Toyohiko Tanaka

CT Diagnosis of Acute Mesenteric Ischemia from Various Causes

OBJECTIVE Acute mesenteric ischemia can be caused by various conditions such as arterial occlusion, venous occlusion, strangulating obstruction, and hypoperfusion associated with nonocclusive vascular disease, and the CT findings vary widely depending on the cause and underlying pathophysiology. The aim of this article is to review the CT appearances of acute mesenteric ischemia in various conditions. CONCLUSION Recognition of characteristic CT appearances and the variations associated with each cause may help in the accurate interpretation of CT in the diagnosis of mesenteric ischemia.

Gastrointestinal tract perforation: CT diagnosis of presence, site, and cause

Gastrointestinal tract perforation is an emergent condition that requires prompt surgery. Diagnosis largely depends on imaging examinations, and correct diagnosis of the presence, level, and cause of perforation is essential for appropriate management and surgical planning. Plain radiography remains the first imaging study and may be followed by intraluminal contrast examination; however, the high clinical efficacy of computed tomographic examination in this field has been well recognized. The advent of spiral and multidetector-row computed tomographic scanners has enabled examination of the entire abdomen in a single breath-hold by using thin-slice sections that allow precise assessment of pathology in the alimentary tract. Extraluminal air that is too small to be detected by conventional radiography can be demonstrated by computed tomography. Indirect findings of bowel perforation such as phlegmon, abscess, peritoneal fluid, or an extraluminal foreign body can also be demonstrated. Gastrointestinal mural pathology and associated adjacent inflammation are precisely assessed with thin-section images and multiplanar reformations that aid in the assessment of the site and cause of perforation.

The first trial of phase contrast imaging for digital full-field mammography using a practical Molybdenum x-ray tube

Rationale and Objectives:The image quality of a newly developed full-field digital phase contrast mammography (PCM) system and of a conventional screen-film (SF) mammography system were compared via images of a phantom and receiver operating characteristic (ROC) analysis of clinical images. Methods:Magnified (1.75×) PCM images were scanned (sampling rate, 43.75 &mgr;m) and then reduced to original-sized, 25-micron pixel images printed on photothermographic film. Along with corresponding SF images, the phantom images were evaluated subjectively, and the clinical images of 38 patients were subjected to ROC analysis of mass and microcalcification. Results:In the image quality of a phantom, the PCM exceeded the SF. In both mass and microcalcification, the ROC analysis Az values of the PCM clinical images surpassed those of the SF images. Conclusion:The PCM provides better images than the SF. Clinical trials suggest superior detection of both mass and microcalcification by full-field digital PCM over conventional SF mammography.

Newly Developed Biodegradable Stents for Benign Gastrointestinal Tract Stenoses: A Preliminary Clinical Trial

We developed an Ultraflex-type stent by knitting polylactic acid monofilaments. The purpose of this study was to evaluate the stent’s clinical usefulness for treating benign stenoses in the gastrointestinal tract. The radial force of the biodegradable stent was compared with those of commercially available metallic stents. The measured radial force of the new biodegradable stent was higher than that of commercially available metallic stents. The biodegradable stents were applied in 2 patients with benign gastrointestinal stenoses. The first patient was a 19-year-old female with esophageal stenosis, due to drinking of caustic potash in an attempt to commit suicide. The second patient was a 75-year-old male who had a stenosis at the anastomotic site after esophageal cancer resection. In both cases, the placement of the stent was performed successfully, and the patients’ complaints improved immediately after stent placement. There were no complications during stent placement. The stenosis had not recurred at the six-month follow-up examination. In conclusion, the newly developed biodegradable stents were useful in treating benign stenoses of the alimentary tract.

Endoscopic transanal decompression with a drainage tube for acute colonic obstruction

PURPOSE: The study was undertaken to evaluate the clinical usefulness of endoscopic transanal decompression with a newly developed drainage tube for the treatment of acute colonic obstruction. METHODS: Thirty-six patients ranging in age from 46 to 87 years (average age = 69 years) with acute colorectal obstruction secondary to carcinoma were treated by means of intubation with a flexible drainage tube using combined endoscopic and fluoroscopic guidance. After tube placement, the obstructed colon was aspirated, decompressed, and cleaned with a 50 ml syringe and saline solution. The drainage tube was kept inserted and the colon was irrigated two or three times per day using 500 to 1,000 ml of saline until there were no contents in the colon. The colon was almost empty at the time of operation. The success rate, benefits, and complications of this technique were evaluated. RESULTS: Placement of the drainage tube was successful in 34 (94.4 percent) of 36 patients. Immediately after aspiration and decompression, symptoms related to obstruction were relieved in 21 patients (61.8 percent), within one hour in 9 patients (26.5 percent) and within four hours in 4 patients (11.8 percent). All 34 patients had elective single-stage surgery without severe complications at the anastomotic site such as anastomotic leakage and postanastomotic stenosis that needed treatment a few days after placement of the drainage tube. In the two cases of unsuccessful placement of the drainage tube, emergent colostomy was performed. CONCLUSION: Decompression with a transanal drainage tube is an easy and safe technique to relieve colonic obstruction effectively without any excess burden to patients. Because the procedure permits single-stage surgery in most cases, it is also cost effective.

An initial clinical study on the efficacy of cisplatin-releasing gelatin microspheres for metastatic liver tumors

PURPOSE To evaluate the antitumor effect and side effects of cisplatin-releasing gelatin microspheres (Cis-GMSs) for metastatic liver tumors. METHODS Cis-GMSs that degraded over 14 days were employed. The subjects comprised a total of nine cases. Transcatheter hepatic artery embolization (TAE) using Cis-GMSs (Cis-GMSs-TAE) was performed 13 times in total. Six cases, each containing one to five tumors in a single segment to an entire lobe were treated by Cis-GMSs-TAE. In the remaining three cases with six or more metastatic liver tumors, the right and left lobes were treated by Cis-GMSs-TAE at a 2-week interval. RESULTS There were two complete response (CR), one partial response (PR) and six stable disease (SD) cases. The response rate was 33.3%. The average rate of reduction in tumor diameter was 32%. Disappearance of metastatic liver tumors was observed in only two of the nine cases. As for side effects and complications, post-embolization syndrome was observed in eight cases, but no severe complications such as cholangitis or liver abscess were observed. CONCLUSION Considering the mild side effects by Cis-GMSs-TAE, it is suggested that Cis-GMSs-TAE should be tried at least once as topical therapy for metastatic liver tumors when the response to systemic chemotherapy and other treatments is not satisfactory.

Prolonged local persistence of cisplatin-loaded gelatin microspheres and their chemoembolic anti-cancer effect in rabbits

PURPOSE To confirm prolonged cisplatin release from drug-loaded gelatin microspheres (GMSs) and their improved chemoembolic anti-cancer effect against VX2 liver tumors in rabbits. MATERIALS AND METHODS Two groups of twelve rabbits each were treated intraarterially either with 2 mg/kg cisplatin-loaded GMSs (=0.04 mg/kg cisplatin) or 0.04 mg/kg cisplatin solution by administering them into the right renal artery. Platinum concentrations within the renal parenchyma were analyzed immediately following infusion (day 0) and on days 1, 3, and 7 using the atomic absorption method. In a second experiment four groups of five rabbits each with implanted VX2 liver tumors were treated intraarterially through the hepatic artery with the following drugs: 2 mg/kg cisplatin-loaded GMSs (=0.04 mg/kg cisplatin) (group I), 2 mg/kg GMSs without any drug (group II), 1.5 mg/kg cisplatin solution (group III) and saline (group IV). Tumor volumes were analyzed pre-injection and 7 days after with MRI allowing calculating the relative tumor growth rate (%). Degree of liver cell necrosis was assessed on the histopathological specimens. RESULTS The renal parenchymal platinum concentrations (microg/ml) with 4.51+/-2.25 (day 0), 1.59+/-0.70 (day 1), 0.72+/-0.10 (day 3) and 0.20+/-0.06 (day 7) were significantly more pronounced after cisplatin-loaded GMS on days one and three compared to cisplatin with 1.99+/-0.55, 0.08+/-0.03, 0.18+/-0.01 and 0.10+/-0.07, respectively. Relative tumor growth rates resulted in 84.5%+/-26.4 (group I); 241.4%+/-145.1 (II); 331.9%+/-72.2 (III), and 413.6%+/-103.6 (IV) with statistical significant differences between groups I and III, and groups I and IV. Similar degrees of necrosis were observed in both GMSs treated groups, while ballooning of hepatocytes was highest in cisplatin-loaded GMSs. CONCLUSIONS With cisplatin-loaded GMSs more pronounced and prolonged local parenchymal cisplatin concentrations may be achieved offering the advantage of an increased and prolonged anti-cancer effect compared to cisplatin alone or controls. Moreover this proves indirectly the breakdown and release of cisplatin from the GMSs which is of primary importance for drug delivery systems.

Embolization Materials Made of Gelatin: Comparison Between Gelpart and Gelatin Microspheres

Purpose:The object of this study was to assess the level of embolization in the embolized artery and the degradation period of these two embolic agents in the renal arteries using rabbit models.Materials and Methods: The renal artery was embolized using 5 mg of gelatin microspheres (GMSs; diameter, 35–100 μm; group 1) or 1 mg of Gelpart (diameter, 1 mm; group 2). For each group, angiographies were performed on two kidneys immediately after the embolic procedure and on days 3, 7, and 14 after embolization. This was followed by histopathological examinations of the kidneys.Results:Follow-up angiograms on each day revealed the persistence of poorly enhanced wedge-shaped areas in the parenchymal phase in all cases. In group 1, four of six cases showed poorly enhanced small areas in the follow-up angiograms. In group 2, all cases showed poorly enhanced large areas. In the histopathological specimens, it was observed that immediately after embolization, the particles reached the interlobular arteries in group 1 and the interlobar arteries in group 2. In all cases in group 1, the particles were histologically identified even on day 14. In one case in group 2 on day 14, the particles were not identified.Conclusion:In conclusion, although GMSs and Gelpart were similar in the point of gelatin particles, the level of embolization and the degradation period were different between GMSs and Gelpart.

Cisplatin-conjugated degradable gelatin microspheres: fundamental study in vitro

The object of this study was to generate cisplatin-conjugated gelatin microspheres (GMSs) and to confirm the subsequent release of cisplatin in vitro. The GMSs (1 mg) were immersed in 50 microl of a cisplatin solution (0.06, 0.15, 0.27, 0.30 or 0.54 mg ml(-1)) at 38 degrees C to allow conjugation. The cisplatin-conjugated GMSs were then extensively washed in double-distilled water and freeze-dried. The platinum concentration in the GMSs samples was investigated as a function of the concentration of cisplatin solution used in their preparation, the number of immersions in cisplatin (1, 2, 3, 4 or 5) and the period of immersion (1, 6 or 11 h). In vitro release tests were performed at different time intervals (1, 3, 6, 12 or 24 h) to allow the rate of cisplatin release to be calculated. The platinum concentration of the GMSs increased in proportion to the concentration of cisplatin solution and the length or number of immersions in cisplatin. In vitro release tests demonstrate that the release rate (%) from GMSs after 1, 3, 6, 12 or 24 h was 4.8, 5.5, 7.6, 10.0 and 12.4, respectively. We demonstrated the ability of GMSs to bind cisplatin forming cisplatin-conjugated GMSs. Moreover, we showed that cisplatin continued to bind GMSs strongly during the in vitro release test.

Pluronic F127: Application in Arterial Embolization

PURPOSE Pluronic is a substance that is widely used in medical and pharmaceutical fields. In particular, 20% Pluronic F127 solution is a unique substance that is liquid at less than 15 degrees C and gelatinous at 25 to 60 degrees C. In this study, the authors took advantage of the gelation property of Pluronic F127 at human body temperature to simulate embolization and dissolution of the embolism in the renal artery and the superior mesenteric artery (SMA) using a rabbit model. MATERIALS AND METHODS Four female Japanese rabbits (weight, 2.5-3 kg each) were used. The renal artery was fitted with a 4-F cobra-type catheter and embolized with a 20% Pluronic F127 solution at a temperature of 20 degrees C. The embolic effect was evaluated by angiography immediately after the initial injection and every 15 minutes for 2.5 hours after embolization. After 24 hours, pathologic changes of the renal parenchyma were also evaluated. The embolic effect for SMA and ischemic changes of the intestine were evaluated in the same manner. RESULTS Angiographic findings showed that Pluronic F127 caused embolization immediately after injection and dissolved in the renal artery and the SMA after 90 to 120 minutes. The pathologic findings showed no ischemic change in the renal parenchyma. Necrosis was not found in the intestine, but focal hemorrhagic changes were extensively present when the gel had dissolved. This suggested that Pluronic F127 dissolved before severe tissue damage could occur. CONCLUSION Pluronic F127 can potentially be used as a temporary embolic material.