S. Kariya

Percutaneous Vertebroplasty for Compression Fracture: Analysis of Vertebral Body Volume by CT Volumetry

Purpose: To evaluate the relationships between volume of vertebral bodies with compression fracture (measured by CT volumetry) before percutaneous vertebroplasty, the amount of bone cement injected, and the effect of treatment. Material and Methods: We examined 49 consecutive patients, with 104 vertebral body compression fractures, who underwent percutaneous injection of bone cement. Vertebral body volume was measured by CT volumetry. The patients pain level was assessed using a visual analog scale (VAS) before and after the procedure. Improvement in VAS was defined as the decrease in VAS after the procedure. Relationships between vertebral body volume, the amount of bone cement, and the effect of treatment were evaluated using Pearsons correlation coefficient test. Results: Average vertebral body volume was 26.3±8.1 cm3; average amount of bone cement was 3.2±1.1 ml; and average improvement in VAS was 4.9±2.7. The vertebral body volume was greater if a larger amount of bone cement was injected. There was a significant positive correlation between vertebral body volume and amount of bone cement (r = 0.44; P<0.0001). However, there was no correlation between vertebral body volume and improvement in VAS, or between amount of bone cement and improvement in VAS. Conclusion: In percutaneous vertebroplasty for vertebral body compression fracture, there is a positive correlation between vertebral body volume and amount of bone cement, but improvement in VAS does not correlate with vertebral body volume or amount of bone cement.

Transcatheter Coil Embolization for Steal Syndrome in Patients with Hemodialysis Access

Background: Drainage of large amounts of shunt blood into deep veins via collaterals reduces resistance to venous outflow and decreases blood flow to the artery distal to the arterial anastomotic site, potentially resulting in steal syndrome. Purpose: To evaluate the effectiveness of transcatheter coil embolization for collateral veins of hemodialysis access in the treatment of steal syndrome. Materials and Methods: Five hemodialysis patients (four male, one female; mean age 58.8 years, range 40–71 years) with symptomatic steal syndrome were treated. Steal syndrome was diagnosed based on decreased or absent distal pulse, coolness, pain, abnormal skin color, ischemic ulceration of digits, numbness, sensory impairment, or motor impairment. Coil embolization was performed to block collaterals communicating with deep veins, with conscious sedation and local anesthesia. Fistulography was performed before, immediately after, and 1 month after embolization. Ultrasonography was performed 2 days after embolization. Symptoms and signs were assessed 2 days after embolization. Clinical findings related to steal syndrome and access failure were observed at each hemodialysis. Results: Blood flow in the collaterals was successfully blocked by coil embolization in all patients. Distal pulse, coolness, pain, and skin color improved in all patients. Numbness, sensory impairment, and motor impairment were unimproved in two patients. In all patients, hemodialysis following embolization was performed normally. The mean observation period after embolization was 33 months (range 9–75 months). Conclusion: Coil embolization of collaterals that drain shunt blood into deep veins is effective for steal syndrome for hemodialysis access originating in the brachial artery.

Computed tomography perfusion of the liver: assessment of pure portal blood flow studied with CT perfusion during superior mesenteric arterial portography

Purpose: To quantitatively assess the portal component of hepatic blood flow using computed tomography (CT) perfusion studies during superior mesenteric arterial portography. Material and Methods: Thirty-four patients with hepatocellular carcinoma and liver cirrhosis (LC) and 13 patients with liver metastasis without chronic liver disease were enrolled in this study. Ten milliliters of a non-ionic contrast medium (150 mgI) was injected at a rate of 5 ml/s via a catheter placed in the superior mesenteric artery. Single-slice cine CT images at the level of the main trunk or the right/left main trunk of the portal vein were acquired over 40 s. The deconvolution method was then used on these CT images to measure blood flow (BF), blood volume (BV), and mean transit time (MTT) in (a) liver parenchyma in patients with HCC and liver cirrhosis; (b) liver parenchyma in patients with liver metastasis without cirrhosis; (c) directly in the HCC; and (d) directly in one of the metastases. Results: In 34 LC patients (a), BF, BV, and MTT in the liver parenchyma were 44.7±24.5 ml/min/100 g, 3.9±2.4 ml/100 g, and 10.9±5.5 s, respectively. In 13 patients without cirrhosis (b), BF, BV, and MTT in the liver parenchyma were 89.6±52.0 ml/min/100 g, 6.3 ±3.2 ml/100 g, and 8.7±3.6 sec, respectively. A significant difference in BF and BV was seen in patients with liver cirrhosis compared to those without cirrhosis. BF, BV, and MTT measured directly in HCC (c) were 6.5±4.5 ml/min/100 g, 0.4±0.4 ml/100 g, and 3.0±3.1 sec respectively, and BF, BV, and MTT in liver metastases (d) were 19.3 ± 21.7 ml/min/100 g, 0.6±0.8 ml/100 g, and 1.8±1.6 s, respectively. Conclusion: CT perfusion studies during superior mesenteric arterial portography allow quantitative assessment of pure portal blood flow in the liver.

Three‐dimensional angiography using rotational digital subtraction angiography: usefulness in transarterial embolization of hepatic tumors

Purpose: To assess the usefulness of three‐dimensional (3D) angiography using rotational digital subtraction angiography (DSA) in transarterial embolization of hepatic tumors. Material and Methods: Thirty‐one 3D angiographies were conducted using rotational DSA during abdominal angiography for transarterial embolization of hepatic tumors. The quality of visualization of the tumor and feeder arteries as imaged by 3D angiography versus DSA anterioposterior (AP) images was compared. Results: 3D rotational angiography provided excellent 3D visualization of the vascular structures of the hepatic artery, and was especially useful in patients with overlapping tumors on DSA AP images and in patients with complex vascular anatomies. Compared to DSA AP images, however, tumor stains could not be detected on 3D‐A, but could be detected on DSA in four patients (13%). In 9 patients, feeding arteries could not be detected on 3D‐A, but could be detected on DSA (29%). Conclusion: 3D rotational angiography alone may not be suitable for pre‐procedural mapping in transarterial embolization of hepatic tumors, but may be of value when information supplementary to DSA AP images is needed.

Percutaneous Transluminal Cutting-Balloon Angioplasty for Hemodialysis Access Stenoses Resistant to Conventional Balloon Angioplasty

Purpose: To examine the value of cutting-balloon percutaneous transluminal angioplasty (PTA) for hemodialysis access with residual stenosis after conventional balloon PTA. Material and Methods: Angioplasty with conventional balloons was performed on 48 hemodialysis access stenoses in 28 patients. If the balloon waist still remained at the rated burst pressure, the balloon was reinflated up to three times. Fifteen of 48 stenoses had residual stenoses of more than 30% after conventional balloon PTA. In these 15 stenoses, additional cutting-balloon PTA was performed. Results: The mean residual percent diameter stenoses before and after conventional balloon PTA were 77.6±3.4% and 48.6±8.5%, respectively. Additional cutting-balloon PTA decreased the mean residual percent diameter to 27.9±10.0%, and the cutting balloon was completely inflated without complication. In 12 patients, the 6-month primary patency rate (±SE) was 90.0% (9.5), and the 1-year primary patency rate (±SE) was 25.0% (14.8). Conclusion: Additional cutting-balloon PTA was found useful for reducing residual stenosis.

Diffusion-weighted imaging for predicting new compression fractures following percutaneous vertebroplasty

Background: Percutaneous vertebroplasty (PVP) is a technique that structurally stabilizes a fractured vertebral body. However, some patients return to the hospital due to recurrent back pain following PVP, and such pain is sometimes caused by new compression fractures. Purpose: To investigate whether the apparent diffusion coefficient (ADC) of adjacent vertebral bodies as assessed by diffusion-weighted imaging before PVP could predict the onset of new compression fractures following PVP. Material and Methods: 25 patients with osteoporotic compression fractures who underwent PVP were enrolled in this study. ADC was measured for 49 vertebral bodies immediately above and below each vertebral body injected with bone cement before and after PVP. By measuring ADC for each adjacent vertebral body, ADC was compared between vertebral bodies with a new compression fracture within 1 month and those without new compression fractures. In addition, the mean ADC of adjacent vertebral bodies per patient was calculated. Results: Mean preoperative ADC for the six adjacent vertebral bodies with new compression fractures was 0.55×10−3 mm2/s (range 0.36–1.01×10−3 mm2/s), and for the 43 adjacent vertebral bodies without new compression fractures 0.20×10−3 mm2/s (range 0–0.98×10−3 mm2/s) (P<0.001). Mean preoperative ADC for the six patients with new compression fractures was 0.55×10−3 mm2/s (range 0.21–1.01×10−3 mm2/s), and that for the 19 patients without new compression fractures 0.17×10−3 mm2/s (range 0.01–0.43×10−3 mm2/s) (P<0.001). Conclusion: The ADC of adjacent vertebral bodies as assessed by diffusion-weighted imaging before PVP might be one of the predictors for new compression fractures following PVP.

Improvement in respiratory function by percutaneous vertebroplasty

Background: Percutaneous vertebroplasty (PVP) improves back pain and corrects spinal misalignment to some extent, and thus may improve respiratory function. Purpose: To retrospectively investigate changes in respiratory function after PVP. Material and Methods: 41 patients (mean age 72.0 years, range 59–86 years; 39 women, two men) who had undergone PVP for vertebral compression fractures (37 thoracic vertebral bodies [Th6–Th12] and 50 lumbar vertebral bodies [L1–L5]) caused by osteoporosis visited our hospital for follow-up consultation between January and June 2005. At this follow-up consultation, respiratory function testing, including percent forced vital capacity (FVC%) and percent forced expiratory volume in 1 s (FEV1%), was performed. We retrospectively compared these values with those taken before PVP using a Wilcoxon signed-rank test. Results: FVC% was 85.2±30.3% before PVP and 91.5±16.8% at follow-up (mean 10 months after PVP), which represented a significant difference (P<0.003). No significant difference in FEV1% was detected. Regarding the number of treatment levels, that is, single vertebroplasty versus multiple vertebroplasty, no significant difference in improvement of FVC% was confirmed (P=0.1). FVC% was abnormally low (≤79%) before PVP in 16 patients and improved to within normal range postoperatively in six of these patients (38%). Conclusion: PVP improves preoperatively decreased lung function, but this improvement takes time.

Composite material stent comprising metallic wire and polylactic acid fibers, and its mechanical strength and retrievability

Background: Although metallic stents are characterized by strong expanse of force, thin walls, and easy stent deployment, their removal from the body is usually difficult or impossible due to the difficulty of unraveling their mesh structure. A stent built of a composite material comprising a metallic wire and a polylactic acid (PLA) fiber, in which the metallic wire component could be unraveled after PLA fiber degradation in the body, should allow easy stent removal. Purpose: To evaluate the mechanical strength and retrievability of a composite material stent comprising a metallic wire and a PLA fiber. Material and Methods: We produced a composite material stent comprising a metallic wire and a biodegradable fiber (hybrid stent). As the metallic wire is not cross-linked with itself, but with the PLA fibers only, the hybrid stent can be easily unraveled after PLA fiber degradation. This stent was built with a 0.2-mm stainless-steel wire and a 0.23-mm PLA fiber knitted in the same textile as an Ultraflex stent. For comparison, an identical stent was built using PLA fiber only (PLA stent). The mechanical strength of these stents was tested by the radial expansive force response against circumferential shrinkage stress load. Change in radial force due to PLA fiber degradation was estimated by adding an artificial PLA degeneration process, by immersing each stent in a water bath at 80°C for 48 hours. Retrievability of the hybrid stent after PLA degeneration was examined by hooking and pulling out the residual stainless-steel wire from a silicon tube. Results: The hybrid stent exhibited a linear response in radial expansive force within the range of 15% diameter reduction. The PLA stent did not exhibit linear response at over 15% diameter reduction. Decrease of radial expansive force after PLA degradation was within 5% of the original force in the hybrid stent, but the PLA stent did not create effective radial expansive force. Hybrid stents, even after PLA degradation, exhibited a linear response in radial expansive force, within the range of 15% diameter reduction. The metallic component of the heat-processed hybrid stent was easily unraveled by pulling out the wire. Conclusion: The hybrid stent comprising a stainless-steel wire and a PLA fiber appears to provide effective radial expansive force and retrievability.

Cerebral microembolisation during radiofrequency ablation of lung tumours: detection by carotid duplex ultrasound

The aim of this study was to investigate the appearance of microbubbles during radiofrequency ablation (RFA) of lung tumours. Eight consecutive patients (mean age, 73.1 years; 3 men and 5 women; 10 malignant lesions; mean lesion size, 24.8 mm) who underwent RFA of lung tumours using internally cooled single electrodes were enrolled. During the RFA procedure, the right internal carotid artery was continuously monitored by duplex ultrasound. High-intensity transient signals (HITS) that occurred in the Doppler blood flow waveform were taken to indicate microbubbles. 21 RFA applications were performed for the 10 lesions. HITS were observed in 19 of 21 RFA applications; the mean frequency in a single application was 10+/-13.3. A statistical correlation was seen between the duration of energy deposition and the number of HITS, and between tumour size and the number of HITS. Microbubbles were detected in all patients in the late phase of the first session of RFA.

Gadolinium-enhanced magnetic resonance imaging after percutaneous vertebroplasty does not improve the short-term prediction of new compression fractures.

Purpose: To investigate the relationships between contrast-enhanced magnetic resonance imaging (MRI) findings and new compression fractures occurring after percutaneous vertebroplasty (PVP) in order to determine the necessity of contrast-enhanced MRI. Material and Methods: The material comprised 13 consecutive patients (27 vertebrae) with compression fractures who underwent vertebroplasty. Twenty-nine adjacent vertebrae were monitored for new compression fractures. We performed contrast-enhanced MRI within the 5 days following PVP. Results: The 29 adjacent vertebrae displayed 10 enhanced lesions and 19 vertebral bodies without enhancement–unenhanced lesions on MRI within the 5 days after PVP. In 4 out of 10 vertebrae, enhanced lesions were seen within the 5 days after PVP, but no abnormalities were seen on preoperative MRI. In these 4 vertebrae, new compression fractures were seen within the 1 month following PVP. In the other 6 vertebrae, enhanced lesions were seen within the 5 days after PVP, and these signal changes were detected by preoperative MRI in the same area. In 3 of these 6 vertebrae, new compression fractures occurred at 4, 8, and 9 months after PVP, respectively. However, all of the enhanced lesions were detectable on unenhanced MRI, which was conducted at the same time as enhanced MRI. Conclusion: New compression fractures after PVP may be predicted with early postoperative MRI. Contrast-enhanced MRI does not improve detection of the new lesions.