Analysis of a Serial/Parallel Type of Electromagnetic Actuator.

This paper describes the design and analysis of a small-sized and high thrust electromagnetic actuator. The proposed actuator is supposed to be used for application control of the hotmelt adhesive. The hotmelt has different characteristics for each material and the electromagnetic actuator is required variable characteristics. However, the problem seems to lie in the fact that it is necessary to remake another mold again to change the characteristics of the conventional electromagnetic actuator. Therefore, this paper presents small-sized electromagnetic actuator called a basic model that can stack it in the axial direction or in the radial direction. As the analysis comparison at the same size, the characteristics of conventional two serial model which stack two basic models in the axial direction and proposed three serial models have been compared by three-dimensional finite element method. In the proposed model, characteristics have been improved by reducing the core volume and increasing the number of stacks in the basic model from the viewpoint of magnetic flux density. In addition, various electromagnetic actuators that stack basic models in the axial direction or in the radial direction have been analyzed. The analysis results have been clearly shown as characteristics mapping and it has indicated that the proposed electromagnetic actuator can be constructed easily by stacking the basic model.

[Investigation of reduction of exposure dose in digital mammography: relationship between exposure dose and image processing].

In digital mammograms, granularity is an important image property for the detection of microcalcifications and masses. Therefore, we investigated the relationship between the conditions of various exposure doses and the detectability of RMI156 phantom images with and without image processing for the reduction of exposure dose. The images are processed with Gaussian filter and unsharp-masking filters to evaluate the effects on image properties by using the digital Wiener spectrum (WS) presampled modulation transfer function (MTF). In addition, observer performance tests for the detectability of microcalcifications and masses are performed. With Gaussian filtering, the WS value decreased to 50% at 2.0 cycles/mm and the detectability score of masses increased 80% and 12%, on 1.34 mGy and 2.62 mGy, respectively (p<0.05). With unsharp-masking (7 x 7 pixels), the MTF value increased to 126% at 2.0 cycles/mm, and the detectability of microcalcification to 32% and 5%, on 1.34 mGy and 5.28 mGy, respectively (p<0.05) compared with the original image. The optimal dose of simulated lesions with unsharp masking became 5.25 mGy. The unsharp masking could reduce 37% of the exposure dose without a loss of detectability of microcalcifications and masses.

Gynecologic abscess: CT-guided percutaneous drainage.

A 42-year-old woman with recurrent bilateral endometrial ovarian cystoma presented with fever and pelvic pain caused by a tubo-ovarian abscess (TOA), which was resistant to several varieties of intravenous and oral antibiotics for 2 weeks (Case 1). Computed tomography (CT)-guided diagnostic aspiration for a rapid enlarged right ovarian cystoma through a transabdominal route confirmed that it had developed into a TOA. Subsequent percutaneous abscess drainage (PAD) and irrigation for 3 days were successful. One-year follow-up revealed no recurrence of TOA. A 58-year-old woman with recurrent cervical cancer after external radiation therapy (RT) presented with fever, confusion and tremor caused by pyometra (Case 2). Since transvaginal drainage was impossible due to cervical os obstruction, the patient had undergone CT-guided transabdominal PAD and irrigation for a month. Thereafter, the clinical findings improved and a tracheloplasty was performed to prevent recurrence. CT-guided PAD may be a useful treatment option for gynecologic abscess as a diagnostic aspiration, a temporizing procedure until surgery, or an alternative surgery.

Pseudoaneurysm embolization and vasopressin infusion for lower gastrointestinal bleeding due to recurrence of urinary bladder carcinoma.

We report a case that was successfully treated for massive lower gastrointestinal (LGI) bleeding due to a recurrent urinary bladder carcinoma. Treatment consisted of combination therapy including embolization of an inferior gluteal artery (IGA) pseudoaneurysm and low-dose arterial vasopressin infusion via a sigmoid artery (SA). A 57-year-old man presented with life-threatening sudden, massive LGI bleeding due to an obturator lymph node (LN) metastasis from a urinary bladder carcinoma. Computed tomography showed that the LN recurrence had invaded all the way to the sigmoid colon, and there was a pseudoaneurysm with extravasation inside the recurrence. An angiogram revealed a left IGA pseudoaneurysm. We therefore excluded the pseudoaneurysm by embolization with microcoils. Following this treatment the bleeding decreased, but intermittent LGI bleeding continued. Endoscopic examination showed the tumor with a huge ulcer inside the colonic lumen, and continuous oozing was confirmed. A second angiogram showed no recurrence of the IGA pseudoaneurysm and no apparent findings of bleeding. Then a 3F microcatheter was placed in the SA selectively using a coaxial catheter system, and vasopressin was infused at a rate 0.05 U/min for 12 h. Bleeding completely ceased 2 days later. There were no signs of ischemic gastrointestinal complications. Massive LGI bleeding has not recurred in 5 months.

Endovascular therapy of pulmonary arteriovenous malformations: Utility of 16-detector-row computed tomography pulmonary angiography as a pre-embolization survey.

The utility of computed tomography pulmonary angiography (CTPA) for coil embolization therapy of pulmonary arteriovenous malformations (PAVMs) was considered. Three consecutive patients (group A) with PAVMs underwent CTPA and coil embolization. The CTPA was performed using a 16-detector-row computed tomography scanner. After careful selection of pulmonary vessel trees, each feeding artery, nidus, and drainage vein was colored using different codes. By using the colored images, a 5-French catheter was shaped to fit to each feeding artery, the best fluoroscopic angle to select each feeding artery was chosen, and interlocking detachable coils (IDCs) were used in embolization. The procedure time and contrast material dose of group A were compared with those of the previous 3 patients (group B) who were treated by the conventional method. All PAVMs of both groups were completely embolized without coil migration. The average procedure time per lesion was 48.4 minutes for group A and 124.0 minutes for group B (P < 0.05). The average contrast material dose per lesion was 37.5 mL in group A and 76.0 mL in group B (P < 0.05). Using CTPA and IDCs, procedure time and contrast material dose were statistically significantly reduced. This combination therapy is useful in treating PAVMs less invasively.