Improvement of diagnostic performance of hyperacute ischemic stroke in head CT using an image-based noise reduction technique with non-black-boxed process.

PURPOSE: This study aims to investigate whether an image-based noise reduction (INR) technique with a conventional rule-based algorithm involving no black-boxed processes can outperform an existing hybrid-type iterative reconstruction (HIR) technique, when applied to brain CT images for diagnosis of early CT signs, which generally exhibit low-contrast lesions that are difficult to detect. METHODS: The subjects comprised 27 patients having infarctions within 4.5 h of onset and 27 patients with no change in brain parenchyma. Images with thicknesses of 5 mm and 0.625 mm were reconstructed by HIR. Images with a thickness of 0.625 mm reconstructed by filter back projection (FBP) were processed by INR. The contrast-to-noise ratios (CNRs) were calculated between gray and white matters; lentiform nucleus and internal capsule; infarcted and non-infarcted areas. Two radiologists subjectively evaluated the presence of hyperdense artery signs (HASs) and infarctions and visually scored three properties regarding image quality (0.625-mm HIR images were excluded because of their notably worse noise appearances). RESULTS: The CNRs of INR were significantly better than those of HIR with P < 0.001 for all the indicators. INR yielded significantly higher areas under the curve for both infarction and HAS detections than HIR (P < 0.001). Also, INR significantly improved the visual scores of all the three indicators. CONCLUSION: The INR incorporating a simple and reproducible algorithm was more effective than HIR in detecting early CT signs and can be potentially applied to CT images from a large variety of CT systems.

Effect of protective glasses on radiation dose to eye lenses during whole breast irradiation.

OBJECTIVES: The efficacy of radiotherapy for breast cancer has greatly improved owing to better irradiation methods. Radiotherapy aims to deliver therapeutic doses to predetermined target volumes while sparing surrounding healthy tissues. However, there are few reports on radiation exposure to eye lenses, and the recommended exposure limits to ocular lens have been substantially reduced in recent years. This study aimed to investigate the amount of radiation exposure to eye lenses using optically stimulated luminescence dosimeters (OSLDs) and determine whether wearing special protective devices to protect the eyes, as an organ at risk, during whole breast irradiation, is necessary. METHODS: This experiment used OSLDs on water-equivalent phantom to measure the change in scattered radiation dose due to the difference of irradiation field while using 4- and 6-MV photons of TrueBeam linear accelerator. Using a total treatment dose of 50 Gy, a target was positioned to approximate the breast, and a plan was formulated to deliver 2 Gy per treatment by tangential irradiation. The mean (SD) irradiation dose at the lens position outside the irradiation field was reported. RESULTS: The scattered radiation dose outside the irradiation field was more affected by the irradiation field size than by the radiation energy. The out-of-field irradiation dose with a larger field of view was higher than that with a smaller field of view. The use of 0.07- and 0.83-mm-thick lead shield protective glasses reduced the radiation dose by 56.1% (P < .001) and 55.6% (P < .001), respectively. CONCLUSIONS: In this experimental model, the amount of radiation the eye was exposed to during whole breast irradiation was determined by the distance of the eye from the radiation field edge and by wearing protective glasses. In clinical practice, the protection offered by eyeglasses may reduce the risk of long-term side effects and allow the use of higher intensive radiotherapy.

[Improvement of Beam Hardening Effects of Virtual Monochromatic Image in Dual-energy CT: A Electron Density Phantom Study].

PURPOSE: A virtual monochromatic image (VMI) is acquired from two different types of polychromatic energy X-rays, not a monochromatic X-ray. The effective energy of monochromatic X-ray does not vary in passing through the patient's body. On the other hand, beam hardening effects are seen in images because of the change of polychromatic X-ray energy. The purpose of the present study was to evaluate the beam hardening improvement effect of VMI using a phantom with a bone mimicking ring. METHOD: We used a water equivalent electron density phantom with a hole in the center for inserting various measurement materials (i.e. fat, two types of bone with differing densities, contrast medium, blood, and water). Then, the CT numbers of each measurement materials were obtained from single energy CT (SECT) images and VMIs, respectively. Also, an additional bone-mimetic ring was used to obtain the CT numbers for evaluation of beam hardening effect. The CT number change rates were calculated from the obtained CT numbers with and without beam hardening effect. RESULT: The rate of CT number, change of VMI was significantly lower than that of SECT for all measured materials. CONCLUSION: In this study, VMI minimized changes in CT numbers due to the beam hardening effect and showed a higher beam hardening reduction effect.

Mountain sickness with delayed signal changes in the corpus callosum on magnetic resonance imaging: a case report.

A 32-year-old man started building a wooden desk atop Mount Fuji at an altitude of 3,776 m. Over the course of the second day, he developed lassitude and cough and experienced a headache that night; however, he continued to work. He was transported to our hospital with an altered level of consciousness. On arrival, chest radiography revealed increased opacities in both lungs, and magnetic resonance imaging (MRI) revealed a high-intensity signal in the splenium on diffusion-weighted imaging. He received mechanical ventilation following tracheal intubation. His respiratory function improved, and he was extubated on the fourth hospital day. Physical examination showed no motor weakness, and although he responded to verbal commands, he was unable to speak and was unresponsive to visual stimulation. On the seventh hospital day, head MRI showed improvement in the lesion in the splenium, although other signal changes were observed in the body of the corpus callosum. His verbal responsiveness and voice volume improved on a daily basis. Two months after the incident, he continued to experience mild recent memory disturbance. The patient described in this case report showed delayed signal changes in the body of the corpus callosum, possibly secondary to the onset of microbleed-induced edema.

Efficacy of oral supplemental hydration for the prevention of contrast-induced nephropathy in rats.

PURPOSE: To compare oral rehydration solution (ORS) with saline infusion for preventing contrast-induced nephropathy (CIN) in a rat model. MATERIALS AND METHODS: Adult male Sprague-Dawley rats (310-360 g) received intravenous indomethacin (10 mg/kg), N G-nitro-L-arginine methyl ester (10 mg/kg), and iohexol (10 mL/kg) to induce acute contrast-induced renal injury (CIN group); control rats received saline only. For hydration, rats received either continuous infusion (20 mL/kg/h) of saline or three oral doses (20 mL/kg each) of ORS. Acute renal injury was evaluated by assaying urine collected for 24 h beginning 2 h before the contrast injection, evaluating blood taken 22 h after the contrast injection, and examining the kidneys histopathologically. RESULTS: Hydration with saline prevented only the contrast-induced increase in plasma creatinine, whereas ORS prevented deleterious changes in plasma creatinine, blood urea nitrogen, and creatinine clearance as well as in urinary protein, albumin, and N-acetyl-D-glucosaminidase concentrations. Histopathologic changes noted in the CIN group were diminished in both saline and ORS groups. CONCLUSION: Both intravenous saline administration and oral hydration with ORS decreased the severity of CIN. Hydration with ORS was comparable to intravenous saline infusion in preventing CIN-associated abnormalities.

Aneurysm of a systemic artery supplying the normal basal segments of the left lower lobe.

The case of an aneurysm of a systemic artery supplying otherwise normal basal segments of the left lower lobe is presented. The diagnosis was correctly made postprocessed with three-dimensional reformatting using a multidetector row CT (MDCT) scanner. Conventional angiography was obviated.