Shortest Perpendicular Distance Research Articles

Evaluation of the Peritubal Region Between the Osseous Eustachian Tube and the Internal Carotid Artery: Usefulness of Oblique Temporal Computed Tomography with Valsalva Maneuver.

As indications for surgical Eustachian tube (ET) procedures have been expanded, it is essential to understand the anatomy of ET surroundings for safe ET interventions. We evaluated the peritubal region using oblique planes of temporal computed tomography (CT) with the Valsalva maneuver and classified the peritubal region between the osseous ET and the internal carotid artery (ICA) into 5 types: 1. bony prominence; 2. air cell; 3. absence of peritubal structures (3a. thick canal [>0.5 mm], 3b. thin canal [<0.5 mm], 3c. dehiscence). Bony prominence and air cell types were observed in 41.0% (50/122 ears) and 13.1% (16/122 ears), respectively. The ICA was located directly medial to the osseous ET in 39.4% (48/114 ears), of which thick and thin canal types were found in 23.8% and 15.6%, respectively. Internal carotid artery canal wall dehiscence was observed in 8 ears (6.6%). The shortest perpendicular distance between the osseous ET and ICA was 1.6 (range: 0.4-4.9) mm and 2.7 (range: 1.3-5.8) mm in the bony prominence and air cell types, respectively. Osseous ET-ICA distances were 1.2 (range: 0.6-3.6) mm and 0.4 (range: 0.1-0.5) mm in thick and thin canal types, respectively. Distinct peritubal structure types were observed on oblique CT planes with Vasalva maneuver. Bony prominence and air cell types provide a protective layer between the osseous ET and ICA. Imaging information on peritubal structures may help to better understand the anatomy of the ET pathway, leading to safe and accurate surgical approaches to the osseous ET.

DETERMINATION OF OPTIMISED PICK-UP AND DROP-OFF LOCATIONS IN TRANSPORT ROUTING – A COST DISTANCE APPROACH

With the emergence of dynamic passenger transport systems, such as demand-responsive transport (DRT) and ride-sharing without predetermined stop locations as used for static bus routes, accurate routing for these flexible door-to-door transport services is needed. Routing between two addresses requires the assignment of addresses to suitable, so-called snapping points as reference points on the road network. Therefore, many conventional routing machines use perpendicular distance to identify the nearest point on the road network. However, this technique tends to produce inaccurate results if the access to a building is not reachable from the road segment with the shortest perpendicular distance. We provide a novel approach to identify the access to buildings (paths) based on remote sensing data to obtain more reasonable stop locations for passenger transport. Multispectral images, OpenStreetMap data, and light detection and ranging (LiDAR) data were used to perform a cost distance analysis based on vegetation cover, building footprints, and the slope of the terrain to identify such optimised stop locations. We assumed that the access to buildings on the shortest route to the building’s entrance consists of little vegetation cover and minimal slope of the terrain; furthermore, the calculated path should not cross building footprints. Thus, snapping points on the road network can be determined based on the most likely path between a building and the road network. We validated our results based on a predetermined ideal snapping area considering different weightings for the parameters slope, vegetation, and building footprints. The results were compared with a conventional routing machine that uses perpendicular distance. This routing machine shows a validation rate of 81.4%, whereas the validation rate of our presented approach is as high as 90.3%. This new approach provides increased accuracy and better comfort for flexible passenger transport systems.

Parallel curves

Properties of curved functions considered to be parallel over their domains are investigated. Parallel curves in a given plane may appear identical but are actually not superimposable and thus are not congruent. Translational shifted functions in a plane are not parallel curves because the shortest perpendicular distance between them is not constant along the curves. It is generally not possible to superimpose parallel curves by simple translational shifting in a given 2-dimensional plane. Although the first derivative of parallel curves in a given plane produces equal magnitudes at points where perpendicular line segments or vectors cross the curves, the second derivatives must always differ in magnitude at these positions. The curvature of parallel curves differs, while the slopes of the curves are identical at corresponding points on the curves where perpendicular segments cross. Examples of parallel curves in nature are presented, and curve fitting is used to estimate the formula for a curve that is parallel to a parabola in the same plane.

Initial phantom studies for an office-based low-field MR system for prostate biopsy

PurposeProstate cancer is the second most prevalent cancer in US men, with about 192,000 new cases and 33,000 deaths predicted for 2020. With only a 31% 5-year survival rate for patients with an initial diagnosis of stage-four prostate cancer, the necessity for early screening and diagnosis is clear. In this paper, we present navigation accuracy results for Promaxo’s MR system intended to be used in a physician’s office for image-guided transperineal prostate biopsy. MethodsThe office-based low-field MR system was used to acquire images of prostate phantoms with needles inserted through a transperineal template. Coordinates of the estimated sample core locations in the office-based MR system were compared to ground truth needle coordinates identified in a 1.5T external reference scan. The error was measured as the distance between the planned target and the ground truth core center and as the shortest perpendicular distance between the planned target and the ground truth trajectory of the whole core. ResultsThe average error between the planned target and the ground truth core center was 2.57 ± 1.02 mm, [1.93–3.21] 95% CI. The average error between the planned target to the actual core segment was 2.05 ± 1.24 mm, [1.53–2.56] 95% CI. ConclusionThe average navigation errors were below the clinically significant threshold of 5 mm. The initial phantom results demonstrate the feasibility of the office-based system for prostate biopsy.

Geometric Changes in the Parotid, Submandibular, and Thyroid Glands during Intensity Modulated Radiotherapy for Nasopharyngeal Carcinoma: A Cohort Study

Background: Intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) acts on the tumor and affects surrounding organs at risk (OARs). This study aimed to quantify the geometric changes in the parotid gland, the submandibular gland (SMG), and the thyroid, during the course of treatment. Methods: Twenty patients diagnosed with locally advanced NPC were consecutively enrolled, and received definitive chemoradiotherapy in 33 fractions over 6.5 weeks. Each patient underwent planning computed tomography (pCT) followed by six weekly repeat CTs (rCTs) without contrast enhancement. Each rCT was rigidly registered to its pCT. Changes in terms of volume, position, and shape of the OARs were assessed. Differences in left- and right-sided OARs were compared. Results: Radiation doses to the parotid, SMG, and thyroid were 32.12 ± 11.2 Gy (mean ± standard deviation SD), 25.46 ± 8.62 Gy, and 18.89 ± 10.24 Gy, respectively. Volume reductions of 28.6% ± 14.6% (mean ± SD), 26.6% ± 17.1%, and 12.3% ± 11.3% were observed in the parotid, SMG, and thyroid, respectively. Rate of volume loss for the parotid and SMG decreased from 1.6-1.7% per day in the first week to 0.5%-0.6% in the last week. Contrarily, not all thyroid lobes decreased in volume during treatment. The center of mass of the parotid shifted 2.0-2.6 mm medially; for the SMG and thyroid, a 0.1-0.5 mm medial shift was noted. The displacement in the anterior-posterior and cranial-caudal directions was &lt; 0.6 mm. The 3-dimensional vector displacements of the parotid and SMG were 2.2-2.9 mm, and that of thyroid was 4.0-4.3 mm. The overlapping metrics of all three OARs decreased over time, and the shortest perpendicular distance increased from 1.5-1.8 mm in the first week to 2.4-2.5 mm in the last week. The geometric differences between weeks were statistically significant (P&lt;0.05). Conclusions: The volume, position, and shape of the OARs changed significantly during IMRT for NPC. These geometric changes displayed a time association, suggesting the necessity to re-plan treatment for better sparing of these OARs.

Geometric Uncertainties of Central Nerve System Related Organs at Risk during Chemoradiotherapy for Nasopharyngeal Carcinoma

Considerable geometrical changes for the organs at risk (OARs) and target volumes occurred during concurrently/sequentially chemoradiotherapy (chemoIMRT) for nasopharyngeal carcinoma(NPC). This study aimed to qualify their longitudinal geometrical variations of the central nerve system related OARs(CNS-related OARs). The computed tomography (CT) images of 20 patients with locally advanced NPC were analyzed retrospectively. Each patient had planning CT (CTplan) with intravenous contrast and six weekly repeat CT (CTrepeat) without contrast. Each CTrepeat was rigidly registrated with bone match to its CTplan. The CNS-related OARs included spinal cord, brainstem, chiasm, optical nerves, eye globes, lens, and inner ear. In cranial-caudal direction, the cervical spinal cord was contoured at seven axial CT sections using seven radiological boundaries. The volume reduction, systematic (∑) and random (δ) errors in different directions, the 3-dimensional vector displacement, Dice similarity coefficiency (DSC), Overlapping index(OI), the shortest perpendicular distance (SPD) as their standardized deviation (SD) were calculated. The margin of CNS-related OARs was estimated with the margin recipe of 1.3∑+0.5σ. The volume loss of spinal cord, brainstem, and eye globes showed a linear decreasing time trend. with the mean of -6.5% ±4.8% (95% CI: -7.4%, -5.6%), -2.6%±2.3%（-3.0%, -2.1%）, -9.5% ±7.4% (-10.4%, -8.6%) as radiation fraction elapsed. The volumetric reductions of spinal cord (R2=0.106, P=0.000) and brain stem (R2=0.378, P=0.000) were significantly correlated to weight loss. The mean DSC of spinal cord, brainstem, and eye globes were > 0.85 throughout the treatment. Both the mean SPD and its SD of spinal cord, brainstem, eye globes were < 1.2 mm during the treatment course. The OARs volume of chiasm, optical nerve, lens, and inner ear were < 1cm3. In addition, their volume changes varied from -15.4% to 2.6%, and DSC and OI were 0.47 - 0.80 and 0.33 - 0.69 respectively. The DSC of lens was < 0.6 throughout the treatment course. For all OARs, ∑ and δ were < 0.4mm and 1.7mm. The margin of OARs was < 3mm in left-right (LR), cranial-caudal (CC) and anterior-posterior (AP) direction. For the different axial levels of spinal cord, both the ∑ increased from the cranial to caudal direction and they were 0.13-0.70 mm and 0.12-0.64mm in LR and AP direction respectively, The δ did 0.40-1.52 mm and 0.4–1.42mm respectively. The recommended margins in different axial levels of spinal cord were 0.37-1.67 mm and 0.21-1.12 mm in LR and AP direction respectively. The volume, position, and shape of CNS-related OARs occurred considerable changes during the chemoIMRT course for NPC. The OARs with small volume occurred more shape variations and the position shifted differently in axial levels of spinal cord. The recommended margin was < 3mm as the individual OAR and its direction.

Analysis of geometric variation of neck node levels during image-guided radiotherapy for nasopharyngeal carcinoma: recommended planning margins.

To quantify the geometrical changes of each neck nodal level (NNL) and estimate the geometric planning target volume (PTV) margin during image-guided radiotherapy (IGRT) for nasopharyngeal cancer (NPC). Twenty patients with locally advanced NPC underwent one planning computed tomography (CTplan) and 6 weekly repeat CT (CTrep) scans during chemoradiotherapy. Each CTrep was rigidly registered to the CTplan. All the NNLs were manually delineated in each transverse CT section. When comparing the NNL in CTrep with CTplan, their volumes, displacement of the center of the mass, and the shortest perpendicular distance (SPD) were automatically calculated. This was followed by calculation of the systematic and random errors, overlapping index (OI), and dice similarity coefficient (DSC). With PTVs isotropically expanded from NNL by 1, 2, 3, 4, and 5 mm, they were compared with NNL itself; OI >0.95 was defined as the acceptable geometrical coverage. The Mann-Whitney test was used for statistical analysis. All volumes, OI, and DSC of the NNLs (not including level IA) showed a linear decrease over time throughout the treatment course. The volume of NNLs decreased by 1-6% in the first week and 10-21% in the sixth week. The mean SPD was 1.3-1.7 and 1.9-3.5 mm in the first and sixth week respectively. The DSCs for nodal level IB, II, III, and IV were >0.7 and that of level V was <0.7 throughout the treatment course. For level IA and VI, DSC was <0.7 after the 2nd week. To maintain the OI >0.95, 2-5 mm was needed to expand the different NNLs. The geometrical changes of each NNL are substantial and the necessary margin of 2-5 mm depended on individual NNL is needed to maintain geometrical coverage throughout the course of IGRT for NPC.

The combination of prostate imaging reporting and data system version 2 (PI-RADS v2) and periprostatic fat thickness on multi-parametric MRI to predict the presence of prostate cancer.

PurposeTo evaluate the auxiliary effectiveness of periprostatic fat thickness (PPFT) on multi-parametric magnetic resonance imaging (mp-MRI) to Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) in predicting the presence of prostate cancer (PCa) and high-grade prostate cancer (HGPCa, Gleason Score ≥ 7).ResultsOverall, there were 371 patients (54.3%) with PCa and 292 patients (42.8%) with HGPCa. The mean value of PPFT was 4.04 mm. Multivariate analysis revealed that age, prostatic specific antigen (PSA), volume, PI-RADS score, and PPFT were independent predictors of PCa. All factors plus abnormal digital rectal exam were independent predictors of HGPCa. In addition, the PPFT was the independent predictor of PCa (Odds ratio [OR] 2.56, p = 0.004) and HGPCa (OR 2.70, p = 0.014) for subjects with PI-RADS grade 3. The present two nomograms based on multivariate analysis outperformed the single PI-RADS in aspects of predicting accuracy for PCa (area under the curve: 0.922 vs. 0.883, p = 0.029) and HGPCa (0.919 vs. 0.873, p = 0.007). Decision-curve analysis also indicated the favorable clinical utility of the present two nomograms.Materials and MethodsThe clinical data of 683 patients who received transrectal ultrasound guided biopsy and prior mp-MRI were reviewed. PPFT was measured as the shortest perpendicular distance from the pubic symphysis to the prostate on MRI. Univariate and multivariate analyses were performed to determine the independent predictors of PCa and HGPCa. We also constructed two nomograms for predicting PCa and HGPCa based on the logistic regression.ConclusionThe PPFT on mp-MRI is an independent predictor of PCa and HGPCa, notably for patients with PI-RADS grade 3. The nomograms incorporated predictors of PPFT and PI-RADS demonstrated good predictive performance.

Technical assessment of forest road network using Backmund and surface distribution algorithm in a hardwood forest of Hyrcanian zone

Aim of study: Corrected Backmund and Surface Distribution Algorithms (SDA) for analysis of forest road network are introduced and presented in this study. Research was carried out to compare road network performance between two districts in a hardwood forest.Area of study: Shast Kalateh forests, Iran. Materials and methods: In uncorrected Backmund algorithm, skidding distance was determined by calculating road density and spacing and then it was designed as Potential Area for Skidding Operations (PASO) in ArcGIS software. To correct this procedure, the skidding constraint areas were taken using GPS and then removed from PASO. In SDA, shortest perpendicular distance from geometrical center of timber compartments to road was measured at both districts. Main results: In corrected Backmund, forest openness in district I and II were 70.3% and 69.5%, respectively. Therefore, there was little difference in forest openness in the districts based on the uncorrected Backmund. In SDA, the mean distance from geometrical center of timber compartments to the roads of districts I and II were 199.45 and 149.31 meters, respectively. Forest road network distribution in district II was better than that of district I relating to SDA.Research highlights: It was concluded that uncorrected Backmund was not precise enough to assess forest road network, while corrected Backmund could exhibit a real PASO by removing skidding constraints. According to presented algorithms, forest road network performance in district II was better than district I.

The tumor shape changes of nasopharyngeal cancer during chemoradiotherapy: the estimated margin to cover the geometrical variation.

Considerable geometrical change occurs during chemoradiotherapy (CRT) course of nasopharyngeal carcinoma (NPC). This aim of this study was to quantify the volumetric and surface variability of the target volumes (TV) and to estimate the expanded margin to maintain acceptable geometrical coverage. Twenty patients with locally advanced nasopharyngeal cancer underwent one planning CT (pCT) and six weekly repeated CT (rCT) scans during the treatment course of definitive CRT. The TV included the gross tumor volume (GTV) of the primary tumor, large (shortest diameter >3.0 cm) and small (diameter >1 cm and ≤3 cm) positive neck lymph nodes, and low-risk clinical target volume (CTV_Lr) that were delineated manually on the pCT and each rCT. When comparing TV in pCT (V_pCT) and TV in rCT (V_rCT), the overlapping index (OI), Dice similarity coefficient (DSC), shortest perpendicular distance (SPD), and overall standard deviation (overall SD) were calculated to present the geometric changes. An isotropical margin was expanded outward around CTV_Lr in pCT to establish the mimic planning target volume (PTV). An OI ≥0.95 was defined as acceptable geometrical coverage. For all TV, DSCs decreased, and the SPDs and overall SD increased with the increasing number of fractions delivered. The DSCs of all gross TV were <70% after the third week. The mean SPDs were 1.5-2.5 mm in the first week and 5.2-6.2 mm in the last week. The OI and DSC in concurrent CRT were smaller than those in the sequential therapy; and similarly the SPD and overall SD in the concurrent therapy were larger than those in the sequential one. To maintain >95% geometrical coverage, a 2-mm additional margin could maintain the coverage throughout the treatment course and a 1-mm margin could maintain the desired coverage if there is an adaptive re-planning no later than the third week of the treatment course. Both volumetric coverage and surface of the tumour underwent the progressive changes during the treatment course of CRT. One to two mm as the expanded margin to establish the PTV is required to maintain >95% geometrical coverage.

Effect of compressed sensing reconstruction on target and organ delineation in cone-beam CT of head-and-neck and breast cancer patients

Background and purposeCompressed sensing (CS) based cone-beam computed tomography (CBCT) reconstruction techniques have been shown to improve image quality. This study was to investigate possible improvements of CBCTCS on manual delineation uncertainties of targets and organs-at-risk. Patients and methodsEight H&N and eight breast cancer patients were selected. Each H&N or breast cancer patient had planning-CT (pCT), repeat-CT (rCT), and CBCT reconstructed by both Feldkamp (CBCTFDK) and compressed sensing methods. On each scan, targets and organs-at-risk were delineated by a radiation oncologist. The impact of reconstruction technique was quantitatively assessed by dice similarity coefficient (DSC) and the shortest perpendicular distance (SPD) between contours of two corresponding scans. ResultsThe mean CBCTCS-to-rCT DSC was 7.2% and 8.0% bigger than the CBCTFDK-to-rCT for H&N and breast cancer patients respectively. The mean CBCTCS-to-rCT SPD was 16.6% and 25.4% smaller than CBCTFDK-to-rCT SPD. Due to anatomical changes, delineation accuracy reduced in reference to pCT, but no time trend was observed in CBCT based delineation accuracy in reference to rCT. ConclusionThis study demonstrated that CBCTCS has the potential to improve delineation accuracy in H&N and breast cancer patients over CBCTFDK, and CBCTCS thus has potential for adaptive radiotherapy.

TH-C-WAB-06: Target Volume Delineation Study of Compressed Sensing Cone-Beam CT for Head-And-Neck and Breast Cancer Patients During Radiation Therapy

Purpose: Cone‐beam (CB) computed tomography (CT) is widely used for image guided radiotherapy. Compressed sensing (CS) based CBCT reconstruction techniques are investigated to improve CBCT image quality to facilitate adaptive radiotherapy applications. The purpose of this study was to assess the impact of CS image quality improvements on delineation uncertainties of targets and organs‐at‐risk in head‐and‐neck (H&N) and breast cancer patients. Methods: Eight H&N and eight breast patients were selected. Each H&N patient had one planning CT (CTP) and three repeat CTs (CTR), and each beast patient had one CTP and one CTR. The corresponding CBCTs on the same day of CTR were reconstructed by both the conventional filtered back‐projection (CBCTCON) and compressed sensing (CBCTCS) methods. All CTR, CBCTCON, and CBCTCS were rigidly registered to their CTP. Then gross tumor volume (GTV), parotid glands, spinal cord, and sternocleidomastoid muscles were manually delineated for H&N cancer patients, and the breast and tumor bed (TB) for breast cancer patients. The delineated volumes were determined, and the impact of image quality differences were quantitatively assessed by dice similarity coefficient (DSC), and the shortest perpendicular distance (SPD) between contours of two images. The paired T‐test was used for statistical comparison. Results: The average volume ratio of CBCTCS/CBCTCON was 0.96, which indicated delineated volumes of CBCTCS were smaller than CBCTCON. The results of DSC and SPD from H&N and breast patients demonstrated that CBCTCS was closer to CTR than CBCTCON, where CTR was considered as the golden standard and they were statistically significant. In the temporal direction of H&N patient, a trend of decreasing DSC in GTV was found to suggest anatomic changes. Conclusion: This study demonstrated that CS CBCT improves delineation accuracy in H&N and breast cancer patients over conventional reconstruction. The results suggest that CS CBCT has potential for image guided adaptive interventions. This research was sponsored by CTMM, project Breast CARE (grant 03O‐104).

1,2-Bis(pyridin-4-yl)diazene–3,4,5-trihydroxybenzoic acid–methanol (3/2/2)

The title compound, 3C10H8N4·2C7H6O5·2CH4O, has a mol­ecular crystal structure which results from the cocrystallization of gallic acid (GA), 4,4′-azodipyridine (AzPy) and methanol in a 2:3:2 molar ratio. The asymmetric unit comprises one molecule each of GA, AzPy and methanol in general positions and half a molecule of AzPy as this is located about a centre of inversion. In the crystal, all the components of the structure are associated via the extended system of hydrogen bonds (O—H⋯O and O—H⋯N) and π–π stacking inter­actions [centroid–centroid distance = 3.637 (3) Å] into two-dimensional supra­molecular layers which are packed parallel to the [101] plane. The shortest perpendicular distance and the slippage between aromatic groups are 3.395 (3) and 2.152 (3) Å, respectively. The AzPy mol­ecules display a trans conformation with respect to the azo groups.

3-Phenyl-1-[2-(3-phenylisoquinolin-1-yl)diselanyl]isoquinoline

The complete molecule of the title compound, C30H20N2Se2, is generated by a crystallographic inversion centre at the mid-point of the Se—Se bond. The dihedral angle between the isoquinoline-1-selenol group and the phenyl ring is 14.92 (2)°. The herringbone-like packing of the structure is supported by inter­molecular π–π stacking inter­actions with a shortest perpendicular distance between isoquinoline groups of 3.514 Å; the slippage between these ring systems is 0.972 Å, and the distance between the centroids of the six-membered carbon rings is 3.645 (3) Å.

CT evaluation of Chamberlain's, McGregor's, and McRae's skull-base lines

To evaluate the mean distance from the odontoid process of C2 to the standard skull-base lines (Chamberlain's, McGregor's, and McRae's lines) on computed tomography (CT) imaging. To compare these measurements to previously documented plain radiograph and magnetic resonance imaging (MRI) measurements. Reformatted midline sagittal CT images of 150 adults were retrospectively evaluated. The shortest perpendicular distance was measured from the Chamberlain's, McGregor's and McRae's baselines for each subject to the odontoid tip. Statistical analysis was performed to compare the CT data with the previously obtained MRI and plain film data. The mean position of the odontoid process was 1.4mm below Chamberlain's line (median 1.2 mm, SD 2.4 mm), 0.8 mm (median 0.9 mm, SD 3 mm) below McGregor's line and 5 mm (median 5 mm, SD 1.8 mm) below McRae's line. There is no significant difference between male and female results (p>0.05) or between these CT and previous MRI measurements (p>0.05). These results provide the mean and range of normal distance from the odontoid process to the most frequently used skull-base lines on the current population on CT.

The use of growth and ingestion rates of Capitella sp. I as the bioassay approaches to determine the sediment quality of coastal wetlands of Taiwan

Food is a limiting factor for the deposit feeders. The availability of sediment nutrients thus has a tight relationship with the growth, survival and development of the animal. There are two purposes of this study: (1) to determine if the ingestion and growth rates can be used as a bioassay approach to assess the sediment nutrients; and (2) use the combination of bioassay approaches and chemical analyses to determine which chemical parameter is the better predicator of the sediment nutrients to the animals. In the preliminary study, the optimal growth length and average ingestion rate of Capitella sp. I were obtained from the laboratory. The standardized relationships of the growth and ingestion rates in response to different nutrients were prepared. Then, the sediments collected from different coastal wetlands in Western Taiwan were used in the feeding, growth experiments and chemical analyses. The comparisons were made between the field and laboratory experiments to determine the sediment nutrients in the wetland of Taiwan. In the growth rate standardized relationship, Capitella sp. I increased its growth rate with the total organic nitrogen (TON) concentration between 0 to 2.8 mgN·g sediment −1, total organic carbon (TOC) concentration between 0 and 22.4 mgC·g sediment −1, and enzymatically hydrolyzable amino acid (EHAA) concentration between 0 and 4.48 mg protein·g sediment −1. After the nutrient concentrations exceed these values, the growth rates decreased gradually. In the ingestion rate standardized relationship, the animal increased its ingestion rate with the total organic nitrogen (TON) concentration between 0 and 2 mgN·g sediment −1, total organic carbon (TOC) concentration between 0 and 14.1 mgC·g sediment −1, and EHAA concentration between 0 and 3.2 mg protein·g sediment −1. After the nutrient concentrations exceed these values, the ingestion rates also decreased. To determine which nutrient parameter is the best predictor for the sediment nutrient in the field, we first analyzed whether the data obtained from the laboratory fell within 99% confidence interval of the regression obtained from the field data. Then, to determine which parameter had the shortest perpendicular distance between the field and the laboratory regression curves. Both the growth and ingestion rates comparisons showed that the EHAA is the best candidate of the sediment nutrient of deposit feeders in the field. The results of this study proved tentatively that the growth and ingestion rates of Capitella sp. I can be used as the bioassay approaches to estimate the sediment nutrients. The combination of the bioassay approaches and the relevant chemical analyses allows us to determine the bioavailability fraction of sediment to the deposit feeders.

A simple radiographic measurement method for polyethylene wear in total knee arthroplasty.

This study describes a new method for evaluating polyethylene wear in total knee arthroplasty. Since the amount of wear is dependent on a number of variables such as the weight and activity of the patient, it should be estimated based on in vivo measurements. We used a computer vision technique called three-dimensional/two-dimensional (3-D/2-D) matching to perform in vivo assessment using a single-plane radiograph. Using the 3-D/2-D matching algorithm we estimated the 3-D position and orientation of each knee implant and then measured the femorotibial distance, which is defined as the shortest perpendicular distance from the tibial tray to the femoral component. The accuracy of the proposed 3-D/2-D matching method was determined by in vitro investigations. The worst errors in in-plane/out-of-plane translations and rotations were 0.20/1.95 mm and 0.17/0.29 degrees, respectively. The root-mean-square error in femorotibial distance measurements using real polyethylene inserts was 0.04 mm. Results of in vivo femorotibial distance measurements are also described.

First-order wall curvature effects upon the Stokes resistance of a spherical particle moving in close proximity to a solid wall

A method for calculating the effect of the curvature of a solid wall bounding a viscous fluid upon the quasi-static Stokes force F and torque T experienced by a spherical particle performing arbitrarily directed translational and rotational motions in close proximity to the wall is given. The results presented herein are valid for values of the ratio κ = a/d (a = sphere radius, d = shortest perpendicular distance from the sphere centre to the wall) over the entire range 0 [les ] κ [les ] 1, provided that β = a/R0 [Lt ] 1 and, simultaneously, d/R0 ≡ β/κ [Lt ] 1 (R0 = characteristic radius of curvature of the wall). Unlike existing wall-effect theories, our results are valud for κ = O(1). It is shown that to the first-order in β (and, concomitantly, in d/R0, wall curvature effects upon F and T depend linearly upon two scalar principal curvature coefficients of the wall at the foot of the shortest normal to the wall from the sphere centre. This single-particle analysis is used to resolve a ‘paradox’ relating to macroscopic slip boundary conditions prevailing at a wall bounding a dilute ferrofluid suspension undergoing rotation relative to a magnetic field.