Pneumothorax and other lung diseases: effect of altered resolution and edge enhancement on diagnosis with digitized radiographs

Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm).     

Neonatal brain: color Doppler imaging. Part I. Technique and vascular anatomy

Color Doppler imaging (CDI) can demonstrate the relative direction and velocity of blood flow in color, superimposed on a conventional gray-scale ultrasound image that depicts stationary tissue. Twenty-five infants were studied with portable CDI in the coronal, sagittal, and axial planes. Bilateral antegrade flow was noted in the anterior, middle, and posterior cerebral arteries in all patients. Multiplanar CDI can image flow in the circle of Willis and its tributaries and branches.     

Multiple cerebral metastases: detectability with Gd-DTPA-enhanced MR imaging

Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.     

Breast MR imaging with loop-gap resonators

Breast images obtained at 1.5 T using a loop-gap resonator pair as both the excitation and detection device are presented. The efficiency of this approach is high, as judged by the low level of radio frequency (RF) power required to obtain a 90 degree pulse and the uniformity of the RF field within the resonator pair. A modification of the pair geometry provides for reasonable observation of the tissues through the chest wall and laterally to the axillae.     

Digital imaging of the chest

During the past several years, image acquisition in nuclear medicine, computed tomography, ultrasonography, subtraction angiography, and magnetic resonance has been by digitization. Despite these advances, research in the development of digital imaging in conventional radiography has lagged behind. Although studies with a variety of digital techniques have been carried out on several fronts, we still do not possess a method that has captured the imagination of the majority of radiologists and other physicians to a point where it could replace conventional screen-film imaging. This article reviews the current status and general principles of the technology, focusing on the four digital radiographic techniques that have shown the greatest promise - film digitization, an image intensifier - based system, photostimulable phosphor plates, and a scanned projection system. The physical aspects of each of the four systems and the clinical results that have been reported to date, as well as the advantages and disadvantages of each system, are presented.     

Glenoid labrum: preliminary work with use of radial-sequence MR imaging

The authors describe a magnetic resonance imaging method for examination of the glenoid labrum of the shoulder joint that utilizes a radial fast-imaging sequence. Seven shoulders were examined: a total of five in three healthy asymptomatic volunteers, one in a symptomatic patient not suspected of having a lesion of the glenoid labrum, and one in a patient with recurrent shoulder dislocation and surgical proof of an extensive tear of the labrum. The preliminary results suggest that this technique may advantageously demonstrate pathologic changes in the glenoid labrum and may contribute to the evaluation of the unstable and painful shoulder.     

A double mobility acetabular implant for primary hip arthroplasty in patients at high risk of dislocation

IntroductionDislocation following total hip replacement continues to be a problem for which no completely satisfactory solution has been found. Several methods have been proposed to reduce the incidence of hip dislocations with varying degrees of success, including elevated rim liners, constrained liners and large diameter bearings. We present our experience with the double mobility acetabular component in patients at high risk of instability.MethodsThis was a retrospective review of 65 primary total hip arthroplasties in 55 patients (15 men, 40 women), performed between October 2005 and November 2009. The majority (80%) of patients had at least two and 26% had at least three risk factors for instability. The mean age was 76 years (range: 44–92 years). The patients were followed up for a mean duration of 60 months (range: 36–85 months).ResultsFourteen patients died and one was lost to follow-up, leaving fifty hips for final assessment. Until the final follow-up appointment, no patients had dislocation and none required revision surgery. The mean Oxford hip score improved from 45.0 to 26.5 (p<0.0001). The mean Merle d’Aubigné pain score improved from 1.4 to 4.9 (p<0.0001), the walking score from 2.3 to 3.1 (p<0.07) and the absolute hip function score from 5.4 to 10.8 (p<0.0001). There were no clinical or radiographic signs of loosening.ConclusionsThe double mobility acetabular component was successful at preventing dislocation during early to medium-term follow-up. However, as data are still lacking with regard to polyethylene wear rates at the additional bearing surface, it would be prudent to restrict the use of this implant to selected patients at high risk of instability.     

High-Resolution MRI Findings following Trigeminal Rhizotomy

BACKGROUND AND PURPOSE:Patients with trigeminal neuralgia often undergo trigeminal rhizotomy via radiofrequency thermocoagulation or glycerol injection for treatment of symptoms. To date, radiologic changes in patients with trigeminal neuralgia post-rhizotomy have not been described, to our knowledge. The aim of this study was to evaluate patients after trigeminal rhizotomy to characterize post-rhizotomy changes on 3D high-resolution MR imaging.MATERIALS AND METHODS:A retrospective review of trigeminal neuralgia protocol studies was performed in 26 patients after rhizotomy compared with 54 treatment-naïve subjects with trigeminal neuralgia. Examinations were reviewed independently by 2 neuroradiologists blinded to the side of symptoms and treatment history. The symmetry of Meckel''s cave on constructive interference in steady-state and the presence of contrast enhancement within the trigeminal nerves on volumetric interpolated breath-hold examination images were assessed subjectively. The signal intensity of Meckel''s cave was measured on coronal noncontrast constructive interference in steady-state imaging on each side.RESULTS:Post-rhizotomy changes included subjective clumping of nerve roots and/or decreased constructive interference in steady-state signal intensity within Meckel''s cave, which was identified in 17/26 (65%) patients after rhizotomy and 3/54 (6%) treatment-naïve patients (P < .001). Constructive interference in steady-state signal intensity within Meckel''s cave was, on average, 13% lower on the side of the rhizotomy in patients posttreatment compared with a 1% difference in controls (P < .001). Small regions of temporal encephalomalacia were noted in 8/26 (31%) patients after rhizotomy and 0/54 (0%) treatment-naïve patients (P < .001).CONCLUSIONS:Post-trigeminal rhizotomy findings frequently include nerve clumping and decreased constructive interference in steady-state signal intensity in Meckel''s cave. Small areas of temporal lobe encephalomalacia are encountered less frequently.

Trigeminal neuralgia is a debilitating condition characterized by sharp pain in the distribution of the trigeminal nerve. First described in 1773 by John Fothergill, trigeminal neuralgia is now a widely recognized and frequently encountered condition with a prevalence as high as 200/100,000 individuals and an overall incidence of 2.7/100,000/year.^1–5 First-line treatment commonly consists of medical management with carbamazepine, followed by additional second- and third-line medical treatments.^1,6 If medical management fails, imaging of the trigeminal nerves is often performed to assess causes such as compression of the cisternal segment of the trigeminal nerve from vascular structures or, less commonly, mass lesions along the course of this nerve.Trigeminal rhizotomy, which is performed by percutaneous insertion of a needle through the foramen ovale into Meckel''s cave to damage the nerve by balloon compression, glycerol injection, or radiofrequency thermocoagulation, is often performed as a first-line procedure and may be the only procedure available to patients unable to undergo the more invasive surgical intervention of microvascular decompression. Microvascular decompression is an invasive method of treatment with reported higher patient satisfaction and an overall lower symptom recurrence rate compared with rhizotomy, but it requires an open neurosurgical approach.^7,8High-resolution MR imaging of the trigeminal nerves has allowed radiologists to see the cisternal and Meckel''s cave segments of the trigeminal nerve with exquisite detail. In particular, constructive interference in steady-state (CISS) imaging, a free precession technique with intrinsic flow suppression and high signal-to-noise ratio, allows visualization of fine structures, including individual rootlets of the trigeminal nerve in Meckel''s cave. We have also observed that CISS is sensitive to small perturbations in the content of fluid and can demonstrate reduced signal compared with CSF, even when differences are not visualized on spin-echo-based imaging. Because patients can have high-resolution imaging after trigeminal rhizotomy for a number of indications, including recurrence of symptoms, the goal of this study was to determine the findings expected on postprocedural imaging following percutaneous rhizotomy.Given the postulated mechanism of action of rhizotomy—that is, changes in osmolarity and resulting demyelination and neurolysis with glycerol or direct heat neurolysis with radiofrequency thermocoagulation—we hypothesized the following: the rootlets of the trigeminal nerve in the region of the injection would demonstrate visible changes in their course due to clumping and adhesion; and the signal on CISS imaging would be reduced within Meckel''s cave due to injectate and/or inflammatory debris.⁹ In addition, we sought to evaluate whether enhancement of the trigeminal nerve or Meckel''s cave should be expected following rhizotomy. The rates of other changes to surrounding structures and the muscles of mastication that are innervated by the mandibular division of the trigeminal nerve (cranial nerve V.3) were recorded.