Donald A. Eckard

The effects of lossy compression on the detection of subtle pulmonary nodules.

We examined the ability of radiologists to detect pulmonary nodules in computed radiographic (CR) chest images subjected to lossy image compression. Low-contrast 1-cm diameter targets simulating noncalcified pulmonary nodules were introduced into clinical images and presented to ten radiologists in a series of two-alternative forced-choice (2AFC) observer experiments. The percentages of correct observer responses obtained while viewing noncompressed images (1:1) were compared with those obtained for the same images compressed 7:1, 16:1, 44:1, and 127:1. The images were compressed using a standard full-frame discrete cosine transform (DCT) technique. The degree of compression was determined by quantizing Fourier components in various frequency channels and then Huffman encoding the result. The data show a measurable decline in performance for each compression ratio. Through signal-to-noise ratio (SNR) analysis, we found that the reduction in performance was due primarily to the compression algorithm that increased image noise in the frequency channels of the signals to be detected.

Imaging of acquired cerebral herniations

The consequences of cerebral herniation are compression of the brain, cranial nerves, and blood vessels that may result in serious neurologic morbidity, coma, and even death. A thorough understanding of the various patterns of cerebral herniation is essential, and it is important to remember that many of these patterns of herniation overlap. CT and MR imaging are effective at establishing the diagnosis of cerebral herniation, which will guide important decisions regarding therapeutic options and prognosis.

Metastatic testicular cancer presenting as spinal cord compression: Report of two cases

BACKGROUND Testicular cancers are heterogenous neoplasms often found in young adults. They tend to metastasize to the chest, retroperitoneum, or neck, but rarely to the long bones or skeleton. However, they can cause neurologic compromise and should be considered in young male patients who present with symptoms of a spine lesion and no known primary cancer. METHODS Two patients presented with back pain and a rapid progression of lower extremity weakness. Both underwent radiographic workup and emergency surgery. Metastatic workup revealed testicular cancer and widespread metastases. RESULTS Both patients improved neurologically after surgery, but neither regained the ability to ambulate independently. They both underwent chemotherapy. One patient is alive at 1 year follow-up; the other died 9 months after surgery of widespread metastases. CONCLUSIONS Vertebral metastases from testicular tumors, although rare, should be considered in young men presenting with spinal cord compression. Work-up should include magnetic resonance imaging (MRI) of the spine and computed tomography (CT) of the chest, abdomen, and pelvis. Urgent intervention may be required, as these two cases show that loss of neurologic function can be rapid and permanent.

Use of the External Jugular Vein Approach for Transvenous Liver Biopsy

Transjugular liver biopsy (TJLB) with use of a right external jugular vein (EJ) approach obviates a deep neck puncture, thereby reducing the risk associated with the procedure in patients with severely disordered coagulation. The EJ approach was successful in 21 of 24 consecutive patients referred for TJLB (88%). The approach was unsuccessful in three cases due to thrombosis or congenital absence of the right EJ. TJLB via the right EJ was successful in all cases in which EJ access could be obtained. In the 21 successful cases, the EJ approach simplified the procedure and shortened its duration. There were no procedure-related complications attributable to the EJ approach. The authors now use the EJ route routinely for patients undergoing TJLB and other transjugular procedures in their laboratory. The EJ approach is particularly recommended in patients with impaired coagulation.

Comparison of iodixanol and ioxaglate for adult aortography and renal/visceral angiography: A phase III clinical trial

RATIONALE AND OBJECTIVES We investigated whether iodixanol offers improved safety or tolerance compared with ioxaglate and evaluated whether iodixanol-enhanced radiographs are diagnostically comparable or superior to those produced with ioxaglate. Iodixanol is a new isosmotic hexa-iodinated nonionic contrast agent being evaluated for intravascular use. METHODS Fifty-four adult patients undergoing renal or visceral angiography, aortography, or both were enrolled in a prospective, randomized, double-blind, two-center study in which iodixanol and ioxaglate were compared. Subjects were monitored for adverse events, injection-associated discomfort, and changes in laboratory parameters and vital signs. Efficacy was measured by the overall quality of angiographic enhancement. RESULTS No serious adverse events occurred during this trial. Mild-to-moderate adverse events were more common in patients receiving ioxaglate (p = .041). Injection-associated pain was reported by three patients receiving ioxaglate and none receiving iodixanol (p = .093). Clinical laboratory and vital-sign data showed no differences between groups, and there was no difference in the overall quality of angiographic visualization (p = .711). CONCLUSION Iodixanol resulted in improved safety and patient tolerability while providing images of equivalent diagnostic efficacy compared with ioxaglate.

Iodixanol and ioxaglate in adult aortography and peripheral arteriography: A phase III clinical trial

RATIONALE AND OBJECTIVES This study compared the safety and efficacy of iodixanol with those of ioxaglate in adult patients undergoing aortography or peripheral arteriography. METHODS Forty-six patients were enrolled in this controlled, randomized, double-blind, two-center study. The patients were monitored for adverse events, injection-related discomfort, and trends in laboratory data or vital signs. Diagnostic efficacy was assessed by the quality of contrast enhancement. RESULTS All procedures were diagnostic, with no significant difference in quality of visualization (p = .205). No significant difference was seen in the number of patients experiencing mild or moderate adverse effects (p = .106). Patients receiving ioxaglate reported a significantly greater incidence of injection-related pain (p = .025). CONCLUSION The results of this study support the conclusion that iodixanol at 320 mg I/kg is safe and effective for adult aortography and peripheral arteriography and causes significantly less injection-related pain than ioxaglate.

Enhancement of storage phosphor plate images: a C-language program.

A C-language software program has been developed for emulating the image enhancement processing of a storage phosphor plate system. This software has been implemented on a VAX 3400 computer. There are 2,100 lines of C-language code in the program. There are seven parameters used to specify the degree of enhancement. The software is being implemented on a single accelerator board.

Temporary subclavian steal to reduce intraprocedural embolic risk during detachable balloon occlusion of vertebrobasilar aneurysms: technical note with two case reports.

Purpose: Unintentional intracerebral embolization is a serious, ever present threat during neurointerventional procedures. We have devised a method to reduce this intraprocedural risk in vertebral artery interventions by creating a temporary subclavian steal. Methods and Results: For this technique, a temporary balloon occlusion catheter is advanced into the proximal subclavian artery via a femoral artery approach, while a second introducer catheter is passed into the target vertebral artery via an axillary artery access. The temporary occluding balloon is then inflated within the proximal subclavian artery, establishing a subclavian steal that diverts blood flow into the arm. Permanent balloon occlusion of the vertebral artery can then be accomplished without fear of intracerebral embolization. Two patients with vertebrobasilar junction aneurysms were successfully treated with detachable balloon embolization using this cerebral protection technique. The permanent occlusion balloons were easily passed through the introducer catheter without difficulty despite reversed vertebral artery flow. No complications were encountered, and the aneurysms were successfully occluded in both patients. Conclusions: Temporary subclavian steal can be easily created to reduce the risk of cerebral embolic complications when performing interventional neuroradiological procedures in the vertebral artery.

Large focal cerebral demyelinating lesions mimicking intracranial neoplasms: imaging features

The CT and MRI features of 41 patients with histologically proven demyelinating lesions that mimicked intracranial neoplasms, both clinically and radiologically, were studied retrospectively. There were 32 patients with single and 9 with multiple lesions. In 40 cases the lesions characteristically involved the hemisphere white matter with no predilection for the periventricular areas, optic pathways or brain stem. The CT and MRI features are nonspecific and the true nature of the lesion was demonstrated by histology. All patients showed marked improvement following steroid therapy.