibular angle, 56.7% (17/30) for hyoid bone, 66.7% (20/30) for thyroid cartilage, and 56.7% (17/30) for cricoid cartilage, respectively. The mean displacement from flexion to extension films were significantly less than 2 cervical segments for the mandibular angle but greater than 2 segments for the other landmarks. Significant differences were found between mandibular angle and the other 3 landmarks for the displacement from flexion to extension. The angle of mandible was found to be the most accurate landmark for identifying the cervical level, which corresponded to C2 and C2-C3 disc space. The hyoid bone, thyroid cartilage, and cricoid cartilage were not reliable to predict the cervical levels.

Evidence-based approach for the best level of transducer when continuous invasive arterial blood pressure monitoring

Objective To find the best level of transducer when continuous invasive arterial blood pressure monitoring using evidence-based approach. Methods Searched in three databases (Cochrane, PubMed,sinoMED), meanwhile the website of related academic societies,supplemented with Citation Index. Results There were 11 articles after selected. The majority of evidences (9 articles) suggested leveling with the heart, one suggested leveling with the catheter tip,and the other one regarded the matter as nothing important. Conclusions Transducer should be leveled to align the heart rather than the tip of arterial catheter when continuous invasive arterial blood pressure monitoring, but it doesn't matter which surface landmark of the heart. It was suggested that changing the level of transducer when changing the patient position or head of bed. Key words: Arterial pressure; Transducers

A new superficial landmark for the odontoid process: a cadaveric study.

When image guidance is not available or when there is a need to confirm the findings of such technology, superficial landmarks can still play a role in providing surgeons with estimations of the position of deeper anatomical structures. To our knowledge, surface landmarks for the position of the odontoid process have not been investigated. We have therefore performed an anatomical study to investigate such a landmark. One-centimeter metallic rods were placed on the philtrum of the upper lip of 20 cadaveric head specimens. To assess the position relative to the odontoid process, we took lateral and anteroposterior radiographs and recorded the measurements. Descriptive findings from radiographic observations indicated a reasonable approximation between the philtrum and the midpoint of the odontoid process. Based on our results, we suggest that the philtrum of the upper lip can serve as a first line estimation of the position of the odontoid process and can assist in verifying this bony structure following the use of image guidance.

Accurate Physics-Based Registration for the Outcome Validation of Minimal Invasive Interventions and Open Liver Surgeries.

The purpose of this paper is to present an outcome validation tool for tumor radiofrequency (RF) ablation and resection. Intervention assessment tools require an accurate registration of both pre- and postoperative computed tomographies able to handle big deformations. Therefore, a physics-based method is proposed with that purpose. To increase the accuracy both automatically detected internal and surface physical landmarks are incorporated in the registration process. The algorithm has been evaluated in 25 clinical datasets containing RF ablations, resections, and patients with recurrent tumors. The achieved accuracy is 1.2 mm measured as mean internal distance between vessel landmarks and a positive predictive value of 0.95. The quantitative and qualitative results of the outcome validation tool show that in 50% of the cases tumors were only partially covered by the treatment. The use of internal and surface landmarks combined with a physics-based registration method increases the accuracy of the results compared to the accuracy of state of the art methods. An accurate outcome validation tool is important in order to certify that the tumor and its safety margin were fully covered by the treatment. An accurate outcome validation tool can result in a decrease of the tumor recurrence rate.