Transverse CT Scans Research Articles

Trochlea morphology demonstrates variability but no gender difference in osteoarthritic patients undergoing total knee arthroplasty

BackgroundIn recent years, coronal lower leg alignment has received significant attention. Two classifications recently described the variability in both femoral and tibial morphology, resulting in differing native lower limb alignment.The native trochlea and the variability in morphology has received less attention. MethodsThis is a prospective cohort study of 200 patients undergoing robotically assisted TKA. Preoperative transverse CT scans were used to determine the posterior condylar axis (PCA), transepicondylar axis (TEA), lateral trochlear inclination (LTI), the sulcus angle (SA) and the anterior trochlear line (ATL). Outliers were defined as values > 1.5 IQR from median value. Trochlea dysplasia was defined as LTI < 12°. Gender differences were compared. ResultsIn total, 99 patients were female (49.4%). SA had a median of 137.0° (IQR 12°), ATL 4° (IQR 4), LTI 18° (IQR 7°). Median TEA-PCA was 5° external (IQR 3°). There were 5.0% outliers in SA, 3.0% of outliers in ATL, 3.5% outliers in LTI and 4.5% outliers in the TEA-PCA. Trochlear dysplasia was present in 11.5% of the measurements. There was no difference in any of the angles between the genders. ConclusionThe present study demonstrates no difference in trochlea morphology between the genders, rather a significant number of overall outliers in trochlear morphology. Larger cohorts but also, more investigations, are needed to better understand the trochlear morphology of patients undergoing total knee arthroplasty. The personalized alignment strategies and implants need to account for this variability in the population.

Influence of High-Frequency Ultrasonic Vibration Load on Pore-Fracture Structure in Hard Rock: A Study Based on 3D Reconstruction Technology.

Rock fracture is a macroscopic fracturing process resulting from the initiation and propagation of microscopic cracks. Therefore, it is crucial to comprehend the damage and fracture mechanism of rock under ultrasonic vibration by investigating the evolutionary pattern of the meso-pore fracture structure in response to high-frequency vibrational loads, as explored in this study. Standard red sandstone samples with a diameter of 50 mm and height of 100 mm were subjected to ultrasonic high-frequency vibration tests. NMR and CT scans were conducted on the rock samples at different stages of ultrasonic vibration excitation to obtain the corresponding transverse relaxation time (T2) spectra and CT scan images for each layer. The NMR test results revealed that smaller pores formed within the rock under high-frequency vibration loads, with a noticeable expansion observed in micropores. Three-dimensional reconstruction analysis based on two-dimensional CT images demonstrated an increase in pore count by 145.56%, 122.67%, and 98.87%, respectively, for the upper, middle, and lower parts of the rock after 120 s of ultrasonic vibration excitation; furthermore, the maximum pore volume increased by 239.42%, 109.16%, and 18.99%, respectively, for these regions during this period as well. These findings contribute towards a deeper understanding regarding the mechanisms underlying rock fragmentation when exposed to high-frequency vibrational loads.

Pre-operative use of CT based three-column concept for fragment specific fixation of proximal tibia fractures in a series of 84 cases

Background: It is important to classify proximal tibia fractures based on CT scan in addition to plain radiograph. The 3-column concept was introduced to classify these fractures based on a transverse CT scan. This study aimed to evaluate the surgical and functional outcomes of fragment specific fixation in proximal tibia fractures using the 3-column concept. Materials and Methods: 84 cases of proximal tibia fractures (mean age: 42.85±11.94 years, range 23-72 years; 65 males and 19 females) were classified based on the 3-column concept (24 - 1 column, 50 – 2 column, 10 – 3 column). The surgical approach was decided for fragment-specific fixation based on the column involved. The clinic-functional assessment was done using fracture union time, range of motion, Oxford Knee Score and Functional Knee Society Score. Results: The mean follow up duration was 1.2-1.5 years. The average fracture union time was 15.63±1.98 weeks (range, 12-21 weeks). The mean flexion achieved at the final follow up was 132.74±4.49 degrees (range, 130-135 degrees). The mean follow-up Oxford Knee Score was 47.98±0.109 (range, 45-48) and the mean Functional Knee Society Score was 99.88±1.09 (range, 90-100) in all patients after 1 year. 2 patients showed they delayed wound healing with superficial infection and 1 patient had a stiff knee. There was no other complication. Conclusion: Using the CT-based three-column concept for fragment-specific fixation pre-operatively helps treat a complex proximal tibia fracture with acceptable complication rates and good functional outcomes.

Muscle volume evaluation using 3DCT for congenital clubfoot.

BackgroundIn congenital clubfoot, the lower leg is very thin and the calf muscles are hypoplasic. However, there are few studies reporting real muscle volume.PurposeThe purpose of this study is to assay the muscle volume in congenital clubfoot using 3DCT and to quantify the degree of the hypoplasia.Material and methodsFrom January 2015 to December 2016, nine consecutive patients, seven male and two female, with unilateral congenital clubfeet were recruited for CT scans. Axial transverse sectional CT scans were acquired from the delineation of the fibular head to the tibial plafond. From the data, we rendered the entire muscle in 3D for muscle volume assay, and further segmented the posterior musculature for comparison between the normal and affected sides.ResultsThe whole muscle volume on the normal side was 291.23 cm3 (181.23–593.49) and that on the affected side was 225.08 cm3 (120.71–429.08), for an affected side to normal side ratio of 0.79 (0.72–0.9), which was significantly smaller (p < .01). Posterior muscle volume on the normal side was 175.81 cm3 (103.72–376.32) and that on the affected side was 106.52 cm3 (58.3–188.39). The ratio of posterior muscle to whole muscle on the normal side was 0.62 (0.46–0.75), and that on the affected side was 0.48 (0.4–0.55), such that the affected side was significantly smaller (p < .01)ConclusionThis study contributes quantitative data supporting the longstanding observations that the posterior calf muscles are significantly smaller on the affected side compared to the normal side in congenital clubfoot, and further underscores the importance of the extending the excursion of these muscles.

Advanced Approach of Material Region Detections on Fibre-Reinforced Concrete CT-Scans

Detections of material regions on CT-scans of solids are commonly treated manually by an expert. Although such manual detections have many advantages, some amount of human error is also incorporated. Moreover, expert opinions may vary significantly. We present an application of the k-means++ clustering as an alternative option to manual way of material area detections. k-means++ clustering is derived from k-means (the method of vector quantization, originally from signal processing), popular for cluster analysis in data mining and image processing communities. The algorithm s main advantages are its simple implementation and fast convergence to a local optimum of an objective function. We benchmark the suggested approach on transverse CT-scans of a fibre-reinforced concrete solid. Moreover, we introduce a technique for processing air distribution, such that the appropriate pixels detected as the pixels of air are converted into pixels representing concrete. The technique is based on the connected component algorithm. Benchmark and results of proposed method conclude the paper.

Use of computed tomography to define a sacral safe corridor for placement of 2.7 mm cortical screws in feline sacroiliac luxation.

Objectives This study aimed to define a safe corridor for 2.7 mm cortical sacroiliac screw insertion in the dorsal plane (craniocaudal direction) using radiography and CT, and in the transverse plane (dorsoventral direction) using CT in feline cadavers. A further aim was to compare the values obtained by CT with those previously reported by radiography in the transverse plane. Methods Thirteen pelvises were retrieved from feline cadavers and dissected to expose one of the articular surfaces of the sacrum. A 2.7 mm screw was placed in the sacrum to a depth of approximately 1 cm in each exposed articular surface. Dorsoventral radiography and CT scanning of each specimen were performed. Multiplanar reconstructions were performed to allow CT evaluation in both the dorsal and transverse planes. Calculations were made to find the maximum, minimum and optimum angles for screw placement in craniocaudal (radiography and CT) and dorsoventral (CT) directions when using a 2.7 mm cortical screw. Results Radiographic measurement showed a mean optimum craniocaudal angle of 106° (range 97-112°). The mean minimum angle was 95° (range 87-107°), whereas the mean maximum angle was 117° (108-124°). Measurement of the dorsal CT scan images showed a mean optimum craniocaudal angle of 101° (range 94-110°). The mean minimum angle was 90° (range 83-99°), whereas the mean maximum angle was 113° (104-125°). The transverse CT scan images showed a mean dorsoventral minimum angle of 103° (range 95-113°), mean maximum angle of 115° (104-125°) and mean optimum dorsoventral angle of 111° (102-119°). Conclusions and relevance An optimum craniocaudal angle of 101° is recommended for 2.7 mm cortical screw placement in the feline sacral body, with a safety margin between 99° and 104°. No single angle can be recommended in the dorsoventral direction and therefore preoperative measuring on individual cats using CT images is recommended to establish the ideal individual angle in the transverse plane.

Computed tomographic findings of pulmonary atelectasis in healthy anesthetized Beagles.

OBJECTIVE To characterize the extent and location of atelectasis in healthy anesthetized dogs positioned in lateral recumbency and to determine whether repositioning dogs in sternal recumbency would resolve atelectasis. ANIMALS 6 healthy adult Beagles. PROCEDURES Each dog was anesthetized and underwent a CT examination twice with a 2-week interval between examinations. Once anesthetized, each dog was positioned in sternal recumbency, and a breath-hold helical transverse thoracic CT scan was acquired. The dog was then positioned in lateral recumbency for 30 minutes, and images were obtained at 5 preselected sites at 3, 8, 13, 20, and 30 minutes after repositioning (phase 1). Then, the dog was repositioned in sternal recumbency, and CT images were obtained at the 5 preselected sites at 5, 10, and 20 minutes after repositioning (phase 2). The protocol for the second examination was the same as the first except the dog was positioned in the opposite lateral recumbency during phase 1. The attenuation and cross-sectional area of the lung lobes at the preselected sites were measured and compared over time. RESULTS Lateral recumbency did not cause atelectasis in any of the dogs. Patchy areas of abnormally increased attenuation were infrequently detected in the left cranial lung lobe when dogs were positioned in left lateral recumbency, and those areas failed to resolve when dogs were positioned in sternal recumbency. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the extent of lung attenuation changes was minimal in healthy anesthetized Beagles positioned in lateral recumbency and should not preclude CT examination.

CT/MRI pelvimetry as a useful tool when selecting patients with rectal cancer for transanal total mesorectal excision.

The quality of a total mesorectal excision (TME) is one of the most important prognostic factors for local recurrence of rectal carcinoma. The aim of this study was to clarify the manner in which lesser pelvis dimensions affect the quality of TME via the transabdominal approach, while simultaneously defining the criteria for selecting patients most likely to have Grade 3 TME outcomes for a transanal approach using the TaTME technique. An analysis from the registry was conducted using 93 of total 198 patients with rectal cancer of the mid- and lower third of the rectum who underwent: (1) a low anterior resection, (2) an ultra-low resection with coloanal anastomosis, or (3) an intersphincteric rectal resection, all with total mesorectal excision. The procedures were carried out at the Department of Surgery at the University Hospital Hradec Králové between 2011 and 2014. Rectal specimens were histopathologically examined according to a standardized protocol. Pelvimetry data were obtained using anteroposterior, transverse, and sagittal CT or MRI scans. A correlation was found between the quality of the TME and pelvimetry parameter A5, i.e., the angle between the longitudinal axis of the symphysis, and the lines between the symphysis and the promontory (R(2) = -0.327, p < 0.001). The ordinal regression method was used to identify parameters of the model describing levels of probability for TME quality. These relationships were described by equations that provide probability of the achievement of each grade of TME. The correlation described by obtained equations between pelvimetry parameters and the quality of TME represents a new tool for use in preoperative decision-making with regard to resection via the transanal approach (TaTME).

Abstract 1885: Quantitative Textural Analysis (QTA) in CT imaging: Identifying markers for genetic instability and overall survival in cohort of previously treated metastatic pancreatic cancer (mPC)

Abstract PURPOSE. To explore the use of helical CT-derived Quantitative Textural Analysis (QTA) parameters in identifying elevated rates of intrachromosomal copy number aberrations in mPC and secondarily in revealing post-treatment QTA prognostic markers. MATERIALS AND METHODS. Metastatic tumor sites were biopsied and molecularly profiled in a cohort patients with mPC (n=35). 85% of the cohort had 1-3 previous treatment regimens, and the remaining 15% had 4-6. Intrachromosal copy number were assessed by CGH in tumor specimens, and patients were treated with commercially available cytotoxic regimens based on these individual molecular profiling results1. Patients with available pre-biopsy transverse abdominal portal-venous phase CT scans were obtained for retrospective analysis (n=17). Analysis of pre-biopsy pancreas imaging was performed by drawing regions of interest around the primary pancreas adenocarcinoma (n=15) and the normal pancreas tissue when available (n=12). Two patients did not have any quantifiable imaging due to surgery or local structural obfuscation and were not included in our cohort. There were 9 males and 6 females all with stage IV cancer from 34 - 71 years old (median 59). QTA parameters were derived using the TexRAD platform at texture filtering densities of medium (3 pixels) and coarse (5 pixels). There values were compared to intrachromosomal copy number aberrations per tumor and overall survival post-treatment using a Spearman's rank correlation coefficient. RESULTS. Intrachromosomal copy number aberrations (median: 14; range: 5 - 52) were negatively correlated with the kurtosis value of the primary tumor mass (median: -0.146; range: -0.810 - 0.633) using medium texture filtering (p = 0.034, n = 15). Secondary analysis of the normal pancreas with coarse texture filtering yielded a correlation between reduced overall survival time post-treatment and increasing entropy (p = 0.0014, n = 12). Using entropy as a cutoff value (median: 4.165; range 2.686 - 4.891), median overall survival was greater in the entropy &amp;lt; 4.165 group versus the entropy &amp;gt; 4.165 group (6.1 v 2.0 months, respectively; hazards ratio [HR] = 11.5; 95% CI 1.36 - 97.4; p = 0.025, n = 12). Median survival for the entire cohort was 120 days and ranged from 1 day to 372 days post-treatment. CONCLUSION. This exploratory study with admittedly limited sample size raises interesting questions about the use of QTA parameters as diagnostic tools and/or biopsy adjuncts in assessing pancreatic adenocarcinoma susceptibility to commercially available cytotoxics. Secondarily, entropy, a potential marker of heterogeneity and inflammation in the normal pancreas, represents an intriguing possibility for gauging prognosis in mPC. (Clinical trial supported by a grant from the SU2C/AACR-pancreatic dream team) REFERENCES. 1. Ramanathan RK et al AACR Annual Meeting. LB-221. 2012. Citation Format: David H. Campbell, Michael Barrett, Ramesh K. Ramanathan, Daniel D. Von Hoff, Ronald Korn. Quantitative Textural Analysis (QTA) in CT imaging: Identifying markers for genetic instability and overall survival in cohort of previously treated metastatic pancreatic cancer (mPC). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1885. doi:10.1158/1538-7445.AM2014-1885

An atypical “arthritis” in a patient with rheumatoid arthritis

A 42-year-old woman presented inflammatory monoarticulararthritis of the proximal interphalangeal joint of the left ring fin-ger with a previous history of rheumatoid arthritis well controlledby abatacept. This mono-arthritis was resistant to non-steroidalanti-inflammatory drugs.Biologicalevaluationswerenormal.Plainradiograph (Fig. 1A), completed by transverse CT scan (Fig. 1B) andcoronal T2-weighted fat-suppressed magnetic resonance imag-ing (Fig. 1C) showed a small, radiolucent, eccentric lesion withinternal ossification on the radial side of the second phalanx ofthe 4th finger with cortex thickening (arrow), edema within andaround the bone but without periosteal bone formation and prox-imal interphalangeal joint involvement with erosion (arrowhead).Histopathological examination confirmed the diagnosis of osteoidosteoma. CT-guided percutaneous radiofrequency thermal abla-tion was refused by the patient, who preferred to wait given the

Confirmation of microevolutionary increase in spina bifida occulta among Swiss birth cohorts

Previous studies on the prevalence of spina bifida occulta have indicated a microevolutionary increase in its frequency and possible population differences in the prevalence of the condition. We studied the frequencies of closed and open sacral canals at each sacral level among two birth cohorts in Switzerland. Transverse CT scans and multiplanar reconstruction images of sacra of 95 males and 96 females born in 1940-1950 and 99 males and 94 females born in 1970-1980 in Switzerland were reviewed. We found that individuals born later have significantly more open sacral arches at all sacral levels compared to those born 30-40years earlier. When results were related to previously published data on Australian cohorts, the trend was the same, but Swiss in both cohorts were less likely to have an open section than Australians at all locations apart from S2. This study confirmed a microevolutionary trend in the opening of sacral canal among two different generations in Switzerland and demonstrated a population difference in the prevalence of spina bifida occulta.

Analysis of the tibial anteroposterior axis and its use in TKA.

Objective To investigate the relationship between tibial anteroposterior axis and other anatomic landmarks in determining the rotation of tibial prosthesis in total knee arthroplasty using computed tomography. Methods Transverse CT scans of 40 volunteers' right knee in full extension were made. The anteroposterior axis of the tibia was defined as a line which was perpendicular to the transepicondylar axis and passing through the middle point of the posterior crnciate ligament. At the tibial plateau and optimum re-section level, the mean medial percentage width of intersection point of the patellar tendon anti the antero-posterior axis was measured. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon and the medial 1/3 of the patellar tendon were measured. Results At the tibial plateau level, the mean medial percentage width of intersection point of the patellar tendon was 10.1%±8.3%. At the optimum resection level, the mean medial percentage width of intersection point of the patellar tendon was 0.2%±10.0%. At the optimum resection lev-el, the mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon was 0.1°±2.7°. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament anti the medial 1/3 of the patellar tendon was 10.3°±3.6°. Conclusion There was a tendency to align the tibial component in external rotation relative to the femoral component when the medial 1/3 of the patellar tendon was used. The line connecting the middle of the posterior cruciate ligament and the medial of the patellar tendon can be used as a reliable axis for correct rotational orientation of the tibial component. Key words: Arthroplasty; replacement; knee; Tomograph; X-ray computed; Tibia

Diagnosis of arterial sequestration using multidetector CT angiography

Background Arterial sequestration is a rare congenital disorder. The diagnostic evaluation of this condition using multidetector computerized tomography (MDCT) has not been described previously. The purpose of this study was to describe the characteristic features of this disorder and to assess the use of MDCT in visualizing the characteristic anatomic features. Methods We retrospectively reviewed the records of seven patients with anomalous systemic blood supply to left lower lobe of the lung. All the patients had undergone MDCT angiography. To evaluate the lung parenchyma, bronchial branching pattern, and vascular anatomy, four series of images were systematically reconstructed as follows: contiguous transverse CT scans viewed at mediastinal and pulmonary window settings, oblique coronal and sagittal maximum intensity projections (MIP), multiplanar reconstruction (MPR), and three-dimensional volume-rendered images (VR) of airway and thoracic vascular structures. Results All 7 cases had isolated and tortuous arterial anatomy from the descending thoracic aorta to the basal segment of the left lower lobe; however, variable distribution of branches was observed. Characteristic findings of anomalous systemic arterial (ASA) supply were distinct from those seen in other pulmonary sequestration syndromes and were well visualized by the use of noninvasive MDCT. Conclusion Complex CT findings allow clear imaging of arterial sequestration and the ASA blood supply; MDCT angiography has demonstrated its value and accuracy in diagnosing this condition, obviating the use of digital subtraction angiography and magnetic resonance angiography for the diagnosis of arterial sequestration.

Hemodynamic Analysis of a Compliant Femoral Artery Bifurcation Model using a Fluid Structure Interaction Framework

The influence of wall motion on the hemodynamic characteristics of the human femoral bifurcation and its effects on the development of peripheral artery disease has not been previously investigated. This study aimed in investigating the hemodynamics of a compliant patient-specific femoral artery bifurcation model by a fluid structure interaction (FSI) scheme. The complex physiological geometry of the femoral artery bifurcation was reproduced from sequentially obtained transverse CT scan images. Velocity waveforms derived from phase contrast MR images were extracted and mapped to define boundary conditions. Equations governing blood flow and wall motion were solved using an FSI framework that utilizes commercial codes: FLUENT for computational fluid dynamics and ANSYS for computational structural dynamics. The results showed that wall compliance decreased flow velocities at the relatively high curvature geometries including common and superficial femoral artery (SFA), and it created strong recirculation in the profunda femoris artery close to the bifurcation. In the SFA region near the apex, time averaged wall shear stress (TAWSS) differences up to 25% between compliant and rigid models were observed. The compliant model also exhibited lower TAWSS and oscillatory shear at the superior section of the common femoral artery close to the bifurcation. The presence of wall motion, however, created minor differences in the general flow-field characteristics. We conclude that wall motion does not have significant influence on the global fluid dynamic characteristics of the femoral artery bifurcation. Longer arterial segments need to be simulated to see the effect of wall motion on tortuousity which was previously cited as an important factor in the development of atherosclerosis at the femoral artery.

Pseudo-myxoma: massive pulmonary vein metastasis from a primary breast carcinoma

Fig. 1. Transverse CTscan showing the tumour originating from the right inferior pulmonary vein (PV) andoccupying thewhole of the left atrium (T). Note the left sided pleural effusion (E) and associated collapsed left lower lobe. Fig. 2. Pre-operative trans-thoracic echocardiography (five chamber view) showing the tumour (T) extending from the pulmonary vein (PV) and the left atrium (LA) into the left ventricle (LV) by popping through themitral valve (MV) with each atrial systole.

Ectopic origin of bronchial arteries: assessment with multidetector helical CT angiography

The purpose of this study was to determine non-invasively the frequency of ectopic bronchial arteries (BA) (i.e., bronchial arteries originating at a level of the descending aorta other than T5-T6 or from any aortic collateral vessel) on multidetector-row CT angiograms (CTA) obtained in patients with hemoptysis. Over a 5-year period (2000-2005), 251 consecutive patients with hemoptysis underwent multidetector-row CT angiography of the thorax. From this population, 37 patients were excluded because of a suboptimal CTA examination (n = 19), the presence of extensive mediastinal disease (n = 15) or severe chest deformation (n = 3) precluding any precise analysis of the bronchial arteries at CTA. Our final study group included 214 patients who underwent a thin-collimated CT angiogram (contrast agent: 300 to 350 mg/ml) on a 4- (n = 56), 16- (n = 119) and 64- (n = 39) detector-row scanner. The site of origin and distribution of bronchial arteries were analyzed on transverse CT scans, maximum intensity projections and volume-rendered images. The site of the ostium of a bronchial artery was coded as orthotopic when the artery originated from the descending aorta between the levels of the fifth and sixth thoracic vertebrae; all other bronchial arteries were considered ectopic. From the studied population, 137 (64%) patients had only orthotopic bronchial arteries, whereas 77 patients (36%) had at least one bronchial artery of ectopic origin. A total of 147 ectopic arteries were depicted, originating as common bronchial trunks (n = 23; 19%) or isolated right or left bronchial arteries (n = 101; 81%). The most frequent sites of origin of the 124 ostiums were the concavity of the aortic arch (92/124; 74%), the subclavian artery (13/124; 10.5%) and the descending aorta (10/124; 8.5%). The isolated ectopic bronchial arteries supplied the ipsilateral lung in all but three cases. Bronchial artery embolization was indicated in 26 patients. On the basis of CTA information, (1) bronchial embolization was attempted in 24 patients; it was technically successful in 21 patients (orthotopic BAs: 6 patients; orthotopic and ectopic BAs: 3 patients; ectopic BAs: 12 patients) and failed in 3 patients due to an instable catheterization of the ectopic BAs; the absence of additional bronchial arterial supply and no abnormalities of nonbronchial systemic arteries at CTA avoided additional arteriograms in these 3 patients; (2) owing to the iatrogenic risk of the embolization procedure of ectopic BAs, the surgical ligation of the abnormal vessels was the favored therapeutic option in 2 patients. This study enabled the depiction of ectopic bronchial arteries in 36% of the studied population, important anatomical information prior to therapeutic decision making.

Lower Tube Voltage Reduces Contrast Material and Radiation Doses on 16-MDCT Aortography

The purpose of our study was to compare aortic CT angiography performed at a low tube voltage and reduced dose of contrast material with standard-voltage, standard-contrast-dose CT angiography. We evaluated 74 patients for aortic disease on MDCT angiography (collimation, 16 x 1.5 mm; beam pitch, 0.9). In 36 patients, we used the standard tube voltage (120 kVp) and a contrast dose of 100 mL (300 mg I/mL) (protocol 1), and in the remaining 38 patients we applied a reduced tube voltage (90 kVp) and a contrast dose of 40 mL (300 mg I/mL) (protocol 2). The patients' weights, CT attenuation of the aorta, visualization of the celiac axis and renal artery, and graininess and streak artifacts on transverse CT scans were evaluated and recorded for each data set. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also measured. For statistical analysis, we used the two-tailed Student's t test and logistic regression; agreement between measurements recorded independently by two blinded reviewers was assessed using Cohen kappa statistics. In both protocols a negative correlation was seen between patient weight and CT attenuation. In three protocol 1 patients weighing more than 70 kg, CT attenuation was less than 200 H. No difference was seen between the two protocols with respect to mean attenuation of the aorta (p = 0.13) or visualization of the celiac axis and renal artery (p = 0.35 and 0.60, respectively). Although the SNR and CNR were significantly higher in protocol 1 than in protocol 2, qualitative evaluation of graininess and streak artifacts showed no statistically significant difference (p = 0.15 and 0.48, respectively). Interobserver agreement for quality assessments was within an acceptable range (kappa = 0.42-0.80). Low-contrast and low-voltage scans are appropriate for lighter patients (< 70 kg in body weight) with aortic disease. Moreover, this method is particularly valuable for follow-up studies of heavier patients (> 70 kg) with renal dysfunction.

Urine Attenuation Ratio: A New CT Indicator of Renal Artery Stenosis

The purpose of our study was to evaluate the value of a ratio of the attenuation measurements of urine in each kidney (hereafter referred to as the urine CT attenuation ratio) in the detection and lateralization of significant renal artery stenosis (RAS). In 33 patients with suspected renovascular hypertension and 43 normotensive patients, 5-mm-thick transverse CT scans of the kidney area were obtained 4 min after helical CT angiography (CTA). The attenuation of urine in each kidney was measured, and its ratio was calculated. All 76 patients underwent intraarterial digital subtraction angiography within 2 days after the CT examination. The results of angiography were correlated with the urine attenuation ratio of both kidneys. Twenty-six patients showed significant RAS: unilaterally in 20 and bilaterally in six patients. Two patients showed moderate stenosis of renal arteries. The other patients with essential hypertension (n = 5) or normal blood pressure (n = 43) showed normal renal arteries. The CT attenuation of urine in each kidney was measured and its ratio calculated in all patients except four patients with unilateral RAS. The urine CT attenuation ratio in 22 patients with significant RAS ranged from 1.11 to 4.76 (mean, 2.07). The two patients with moderate RAS showed ratios of 1.83 and 1.23. The others (n = 48) had a urine CT attenuation ratio that ranged from 1.00 to 1.54 (mean, 1.07). The difference of the ratio between the RAS group and the normal group was statistically significant (p < 0.01). The mean urine CT attenuation ratio was 2.18 in patients with unilateral RAS (n = 16) and 1.75 in patients with bilateral RAS (n = 6). The difference of the ratio between the two groups was not statistically significant (p = 0.16). At a cutoff value of 1.22, the sensitivity, specificity, positive predictive value, and negative predictive value of the urine CT attenuation ratio in the diagnosis of significant RAS were 95%, 96%, 91%, and 98%, respectively. The urine CT attenuation ratio is a simple and reliable indicator with which to detect and lateralize significant RAS and is a useful adjunct to helical CTA.

Acetabular Dome Retroversion: Radiological Appearance, Incidence and Relevance

Interest in acetabular version arose from the study of unstable developmental dysplastic hips (DDH). Initial studies and clinical observations described the dysplastic hip as being excessively anteverted. Doubts on this view arose from analysis of complications such as persistent posterior subluxation after acetabular reorienting procedures. Computed tomography fails to determine conclusively whether or not the dysplastic acetabulum is abnormally anteverted. Controversy evolves from different methods of measuring and from the fact that the acetabular opening gradually spirals from mild anteversion proximally to increasing anteversion distally. This renders the measurement of version dependent on pelvic inclination and the level of the transverse CT scan slice. On an orthograde pelvic radiograph, both pelvic inclination and rotation can be controlled. Therefore, acetabular version is best estimated based on the relationship of the anterior and posterior acetabular rims to each other on an orthograde pelvic radiograph. Acetabular retroversion has been found to be a characteristic feature of specific hip disorders such as post-traumatic dysplasia, proximal femoral focal deficiency and bladder exstrophy. In addition, acetabular retroversion has been described in DDH as well as in dysplastic hips in the context of neuromuscular and genetic disorders. Iatrogenic acetabular retroversion can also result from corrective pelvic osteotomies in childhood. Finally, retroverted acetabula may be found in otherwise nondysplastic hips. The relevance of acetabular retroversion is twofold: First, it demands a more individualized approach to acetabular dysplasia because the presence of retroversion will affect the manner in which the corrective osteotomy should be done. Second, the long-term effect of acetabular retroversion is harmful.

CT changes after trochleoplasty for symptomatic trochlear dysplasia

Trochlear dysplasia is an important risk factor for patellar instability. Because of a decreased trochlear depth in combination with a low lateral femoral condyle, the patella cannot engage properly in the trochlea. Trochleoplasty is a surgical procedure, which strives to correct such bony abnormalities. The aim of this study was to describe morphological features of trochlear dysplasia and the corrective changes after trochleoplasty on CT scan. The study group consists of 17 knees with trochlear dysplasia having undergone trochleoplasty for recurrent patellofemoral dislocation at a mean age of 22.4 years. The evaluation consisted in pre- and postoperative measurements on the proximal and distal trochlea on transverse CT scans in order to determine the morphological features. We measured the transverse position and depth of the trochlear groove, the transverse position of the patella, the ratio between the posterior patellar edge and the trochlear groove, the lateral patellar inclination angle, the sulcus angle, and the lateral trochlear slope. The trochlear groove lateralised a mean of 6.1 mm in the proximal aspect and 2.5 mm in the distal aspect of the trochlea, while the patella medialised a mean of 5 mm. Preoperatively the patella was lateral in relation to the trochlear groove in 13 cases, neutral in two cases, and medial in two cases. Postoperatively it was lateral in four cases, in neutral position in seven cases, and medialised in six cases, referenced to the trochlear groove. The trochlear depth increased from 0 to 5.9 mm postoperatively in the proximal aspect of the trochlea, and from 5.5 to 8.3 mm postoperatively in the distal trochlea. The lateral patellar inclination angle decreased from a mean of 21.9 degrees to a mean of 7.8 degrees . The sulcus angle decreased from a mean of 172.1 degrees to a mean of 133 degrees in the proximal trochlea and from a mean of 141.9 degrees to a mean of 121.7 degrees in the distal trochlea. The lateral trochlear slope changed from 2.8 degrees to 22.7 degrees in the proximal and from 14.9 degrees to 26.9 degrees in the distal part of the trochlea. In the CT scan patients with trochlear dysplasia demonstrated a poor depth, or even a flat or convex trochlea with a greater sulcus and lateral trochlear slope angle, a lateralised patella to the trochlear groove with poor congruency, and a greater lateral patellar inclination angle. Trochleoplasty can correct the pathological features of trochlear dysplasia by surgically creating more normal anatomy. The goal of this surgical procedure is to steepen and lateralise the trochlear groove for a better engagement of the patella.