Clinical prediction rules in trauma imaging: who, how, and why?

Clinical prediction rules are multifactorial tools used to aid in clinical decision making. In radiology, clinical prediction rules are an important method for determining who should undergo imaging and, in combination with cost-effectiveness analysis, how imaging should be performed. To be useful, clinical prediction rules should be clinically important, have face validity, be reproducible and easy to use, be clinically relevant, and suggest a course of action. To insure generalizability, clinical prediction rules should also be validated in subjects distinct from those used to develop the rule. In this review, several examples from trauma imaging are used to demonstrate the development, validation, and use of clinical prediction rules.     

Peak contrast enhancement in CT and MR angiography: when does it occur and why? Pharmacokinetic study in a porcine model

PURPOSE: To investigate pharmacokinetic and physiologic factors that determine the time to peak intravenous contrast medium enhancement in computed tomographic (CT) and magnetic resonance (MR) angiography in the porcine mid-abdominal aorta. MATERIALS AND METHODS: Four pigs were imaged repeatedly in seven to eight sets: For each set, 20 dynamic CT scans were obtained at a fixed aortic level after intravenous injection of contrast medium. From a physiologically based compartment model, aortic contrast enhancement curves were generated by varying contrast medium injection duration from 1 to 40 seconds. Contrast enhancement curves and times to peak aortic enhancement from the experiment and model were compared. Time to peak aortic enhancement obtained from the injection with the shortest duration was considered the time to peak test bolus contrast enhancement. Mathematic and pharmacokinetic analyses were performed to investigate factors that determine peak enhancement. RESULTS: Empiric and compartmental model times to peak aortic enhancement were in good agreement. Time to peak aortic enhancement corresponded to the weighted sum of injection duration and time to peak test bolus enhancement. With increasing injection duration, the relative contribution of injection duration to peak aortic enhancement time increased. When injection duration was longer than time to peak test bolus enhancement, time to peak aortic enhancement increased linearly with injection duration and occurred shortly after completion of injection. However, when injection duration was shorter than time to peak test bolus enhancement, time to peak aortic enhancement was determined predominantly by time to peak test bolus enhancement and only gradually increased with injection duration. CONCLUSION: Time to peak aortic enhancement is determined by the relative contributions of injection duration and contrast medium traveling time and may well be explained by contrast medium volumetric inflow and recirculation physiology.     

Imaging in scoliosis: what,why and how?

Scoliosis may be a spinal manifestation of underlying disease and although most cases of scoliosis are idiopathic, imaging plays a very important role in determining the underlying aetiology and in monitoring the changes of the deformity that take place with growth. As a clinical problem scoliosis may present directly to the radiology department through a primary healthcare referral, or it may be referred from the paediatric, orthopaedic, spinal and neurosurgical hospital services. Growth affects all types of scoliosis irrespective of cause. There are no reliable predetermined algorithmic steps in the management of scoliosis, and treatment decisions require the inclusion of multiple extrinsic (e.g age, menarche) and intrinsic (curve magnitude, vertebral anomaly) factors. It is important to remember that most of what is known about curve behaviour and its progression applies to idiopathic scoliosis, and it is inappropriate to apply these criteria to the other specific types of scoliosis. It is imperative that radiation techniques are used judiciously to minimize the radiation burden. Although magnetic resonance imaging (MRI) has had a significant impact in the understanding of the scoliotic deformity, it is still evolving and it may well eventually play a very important role in uncovering the underlying aetiology of 'idiopathic' scoliosis.     

MR imaging of CNS tumors: are all contrast agents created the same?

The challenging and multiple goals and requirements of CNS tumor imaging require optimization of the CNS imaging protocols, including selection of the optimal contrast medium. There are several gadolinium compounds available for imaging the CNS, and all of these except the compound Gd-BOPTA have nearly identical profiles. The unique protein interaction of Gd-BOPTA results in double T1 and T2 relaxivity. This article summarizes the advantages of Gd-BOPTA over conventional gadolinium compounds in both conventional and functional MR imaging. The results of recent studies in adults and pediatric patients are presented and discussed. The principal conclusion of this article is that not all contrast agents approved for MR imaging of the CNS behave in the same way. The use of the high-relaxivity agent Gd-BOPTA for morphological and functional MR imaging allows improved detection and delineation of CNS lesions compared to conventional gadolinium agents. This not only permits more confident diagnoses, but also results in a substantially improved differential diagnostic process. The higher relaxivity of Gd-BOPTA helps to optimize functional MR imaging studies e.g. perfusion MR imaging and other dynamic MR imaging protocols.     

Parathyroid scintigraphy: when, how, and why? A concise systematic review

In recent years, preoperative imaging has become essential in the evaluation of sporadic primary hyperparathyroidism (HPT) for selecting good candidates for minimally invasive HPT. Its role in patients with secondary/tertiary HPT is under investigation. Imaging is mandatory before reoperative parathyroid surgery for persistent or recurrent HPT, whatever the setting. This review provides detailed information regarding the nuclear imaging methods (dual phase, subtraction), the role of SPECT and SPECT/CT, and the clinical results of parathyroid scintigraphy in different clinical situations.     

Muscle reflexes in motion: how, what, and why?

Methods have been developed to study excitatory and inhibitory reflexes during human movements because dramatic task-dependent changes occur between different voluntary activities, and phase-dependent changes occur within cyclic movements. Interestingly, segmental reflexes are relatively unimportant for standing balance, although reflex responses are strong, yet they contribute substantially to force in several muscles during walking, when some reflex responses are weaker.     

Positional MR imaging of the lumbar spine: does it demonstrate nerve root compromise not visible at conventional MR imaging?

PURPOSE: To evaluate whether positional magnetic resonance (MR) images of the lumbar spine demonstrate nerve root compromise not visible on MR images obtained with the patient in a supine position (conventional MR images). MATERIALS AND METHODS: Thirty patients with chronic low back pain unresponsive to nonsurgical treatment and with disk abnormalities but without compression of neural structures were included. Positional MR images were obtained by using an open-configuration, 0.5-T MR imager with the patients seated and with flexion and extension of their backs. The disk and nerve root were related to the body position. Nerve root compression and foraminal size were correlated with the patient's symptoms, as assessed with a visual analogue scale. RESULTS: Nerve root contact without deviation was present in 34 of 152 instances in the supine position, in 62 instances in the seated flexion position, and in 45 instances in the seated extension position. As compared with the supine position, in the seated flexion position nerve root deviation decreased from 10 to eight instances; in the seated extension position, it increased from 10 to 13 instances. Nerve root compression was seen in one patient in the seated extension position. Positional pain score differences were significantly related to changes in foraminal size (P =.046) but not to differences in nerve root compromise. CONCLUSION: Positional MR imaging more frequently demonstrates minor neural compromise than does conventional MR imaging. Positional pain differences are related to position-dependent changes in foraminal size.     

Rectal cancer: MR imaging in local staging--is gadolinium-based contrast material helpful?

PURPOSE: To determine retrospectively whether addition of gadolinium-enhanced T1-weighted magnetic resonance (MR) sequence to T2-weighted turbo spin-echo (SE) MR imaging is valuable for preoperative assessment of T stage and circumferential resection margin in patients with primary rectal cancer. MATERIALS AND METHODS: Local institutional review board approved study and waived informed patient consent. Eighty-three patients with operable primary rectal cancer underwent preoperative MR imaging. Retrospectively, two observers independently scored T2-weighted turbo SE MR images and, in a second reading, T2-weighted images combined with gadolinium-enhanced T1-weighted turbo SE MR images for tumor penetration through rectal wall and tumor extension into mesorectal fascia. A confidence level scoring system was used, and receiver operating characteristic (ROC) curves were generated. Histologic findings were standard of reference. Difference in performance of T2-weighted and combined T2-weighted plus gadolinium-enhanced T1-weighted sequences was analyzed by comparing corresponding areas under ROC curves (A(z)) for each observer. Interobserver agreement was calculated by using linear weighted kappa statistics. RESULTS: Addition of contrast-enhanced T1-weighted to T2-weighted MR imaging did not significantly improve diagnostic accuracy for prediction of tumor penetration through rectal wall (A(z) of T2-weighted vs T2-weighted plus T1-weighted images for observer 1, 0.740 vs 0.764; observer 2, 0.856 vs 0.768) and tumor extension into mesorectal fascia (A(z) for observer 1, 0.962 vs 0.902; observer 2, 0.902 vs 0.911). Diagnostic performance (A(z)) of MR and interobserver agreement were high for prediction of tumor extension into mesorectal fascia (kappa = 0.61, 0.74) but only moderate for penetration through rectal wall (kappa = 0.47, 0.45). CONCLUSION: Gadolinium-enhanced MR sequences did not improve diagnostic accuracy for assessment of tumor penetration through rectal wall and tumor extension into mesorectal fascia.     

Body diffusion-weighted MR imaging of uterine endometrial cancer: Is it helpful in the detection of cancer in nonenhanced MR imaging?

Objective

In this study, the authors discussed the feasibility and value of diffusion-weighted (DW) MR imaging in the detection of uterine endometrial cancer in addition to conventional nonenhanced MR images.

Methods and materials

DW images of endometrial cancer in 23 patients were examined by using a 1.5-T MR scanner. This study investigated whether or not DW images offer additional incremental value to conventional nonenhanced MR imaging in comparison with histopathological results. Moreover, the apparent diffusion coefficient (ADC) values were measured in the regions of interest within the endometrial cancer and compared with those of normal endometrium and myometrium in 31 volunteers, leiomyoma in 14 patients and adenomyosis in 10 patients. The Wilcoxon rank sum test was used, with a p < 0.05 considered statistically significant.

Results

In 19 of 23 patients, endometrial cancers were detected only on T2-weighted images. In the remaining 4 patients, of whom two had coexisting leiomyoma, no cancer was detected on T2-weighted images. This corresponds to an 83% detection sensitivity for the carcinomas. When DW images and fused DW images/T2-weighted images were used in addition to the T2-weighted images, cancers were identified in 3 of the remaining 4 patients in addition to the 19 patients (overall detection sensitivity of 96%). The mean ADC value of endometrial cancer (n = 22) was (0.97 ± 0.19) × 10⁻³ mm²/s, which was significantly lower than those of the normal endometrium, myometrium, leiomyoma and adenomyosis (p < 0.05).

Conclusion

DW imaging can be helpful in the detection of uterine endometrial cancer in nonenhanced MR imaging.     

Evidence-based radiology: why and how?

Purpose

To provide an overview of evidence-based medicine (EBM) in relation to radiology and to define a policy for adoption of this principle in the European radiological community.

Results

Starting from Sackett’s definition of EBM we illustrate the top-down and bottom-up approaches to EBM as well as EBM’s limitations. Delayed diffusion and peculiar features of evidence-based radiology (EBR) are defined with emphasis on the need to shift from the demonstration of the increasing ability to see more and better, to the demonstration of a significant change in treatment planning or, at best, of a significant gain in patient outcome. The “as low as reasonably achievable” (ALARA) principle is thought as a dimension of EBR while EBR is proposed as part of the core curriculum of radiology residency. Moreover, we describe the process of health technology assessment in radiology with reference to the six-level scale of hierarchy of studies on diagnostic tests, the main sources of bias in studies on diagnostic performance, and levels of evidence and degrees of recommendations according to the Centre for Evidence-Based Medicine (Oxford, UK) as well as the approach proposed by the GRADE working group. Problems and opportunities offered by evidence-based guidelines in radiology are considered. Finally, we suggest nine points to be actioned by the ESR in order to promote EBR.

Conclusion

Radiology will benefit greatly from the improvement in practice that will result from adopting this more rigorous approach to all aspects of our work.