Attempts to improve absolute quantification of cerebral blood flow in dynamic susceptibility contrast magnetic resonance imaging: a simplified T1-weighted steady-state cerebral blood volume approach

Background: Attempts to retrieve absolute values of cerebral blood flow (CBF) by dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) have typically resulted in overestimations.

Purpose: To improve DSC-MRI CBF estimates by calibrating the DSC-MRI-based cerebral blood volume (CBV) with a corresponding T1-weighted (T1W) steady-state (ss) CBV estimate.

Material and Methods: 17 volunteers were investigated by DSC-MRI and ¹³³Xe SPECT. Steady-state CBV calculation, assuming no water exchange, was accomplished using signal values from blood and tissue, before and after contrast agent, obtained by T1W spin-echo imaging. Using steady-state and DSC-MRI CBV estimates, a calibration factor K = CBV(ss)/CBV(DSC) was obtained for each individual. Average whole-brain CBF(DSC) was calculated, and the corrected MRI-based CBF estimate was given by CBF(ss) = K×CBF(DSC).

Results: Average whole-brain SPECT CBF was 40.1±6.9 ml/min·100 g, while the corresponding uncorrected DSC-MRI-based value was 69.2±13.8 ml/min·100 g. After correction with the calibration factor, a CBF(ss) of 42.7±14.0 ml/min·100 g was obtained. The linear fit to CBF(ss)-versus-CBF(SPECT) data was close to proportionality (R = 0.52).

Conclusion: Calibration by steady-state CBV reduced the population average CBF to a reasonable level, and a modest linear correlation with the reference ¹³³Xe SPECT technique was observed. Possible explanations for the limited accuracy are, for example, large-vessel partial-volume effects, low post-contrast signal enhancement in T1W images, and water-exchange effects.     

Percutaneous transluminal cutting-balloon angioplasty for hemodialysis access stenoses resistant to conventional balloon angioplasty

Purpose: To examine the value of cutting-balloon percutaneous transluminal angioplasty (PTA) for hemodialysis access with residual stenosis after conventional balloon PTA.

Material and Methods: Angioplasty with conventional balloons was performed on 48 hemodialysis access stenoses in 28 patients. If the balloon waist still remained at the rated burst pressure, the balloon was reinflated up to three times. Fifteen of 48 stenoses had residual stenoses of more than 30% after conventional balloon PTA. In these 15 stenoses, additional cutting-balloon PTA was performed.

Results: The mean residual percent diameter stenoses before and after conventional balloon PTA were 77.6±3.4% and 48.6±8.5%, respectively. Additional cutting-balloon PTA decreased the mean residual percent diameter to 27.9±10.0%, and the cutting balloon was completely inflated without complication. In 12 patients, the 6-month primary patency rate (±SE) was 90.0% (9.5), and the 1-year primary patency rate (±SE) was 25.0% (14.8).

Conclusion: Additional cutting-balloon PTA was found useful for reducing residual stenosis.     

Retropharyngeal tendinitis: radiographic and magnetic resonance imaging findings

Purpose: To describe the magnetic resonance imaging (MRI) findings in retropharyngeal tendinitis.

Material and methods: Within 1 year, four patients presenting with symptoms of retropharyngeal tendinitis were examined by radiography and MRI.

Results: On MRI and radiographs, all patients had characteristic soft-tissue swellings and calcifications related to the tendon of the longus colli muscle situated inferior to the anterior arc of C1. MRI showed well-defined edema, with high signal in the retropharyngeal tissue anterior to C1-C5 on short T1 inversion recovery (STIR) sequences, low signal on T1-weighted sequences, and low signal in the calcification on both sequences. In addition, three patients had high signal intensity changes on STIR sequences in the atlantoaxial joint situated posterior to the anterior arc of C1.

Conclusion: MRI is a sensitive and accurate method in the diagnosis of retropharyngeal tendinitis. A new finding in this condition is an effusion or synovitis in the anterior atlantoaxial joint. MRI is a valuable tool in differentiating retropharyngeal tendinitis from other diagnoses such as retropharyngeal abscess, pyogenic spondylitis, and spondyloarthropathy.     

Diagnostic efficacy in knee MRI comparing conventional technique and multiplanar reconstruction with one-millimeter FSE PDW images

Background: Magnetic resonance (MR) imaging has proved to be an excellent tool in diagnosing injuries of the cruciate ligaments and menisci. However, multiple planes and sometimes optimal oblique or double-oblique scan planes are needed due to the variability in the positioning of important structures, which means there is a lower throughput and longer scanning time.

Purpose: To compare the performance of a 1-mm-thickness fast spin-echo (FSE) proton-density-weighted (PDW) MR imaging technique with multiplanar reconstruction (MPR) in diagnosing tears of the menisci and cruciate ligaments with that of conventional MR imaging.

Material and Methods: Twenty-five consecutive patients underwent preoperative conventional and 1-mm-thickness FSE PDW MR imaging with subsequent knee arthroscopic surgery. Two musculoskeletal radiologists evaluated the status of the cruciate ligaments and menisci using two sets of MR images (method A: conventional images including seven sequences, taking 26 min; method B: 1-mm-thickness FSE PDW images with MPR, taking 7 min 20 s). The diagnostic efficacies of both methods for tears of the cruciate ligament and menisci were calculated and compared.

Results: Arthroscopic surgery revealed 10 anterior cruciate ligament (ACL) tears, one posterior cruciate ligament (PCL) tear, and 26 meniscal tears. The diagnostic values of both methods were 100% for a cruciate ligament tear. The diagnostic values (sensitivity, specificity, accuracy, positive predictive value, and negative predictive value) for meniscal tears were 90%, 100%, 96%, 100%, and 94% for method A, and 95%, 100%, 98%, 100%, and 97% for method B, respectively. There were no significant differences in the diagnostic values between methods A and B.

Conclusion: 1-mm-slice-thickness FSE PDW imaging with MPR showed comparable performance in diagnosing tears of the cruciate ligaments and menisci to conventional sequences but the scan time was much shorter. Therefore, this technique (method B) might improve the throughput of a 3T MR imaging system.     

Detection of cerebrospinal fluid leakage: initial experience with three-dimensional fast spin-echo magnetic resonance myelography

Background: The pathogenesis of cerebrospinal fluid (CSF) hypovolemia is supposed to be caused by CSF leakage through small dural defects.

Purpose: To compare source three-dimensional (3D) fast spin-echo (FSE) images of magnetic resonance (MR) myelography with radionuclide cisternography findings, and to evaluate the feasibility of MR myelography in the detection of CSF leakage.

Material and Methods: A total of 67 patients who were clinically suspected of CSF hypovolemia underwent indium-111 radionuclide cisternography, and 27 of those who had direct findings of CSF leakage were selected for evaluation. MR myelography with 3D FSE sequences (TR/TE 6000/203 ms) was performed at the lumbar spine for all patients. We evaluated source images and maximum intensity projection (MIP) images of MR myelography, and the findings were correlated with radionuclide cisternography findings. MR myelography of five healthy volunteers was used as a reference. The MR visibility of the CSF leakage was graded as definite (leakage clearly visible), possible (leakage poorly seen), or absent (not shown).

Results: CSF leakage was identified with source 3D FSE images in 22 (81.5%) of 27 patients. Of the 22 patients, 16 were graded as definite and six were graded as possible. For the definite cases, 3D FSE images clearly showed the extent of the leaked CSF in the paraspinal structures. In the remaining five patients with absent findings, radionuclide cisternography showed only slight radionuclide activity out of the arachnoid space.

Conclusion: Source 3D FSE images of MR myelography seem useful in the detection of CSF leakage. Invasive radionuclide cisternography may be reserved for equivocal cases only.     

3D imaging of the whole spine at 3T compared to 1.5T: initial experiences

Purpose: To describe our first experiences with a recently introduced 3T system for T2-weighted isotropic 3D whole-spine imaging.

Material and Methods: Magnetic resonance imaging of the whole spine was performed by implementing an isotropic 3D fast spin-echo sequence with variable flip-angle refocusing pulses at 3T and 1.5T. Signal-to-noise ratio (SNR) was compared on both systems in eight subjects.

Results: Mean values for SNR were significantly higher at 3T (346±214) for 1.0 mm voxel size compared to 1.5T (202±41), but showed considerably higher variability at 3T. At 3T, measurements with 0.9 mm voxel size were possible with similar SNR as with 1.0 mm voxel size at 1.5T.

Conclusion: High-resolution 3D imaging of the whole spine is feasible at 3T with an increased SNR compared to 1.5T. Signal gain at 3T can be used to further increase spatial resolution. Pronounced interpatient variability of SNR at 3T may be a result of inhomogeneous RF deposition due to dielectric effects.     

Value of apparent diffusion coefficient calculation in the differential diagnosis of parotid gland tumors

Background: The differential diagnosis of parotid gland tumors is often difficult with conventional magnetic resonance imaging.

Purpose: To determine whether the calculation of the apparent diffusion coefficient (ADC) is valuable for making the differential diagnosis of parotid tumors.

Material and Methods: Thirty parotid masses in 28 patients and 24 healthy parotid glands in 12 controls were examined in this prospective study. Diffusion-weighted magnetic resonance imaging with echo-planar spin-echo sequences was used to evaluate each subject. The ADC of each tumor and each healthy parotid gland was calculated. Tumor diagnoses were confirmed by the results of histopathologic analysis.

Results: The following types of masses were identified: 11 Warthin tumors, nine pleomorphic adenomas, seven malignant tumors, one basal cell adenoma, and two benign cysts. The mean ADC value for the Warthin tumors was 0.97±0.16×10^-3 mm²/s, for the pleomorphic adenomas was 1.74±0.37×10^-3 mm²/s, for the malignant tumors was 1.04±0.35×10^-3 mm²/s, and for the normal parotid glands was 0.34±0.20×10^-3 mm²/s. The respective ADC value for the single basal cell adenoma was 1.40×10^-3 mm²/s. Statistically significant differences were identified between the subjects with pleomorphic adenoma and those with another type of parotid tumor, and between subjects with healthy parotid glands and those with a tumor.

Conclusion: Calculating the ADC appears to be useful in differentiating pleomorphic adenomas from other types of parotid gland tumors.     

Comparison study of intraarticular and intravenous gadolinium-enhanced magnetic resonance imaging of cartilage in a canine model

Background: Magnetic resonance (MR) imaging and measurement of glycosaminoglycan (GAG) have potential for characterization of hyaline articular cartilage. Recently, some reports have demonstrated the potential of direct administration of contrast media for MR imaging of cartilage.

Purpose: To prove the feasibility of intraarticular gadolinium-enhanced MR imaging of cartilage (iGEMRIC) and T1 relaxation mapping of the articular cartilage in vivo with intraarticular injection of Gd-DTPA^2-.

Material and Methods: Five healthy beagle dogs underwent MR imaging and T1 relaxation mapping of the knee joints of both hind legs. The delayed gadolinium-enhanced MR imaging of cartilage (dGEMRIC) and iGEMRIC techniques were interchanged with MR imaging. For dGEMRIC, a double routine dose of Gd-DTPA^2- (0.2 mM/kg) was administered intravenously. For iGEMRIC, 2.5 and 1.25 mmol/l saline-diluted Gd-DTPA^2- solutions were separately injected into the right and left knee joints, respectively, prior to MR imaging. Color-coded T1 maps of 20 femoral condyles were obtained from the dGEMRIC and iGEMRIC images. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and glycosaminoglycan (GAG) delineation of articular cartilage were compared between the dGEMRIC and iGEMRIC techniques.

Results: The mean SNR was higher with dGEMRIC than with iGEMRIC, but the difference was not statistically significant (P = 0.174). The mean (±SD) CNR was higher with iGEMRIC (-11.6±3.4) than with dGEMRIC (-16.7±4.0; P = 0.000), although the absolute value of the CNR was higher with dGEMRIC. The layering and gradient distribution of GAG were more clearly visualized on the iGEMRIC images. The mean scores of GAG delineation with dGEMRIC and iGEMRIC were 0.7±0.6 and 2.2±1.7, respectively. The iGEMRIC method better visualized GAG distribution (P = 0.001).

Conclusion: Although the SNR did not differ significantly between the iGEMRIC and dGEMRIC techniques, the color-coded T1 map produced with iGEMRIC allowed better cartilage evaluation. Thus, iGEMRIC exhibits the useful features of both MR arthrography and dGEMRIC, and provides a color-coded T1 map that is useful for diagnosing early articular cartilage damage.     

Hyperperfusion on perfusion computed tomography following revascularization for acute stroke

Purpose: To describe the findings of hyperperfusion on perfusion computed tomography (CT) in four patients following revascularization for acute stroke.

Material and Methods: In 2002-2003, among a series of 6 patients presenting with an acute stroke and treated with intra-arterial thrombolysis, we observed the presence of hyperperfusion in 3 patients on the follow-up CT perfusion. We included an additional patient who was treated with intravenous thrombolysis and who had hyperperfusion on the follow-up CT perfusion. We retrospectively analyzed their CT perfusion maps. Cerebral blood volume (CBV) and cerebral blood flow (CBF) maps were compared between the affected territory and the normal contralateral hemisphere.

Results: In the four patients, the mean CBV and CBF were 3.6±2.0 ml/100 g and 39±25 ml/100 g/min in the affected territory compared to the normal side (mean CBV = 2.7±2.1 ml/100 g, mean CBF = 27±23 ml/100 g/min). There was no intracranial hemorrhage in the hyperperfused territories. At follow-up CT, some hyperperfused brain areas progressed to infarction, while others retained normal white to gray matter differentiation.

Conclusion: CT perfusion can demonstrate hyperperfusion, which can be seen in an ischemic brain territory following recanalization.     

Percutaneous vertebroplasty for patients with osteoporosis: a one-year follow-up

Purpose: To evaluate changes in height and wedge angle of treated vertebral bodies and kyphosis angle 1 year after vertebroplasty.

Material and Methods: We reviewed radiographs of 95 vertebral bodies treated with vertebroplasty in 60 patients with osteoporosis. Only vertebral bodies with imaging evidence of a new fracture or avascular necrosis received vertebroplasty. Images were obtained for evaluation before vertebroplasty (B), within 2 weeks after vertebroplasty (T), and after 1 year (T1).

Results: The mean wedge angle decreased by 5.4° from B to T1. Mean of the anterior, central, and posterior heights of the fractured bodies increased by 12.6%, 9.6%, and 3.1%, respectively, from B to T1. The kyphosis angle improved by 3.2° initially from B to T, but the improvement later disappeared. In 48% of these patients, a new fracture developed after vertebroplasty, and 63% of the fractures were adjacent to a vertebroplasty-treated vertebral body.

Conclusion: The increase in height and wedge angle of the vertebral bodies generally lasted at least 1 year. Improvement in kyphosis angles was lost 1 year after vertebroplasty because new fractures occurred in 48% of these patients. Prevention of new fractures after vertebroplasty remains an important task.     

Magnetic resonance renography findings and their clinical associations in nephropathia epidemica

Purpose: To evaluate, with magnetic resonance renography (MRR), the dynamics of renal function in patients with nephropathia epidemica (NE) and to correlate the findings with the clinical course of NE.

Material and Methods: MRR was performed on 20 hospitalized NE patients during the acute phase of the disease. A repeat MRR study was done 5-8 months later. Primary and repeat MRR studies were compared and functional findings evaluated.

Results: The uptake slope of the contrast enhancement curve was abnormal in the primary study in 14 patients, maximum level of enhancement in 11, decreasing slope of contrast enhancement curve in 14, and signal drop at time in 10 patients when the primary and repeat studies were compared. The greater change in the uptake slope of contrast enhancement, maximum level of enhancement, decreasing slope of enhancement, and signal drop at time between primary and repeat MRR studies evinced a mild association with the severity of clinical renal insufficiency and fluid volume overload.

Conclusion: Measurable functional MRR findings were recorded in 14/20 NE patients. The severity of the findings was mildly associated with the degree of clinical renal insufficiency and fluid volume overload.     

Contrast-enhanced magnetic resonance cholangiography with Gd-BOPTA and Gd-EOB-DTPA in healthy subjects

Purpose: To evaluate the biliary enhancement dynamics of the two gadolinium chelates Gd-BOPTA (MultiHance®) and Gd-EOB-DTPA (Primovist®) in normal healthy subjects.

Material and Methods: Ten healthy volunteers were evaluated with both agents by magnetic resonance (MR) imaging at 1.5T using a breath-hold gradient-echo T1-weighted VIBE sequence. The relative signal intensity (SI) differences between the common hepatic duct (CHD) and liver parenchyma were measured before and 10, 20, 30, 40, 130, 240, and 300 min after contrast medium injection.

Results: Biliary enhancement was obvious 10 min post-injection for Gd-EOB-DTPA and was noted at 20 min for Gd-BOPTA. At 40 min delay, Gd-BOPTA reached its peak biliary enhancement, but at neither 30 nor 40 min delay was there any significant difference compared with that of Gd-EOB-DTPA. At later delays, the contrast between CHD and liver continued to increase for Gd-EOB-DTPA, whereas it decreased for Gd-BOPTA.

Conclusion: The earlier onset and longer duration of a high contrast between CHD and liver for Gd-EOB-DTPA facilitates examination of hepatobiliary excretion. Therefore, Gd-EOB-DTPA may provide adequate hepatobiliary imaging within a shorter time span than Gd-BOPTA and facilitate scheduling at the MR unit. Further studies in patients are required to compare the imaging advantages of Gd-EOB-DTPA and Gd-BOPTA in clinical practice.     

Clinical 1H magnetic resonance spectroscopy of brain metastases at 1.5T and 3T

Purpose: To investigate whether improvements in signal-to-noise ratio (SNR) and spectral resolution are found in spectra from patients with brain metastases obtained at higher magnetic field strengths using standard clinical instrumentation.

Material and Methods: Six patients with brain metastases, 13 healthy volunteers, and a phantom containing brain metabolites were examined using two clinical MR instruments operating at 1.5T (Siemens) and 3T (Philips) with standard clinical head coils. Spectra were obtained using a point resolved spectroscopy pulse sequence, echo times (TE) 32 ms and 144 ms, and repetition time 2000 ms from a volume-of-interest (VOI) of size 15×15×15 mm³. SNR and spectral resolution of the metabolites N-acetylaspartate, choline, and creatine compounds in spectra from 3T were compared to the 1.5T spectra.

Results: In general, spectral resolution was improved by 25-30% at higher magnetic field strength. Only minor improvements in SNR were obtained at 3T using short echo time and 20-50% at long echo time.

Conclusion: SNR and spectral resolution were improved at higher magnetic field strength, especially with TE 144 ms, including spectra from patients with heterogeneous brain tumors. However, differences in the defined effective VOI, particularly at short echo time, reduced the expected effect of increased magnetic field strength on the measured SNR.     

Assessment of 3D-TOF-MRA at 3.0 Tesla in the characterization of the angioarchitecture of cerebral arteriovenous malformations: a preliminary study

Background: The characterization of brain arteriovenous malformation (AVM) angioarchitecture remains rewarding in planning and predicting therapy. The increased signal-to-noise ratio at higher field strength has been found advantageous in vascular brain pathologies.

Purpose: To evaluate whether 3.0T time-of-flight (TOF) magnetic resonance angiography (MRA) is superior to 1.5T TOF-MRA for the characterization of cerebral AVMs.

Material and Methods: Fifteen patients with AVM underwent TOF-MRA at 3.0T and 1.5T and catheter angiography (DSA), which was used as the gold standard. Blinded readers scored image quality on a four-point scale, nidus size, and number of feeding arteries and draining veins.

Results: Image quality of TOF-MRA at 3.0T was superior to 1.5T but still inferior to DSA. Evaluation of nidus size was equally good at 3.0T and 1.5T for all AVMs. In small AVMs, however, there was a tendency of size overestimation at 3.0T. MRA at 3.0T had increased detection rates for feeding arteries (+21%) and superficial (+13%) and deep draining veins (+33%) over 1.5T MRA.

Conclusion: 3.0T TOF-MRA offers superior characterization of AVM angioarchitecture compared with 1.5T TOF-MRA. The image quality of MRA at both 3.0 and 1.5T is still far from equal to DSA, which remains the gold standard for characterization of AVM.     

Split renal function in patients with suspected renal artery stenosis: a comparison between gamma camera renography and two methods of measurement with computed tomography

Purpose: To validate a method for calculating split renal function from computed tomography (CT) compared with gamma camera renography, and to test a new method for the measurement based on a volume-rendering technique.

Material and Methods: Thirty-eight patients, aged 65.7±11.6 (range 37.8-82.1) years, who had undergone both CT angiography and gamma camera renography for a suspected renal artery stenosis were included in this study. Split renal function was calculated from the CT examinations by measuring area and mean attenuation in the image slices of the kidneys, and also by measuring volume and mean attenuation from a 3D reconstruction of the kidneys. Gamma camera renography with ^99mTc-MAG3 with or without captopril enhancement was used as a reference.

Results: The 2D CT method had good correlation with renography (r = 0.93). Mean difference was 4.7±3.6 (0-12) percentage points per kidney. There was also excellent correlation between the two CT methods (r = 1.00).

Conclusion: CT is equivalent to renography in determining split renal function, and the measurement from the CT examination can be made more quickly and equally accurately with a 3D technique.     

F18-FDG coincidence-PET in patients with suspected gynecological malignancy

Purpose: To assess the role of F18-FDG imaging with a dual-head coincidence mode gamma camera (Co-PET) in identifying malignant tumors in patients with a suspicious adnexal mass depicted by conventional imaging methods.

Material and Methods: F18-FDG Co-PET was performed preoperatively in 18 women (mean age 56.38 years) with suspected malignant gynecologic tumors according to clinical and abdomino-pelvic/transvaginal ultrasound or computed tomography findings. Exploratory laparotomy was performed in all patients within the 10 days post-F18-FDG Co-PET study, and the definitive diagnosis of the adnexal masses was established by histopathological examination.

Results: Histopathological examinations of the surgically excised adnexal masses revealed eight malignant, one borderline, and nine benign neoplastic tumors. Four benign tumors had no F18-FDG uptake, while the remaining five tumors, all leiomyomas, showed mild FDG accumulation. Eight malignant tumors showed intense F18-FDG uptake. Sensitivity, specificity, PPV, and NPV of F18-FDG co-PET in differentiating benign from malign adnexal masses were 88%, 44%, 61%, and 80%, respectively. Tumor to background ratios (T/B) in benign lesions (2.04 ± 0.27) were significantly lower than in malignant lesions (7.4 ± 0.99).

Conclusion: F18-FDG Co-PET is of clinical value when assessing suspicious malignant adnexal masses. False-negative F18-FDG results might arise from borderline disease. Moderate F18-FDG uptake in leiomyomas can result false-positive, but T/B ratios may be helpful in such cases.     

Granulomatous mastitis: radiological findings

Purpose: To evaluate the radiological, ultrasonographic, and magnetic resonance imaging (MRI) findings of idiopathic granulomatous mastitis.

Material and Methods: Between April 2002 and June 2005, the mammography, ultrasound, color Doppler ultrasound, nonenhanced MR, and dynamic MR findings of nine patients with the preliminary clinical diagnosis of malignancy and the final diagnosis of granulomatous mastitis were evaluated.

Results: On mammography, asymmetrical focal densities with no distinct margins, ill-defined masses with spiculated contours, and bilateral multiple ill-defined nodules were seen. On ultrasound, in four patients a discrete, heterogenous hypoechoic mass, in two patients multiple abscesses, in one patient bilateral multiple central hypo peripheral hyperechoic lesions, in two patients heterogeneous hypo- and hyperechoic areas together with parenchymal distortion, and in one patient irregular hypoechoic masses with tubular extensions and abscess cavities were seen. Five of the lesions were vascular on color Doppler ultrasound. On MR mammography, the most frequent finding was focal or diffuse asymmetrical signal intensity changes that were hypointense on T1W images and hyperintense on T2W images, without significant mass effect. Nodular lesions were also seen. On dynamic contrast-enhanced mammography, mass-like enhancement, ring-like enhancement, and nodular enhancement were seen. The time-intensity curves differed from patient to patient and from lesion to lesion.

Conclusion: The imaging findings of idiopathic granulomatous mastitis have a wide spectrum, and they are inconclusive for differentiating malignant and benign lesions.     

Preliminary study of hemodynamics in human carotid bifurcation by computational fluid dynamics combined with magnetic resonance angiography

Background: A longstanding hypothesis that correlates fluid dynamic forces and atherosclerotic disease has led to numerous analytical, numerical, and experimental studies over the years because it is very difficult to measure the hemodynamic variables of blood in vivo.

Purpose: To investigate the technique of visualization and quantitation of hemodynamic variables at carotid artery bifurcation in vivo by combining computational fluid dynamics (CFD) and vascular imaging.

Material and Methods: Twenty-six healthy volunteers underwent magnetic resonance (MR) angiography of the bilateral carotid artery by a 3.0T whole-body scanner. Hemodynamic variables at these carotid bifurcations were calculated and visualized by combining vascular imaging post-processing and CFD.

Results: The average velocity of the carotid bifurcation in the systolic phase and the diastolic phase was 0.46±0.24 m/s and 0.23±0.05 m/s, respectively. Eddy current and back flows were observed at bifurcation and the lateral part of the proximal internal carotid arteries (ICA) and external carotid arteries (ECA), and the shapes of them changed with phases of the cardiac cycle, which were significant at the middle of the systolic phase and faded out quickly downstream of the ICA and ECA. The average range of wall shear stress (WSS) at the bifurcation was 4.36±1.32 Pa, and the maximum WSS was 18.02±4.11 Pa. The WSS map revealed a large region of low WSS at the carotid bulb and extended to the outer wall in the proximal end of the ICA (the lowest value was below 0.5 Pa), and there was also a small region of low WSS at the outer wall in the proximal end of the ECA.

Conclusion: CFD combined with vascular imaging can calculate and visualize hemodynamic variables at carotid bifurcation in vivo individually.     

Value of fat-suppressed proton-density-weighted turbo spin-echo sequences in detecting meniscal lesions: comparison with arthroscopy

Purpose: To evaluate fat-suppressed (FS) proton-density-weighted (PDw) turbo spin-echo (TSE) magnetic resonance imaging (MRI) compared to arthroscopy in the detection of meniscal lesions.

Material and Methods: In a prospective study, 31 knee joints were imaged on a 1.5T MR scanner before arthroscopy using the following sequences: (a) coronal and sagittal FS-PDw TSE (TR/TE: 4009/15 ms); (b) coronal T1w SE (TR/TE: 722/20 ms), and sagittal PDw TSE (TR/TE: 3800/15 ms). Other imaging parameters were: slice thickness 3 mm, FOV 160 mm, matrix 256×256. A total of 186 meniscal regions (62 menisci; anterior horn, body, posterior horn) were evaluated. Standard of reference was arthroscopy. Sensitivity, specificity, negative predictive value (npv), positive predictive value (ppv), and accuracy were calculated.

Results: Arthroscopically, meniscal lesions were detected in 55/186 segments (35 medial and 20 lateral meniscal lesions). Sensitivity, specificity, npv, ppv, and accuracy for combination of coronal and sagittal FS PDw TSE were 91.4%, 98.3%, 95%, 97%, and 93.5% for the medial meniscus, and 90%, 98.6%, 97.3%, 94.7%, and 96.8% for the lateral. The results were comparable to the combination of coronal T1w SE and sagittal PDw TSE for the medial (88.6%, 98.3%, 93.4%, 96.9%, 91.4%) and the lateral (90%, 95.9%, 97.2%, 85.7%, 92.5%) meniscus.

Conclusion: FS PDw TSE-MR sequences are an excellent alternative for the detection of meniscal lesions in comparison with diagnostic arthroscopy.     

Assessing wear of the acetabular cup using computed tomography: an ex vivo study

Purpose: To validate a clinically useful method for measuring acetabular cup wear using computed tomography (CT).

Material and Methods: Eight uncemented acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral component head into the cup and the thickness of the remaining polyethylene liner were measured in the CT volumes using dedicated software. Two independent examiners twice assessed each volume. The CT measurements were compared to direct measurements using a coordinate measuring device and micrometer measurements.

Results: Accuracy of wear measurements expressed as penetration depth was ±0.6 and ±1.0 mm for the two examiners, respectively, with no significant differences between examiners, trials, and CT scans. Accuracy of measurements of remaining polyethylene was ±1.3 and ±1.0 mm, respectively, for the two examiners. Systematic differences between examiners were found, but no significant differences between trials and CT scans. These differences were due to different interpretations of metal artifacts in the volumes.

Conclusion: The proposed CT method for evaluating wear as head penetration depth allows for reliable wear detection at a clinically relevant level. Measurements of remaining polyethylene on CT volumes are not as reliable as wear measurements owing to metal artifacts.