New insights into lung diseases using hyperpolarized gas MRI.

Hyperpolarized (HP) gases are a new class of contrast agents that permit to obtain high temporal and spatial resolution magnetic resonance images (MRI) of the lung airspaces. HP gas MRI has become important research tool not only for morphological and functional evaluation of normal pulmonary physiology but also for regional quantification of pathologic changes occurring in several lung diseases. The purpose of this work is to provide an introduction to MRI using HP noble gases, describing both the basic principles of the technique and the new information about lung disease provided by clinical studies with this method. The applications of the technique in normal subjects, smoking related lung disease, asthma, and cystic fibrosis are reviewed.

Evaluation of the stimulated menstrual cycle by magnetic resonance imaging.

Changes in uterine zonal anatomy in six women during a cycle of treatment with clomiphene citrate is studied by magnetic resonance imaging. There was a rapid rate of increase in endometrial thickness during the periovulatory period that was similar to the pattern seen in a prior study of women with normal (nonstimulated) cycles. Junctional zone thickness did not parallel the endometrial pattern and differed from the response seen in nonstimulated cycles. Results of large scale studies may help to further understand the effects of these medications.

Magnetization prepared rapid gradient-echo (MP-RAGE) MR imaging of the liver: comparison with spin-echo imaging.

We have implemented an MR technique that employs a rapid gradient echo sequence, preceded by magnetization preparation pulses to provide T1- and T2-weighted tissue contrast. With this technique, which can be identified as a member of a new family of pulse sequences, generically named Magnetization Prepared RApid Gradient Echo (MP-RAGE), very short repetition times are used, allowing acquisition times of less than one second and images virtually free of motion-induced artifacts during quiet respiration. Fifteen patients with known liver lesions (metastases, hemangiomas, and cysts) were examined using T1- and T2-weighted 2-dimensional MP-RAGE sequences, and the images were compared with conventional T1- and multi-echo T2-weighted spin-echo (SE) sequences. Signal difference-to-noise ratios (SD/Ns) of the lesions were calculated for all pulse sequences using corresponding axial images and were normalized for voxel volume. The mean normalized SD/Ns of the MP-RAGE sequences were generally comparable to those for the SE sequences. In addition, there were no noticeable respiratory artifacts on the MP-RAGE images whereas these were clearly present on the T2-weighted SE images and to a lesser degree on the T1-weighted SE images. It is concluded that the MP-RAGE technique could become an important method for evaluating the liver for focal disease.

An in vivo evaluation of the reproducibility of intima-media thickness measurements of the carotid artery segments using B-mode ultrasound.

B-mode ultrasound may be used to measure the intima-media thickness (IMT) in subjects with a history of atherosclerosis. The variability between measurements depends on the subjective interpretation of ultrasonographers and readers. The two carotid arteries, subdivided in common (CCA), bulbus (BUL) and internal (ICA) of 10 men with proven coronary disease, were scanned twice by two ultrasonographers with a 1-week interval. The IMTs were measured off-line by two readers. The number of IMT measurements was 75 (94%) of 80 in the CCA, 61 (76%) of 80 in the BUL and 43 (54%) of 80 in the ICA segment. In the CCA segment, the agreement between readers (mean = 0.02 mm; limits: -0.26 to +0.3 mm) and between visits for each reader separately (reader 1: mean = 0.01 mm; limits: -0.33 to +0.35 mm and, reader 2: mean = 0.04 mm; limits: -0.36 to +0.44 mm) was better than in the more distal segments. Therefore, it is concluded that IMT measurements are best performed in the CCA segment.

In vitro measurement of kidney size: comparison of ultrasonography and MRI.

In this in vitro study, the accuracy and repeatability of magnetic resonance imaging (MRI) and ultrasound (US) in assessing renal length and volume were determined. US and MR images of 20 cadaver pig kidneys were obtained twice and evaluated by two observers for each modality. The fluid displacement method provided the "gold standard." Renal volumes were calculated from the US and MR images using the ellipsoid formula. Additional volume calculations after segmentation of the kidney on MR images were done using the voxel-count method. Volumes calculated with the ellipsoid formula resulted in an average of 24% underestimation (range 5%-48%) of the renal volume for both US and MRI. With the voxel-count method, no significant deviation from the true renal volume was encountered. Repeatability was also greatest with the voxel-count method. Measuring renal length, repeatability was, again, better with MRI compared to US. For reliable calculation of renal size in vitro, MRI with use of the voxel-count method is preferred.

Comment to the paper "Ultrasound and computer tomography in staging of bladder tumours".

The interference of Transurethral Resection (TUR) with CT staging of bladder cancer is discussed in reaction to a recent publication.

Radiographic examination of the stomach and duodenum: comparison of single-, double- and biphasic-contrast methods.

We compared retrospectively three groups of 150 patients who had undergone radiologic examinations of the stomach and duodenum. Each group was examined with a different barium suspension and radiographic technique: single-contrast (SC), double-contrast (DC), or biphasic-contrast (BC). The radiographs of each study were evaluated for technical quality and visualization of lesions. The number of X-ray exposures, films, and the amount of fluoroscopic time for each study were tabulated. The total radiation dose and cost for each technique were calculated. The BC examinations required the greatest number of radiographic exposures and X-ray films; however, cost was highest for the DC method. Fluoroscopy was significantly longer during the DC procedures, and the total radiation dose was also highest with this technique. Gaseous distention and barium coating of the stomach were equally good for the BC and DC groups, but X-ray penetration of the barium suspension during compression filming was significantly better in the BC and SC groups. Areae gastricae were most frequently seen during the BC studies and artifacts from excess secretions, barium flocculation or gas bubbles were least commonly present using this technique. Significantly more lesions were demonstrated in the stomach with the BC technique than with the other methods; however, the number of lesions found in the duodenum was the same for each technique.

Antegrade ureteral stent placement: positioning without use of a retraction string.

PURPOSE: To evaluate a simple method of antegrade ureteral stent insertion allowing optimal positioning of the stent without the use of a retraction string. PATIENTS AND METHODS: Seventeen stents were placed in sixteen patients with ureteral obstruction. Materials included a long vascular introducer sheath and radiopaque markers on the tips of both the sheath and the pusher catheter. For optimal positioning of the proximal pigtail in the renal pelvis, the distal end of the sheath was used to hold a large portion of the pigtail in the extended state prior to its deployment. RESULTS: All stent placements were successful. In one case, the tip of the proximal pigtail was caught in a lower-pole calix. In another case, repeat stent placement was necessary because of recurrent stricture several months after removal of the first stent. All stents functioned properly, as demonstrated by follow-up nephrostography 2 or 3 days after each procedure. CONCLUSION: The insertion method we describe is simple, easy to perform, and fast and avoids the risks associated with the use of a retraction string.

Hyperpolarized noble gas MR imaging of the lung: potential clinical applications.

Hyperpolarized noble gases are a new class of MR contrast agent. Since the first hyperpolarized gas MR images of the lung were reported, there has been considerable interest in using hyperpolarized gas to obtain high spatial and temporal resolution images of the air spaces of the lung. In addition to static images of lung ventilation, new techniques are being developed using hyperpolarized gas to obtain dynamic, diffusion and oxygen concentration images of the lung. In this article, we review the potential clinical applications of pulmonary hyperpolarized gas MRI and discuss the preliminary findings in a variety of lung diseases. Hyperpolarized gas MRI has the potential to provide a comprehensive morphologic and functional assessment of the lung.

Radiographic features of gastritis using the biphasic contrast technique.

Gastritis is a group of inflammatory disorders that can be diagnosed radiographically. The optimum radiographic examination of the stomach is the biphasic-contrast technique, which includes the use of a medium-dense barium sulfate suspension and a hypotonic agent. Knowledge of the forms of gastritis, a careful application of biphasic-contrast technique, and a perceptive evaluation of information will help the radiologist to detect this entity with great frequency.

Gastrointestinal foreign bodies and strictures: radiologic interventions.

Food impaction and foreign body ingestion are significant and sometimes life-threatening medical problems. As described in part 1 of this monograph, a variety of techniques and instruments are available to diagnose and treat these conditions. The radiologist interested in interventional procedures can find ample opportunities to participate in the management of esophageal obstructions by applying radiographic and fluoroscopic techniques to the diagnosis and removal of foreign bodies and food impactions. The recommended radiologic procedures are relatively safe, cost-effective, and efficient methods of addressing these serious situations. Stricture formation in the gastrointestinal tract is another significant medical problem that can often be managed nonoperatively by the radiologist. Fluoroscopically guided balloon dilatation has become an accepted method of effectively treating a large variety of strictures. As described in part 2 of this article, the technique is easy to perform, usually with very little inconvenience to the patient, and the risks of complications are very low. The procedure is relatively inexpensive and does not require the acquisition of any specialized or high-technology equipment. Also, the technique can be performed easily by any radiologist with interest in interventional procedures on the gut. A wide use of the fluoroscopic methods for treatment of impacted foreign bodies and strictures of the gastrointestinal tract is recommended.

Assessing the subtalar joint: the Brodén view revisited.

We prospectively evaluated subtalar inversion stress views (Brodén view) with inversion stress views on helical CT in a group of 10 patients with unilateral instability. The contralateral, asymptomatic ankle was used as control. All patients were examined with inversion stress views on plain stress radiography and helical CT. Subtalar tilt was demonstrated in all cases on conventional stress radiography. Helical CT didn't show tilting in any of the patients except in the subluxated posteromedial part of the subtalar joint. Our data do not support prior reports that the Brodén view is useful for screening patients with subtalar instability.

MR grid-tagging using hyperpolarized helium-3 for regional quantitative assessment of pulmonary biomechanics and ventilation.

A new technique is demonstrated in six healthy human subjects that combines grid-tagging and hyperpolarized helium-3 MRI to assess regional lung biomechanical function and quantitative ventilation. 2D grid-tagging, achieved by applying sinc-modulated RF-pulse trains along the frequency- and phase-encoding directions, was followed by a multislice fast low-angle shot (FLASH)-based acquisition at inspiration and expiration. The displacement vectors, first and second principal strains, and quantitative ventilation were computed, and mean values were calculated for the upper, middle, and lower lung regions. Displacements in the lower region were significantly greater than those in either the middle or upper region (P < 0.005), while there were no significant differences between the three regions for the two principal strains and quantitative ventilation (P = 0.11-0.92). Variations in principal strains and ventilation were greater between subjects than between lung zones within individual subjects. This technique has the potential to provide insight into regional biomechanical alterations of lung function in a variety of lung diseases.

Cross-sectional imaging of the liver.

The liver can be affected by a number of conditions that can involve the liver focally or diffusely. CT and MRI are reliable techniques for demonstrating these abnormalities, and both imaging tools play an important role in the clinical evaluation of the patients. However, each technique provides different information, and the most appropriate cross-sectional technique used should be tailored in each instance to the individual patient situation.

Radiographic position of the trigeminal nerve in the skull for angiographic determination of arterial-nerve relationship in trigeminal neuralgia: results of a radiologic-anatomic study.

The positions of 20 trigeminal nerves in the skulls of 12 cadavers were evaluated radiographically. Small metal clips were attached to the nerves and radiographs were obtained in straight AP, Towne and lateral projections. It was found that the trigeminal nerve had a fairly constant position in the skull with respect to the internal auditory meatus in the AP and Towne projections and the petrous ridges in the lateral view. This information can be used during vertebral angiography to predict whether an arterial loop is sufficiently close to the trigeminal nerve root for arterial compression of the nerve, causing trigeminal neuralgia, to be a realistic possibility.