CT scanograms compared with conventional orthoroentgenograms in long bone measurement

In this article the standard orthoroentgenograph is compared with computed tomography (CT) scanography in determining bone length discrepancies. Dried femur bones are studied by both methods. The CT scanogram method is found to be more accurate than the orthoroentgenography method.     

Shielded biplanar gradient coil design.

An application of the target field method to the design of shielded biplanar gradient coils for magnetic resonance imaging electromagnets is presented. Some specific cases are studied, and optimized geometries are proposed for the axial and transverse gradient coils that eliminate the third- and minimize the fifth-order terms in the magnetic field expansion.     

CT determination of femoral torsion

Femoral torsion has been measured in infants and children by computed tomography. The method requires two scans, one through the femoral neck, another through the femoral condyles. A specially designed device and packing about the knees assures immobilization of the legs. Slight variations in the positions of the sections in the neck and condyles do not alter the measurement significantly. Intraobserver and interobserver errors are low, 2 degrees and 3 degrees mean error, respectively. The radiation required involves small tissue volumes at about 1.7 R (4.4 x 10(-4) C/kg). Measurements are more difficult when the femoral necks are short or vertically oriented. The method appears to have sufficient accuracy for clinical purposes.     

Estimating splenic volume: sonographic measurements correlated with helical CT determination

OBJECTIVE: The purpose of this study was to determine which sonographic measurements of the spleen most closely correlate with splenic volume as determined on helical CT. MATERIALS AND METHODS: From October 17, 2000, to April 27, 2001, 142 consecutive patients prospectively underwent abdominal helical CT and sonography as part of an evaluation for liver disease. Calculations of splenic volumes were based on 10-mm unenhanced images. Maximum length (ML) and width (W), thickness (T), and craniocaudal length (CCL) were measured sonographically. Standard ellipsoid volume formulas (with the addition of new ellipsoid coefficients) and linear regression formulas were calculated for 117 patients whose examinations were performed within 30 days of each other. Mean percent differences, standard deviations, and 95% confidence intervals (CI) were calculated. RESULTS: We calculated the average difference between sonography- and CT-measured volume and the 95% CI for each of the four initial sonographic volume estimates with the ellipsoid method using two lengths and linear regression using two lengths and compared them to CT-determined volume. The ellipsoid formulas were then adjusted for bias. Linear regression formulas were derived in which splenic volumes were separately calculated on the basis of each of the two lengths. Mean percent differences and standard deviations for ellipsoid formulas with varying coefficients using the three length measurements were also calculated. CONCLUSION: Sonographic measurements allow accurate determination of splenic volume. Estimating splenic volume with the formula 0.524 x W x T x (ML + CCL) / 2 provides the greatest overall accuracy.     

Leg length determination by CT digital radiography

CT digital radiography is a new accurate technique for measuring leg length discrepancy. It is easily performed on commercially available equipment with a radiation dose of 3-6 times less than the conventional technique. Because of the short time required to complete the examination, charges are comparable with those for existing procedures. Good correlation in total limb length measurements between this new technique and spot scanography was noted in 24 patients. CT digital radiography should be the preferred method for evaluation for limb length discrepancy, particularly in children, because of the simple technique and lowering of radiation dose.     

Three-dimensional hindfoot alignment measurements based on biplanar radiographs: comparison with standard radiographic measurements

Objective

To establish a hindfoot alignment measurement technique based on low-dose biplanar radiographs and compare with hindfoot alignment measurements on long axial view radiographs, which is the current reference standard.

Materials and methods

Long axial view radiographs and low-dose biplanar radiographs of a phantom consisting of a human foot skeleton embedded in acrylic glass (phantom A) and a plastic model of a human foot in three different hindfoot positions (phantoms B1–B3) were imaged in different foot positions (20° internal to 20° external rotation). Two independent readers measured hindfoot alignment on long axial view radiographs and performed 3D hindfoot alignment measurements based on biplanar radiographs on two different occasions. Time for three-dimensional (3D) measurements was determined. Intraclass correlation coefficients (ICC) were calculated.

Results

Hindfoot alignment measurements on long axial view radiographs were characterized by a large positional variation, with a range of 14°/13° valgus to 22°/27° varus (reader 1/2 for phantom A), whereas the range of 3D hindfoot alignment measurements was 7.3°/6.0° to 9.0°/10.5° varus (reader 1/2 for phantom A), with a mean and standard deviation of 8.1°?±?0.6/8.7°?±?1.4 respectively. Interobserver agreement was high (ICC?=?0.926 for phantom A, and ICC?=?0.886 for phantoms B1–B3), and agreement between different readouts was high (ICC?=?0.895–0.995 for reader 1, and ICC?=?0.987–0.994 for reader 2) for 3D measurements. Mean duration of 3D measurements was 84?±?15/113?±?15 s for reader 1/2.

Conclusion

Three-dimensional hindfoot alignment measurements based on biplanar radiographs were independent of foot positioning during image acquisition and reader independent. In this phantom study, the 3D measurements were substantially more precise than the standard radiographic measurements.     

CT determination of tibial tubercle lateralization in patients presenting with anterior knee pain

Anterior knee pain is commonly associated with patellofemoral malalignment. Both conventional radiographic measurements and CT measurements have been proposed to define and confirm the sometimes difficult clinical diagnosis of anterior knee pain secondary to patellofemoral malalignment. Using CT imaging with computerized technique to measure anatomic relationships, we evaluated patients (n=50) with anterior knee pain for excessive lateralization of the tibial tubercle. The symptomatic knee of each patient was compared with their asymptomatic knee as well as with the knees of patients with other causes of anterior knee pain (n=10) and with the knees of asymptomatic controls (n=10). The symptomatic knee of patients with suspected patellofemoral malalignment demonstrated significantly greater lateralization of the tibial tubercle (12.2±0.5 mm) than did the asymptomatic knee (9.0±0.7 mm). The symptomatic knees of patients with patellofemoral malalignment also demonstrated significantly greater lateralization of the tibial tubercle than did the knees of patients with other causes of anterior knee pain (5.9±0.9 mm). When a control population was added to the analysis, the patients with symptomatic patellofemoral malalignment demonstrated significantly greater lateralization of the tibial tubercle than did the controls (6.4±0.4 mm). Using a critical value of 9 mm lateralization, the CT diagnosis of patellofemoral malalignment had a specificity of 95% and a sensitivity of 85%. We conclude that CT determination of tibial tubercle position assists the diagnosis of patellofemoral malalignment.     

Age determination of subdural hematomas with CT and MRI: A systematic review

Objectives

To systematically review the literature on dating subdural hematomas (SDHs) on CT and MRI scans.

Methods

We performed a systematic review in MEDLINE, EMBASE and Cochrane to search for articles that described the appearance of SDHs on CT or MRI in relation to time between trauma and scanning. Two researchers independently screened the articles, assessed methodological quality and performed data extraction. Medians with interquartile ranges were calculated. Differences were tested with a Mann–Whitney U or Kruskal–Wallis H test.

Results

We included 22 studies describing 973 SDHs on CT and 4 studies describing 83 SDHs on MRI. Data from 17 studies (413 SDHs) could be pooled. There were significant differences between time intervals for the different densities on CT (p < 0.001). Time interval differed significantly between children and adults for iso- and hypodensity (p = 0.000) and hyperdensity (p = 0.046). Time interval did not differ significantly between abused and non-abused children. On MRI, time intervals for different signal intensities on T1 and T2 did not differ significantly (p = 0.108 and p = 0.194, respectively).

Conclusions

Most time intervals of the different appearances of SDHs on CT and MRI are broad and overlapping. Therefore CT or MRI findings cannot be used to accurately date SDHs.     

Tracheal cross-sectional area in children: CT determination

A computer method that calculates tracheal cross-sectional area by compensating for partial volume averaging was developed and validated in a study with phantoms. The program was then used to determine the tracheal cross-sectional area of 30 normal children who ranged in age from four months to 18 years. CT-derived cross sections were correlated with age, height, weight, and body-surface area, and they were compared with findings of published clinical and post-mortem studies. CT cross-sectional areas ranged from 20-275 mm2, varied by as much as 22% at the three different tracheal levels studied, and appeared to correlate most closely with body height. CT-derived tracheal cross-sectional areas are quite similar to those in published reports of postmortem and clinical studies. Measurement of tracheal cross section by CT may prove useful in quantitating tracheal compromise by intrinsic or extrinsic causes.     

Ultrasound-guided prostatic biopsy using biplanar transrectal probe. Our experience

In the last three years we performed more than 200 echo-guided prostatic biopsies using different probes. Recently, thanks to the availability of a bi-planar transrectal probe we have developed a technique that resulted simple rapid well accepted by the patients and above all able to center small prostatic nodules. We have studied with this technique 96 patients performing 120 biopsies. For the biopsy we used a 19 G cutting-needle introduced under local anaesthesia parallel to the probe (linear array) when the needle is on the target we turn on the axial view and we check the position with respect to the center of the lesion, then, returning to the sagittal view we perform 1 to 3 biopsies for microhistological and cytological examination. With this method we have reached a better accuracy of diagnosis.     

Quantitative determination of coronary vascular calcinosis (coronary calcium score) with double-helical CT

Coronary heart disease is a common disease, with the typical characteristic of coronary sclerosis, an abnormal calcification of the heart's blood vessels. The amount of coronary calcification is in direct correlation to the extent of coronary heart disease. With the double-detector-helical-CT it is possible to detect and quantify these calcifications. The correlation of the "Calcium-Scoring" with the results of coronary-angiography, myocardial scintigraphy and clinical findings shows the value of this method of coronary heart diagnostic. False negative results, based on low calcified fatty stenotic plaques and false positive results, based on high calcificated plaques without significant stenosis should be taken into account.     

Low-dose biplanar skeletal survey versus digital skeletal survey in multiple myeloma

Objectives

To evaluate the low-dose biplanar (LDB) skeletal survey (SS) for the assessment of focal bone involvement in patients with multiple myeloma (MM) as compared with digital SS and to compare the two techniques in terms of image quality, patient comfort and radiation exposure.

Methods

Fifty-six consecutive patients with newly diagnosed or first relapsed MM underwent LDB and digital SS on the same day. These were assessed by two radiologists for the detection of focal bone lesions. In the case of discordance, whole-body MR imaging was performed. Image quality, patient comfort and radiation dose were also assessed.

Results

Fifty-six patients (M:30, F:26, mean age, 62 years) with newly diagnosed (n = 21) or first relapse MM (n = 35) were enrolled. A total of 473 bone lesions in 46 patients (82 %) were detected. Out of that total, digital SS detected significantly more lesions than LDB SS (451 [95.35 %] versus 467 [98.73 %]), especially in osteopenic and obese patients. Overall patient satisfaction was greater with LDB SS (48.6 %) compared with digital SS (2.7 %). The radiation dose was significantly reduced (by a factor of 7.8) with the LDB X-ray device.

Conclusions

Low-dose biplanar skeletal surveys cannot replace digital SS in all patients suffering from multiple myeloma.

Key Points

? Low-dose biplanar skeletal surveys can readily assess bone lesions in multiple myeloma. ? In marked radiographic osteopenia and obesity, LDB SS diagnostic performance is reduced. ? Low-dose biplanar skeletal surveys cannot yet replace digital SS in all MM patients.     

Needle aspiration and core biopsy of prostate cancer: comparative evaluation with biplanar transrectal US guidance

Biplanar, transrectal ultrasound (US) guidance of needles was used in the transperineal biopsy of possibly malignant prostatic lesions in 80 patients (83 biopsies). A 22-gauge cytologic needle was used to locate and fixate the lesion, and aspiration specimens for cytologic and histologic evaluation were obtained (with 22- and 14-gauge needles, respectively). Twenty-one 19-gauge needle core biopsies were also performed. Forty-nine patients (61%) had histologically prove adenocarcinoma. The rate of cancer diagnosis was 53% with cytologic evaluation and 54% with histologic evaluation (combined yield, 61%). This included 34% of cancers less than 1.0 cm in diameter and 56% of those 1.0-1.5 cm. Thirteen of 23 (57%) of these lesions were nonpalpable or equivocal on digital rectal examination. These results suggest that transrectal US guidance of thin-needle biopsies is useful in diagnosing early prostate cancer.     

On visual determination of full inspiration on CT images

The aim of this study was to evaluate the ability of experienced thoracic radiologists to assess full inspiration based on two CT slices, one above and one below the carina, in normal subjects. Ten healthy volunteers were studied. Total lung capacity (TLC) was measured with a body plethysmograph. High-resolution computed tomography (HRCT) was performed in two slices at TLC and at various expired volumes. Mean Hounsfield values (HU) were calculated. Unidentifiable images, stored on a web server, were analysed visually by experienced thoracic radiologists. The results show that the mean lung density at TLC varied by approximately 40 HU between individuals. Within an individual this may correspond to a decrease in lung volume of approximately 25% of TLC. On visual determination of images taken at 65–74% of TLC, more than one-third of the images were assessed as taken at full inspiration; of the images taken at 75–84% of TLC, approximately 50% were assessed as taken at full inspiration. We conclude that visual determination of full inspiration on CT images in normal subjects is highly inaccurate. If quantitative density measurements are to be used in the diagnosis or follow-up of lung disease, thorough control of full inspiration is recommended. Electronic Publication     

Quantitative CT for determination of thorium in thorotrast patients

The concentrations of thorium in the liver, spleen, and their efferent lymph nodes were determined in six thorotrast patients by quantitative CT scanning. Thorium concentration per CT number was calibrated by scanning a phantom that contained a known concentration of thorium nitrate solution. The total amount of thorium determined by the quantitative CT method in the liver, spleen, and lymph nodes was compared with that determined by gamma-ray measurement of the upper abdomen using a whole body counter. A linear relationship was obtained between the amount of thorium determined by the CT method and that determined by the gamma-ray measurement method, although the correlation was not high. The quantitative CT method appears to be useful for determining, with some accuracy, the concentration of thorium in the liver, spleen, and lymph nodes of thorotrast patients.     

Adverse reactions to xenon-enhanced CT cerebral blood flow determination

Fourteen institutions performed 1,830 computed tomographic (CT) cerebral blood flow (CBF) examinations with 32% inhaled stable xenon. Respiratory rate delay greater than 10 seconds occurred in 3.6% of patients, with 83% of the delays lasting 10-15 seconds. There was no incident of prolonged respiratory difficulty. Headache (0.4%), seizures (0.2%), nausea and vomiting (0.2%), and change in neurologic status (0.1%) were uncommon, and there were no transient ischemic attacks. The CT CBF method with 32% inhaled stable xenon is thus associated with an acceptably low incidence of adverse reactions.     

Calculation of three-dimensional left ventricular strains from biplanar tagged MR images.

The noninvasive measurement of time-resolved three-dimensional (3D) strains throughout the myocardium could greatly improve the clinical evaluation of cardiac disease and the ability to mathematically model the heart. On the basis of orthogonal arrays of tagged magnetic resonance (MR) images taken at several times during systole, such strains can be determined, but only after heart motion through the image planes is taken into account. An iterative material point-tracking algorithm is presented to solve this problem. It is tested by means of mathematical models of the heart with cylindric and spherical geometries that undergo deformations and bulk motions. Errors introduced by point-tracking interpolation were found to be negligible compared with those due to marker identification on the images. In a human heart studied with this technique, the corrected radial strains at the left ventricular base were approximately 2.5 times the two-dimensional estimates derived from the fixed image planes. The authors conclude that material point tracking allows accurate, time-resolved 3D strains to be calculated from tagged MR images, and that prior correction for motion of the heart through image planes is necessary.