High‐resolution peripheral quantitative computed tomography can assess microstructural and mechanical properties of human distal tibial bone

High‐resolution peripheral quantitative computed tomography (HR‐pQCT) is a newly developed in vivo clinical imaging modality. It can assess the 3D microstructure of cortical and trabecular bone at the distal radius and tibia and is suitable as an input for microstructural finite element (µFE) analysis to evaluate bone's mechanical competence. In order for microstructural and image‐based µFE analyses to become standard clinical tools, validation with a current gold standard, namely, high‐resolution micro‐computed tomography (µCT), is required. Microstructural measurements of 19 human cadaveric distal tibiae were performed for the registered HR‐pQCT and µCT images, respectively. Next, whole bone stiffness, trabecular bone stiffness, and elastic moduli of cubic subvolumes of trabecular bone in both HR‐pQCT and µCT images were determined by µFE analysis. The standard HR‐pQCT patient protocol measurements, derived bone volume fraction (BV/TV^d), trabecular number (Tb.N*), trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), and cortical thickness (Ct.Th), as well as the voxel‐based direct measurements, BV/TV, Tb.N*, Tb.Th*, Tb.Sp*, Ct.Th, bone surface‐to‐volume ratio (BS/BV), structure model index (SMI), and connectivity density (Conn.D), correlated well with their respective gold standards, and both contributed to µFE‐predicted mechanical properties in either single or multiple linear regressions. The mechanical measurements, although overestimated by HR‐pQCT, correlated highly with their gold standards. Moreover, elastic moduli of cubic subvolumes of trabecular bone predicted whole bone or trabecular bone stiffness in distal tibia. We conclude that microstructural measurements and mechanical parameters of distal tibia can be efficiently derived from HR‐pQCT images and provide additional information regarding bone fragility. © 2010 American Society for Bone and Mineral Research     

Is there a role for magnetic resonance imaging in renal trauma?

BACKGROUND: Computed tomography (CT) has been the most informative imaging method in renal trauma. Despite the good sensitivity of magnetic resonance imaging (MRI) to the presence of hematoma, edema and ischemia, MRI has not been widely studied in patients with renal trauma. The present study was initiated to evaluate the role of MRI in patients with renal trauma. METHODS: Between June 1998 and September 1999, CT and MRI were prospectively performed on 12 patients who suffered from renal trauma and the results reviewed. RESULTS: The presence and size of perirenal hematoma could be detected by both CT and MRI. Magnetic resonance imaging could differentiate intrarenal hematoma from perirenal hematoma more accurately, and provided additional information about the hematoma as T1- and T2-weighted MRI were able to determine recent bleeding in the hematoma by regional differences in signal intensity. Magnetic resonance imaging clearly revealed renal fracture with non-viable fragment and detected focal renal laceration that was not detected on CT due to perirenal hematoma associated with renal infarction. However, although MRI had many advantages over CT, it had also major drawbacks, which were that it required longer imaging time and increased the cost. CONCLUSIONS: Magnetic resonance imaging may be useful in renal trauma. However, it is suggested that MRI should be limited to carefully selected patients, such as those with severe renal injury or equivocal findings on CT.     

Emerging role of high‐resolution imaging in the detection of renal osteodystrophy

The term renal osteodystrophy refers to changes in bone morphology induced by chronic kidney disease (CKD) and represents the skeletal component of the entity ‘chronic kidney disease – mineral and bone disorder’. Changes in turnover, mineralization, mass and microarchitecture impair bone quality, compromising strength and increasing susceptibility to fractures. Fractures are more common in CKD compared with the general population and result in increased morbidity and mortality. Screening for fracture risk and management of renal osteodystrophy are hindered by the complex, and still only partially understood, pathophysiology and the inadequacy of currently available diagnostic methods. Bone densitometry and bone turnover markers, although potentially helpful, have significant limitations in patients with CKD, and the ‘gold standard’ test of bone biopsy is infrequently performed in routine clinical practice. However, recent advances in high‐resolution bone microarchitecture imaging may offer greater potential for quantification and assessment of bone structure and strength and, when used in conjunction with serum biomarkers, may allow non‐invasive testing for a diagnostic virtual bone biopsy.     

Contrast enhanced computed tomography and magnetic resonance imaging in the diagnosis of recurrent disc herniation

Summary A positive result of re-operation in patients with recurrent symptoms after lumbar disc surgery is likely only if a new disc herniation is present. An improved ability to differentiate between recurrent disc herniation and scar tissue by contrast enhanced CT and MRI is suggested in earlier studies.In a prospective study 29 patients were selected for operation for suspected recurrent disc herniation. The inclusion of the patients was based on clinical symptoms and signs and myelography or non-enhanced CT. All patients were examined by CT and MRI both with and without intravenous contrast pre-operatively. The examinations were evaluated blind on a five point scale and statistical analysed by a regret function.Intravenous contrast improved the diagnostic power of both CT and MRI. MRI was superior to CT in both non-enhanced and enhanced examinations. MRI with intravenous contrast enhancement is proposed as the primary examination in patients with suspected recurrent disc herniation.     

骨质疏松症骨髓脂肪的影像学研究进展

骨质疏松症(osteoporosis,OP)是一种以骨强度降低、易导致脆性骨折为特征的全身代谢性疾病.骨髓脂肪细胞是影响OP发生、发展的重要因素.早期监测骨髓脂肪含量的变化有助于OP的临床诊断和治疗.已有较多影像学方法用于OP骨髓脂肪的评估,包括双能定量CT、显微CT、水脂分离技术以及磁共振波谱,本文就这些影像学方法对...     

Accuracy of ultrasonography and magnetic resonance imaging in the diagnosis of non-palpable testis

BACKGROUND: Studies were needed to evaluate the accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) for diagnosing non-palpable testis, and to study the clinical usefulness of US and MRI before surgical exploration. METHODS: Fifty-six patients with non-palpable testis aged 1--12 years were examined between 1993 and 2002. Forty-six patients (55 non-palpable testes) underwent US. Forty patients (47 non-palpable testes) were examined using MRI. Both US and MRI were used in 29 patients (34 non-palpable testes). We used Fisher's exact probability test to compare the results of these graphic examinations with the surgical or laparoscopic findings for the non-palpable testis. RESULTS: Ultrasonography had a sensitivity of 76%, a specificity of 100%, and an accuracy of 84% in the diagnosis of non-palpable testis, whereas MRI had a sensitivity of 86%, a specificity of 79%, and an accuracy of 85%. CONCLUSIONS: There were no statistically significant differences in the accuracy rates of US and MRI for diagnosing non-palpable testis. Laparoscopy or inguinal exploration should be performed even if these graphic examinations demonstrate the absence of a testis, because some patients with a non-palpable testis were found to be false negatives. We recommend US as the first step after clinical examination, and MRI could be performed when the US findings are negative preoperatively for a non-palpable testis.     

Functional dependence of cancellous bone shear properties on trabecular microstructure evaluated using time‐lapsed micro‐computed tomographic imaging and torsion testing

When compressed axially, cancellous bone often fails at an oblique angle along well‐defined bands, highlighting the importance of cancellous bone shear properties. Torsion testing to determine shear properties of cancellous bone has often been conducted under conditions appropriate only for axisymmetric specimens comprised of homogeneous and isotropic materials. However, most cancellous bone specimens do not meet these stringent test conditions. Therefore, we studied the application of the stepwise torsion testing system in biologic specimens with viscoelastic behavior. We explore the functional dependence of cancellous bone shear properties on trabecular microstructure and its spatial distribution, specifically the contribution of the subregion with the minimum polar moment of inertia to the overall failure properties. Torsional properties of whale trabecular specimens obtained by the incremental application of stepwise torque were not different from those obtained via continuous testing. Average polar moment of inertia accounted for 82 and 67% of the variation in shear modulus and shear stress, respectively. However, torsional properties were better predicted by the subregion with minimum polar moment of inertia, describing 87 and 74% of the variation in shear modulus and shear stress. The use of a novel torsion testing system for nonhomogeneous, orthotropic cancellous bone using stepwise application of torsion and simultaneous micro‐computed tomographic imaging was further studied. Most importantly, a heterogeneous cancellous bone microstructural environment, the subregion with the minimum polar moment of inertia, hence the weakest spatial distribution of bone, predicted the shear properties for the entire bone volume. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1667–1674, 2009     

Can magnetic resonance imaging–derived bone models be used for accurate motion measurement with single‐plane three‐dimensional shape registration?

The purpose of this study was to compare three-dimensional (3D) kinematic measurements from single-plane radiographic projections using bone models created from magnetic resonance imaging (MRI) and computed tomography (CT). MRI is attractive because there is no ionizing radiation, but geometric field distortion and poor bone contrast degrade model fidelity compared to CT. We created knee bone models of three healthy volunteers from both MRI and CT and performed three quantitative comparisons. First, differences between MRI- and CT-derived bone model surfaces were measured. Second, shape matching motion measurements were done with bone models for X-ray image sequences of a squat activity. Third, synthetic X-ray images in known poses were created and shape matching was again performed. Differences in kinematic results were quantified in terms of root mean square (RMS) error. Mean differences between CT and MRI model surfaces for the femur and tibia were -0.08 mm and -0.14 mm, respectively. There were significant differences in three of six kinematic parameters comparing matching results from MRI-derived bone models and CT-derived bone models. RMS errors for tibiofemoral poses averaged 0.74 mm for sagittal translations, 2.0 mm for mediolateral translations, and 1.4 degrees for all rotations with MRI models. Average RMS errors were 0.53 mm for sagittal translations, 1.6 mm for mediolateral translations, and 0.54 degrees for all rotations with the CT models. Single-plane X-ray imaging with model-based shape matching provides kinematic measurements with sufficient accuracy to assess knee motions using either MRI- or CT-derived bone models. However, extra care should be taken when using MRI-derived bone models because model inaccuracies will affect the quality of the shape matching results.     

自身免疫性胰腺炎的CT和MRI的影像学表现

目的探讨自身免疫性胰腺炎CT和MRI的影像学特点,提高对自身免疫性胰腺炎的认识和影像学诊断水平。方法回顾性分析45例经激素治疗或手术病理证实的自身免疫性胰腺炎患者的CT和MRI影像学资料,观察胰腺及周围组织、胰管和胆管的影像学表现,总结自身免疫性胰腺炎CT和MRI的影像学特点。结果 45例自身免疫性胰腺炎患者中,男性32例,女性13例,其中37例患者表现为胰腺的弥漫性肿大,8例患者表现为胰腺局限性肿大,CT检查中有27例患者的胰腺病灶平扫密度减低;MRI检查中有16例患者胰腺病灶出现信号的改变,表现为T1WI上低信号,T2WI上稍高信号;45例患者胰腺病灶均表现为延迟强化方式改变。10例患者的CT和7例患者的MRI表现为胰管狭窄,2例患者的CT和1例的患者MRI表现为胆总管狭窄。14例患者的CT及MRI表现胰腺周围的"假包膜"征象。结论自身免疫性胰腺炎在CT和MRI上具有一定的影像学特点,结合实验室相关检查有助于该疾病的诊断。     

A prospective comparison between multidetector-row computed tomography and magnetic resonance imaging in the preoperative evaluation of rectal carcinoma

BACKGROUND: Multidetector-row computed tomography (MDCT, or multislice CT) is a new modality with four detectors, which makes examination time shorter and produces higher resolution and multiplanar reformation of the images. Its diagnostic role in patients with rectal carcinoma has not been determined. METHODS: Twenty-one patients with rectal carcinoma were preoperatively examined by both MDCT and magnetic resonance imaging (MRI). Diagnostic accuracies of both modalities were compared regarding depth of tumor invasion and lymph node metastasis based on the pathologic findings. RESULTS: Both examinations detected all tumors. Regarding depth of tumor invasion, the concordance was 95.2% (20 of 21) for MDCT and 100% (21 of 21) for MRI. Regarding lymph node metastasis, the overall accuracy was 61.9% for MDCT and 70.0% for MRI. CONCLUSIONS: Multidetector-row computed tomography was equal to MRI in the preoperative local staging of rectal carcinoma.     

Accuracy of multiparametric magnetic resonance imaging in detecting recurrent prostate cancer after radiotherapy

OBJECTIVE

To assess the role of multiparametric magnetic resonance imaging (mp‐MRI) of the prostate in evaluating local recurrence of prostate cancer, using transperineal template‐guided 5 mm‐spaced biopsies as a reference standard, in men treated with external beam radiotherapy (EBRT) for prostate cancer.

PATIENTS AND METHODS

The study included 13 patients with evidence of biochemical recurrence after EBRT who had undergone mp‐MRI and prostate mapping. Each MRI scan (consisting of T1/T2 weighting, dynamic contrast enhancement and diffusion weighting) was reported by two expert uro‐radiologists. Each prostate was divided into four regions of interest (ROI), generating 52 paired datasets for analysis.

RESULTS

The mean (range) age of the men was 65.5 (55–70) years, the mean prostate‐specific antigen (PSA) level before EBRT was 36.6 (4.5–150) ng/mL, the mean time from EBRT to biochemical recurrence was 5.7 (3–10) years and the mean PSA level at the time of recurrence was 7.1 (0.83–27.9) ng/mL. Eleven men had histological evidence of recurrence, with 23 of 52 ROIs involved with cancer. Overall accuracy, as expressed by the area under a receiver‐operator curve, was 0.77 and 0.89 for all cancer, with accuracies of 0.86 and 0.93 for those cancers with ≥3 mm biopsy core length. Inter‐observer variability was measured by calculating κ coefficients, which showed fair and moderate agreement between radiologists.

CONCLUSIONS

Interpretation of mpMRI of the prostate after previous EBRT is challenging. Our results show that the accuracy is good using an accurate reference standard. These results need verification in more patients, but have implications for determining presence or absence of local recurrence and subsequent local salvage therapy.     

Assessment of trabecular bone structure comparing magnetic resonance imaging at 3 Tesla with high-resolution peripheral quantitative computed tomography ex vivo and in vivo

Summary In vivo high-resolution peripheral quantitative micro-CT (HR-pQCT) is a new modality for imaging peripheral sites like the distal tibia and the distal radius, providing structural bone parameters. Comparing HR-pQCT with MRI, we found that both modalities are capable of offering meaningful information on trabecular structure. Background Magnetic resonance imaging (MRI) has emerged as the leading in vivo method for measuring trabecular bone micro-architecture and providing structural information. Recently, an in vivo HR-pQCT modality was introduced for imaging peripheral sites like the distal tibia and the distal radius, providing structural bone parameters. The goal of this work was to compare and evaluate the performances and in vivo capabilities of HR-pQCT in comparison with MRI at 3 Tesla. Methods To this end images of 8 human specimens (5 tibiae and 3 radii) and 11 participants (6 tibia and 5 radii) were acquired with both modalities. Additionally, the radius specimens were scanned with micro-CT (μCT), which was used as a standard of reference. Structural parameters calculated from MRI were compared with results from HR-pQCT images and additionally μCT for the radii specimens. Results High correlations (r > 0.7) were found for trabecular number and trabecular spacing between the two modalities in vivo and ex vivo. 2D and 3D analysis revealed high correlations (r > 0.8) in structural bone parameters for all measurements. Using micro-CT as standard of reference both results from QCT and MRI correlated well. Conclusion Both imaging modalities were found to perform equally well regarding trabecular bone measurements.