CT Scanning Technique Research Articles

An evaluation of CT-scan to locate the femoral head centre and its implication for hip surgeons

The aim of this preliminary study was to determine the accuracy of CT-scan to locate the femoral head centre. Eleven dried femurs were included for study. Three techniques were compared to determine femoral head centre (FHC) location: CT-scan, Motion Analysis and Faro-Arm. Markers were stuck on each femur to create a system of coordinates. Femurs lied on their posterior parts (bicondylar plane). Several points around the femoral head were palpated (Motion Analysis and Faro-Arm) or determined (Amira software for CT-scans). By a least-square regression method, the FHC location in 3D was defined for each technique. The results of the FHC location determined by the CT-scan technique were compared with those measured by the faro-arm and the Motion Analysis techniques. The coordinates (X, Y, Z) of the FHC were compared between the three methods, and no statistical difference was found (p = 0.99). In a 3D plot, this gave a mean difference of 1.3 mm. The mean radius of the femoral head was of 22.5 mm (p = 0.6). CT-scan is as accurate and reliable as gold-standard techniques (motion and faro-arm). Locating FHC before and after hip arthroplasty would allow hip surgeons to determine and compare 3D orientation of the upper-end of femur: offset, height and anteversion.

Does computer-assisted total knee arthroplasty improve the overall component position and patient function?

There remains controversy as to whether computer-navigated total knee replacement (TKR) improves the overall prosthesis alignment and patient function. The aim of this study was to determine whether computer-assisted total knee arthroplasty provides superior prosthesis positioning when compared to a conventional jig-assisted total knee replacement and whether this affected the functional outcome. This prospective, randomised controlled study compared computer navigated and conventional jig-assisted total knee replacement in 37 patients who underwent bilateral TKR. A quantitative assessment of the spatial positioning of the implant in the 74 total knee replacements was determined using a low-dose dual-beam CT scanning technique. This resulted in six parameters of alignment that were compared. Functional outcomes using the high activity arthroplasty score and Knee Society score were assessed pre-operatively, postoperatively, at three years and at five years. Patients also indicated which knee they felt was subjectively the best. There was no statistically significant difference in the prosthesis alignment between both groups and the number of outliers was not decreased with navigation. All function scores improved from pre-operative to postoperative but there was no statistically significant difference between the groups at five years. At five years, 40.6% of patients thought their jig-assisted knee was the better knee compared with 21.9% their computer assisted knee and 37.5% of patients who felt they were the same. Computer-assisted implantation of total knee replacements does not offer a significant advantage in prosthesis alignment. There was no difference in functional outcome or subjective "best knee" between the computer-assisted or jig-assisted knee.

Dynamic monitoring of physical models beach morphodynamics and sediment transport using X-ray CT scanning technique

ABSTRACT Yamada, F., Tateyama, R., Tsujimoto, G., Suenaga, S., Long, B. and Pilot, C. 2013. Dynamic monitoring of physical models beach morphology and sediment transport using X-ray CT scanning technique A medical X-ray CT scanner was applied to dynamic measurements of beach profile changes, sedimentary structures, and sediment transport processes during wave actions in the laboratory experiments. An acrylic flume 7 m long and with an inner rectangular cross-section of 0.3 m × 0.3 m passes through the mobile gantry of a medical X-ray CT-scanner. The experiments were conducted at the Institut National de la Recherche Scientifique (INRS) at the University of Quebec from August 18 to October 16, 2011. The flume was filled with Ottawa sand (d50 = 0.147 mm) with uniform slope of 1/15. The water depth over a horizontal bed is 0.2 m. Regular waves were used with wave height of 4.0 cm and wave period of 0.7 s. In order to measure the cross-shore evolutions both of beach profiles and sediment transport process, th...

Idiopathic pulmonary fibrosis in 2011: key updates on guidelines and therapeutics

This first Advancing in Idiopathic pulmonary fibrosis Research (AIR) meeting took place in Berlin, on the 4th and 5th of November 2011, bringing leading experts in the field of Idiopathic Pulmonary Fibrosis (IPF) and European clinicians together to share knowledge on recent advances and practical experience in the management of this devastating disease. It is widely recognised that although IPF is a rare fibrosing lung disease it is associated with a tremendous burden. The estimated median survival of patients with IPF is 2–5 years following diagnosis, and the mortality rate is greater than that associated with numerous malignancies [1,2]. This has presented significant challenges in patient management and until recently there were no pharmacological treatments approved for patients with IPF in Europe. The timing of this meeting was therefore particularly relevant as there were a number of important advances and new findings during 2011, which included the publication of the updated guidelines from the ATS/ERS/JRS/ALAT Committee and the approval of pirfenidone for the treatment of mild-to-moderate IPF in Europe [3,4]. In addition, a press release from the National Institutes of Health reported that one arm of an ongoing trial, PANTHER-IPF, had been stopped because patients with IPF receiving a currently used triple-drug therapy consisting of prednisone, azathioprine, and N-acetylcysteine (NAC) had worse outcomes than those who received matching placebo. The interim results from PANTHER-IPF have since been published [5]. This supplement to Respiratory Research reported the proceedings from this first European IPF meeting, with key articles selected by the AIR Scientific Committee, which were considered essential reading for all clinicians managing patients with IPF in Europe. Articles in this supplement included a review of the recently updated ATS/ERS/JRS ALAT diagnostic criteria by Professor Athol Wells, and discussion on how these can facilitate early diagnosis of IPF. It also considered issues that may remain unclear despite the updated guidance. Linked to the diagnosis of IPF, Nicola Sverzellati gave a master class on HRCT imaging and practical requirements for optimising CT scanning techniques. Presentations then focused on the management of IPF. Professor Luca Richeldi discussed the Cochrane Collaboration approach to analysing clinical trial data and the findings of Cochrane meta-analyses that have been performed to determine the effect of treatments used in the management of IPF. This was followed by Professor Vincent Cottin, who summarised the outcomes from prior clinical trials in IPF and the recently published Phase III studies of pirfenidone that led to its approval in Europe. Following these updates, Professor Jurgen Behr and Luca Richeldi discussed how these data can be interpreted in light of the updated recommendations of the ATS/ERS/JRS/ALAT Committee regarding treatment of IPF. Professor Carlo Albera outlined the implications of the press release from the NIH regarding the PANTHER-IPF study. Hopefully the selected proceedings from this meeting will provide IPF clinicians with new insights and support in the management of their patients. The intention is for the AIR meeting to become a fixed date in the calendar for respiratory physicians and researchers dedicated to improving knowledge and bringing new hope for IPF patients.

CT Scan Technique Boosts 3D Mammography

Abstract Using phase contrast tomography, researchers at the University of California, Los Angeles, and their colleagues have produced high-resolution 3D images of breast tissue with radiation exposure that is less than that from today's 2-dimensional screening mammograms.

Optimization of Kilovoltage and Tube Current–Exposure Time Product Based on Abdominal Circumference: An Oval Phantom Study for Pediatric Abdominal CT

This CT study evaluates image noise and radiation dose using a modified CT dose index phantom to approximate pediatric abdominal shape. Contrast-to-noise ratio (CNR) and radiation dose were measured. The oval shape was simulated by fixing 1000-mL saline bags aside cylindric phantoms with variable circumferences. The doses at the center and peripheral holes in the phantom were recorded. Measurements were obtained at 50-400 mAs and 80-140 kVp. Diluted iodine contrast agent filled the center hole, and distilled water filled the peripheral holes. CNR was defined as the difference in CT number between diluted iodine and water divided by the standard deviation (SD) of CT number of water. Dose increased linearly with increases in tube current-exposure time product and by a power function (proportional to kVp(n), where n = 2.64-3.09) for increases in kilovoltage. A range of scanning parameters was established for each circumference from which technique optimization curves were created to determine the best tube current-time product and kilovoltage pairs when noise was less than 20 HU and dose was less than 2.5 cGy. CNR increased by 40% as kilovoltage was reduced from 140 to 80 kVp. A dose reduction of 70% was observed for 140 versus 80 kVp for the same CNR. Because pediatric patients of the same age and weight come in all shapes and sizes, abdominal circumference is a useful clinical parameter on which to base CT scan techniques controlling radiation output--namely kilovoltage and tube current-time product. Low-kilovoltage techniques for patients with small circumference show better iodine CNR.

A test of a new method and software for the rapid estimation of cross-sectional geometric properties of long bone diaphyses from 3D laser surface scans

This paper introduces a new methodological approach to the quantification of cross-sectional geometric properties based on 3D laser scan data. A variety of methods have been used to calculate estimates of rigidity in the diaphyses of long bones. CT scan, biplanar radiograph, and periosteal mould techniques have all been applied to collect image data of bone sections to assess biomechanical properties (cross-sectional area and second moments of area). Whilst direct quantification of both endosteal and periosteal contours allows the greatest accuracy, such data correlate highly with a periosteal-only approach that is of greater practical application in many contexts. The advent of non-invasive 3D laser scan technologies presents a method to capture bone surface morphology that can be applied to the study of variation in the cross-sectional properties of human bones. This study tests the correspondence between cross-sectional geometric properties derived from laser scans to those obtained through traditional approaches (periosteal moulding and biplanar radiography). A custom-built program, AsciiSection, is introduced for the automated analysis of biomechanical properties direct from 3D coordinate data. The results indicate that the AsciiSection method is of comparable if not greater accuracy than traditional moulding techniques. The study suggests that there is a strong correlation between mid-diaphyseal cortical bone distribution and cross-sectional geometry calculated using laser scans. The approach provides a viable alternative to traditional techniques for the estimation of biomechanical properties and also allows the collection of rich data and descriptions of morphological variation along the diaphysis.

Multi-detector CT angiographic imaging in the follow-up of patients after endovascular abdominal aortic aneurysm repair (EVAR)

BackgroundMultidetector computed tomography (MDCT) angiography represents the standard of reference in the follow-up of patients after endovascular abdominal aortic aneurysm repair (EVAR), being effective in the detection of the full spectrum of possible complications on both axial and 3D images.MethodsThe purpose of this article is to review the normal CT angiography findings of the different types of stent-grafts and to describe the radiological findings of early and late complications after EVAR on axial and reconstructed images. A selection of cases of post-EVAR MDCT angiography is presented to learn the techniques most commonly used for endovascular treatment, the correct CT scanning technique to acquire the data, the full gamut of possible procedure-related complications and how these complications usually appear on CT images.ConclusionMDCT angiography is an effective and specific technique in both the pre- and postoperative settings of EVAR procedures. A better understanding of the procedure, the devices, the normal postoperative imaging features and the possible procedure-related complications ensures optimal planning and follow-up of patients undergoing an EVAR procedure.

Assessment of an iterative reconstruction algorithm (SAFIRE) on image quality in pediatric cardiac CT datasets

Pediatric cardiac patients often undergo repeat diagnostic testing, resulting in relatively high cumulative medical radiation exposure. Low-dose CT scanning techniques used to decrease radiation exposure may result in reduced image quality. This study evaluates a prototype iterative reconstruction algorithm, sinogram-affirmed iterative reconstruction (SAFIRE), to determine the effect on qualitative and quantitative measures of image quality in pediatric cardiac CT datasets, compared with a standard weighted filtered back projection (wFBP) algorithm. Seventy-four datasets obtained on a 128-slice dual-source CT system were evaluated for image quality using both the wFBP and the prototype iterative reconstruction algorithm. Contrast, noise, contrast-to-noise ratio, signal-to-noise ratio, and qualitative image quality were compared between groups. Data were analyzed as medians and 25th and 75th percentiles, and groups were compared with the use of the Wilcoxon singed-rank test or k sample equality of medians test. There was a 34% decrease in noise, a 41% increase in contrast-to-noise ratio, and a 56% increase in signal-to-noise ratio in the prototype iterative reconstruction, compared with wFBP. All differences were statistically significant (P < 0.001). Qualitative measures of image noise and noise texture were also improved in the iterative reconstruction group (P < 0.001 for both). Diagnostic confidence was similar between reconstruction techniques. Median scan dose length product was 15.5 mGy · cm. The prototype iterative reconstruction algorithm studied significantly reduces image noise and improves qualitative and quantitative measures of image quality in low-dose pediatric CT datasets, compared with standard wFBP.

Numerical and experimental aluminum foam microstructure testing with the use of computed tomography

Metal foams are a new, as yet imperfectly characterized, class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They offer potential for lightweight structures, for energy absorption, and for thermal management; and some of them, at least, are cheap. The paper deals with the experimental and numerical studies of the open-cell aluminum foam microstructural behavior. The aim of the research was to describe and to assess the main mechanisms that appear in the foam structure during the compression and how they influence the material energy absorbing capabilities. The research was carried out with the use of CT-scanning technique. The first step of the research was the compression test of the samples in the tomography testing stage that was coupled with sample X-ray scanning to describe the deformations in the researched material for the numerical model verification. The next step of the study was the development and the analyzes of the numerical model of tested undeformed sample in accordance to computed tomography results. The model was built with the use of a unique computer code created to transform the scan point cloud into FE raster model based on solid 8-node elements. The experimental and numerical test results were compared and showed good compatibility. The stress distributions were studied to describe the main mechanisms in the structure. The most important conclusion is that the foam structures can be considered as the complex beam constructions where the local instabilities decide about the energy absorbing capabilities.

Effective factors on linguistic disorder during acute phase following traumatic brain injury in adults

Traumatic brain injury (TBI) has been known to be the leading cause of breakdown and long-term disability in people under 45 years of age. This study highlights the effective factors on post-traumatic (PT) linguistic disorder and relations between linguistic and cognitive function after trauma in adults with acute TBI. A cross-sectional design was employed to study 60 post-TBI hospitalized adults aged 18–65 years. Post-traumatic (PT) linguistic disorder and cognitive deficit after TBI were respectively diagnosed using the Persian Aphasia Test (PAT) and Persian version of Mini-Mental State Examination (MMSE) at discharge. Primary post-resuscitation consciousness level was determined using the Glasgow Coma Scale (GCS). Paracilinical data was obtained by CT scan technique. Multiple logistic regression analysis illustrated that brain injury severity was the first powerful significant predictor of PT linguistic disorder after TBI and frontotemporal lesion was the second. It was also revealed that cognitive function score was significantly correlated with score of each language skill except repetition. Subsequences of TBI are more commonly language dysfunctions that demand cognitive flexibility. Moderate, severe and fronto-temporal lesion can increase the risk of processing deficit in linguistic macrostructure production and comprehension. The dissociation risk of cortical and subcortical pathways related to cognitive-linguistic processing due to intracranial lesions can augment possibility of lexical-semantic processing deficit in acute phase which probably contributes to later cognitive-communication disorder.

Optimizing CT Dose and Image Quality for Radiotherapy Patients

With the successes of CT dose reduction programs such as Image Gently [1] and Image WiselyTM 2], many organizations have signed n to these programs, and CT proocols across the country have been djusted to match CT dose to the mage quality necessary for a given iagnostic examination. Most of he protocols call for lower doses ompared with the technique in use reviously to scan patients, again n the basis of obtaining sufficient mage quality to allow a diagnosis o be made. With the increased meia attention to CT protocol errors nd misadministrations using highose CT techniques and the inreased frequency of physicians’ orering CT studies to obtain diagnoses, here has been a plethora of articles sugesting CT dose reduction strategies in he recent literature [3-6]. Although CT dose reduction strtegies have been used across the ountry in response to these efforts, hey may not apply to all patients ho require CT scans for their medcal conditions. In particular, patients resenting for CT scans for radioherapy planning may not benefit rom the extremely reduced dose trategies. These patients will have igh-energy x-radiation (an order of agnitude greater than what is reeived with imaging) through the rea being scanned for planning puroses (about 10-80 Gy), and the CT ose (about 1-100 mGy) presents nly a small fraction of the dose the atients will receive to control their disease. In fact, the new techniques in radiation oncology will use further low-energy imaging techniques to align patients during their radiotherapy procedures (“image-guided radiation therapy”). Hence, as mentioned, the CT planning doses will not be of great concern to these patients and their attending radiation oncologists. From the viewpoint of obtaining sufficient image quality for the myriad radiotherapy planning procedures in use today, radiology and radiation oncology department staff members should consult with the attending radiation oncologist to adjust CT scan protocols to obtain sufficient CT image rendition for the planning procedure at hand. This may require an actual increase in CT scan technique from that used for reduced-dose diagnostic techniques. This is especially important when using CT imaging for planning whose image sets will be fused with those from other imaging modalities, such as MRI or PET/CT, to allow the radiation oncologist to accurately contour the tumor targets that will be the subject of the radiotherapy procedure. Image fusion requires matching anatomic regions in both the CT image set and the MRI data, for example, to attack intracranial tumors that are more visible on the MRI data sets. If the CT data set for this fusion is suboptimal (“noisy”) because a reduced-dose CT technique was used, the image fusion may not be rendered accurately,

Clinical application of low-dose CT scan technique in orbit

Objective To explore the effects of low-dose CT scan on diagnostic quality of images and the radiation dose to the lens.Methods 60 cases were scanned in axial orientation at different mA.Lens radiation dose was measured and image quality was evaluated.Results Image quality score of group A was(11.2 ± 0.7)points,higher than the group C(4.9 ± 1.8)points(t =12.634,P ＜0.05),and score difference of group B(10.6 ± 1.1)was significantly different(P ＞ 0.05).CTDIvol of group A,group B and group C were 18.32mGy,7.63mGy and 4.58mGy,group B,group C and group A difference was statistically significant(t =15.625 and 14.037,P ＜ 0.05).Group B and C groups difference was not statistically significant(P ＞ 0.05).Conclusion Low dose CT scanning(50mA)in orbit not only could assure the image quality,but also decrease the radiation dose. Key words: Tomography,X-ary computed; Radiation dosage; Orbit

Physiological function of the angiotensin AT1a receptor in bone remodeling

In order to determine whether the renin-angiotensin system (RAS) has any physiologic function in bone metabolism, mice lacking the gene encoding the major angiotensin II receptor isoform, AT1a, were studied using micro CT scanning, histomorphometric, and biochemical techniques. Three-dimensional (3D) micro CT analysis of the tibial metaphysis revealed that both male and female AT1a knockout mice exhibited an increased trabecular bone volume along with increased trabecular number and connectivity. Histomorphometric analysis of the tibial metaphysis indicated that the parameters of bone formation as well as resorption were increased, which was also supported by elevated serum osteocalcin and carboxy-terminal collagen crosslink (CTX) concentrations in the AT1a-deficient mice. Osteoclastogenesis and osteoblastogenesis assays in ex vivo cultures, however, did not reveal any intrinsic alterations in the differentiation potential of AT1a-deficient cells. Quantitative RT-PCR using RNA isolated from the tibia and femur revealed that the receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) ratio and the expression of stromal cell-derived factor (SDF)1α were increased, whereas that of SOST was decreased in AT1a-deficient bone, which may account for the increased bone resorption and formation, respectively. AT1a-deficient mice also displayed a lean phenotype with reduced serum leptin levels. They maintained high bone mass with advancing age, and were protected from bone loss induced by ovariectomy. Collectively, the data suggest that RAS has a physiologic function in bone remodeling, and that signaling through AT1a negatively regulates bone turnover and bone mass.

SU‐E‐J‐125: CT Dose Survey for Simulations in Radiation Oncology

Purpose: To establish baseline values and ranges for CTDIvol and DLP as a function of treatment site to be used to monitor CT simulation protocols and scan techniques for inadvertent changes and patient specific anomalies. Methods: We have collected CTDIvol (mGy) and DLP (mGy cm) values reported for all CT simulations performed on two large bore GE lightspeed RT scanners and one GE PET/CT scanner located in the Radiation Oncology facilities of the University of California San Diego for the calendar year 2010. Additional acquired data included patient identifier, scan date, scan type, intended treatment site and scanner location. Data was analyzed to calculate averages and standard deviations of CTDIvol and DLP as a function of intended treatment site and scan type. Results: The average CTDIvol for all helical scans was 32.3 with a standard deviation of 16.3 while the average DLP was 1095 with a standard deviation of 570. The average CTDIvol for all CINE scans was 115.6 with a standard deviation of 40.3. while the average DLP was 2064 with a standard deviation of 1625. As a function of treatment site for the helical scans, average values for CTDIvol ranged from 16.7 for TBI to 49.1 for brain while DLP ranged from 755 for breast to 1888 for TBI. For the CINE scans, average values for CTDIvol ranged from 113 for lung to 155 for liver while DLP ranged from 1630 for lung to 3929 for liver. Conclusions: The collected data provides expected ranges for CTDIvol and DLP for technologists to use in evaluating CT scans to look for anomalies which may be caused by changes in scan protocols or incorrect protocol or scan parameter selection. This will allow us to set up a quality assurance program to detect, report and correct such errors as they occur.

Osteomyelitis in a Paleozoic reptile: ancient evidence for bacterial infection and its evolutionary significance

We report on dental and mandibular pathology in Labidosaurus hamatus, a 275 million-year-old terrestrial reptile from North America and associate it with bacterial infection in an organism that is characterized by reduced tooth replacement. Analysis of the surface and internal mandibular structure using mechanical and CT-scanning techniques permits the reconstruction of events that led to the pathology and the possible death of the individual. The infection probably occurred as a result of prolonged exposure of the dental pulp cavity to oral bacteria, and this exposure was caused by injury to the tooth in an animal that is characterized by reduced tooth replacement cycles. In these early reptiles, the reduction in tooth replacement is an evolutionary innovation associated with strong implantation and increased oral processing. The dental abscess observed in L. hamatus, the oldest known infection in a terrestrial vertebrate, provides clear evidence of the ancient association between terrestrial vertebrates and their oral bacteria.

First Castorid (Mammalia, Rodentia) from the Middle Miocene of Southeast Asia

Today and in the Tertiary, the geographical distribution of castorids is limited throughout all of the northern continents. Fossils of the Castoridae genus Steneofiber are abundant in many localities of Eurasia from the late Oligocene to Pliocene period. Recently, Steneofiber fossils were discovered in two localities of northern Thailand, Mae Moh and Chiang Muan coal mines, in layers of late middle Miocene age. These discoveries represent the first records of castorids from Southeast Asia and correspond to their southernmost known range. The focus of this study is to describe this new Thai species of Steneofiber and to define its wear stages from the molar occlusal surfaces by using micro-CT scan analysis. The CT scan technique permits the analysis of the virtual occlusal surface changes from wear, allowing easier comparison to related species of Steneofiber cheek teeth without destroying the teeth. The new species, Steneofiber siamensis n. sp., can be distinguished from the other species of Steneofiber by several distinct characters, longer mesostriid on p4, presence of premesostria and metastria on P4, which are smaller than most of the other known species. The occurrence of this new castorid also supports a subtropical to tropical paleoclimate for these two localities of northern Thailand.

Using X-ray images to analyse graptolite distribution and alignment in Welsh mudrocks

SUMMARY X-ray imaging of graptolites is here shown to enhance greatly the amount and type of fossil evidence available, both for biostratigraphical study and for palaeoceanographical and palaeoecological analysis. The technique requires there to be sufficient density contrast between the fossils and the enclosing rock, as with the pyritized graptolites within the Silurian (Llandovery, Aeronian) mudrocks of central Wales investigated herein. Graptolite species previously not encountered using traditional collecting techniques were recorded in significant numbers using X-ray imaging and include two species recorded for the first time in Britain. Stratigraphic variation has been found in the numbers of pyritized graptolites, and this is inversely related to the amount of free aggregated pyrite within the rock. Biserial graptolite specimens show systematic patterns of alignment by currents, and construction of stereo and anaglyph images enables 3-dimensional visualisation of spatial information, allowing the geometry and microstratigraphic relationship of one graptolite to another to be discerned. CT-scan techniques show better-resolved 3D morphology, but digital X-ray techniques, being more rapid, may remain optimal for many routine uses in palaeontology.

Measurement of femoral head penetration in polyethylene using a 3-dimensional CT-scan technique

Background Current techniques for measuring in vivo polyethylene wear suffer from a range of problems, resulting in an unacceptable lack of repeatability and/or insufficient accuracy when they are used to measure the low wear rates associated with new, highly crosslinked polyethylene. We describe an improved CT method for measurement of 3D femoral head penetration in PE acetabular cups that has sufficient accuracy and repeatability to allow assessment of the wear potential of modern implants.Method The accuracy and repeatability of the CT-scan method was determined by blindly repeating measurements on a precisely calibrated 28-mm prosthetic head and by comparing them with direct metrological measurements on 10 acetabular specimens with in vitro wear from machining, and on 8 explanted acetabular specimens with in vivo wear.Results The intra- and interobserver errors in femoral head diameter were 0.036 mm (SD 0.044) and 0.050 mm (SD 0.022), respectively. CT estimated femoral head penetration in both all-poly and metal-backed acetabular components with accuracy ranging from 0.009 to 0.245 mm (mean 0.080; SD 0.067).Interpretation We found that the CT method is rapid, is accurate, and has repeatability and ease of availability. Using a slice thickness of 0.0625 mm, this method can detect wear—and also the threshold for the wear rate that causes osteolysis—much earlier than previous methods.

Alternative oblique head CT scanning technique reduces bone artifact and improves interpretability of brainstem anatomy

Brainstem pathology due to infections, infarcts and tumors are common in developing countries, but neuroimaging technology in these resource-poor settings is often limited to single slice, and occasionally spiral, CT. Unlike multislice CT and MRI, single slice and spiral CT are compromised by bone artifacts in the posterior fossa due to the dense petrous bones, often making imaging of the brainstem non-diagnostic. With appropriate head positioning, the petrous ridges can be avoided with 40° sagittal oblique scans parallel to either petrous ridge. We describe an alternative sagittal oblique scanning technique that significantly reduces brainstem CT artifacts thereby improving clarity of anatomy. With Institutional Ethical approval, 13 adult patients were enrolled (5 males; 39%). All patients had routine axial brain CT and sagittal oblique scans with no lesions found. Images were read by 2 readers who gave a score for amount of artefact and clarity of structures in the posterior fossa. The mean artifact score was higher for routine axial images compared to sagittal oblique (2.92 vs. 1.23; P<0.0001). The mean anatomical certainty scores for the brainstem were significantly better in the sagittal oblique views compared to routine axial (1.23 vs. 2.77; P<0.0001). No difference was found between the two techniques with respect to the fourth ventricle or the cerebellum (axial vs. sag oblique: 1.15 vs. 1.27; P=0.37). When using single slice CT, the sagittal oblique scanning technique is valuable in improving clarity of anatomy in the brainstem if axial images are non-diagnostic due to bone artifacts.