The 3D-based scaling index algorithm: a new structure measure to analyze trabecular bone architecture in high-resolution MR images in vivo

INTRODUCTION

The purpose of this study was to obtain different structure measures as the three-dimensional (3D)-based scaling index method (SIM) and standard two-dimensional (2D) bone histomorphometric parameters from high-resolution (HR) magnetic resonance (MR) images of the distal radius and to compare these parameters with bone mineral density (BMD) in their diagnostic performance to differentiate postmenopausal patients with and without vertebral fractures.

METHODS

Axial HR-MR images of the distal radius were obtained at 1.5 T in 40 postmenopausal women (17 with osteoporotic spine fractures and 23 controls). Trabecular microarchitecture analysis was performed using the new structure measure mP(alpha), derived from the SIM, as well as standard morphological 2D parameters. BMD of the spine was obtained using quantitative computed tomography (QCT). Receiver operating characteristic (ROC) analyses were used to determine diagnostic performance in differentiating both groups. Results were validated by bootstrapping techniques.

RESULTS

Significant differences between both patient groups were obtained using mP(alpha), 2D parameters, and spine BMD (p<0.05). In comparison with the 2D texture parameters [area under the curve (AUC) up to 0.67], diagnostic performance was significantly higher for mP(alpha)(AUC=0.85; p<0.05). There was a trend for a higher AUC value for mP(alpha) compared with BMD of the spine (AUC=0.71; p=0.81).

CONCLUSION

mP(alpha) yielded a robust measure of trabecular bone microarchitecture for HR-MR images of the radius, which significantly improved the diagnostic performance in differentiating postmenopausal women with and without osteoporotic spine fractures compared with standard 2D bone histomorphometric parameters. This 3D characterization of trabecular microarchitecture may provide a new approach to better assess the strength of human cancellous bone using HR-MR image data.

Rotator cuff tears: assessment with MR arthrography in 275 patients with arthroscopic correlation

We assessed the diagnostic performance of magnetic resonance (MR) arthrography in the diagnosis of articular-sided partial-thickness and full-thickness rotator cuff tears in a large symptomatic population. MR arthrograms obtained in 275 patients including a study group of 139 patients with rotator cuff tears proved by arthroscopy and a control group of 136 patients with arthroscopically intact rotator cuff tendons were reviewed in random order. MR imaging was performed on a 1.0 T system (Magnetom Expert, Siemens). MR arthrograms were analyzed by two radiologists in consensus for articular-sided partial-thickness and full-thickness tears of the supraspinatus, infraspinatus, and subscapularis tendons. At arthroscopy, 197 rotator cuff tears were diagnosed, including 105 partial-thickness (93 supraspinatus, nine infraspinatus, three subscapularis) and 92 full-thickness (43 supraspinatus, 20 infraspinatus, 29 subscapularis) tendon tears. For full-thickness tears, sensitivity, specificity, and accuracy were 96%, 99%, and 98%, respectively, and for partial tears 80%, 97%, and 95%, respectively. False negative and positive assessments in the diagnosis of articular-sided partial-thickness tears were predominantly [78% (35/45)] observed with small articular-sided (Ellman grade1) tendon tears. MR arthrography is highly accurate in the diagnosis of full-thickness rotator cuff tears and is accurate in the diagnosis of articular-sided partial-thickness tears. Limitations in the diagnosis of partial-thickness tears are mainly restricted to small articular-sided tears (Ellman grade 1) due to difficulties in differentiation between fiber tearing, tendinitis, synovitic changes, and superficial fraying at tendon margins.

[Magnetic resonance imaging of glenohumeral instability]

Conventional MR imaging and MR arthrography are established diagnostic imaging modalities for investigating shoulder instability. Since there are currently various surgical shoulder stabilization methods as well as conservative treatment strategies, the role of imaging is to provide diagnostic information to help determine the therapeutic approach. Whereas conventional MR imaging is usually sufficient for the evaluation of acute shoulder injuries due to the presence of a posttraumatic joint effusion, MR arthrography is the imaging modality of choice for chronic shoulder instability. Atraumatic and microtraumatic instability of the shoulder must be distinguished from traumatic instability since clinical findings and secondary or associated injuries differ from those of traumatic instability. Injuries of the IGHL-complex can be reliably diagnosed with MR arthrography. Traumatic anteroinferior luxation causes labroligamentous injuries at the glenoid insertion (Bankart-, Perthes-, ALPSA-, and non-classifiable chronic lesions) and injuries of the IGHL and its humeral insertion (HAGL-, BHAGL-, and floating AIGL-lesions). The type of injury and extent of degenerative changes or scarring that can be assessed with MR arthrography influence the therapeutic approach and in particular the decision between arthroscopic and open surgical methods of stabilization.

[Fracture diagnosis in osteoporosis]

As life expectancy rises the prevalence of osteoporosis also increases, which represents a growing burden for the populace and the healthcare system. Vertebral fractures are the most frequent type of all osteoporotic fractures. Since they can be diagnosed by radiology, these examinations are particularly important for devising suitable treatment strategies. The goal of activities undertaken by osteoporosis organizations is to put across to radiologists the importance of accurate evaluation of these fractures. Identification of osteoporotic vertebral fractures is however problematic since the transition from healthy vertebral bodies to those deformed by osteoporosis constitutes a continuum and it is often difficult in deformed vertebral bodies to distinguish between an osteoporotic fracture and a non-osteoporotic deformity. This overview attempts to heighten awareness of the significant role the radiologist plays in the diagnostic work-up of osteoporosis and to provide diagnostic aids for assessing osteoporotic vertebral fractures including differential diagnoses.

Assessment of the extent of metastases of gastrointestinal carcinoid tumors using whole-body PET, CT, MRI, PET/CT and PET/MRI

OBJECTIVE

To assess the diagnostic value of whole-body positron emission tomography (PET), computed tomography (CT), magnetic resonance imaging (MRI), and the fusion of PET and CT (PET/CT) and PET and MRI (PET/MRI) in the detection of metastatic disease of gastrointestinal carcinoid tumors.

MATERIALS AND METHODS

This prospective study included six patients with extensive nonresectable metastases of gastrointestinal carcinoid tumors which were consecutively examined from the base of the skull to the proximal thigh using a state-of-the-art PET/CT scanner and a 1.5 Tesla whole-body MRI scanner. PET was performed with a carbohydrated F-18-labeled somatostatin-receptor ligand ([ superset18 F]FP-Gluc-TOCA) using a Pico-3D PET scanner. CT was performed with a venous-dominant contrast-enhanced phase using a 16-slice CT scanner. MRI was performed with a coronal T2-weighted Half-Fourier Acquired Single-Shot Turbo Spin Echo (HASTE) sequence, a coronal T2-weighted Turbo-Short Tau Inversion-Recovery (STIR) sequence, a coronal T1-weighted Turbo Spin Echo (TSE) sequence and a high resolution axial T2-weighted TSE sequence. The data sets from PET and CT were fused automatically. The PET and MRI data sets were fused manually. Lesions were rated as metastases if they were not clearly identified as benign lesions according to standard radiological criteria.

RESULTS

For PET, CT, MRI, PET/CT, and PET/MRI, the lesion-by-lesion based analysis showed an overall detection rate for liver metastases (n = 391) of 49.9% (P<.001), 37.1% (P<.001), 98.2%, 50.9% (P<.001) and 100%, for lymph node metastases (n = 37) of 91.9%, 83.8%, 64.9%, 100% and 97.3% and for osseous metastases (n = 12) of 100%, 8.3% (P<.005), 66.7%, 100% and 100%.

CONCLUSIONS

PET as single modality revealed the most lymph node and osseous metastases. MRI as single modality revealed the most liver metastases. The combination of molecular/metabolic with anatomical/ morphological information improves the diagnostic accuracy for the detection of metastases in comparison to the single modalities. Whole-body PET/MRI is a very promising diagnostic modality for oncological imaging due to the missing radiation exposure and the high soft tissue resolution of MRI in contrast to CT.

Detection of osteoporotic vertebral fractures using multidetector CT

INTRODUCTION

Goals were to compare the performance of lateral radiographs and sagittal reformations (SR) of axial computed tomography (CT) datasets in identification of osteoporotic vertebral fractures and to assess for optimal slice thickness in axial CT datasets needed for reliable classification of these fractures.

METHODS

Sixty-five vertebrae were harvested from 21 human cadaver spines and examined with a 64-row multidetector CT scanner. Axial images were acquired with a slice thickness of 0.6, 1, 2, 3 and 5 mm and SR were obtained using these datasets. In addition, specimens were radiographed in antero-posterior and lateral orientation. Vertebrae visualized in the different image datasets were separately graded by four radiologists according to the spinal fracture index (SFI) classification. Fracture status determined in a consensus reading of interactive reformations of the 0.6-mm CT dataset in all three dimensions served as a standard of reference in combination with pathological examinations.

RESULTS

The average agreement for the 0.6-mm SR obtained between each radiologist and standard of reference for the grading of the fractures was very good (kappa=0.81). It was good for the 1-, 2- and 3-mm SR (kappa=0.70, 0.69 and 0.64), but only moderate for the radiographs (kappa=0.52), and fair for the 5-mm SR (kappa=0.33). When focusing only on detection of fractures, independent of the grading, all kappa values improved by about 0.15, resulting in excellent values for the 0.6-mm through 3-mm SR (0.95<kappa<0.79) and good values for the radiographs (kappa=0.72). Ninety-five percent of the fractures could be identified using the 1-mm SR, but 18% of the fractures were missed on the radiographs.

CONCLUSIONS

Sagittal CT reformations could more accurately assess vertebral fractures than standard radiographs. But for reliable detection of these fractures, SR derived from axial images with a slice thickness of 3 mm or less are required. The thinnest available axial slice thickness performed best in fracture grading.

Suspected and incidental pulmonary embolism on multidetector-row CT: Analysis of technical and morphological factors influencing the diagnosis in a cross-sectional cancer centre patient cohort

AIM

To assess technical and computed tomography (CT) predictors of true-positive (TP) and false-negative (FN) radiological diagnoses in a retrospective patient cohort with pulmonary embolism (PE) in the setting of a cancer centre.

MATERIALS AND METHODS

Two thousand, four hundred and twelve consecutive chest multidetector-row CT images from 1869 patients were reviewed for presence of PE. CT protocols and TP and FN radiological reports were determined and the clinical files reviewed for suspicion of PE. The severity of PE was assessed by an arterial obstruction index. Ancillary pulmonary findings were scored qualitatively and on a lobar basis. Statistical tests included analysis of variance and univariate and multivariate logistic regressions.

RESULTS

Ninety-one out of a total of 111 PE-positive images were included. Thirty-five patients had clinically suspected PE; 56 were not suspected of having PE. Forty-eight patients had TP diagnoses; 43 (39 of whom were not suspected of having PE) had FN radiological diagnoses. FN diagnoses were most frequent in oesophageal (17/19; 89.5%) and standard chest CT (19/35; 54.3%). Pulmonary CT angiography was associated with TP diagnosis (p<0.0001), whereas oesophageal CT was associated with FN diagnosis (p=0.001). Artefacts and arterial attenuation did not influence PE detection (p=0.017 and 0.066 for artefacts and arterial attenuation, respectively). However, the arterial obstruction index strongly predicted PE diagnosis (p=0.001). This was confirmed on multivariate analysis (p=0.041, 0.027 and 0.020 for pulmonary CT angiography, oesophageal protocols and arterial obstruction index, respectively). When stratified for clinically unsuspected cases, the arterial obstruction index remained the only predictor of PE diagnosis (p=0.009).

CONCLUSION

Predictors of PE diagnosis were PE severity and technical factors; the latter were linked to clinical suspicion of PE. Arterial enhancement appears unlikely to contribute to missed diagnoses, if judged adequate for diagnosis of PE, and ancillary chest findings are unlikely to improve embolus detection.

[Modern imaging for liver metastases from colorectal tumors]

Cross-sectional imaging modalities such as ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and Positron emission tomography (PET)/CT have benefited from rapid technical advances in recent years. In patients with colorectal tumors, multislice CT is the standard technique for preoperative evaluation and follow-up. It is faster than single-slice helical CT and allows for excellent 3D imaging of liver anatomy and tumor volumetry. The most accurate technique for detecting and characterizing focal liver lesions is MRI using state-of-the-art scanners and liver-specific contrast agents and should be used for preoperative evaluation of all possible surgical candidates. Whole-body FDG-PET and PET/CT are most useful in the detection of extrahepatic disease and may alter clinical management in up to 20% of patients by detecting extrahepatic spread of disease.

Case report: Fatal acute exacerbation of usual interstitial pneumonia in ulcerative colitis

Pulmonary involvement in ulcerative colitis may manifest as a variety of disorders. Ulcerative colitis-related interstitial lung disease is exceedingly rare and has been reported to be steroid-responsive. We describe the first case of a patient with acute exacerbation of ulcerative colitis-induced usual interstitial pneumonia, who did not respond to corticosteroid therapy and died 12 weeks after the onset of pulmonary symptoms. Early recognition of pulmonary disease in patients with ulcerative colitis is necessary to initiate further diagnostic work-up and may aid treatment decisions.

[Computer-aided diagnosis and volumetry of pulmonary nodules: current concepts and future perspectives]

For computer-aided detection (CAD) and volumetry of small pulmonary nodules, a number of algorithms have been developed for multislice CT data sets in recent years, with the goal of improving the diagnostic work-up and the follow-up of findings. Recent data show that the detection of small lesions may improve with CAD, suggesting that especially experienced readers may benefit from using CAD systems. This has lead to the recommendation of CAD as a replacement of the second reader in clinical practice. Furthermore, computer-aided volumetry of pulmonary nodules allows a precise determination of nodular growth rates as a prerequisite for a better classification of nodules as benign or malignant. In this article, we review recent developments of CAD and volumetry tools for pulmonary nodules, and address open questions regarding the use of these software tools in clinical routine.

Detection of hepatocellular carcinoma: comparison of Gd-DTPA- and ferumoxides-enhanced MR imaging

The aim was to compare the diagnostic performance of dynamic Gd-DTPA- and ferumoxides-enhanced MRI for hepatocellular carcinoma (HCC). Twenty-five patients with chronic hepatitis or liver cirrhosis underwent both dynamic gadopentetate- and ferumoxides-enhanced MRI studies of the liver for HCC detection on the same day. MR data of both studies were retrospectively and independently analyzed. Two observers determined in consensus the grade of diffuse fibrotic liver changes (mild, moderate or severe) and the number of focal lesions. HCCs were confirmed by histology (n=22) and/or follow-up studies for at least six months (n=64). Differences in results obtained from both MR data sets were tested for significance with the McNemar's test (p<0.05). Ferumoxides-enhanced MR images detected 84 of 99 hepatic lesions, including 82 of 86 HCCs and 2 false positive, nonmalignant lesions, while Gd-DTPA-enhanced MR images detected 92 of 99 hepatic lesions, including 81 of 86 HCCs and 11 false positive, nonmalignant lesions. Sensitivity of MRI for detection of HCCs was not significantly different between ferumoxides-enhanced (95.3%; p>0.05) and Gd-DTPA-enhanced scans (94.2%). Gd-DTPA- and ferumoxides-enhanced MRI perform equally well for HCC detection. The majority of small hypervascular hepatic lesions, detected on dynamic Gd-DTPA-enhanced MRI but not on ferumoxides-enhanced MRI, represent no HCCs.

Computer-aided detection of pulmonary nodules: influence of nodule characteristics on detection performance

AIM

To evaluate prospectively the influence of pulmonary nodule characteristics on detection performances of a computer-aided diagnosis (CAD) tool and experienced chest radiologists using multislice CT (MSCT).

MATERIALS AND METHODS

MSCT scans of 20 consecutive patients were evaluated by a CAD system and two independent chest radiologists for presence of pulmonary nodules. Nodule size, position, margin, matrix characteristics, vascular and pleural attachments and reader confidence were recorded and data compared with an independent standard of reference. Statistical analysis for predictors influencing nodule detection or reader performance included chi-squared, retrograde stepwise conditional logistic regression with odds ratios and nodule detection proportion estimates (DPE), and ROC analysis.

RESULTS

For 135 nodules, detection rates for CAD and readers were 76.3, 52.6 and 52.6%, respectively; false-positive rates were 0.55, 0.25 and 0.15 per examination, respectively. In consensus with CAD the reader detection rate increased to 93.3%, and the false-positive rate dropped to 0.1/scan. DPEs for nodules < or = 5 mm were significantly higher for ICAD than for the readers (p < 0.05). Absence of vascular attachment was the only significant predictor of nodule detection by CAD (p = 0.0006-0.008). There were no predictors of nodule detection for reader consensus with CAD. In contrast, vascular attachment predicted nodule detection by the readers (p = 0.0001-0.003). Reader sensitivity was higher for nodules with vascular attachment than for unattached nodules (sensitivities 0.768 and 0.369; 95% confidence intervals = 0.651-0.861 and 0.253-0.498, respectively).

CONCLUSION

CAD increases nodule detection rates, decreases false-positive rates and compensates for deficient reader performance in detection of smallest lesions and of nodules without vascular attachment.

Comparison of multislice CT arthrography and MR arthrography for the detection of articular cartilage lesions of the elbow

The objective of this study was to compare the value of multislice CT arthrography and MR arthrography in the assessment of cartilage lesions of the elbow joint. Twenty-six cadaveric elbow specimens were examined with the use of CT arthrography and MR arthrography prior to joint exploration and macroscopic inspection of articular cartilage. Findings at CT and MR arthrography were compared with macroscopic assessments in 104 cartilage areas. At macroscopic inspection, 45 cartilage lesions (six grade 2 lesions, 25 grade 3 lesions, 14 grade 4 lesions) and 59 areas of normal articular cartilage were observed. With macroscopic assessment as the gold standard CT and MR arthrography showed an overall sensitivity/specificity of 80/93% and 78/95% for the detection of cartilage lesions, respectively. Only two of six grade 2 lesions were detected by CT and MR arthrography. For the diagnosis of grade 3 and 4 lesions, the sensitivity/specificity was 87/94% with CT arthrography, and 85/95% with MR arthrography. In an experimental setting multislice CT arthrography and MR arthrography showed a similar performance in the detection of cartilage lesions. Both methods indicated limited value in the diagnosis of grade 2 articular cartilage lesions.

Electrocardiographic assistance in multidetector CT of thoracic disorders

ECG-synchronized multislice spiral CT (MSCT) allows a significant reduction of cardiac motion artefacts and as a result a virtually artefact-free display of intrathoracic structures. With their advantages in imaging geometry and continuous spiral image acquisition multislice CT scanners provide superior image quality and spatial resolution in these patients. Possible clinical applications for ECG assistance in MSCT include CT angiography of the coronary arteries, functional cardiac CT imaging and imaging of the cardiac valves, CT angiography of the aorta or pulmonary vascular tree as well as ECG-gated imaging of the lung parenchyma. Prospective ECG triggering and retrospectively ECG-gated image reconstruction comprise the technical corsage for reduction of pulsation artefacts in cardiac and other thoracic CT applications. In addition the development of time-optimised reconstruction algorithms for retrospective cardiac gating in 8- and 16 slice spiral CT scanners have enabled further improvements in temporal resolution. This overview describes the technique, its clinical indications and the merits of electrocardiographic assistance in MSCT of chest disorders.