Evaluation of Conditions for the Development of Cryogenic Spinal Cord Injury Using a Canine Model: An Experimental Study on the Safety of Cryoablation for Metastatic Spinal Tumors.

BACKGROUND AND PURPOSE: Although the application of cryoablation to metastatic spinal tumors has been attempted, spinal cryoablation has the unique complication of cryogenic spinal cord injury. This study aimed to elucidate the conditions for the development of cryogenic spinal cord injury. MATERIALS AND METHODS: Fifteen canines were used in this study. A metal probe was inserted into the 13th thoracic vertebral body. Cryoablation was performed for 10 minutes by freezing the probe in liquid nitrogen. The control canine underwent probe insertion only. Spinal cord monitoring, epidural temperature measurement, motor function assessment, and pathologic examination of the spinal cord were performed. RESULTS: During the 10 minutes of cryoablation, the epidural temperature decreased and reached the lowest epidural temperature (LET) at the end of cryoablation. The LETs (degrees celsius [°C]) of each canine were -37, -30, -27, -8, -3, -2, 0, 1, 4, 8, 16, 18, 20, and 25, respectively. As the epidural temperature decreased, waveform amplitudes also decreased. At the end of cryoablation (10 minutes after the start of cryoablation), abnormal waves were observed in 92.9% (13/14) of canines. With epidural rewarming, the amplitude of the waveforms tended to recover. After epidural rewarming (2 hours after the start of cryoablation), abnormal waves were observed in 28.6% (4/14) of canines. The LETs (°C) of the canines with abnormal waves after epidural rewarming were -37, -30, -27, and -8. None of the canines with normal waves after epidural rewarming had any motor impairment. In contrast, all canines with remaining abnormal waves after epidural rewarming had motor impairment. In the pathologic assessment, cryogenic changes were found in canines with LETs (°C) of -37 -30, -27, -8, 0, and 1. CONCLUSIONS: This study showed that 10-minute spinal cryoablation with LETs (°C) of -37, -30, -27, -8, 0, and 1 caused cryogenic spinal cord injury. There was no evidence of cryogenic spinal cord injury in canines with LET of ≥4°C. The epidural temperature threshold for cryogenic spinal cord injury is between 1 and 4°C, suggesting that the epidural temperature should be maintained above at least 4°C to prevent cryogenic spinal cord injury.

Stent Graft Placement for Injured Visceral Artery.

Injury of the visceral artery is a potentially fatal complication of iatrogenic procedures, trauma, and tumors. A stent graft can achieve rapid exclusion of the injured arterial portion and minimize the risk of ischemic complications by preserving arterial flow to organs. Although various types of stent grafts are available worldwide, Viabahn has only been approved for visceral arterial injury in Japan. The reported technical and clinical success rates, including cases with injured pelvic or thoracic arterial branches, are 80%-100% and 66.7%-100%, respectively. Severe ischemic complications are rare; however, fatal ischemia occurs when the stent graft is immediately occluded. The necessity of antiplatelet therapy is controversial, and a target artery diameter ≤ 4 mm is a significantly higher risk factor of stent-graft occlusion.

Tumor-Specific Immunoenhancing Effects after Local Cryoablation for Metastatic Bone Tumor in a Mouse Model.

We investigated the abscopal effect after cryoablation (CA) on bone metastasis using a mouse model. Breast cancer cells were implanted in the bilateral tibiae of mice. The left tumor was treated locally with CA, and the right abscopal tumor (AT) was left untreated. The mice were divided into four groups based on the combination of CA and intraperitoneal administration of anti-PD-1 antibody (PD) as treatment interventions (Control, CA, PD, and CA + PD). The reduction ratio of the size of AT, the quantitative immune effects at enzyme-linked immunospot (ELISPOT) assay, and the intensity of infiltration of immune-related cells to AT were compared among the groups. CA alone showed a significant immunoenhancing effect on the volume change ratio of AT from day 0 to day 14 (Control-CA: p < 0.05), ELISPOT assay (Control-CA: p < 0.01), and CD4+ cell count in immunostaining (Control-CA: p < 0.05). CA alone showed no significant immunoenhancing effect on CD8+ and Foxp3+ cell counts in immunostaining, but the combination of CA and PD showed a significant immunoenhancing effect (Control-CA + PD: p < 0.01 [CD8, Foxp3]). The results suggested that the abscopal effect associated with the local cryotherapy of metastatic bone tumors was activated by CA and enhanced by its combination with PD.

Coil-assisted retrograde transvenous obliteration (CARTO) for the treatment of gastric varices via a single access route using steerable microcatheter: a case report.

BACKGROUND: Coil-assisted retrograde transvenous obliteration (CARTO) is a modified balloon-occluded retrograde transvenous obliteration (BRTO) technique using coils instead of an indwelling balloon. A method involving two microcatheter systems forming a double access route has been reported. We report a case of CARTO using a steerable microcatheter to successfully treat gastric varices (GV). CASE PRESENTATION: A 79-year-old man was admitted for treatment of intractable GV due to liver cirrhosis. The GV were drained mainly into the left inferior phrenic vein, not the usual gastrorenal shunt. Introducing the balloon catheter to the left inferior phrenic vein was difficult due to mild stenosis between the inferior vena cava and inferior phrenic vein and the shunt angle. A CARTO technique was performed with 5% ethanolamine oleate with iopamidol from a single access route by inverting the steerable microcatheter distal to the coil placement site. CONCLUSION: CARTO has advantages in cases where performing BRTO is difficult. Using a steerable microcatheter simplifies the procedure by reducing the required access routes in CARTO.

Peribiliary glands: development, dysfunction, related conditions and imaging findings.

Peribiliary glands are minute structures that are distributed along the intrahepatic large bile ducts, extrahepatic bile duct, and cystic duct. These glands regulate many physiological functions, such as enzyme secretion. Pancreatic exocrine tissues and enzymes are often observed in peribiliary glands; thus, peribiliary glands are involved in enzyme secretion. As such, these glands can be affected by conditions such as IgG4-related sclerosing cholangitis based on commonalities with their pancreatic counterparts. Cystic changes in peribiliary glands can occur de novo, as part of a congenital syndrome, or secondary to insults such as alcoholic cirrhosis. Biliary tree stem/progenitor cells have recently been identified in peribiliary glands. These cells are involved in turnover and regeneration of biliary epithelia as well as in sclerosing reactions in some pathological conditions, such as primary sclerosing cholangitis and hepatolithiasis. Notably, hepatolithiasis is involved in mucin secretion by the peribiliary glands. Additionally, these cells are associated with the manifestation of several neoplasms, including intraductal papillary neoplasm, cystic micropapillary neoplasm, and cholangiocarcinoma. Normal peribiliary glands themselves are particularly small structures that cannot be recognized using any available imaging modalities; however, these glands are closely associated with several diseases, as mentioned above, which have typical imaging features. Therefore, knowledge of the basic pathophysiology of peribiliary glands is helpful for understanding biliary diseases associated with the peribiliary glands.

CT imaging comparison between intraductal papillary neoplasms of the bile duct and papillary cholangiocarcinomas.

OBJECTIVES: To identify imaging features that assist in discriminating intraductal papillary neoplasms of the bile duct (IPNBs) from papillary cholangiocarcinomas (PCCs). METHODS: This study was approved by the institutional review board. Using the recently proposed histological diagnostic criteria for biliary papillary neoplasms, IPNBs and PCCs were selected from 537 biliary neoplasms consecutively resected in a 12.5-year period. Clinical and imaging features were compared between the two groups. RESULTS: The histology review identified 19 IPNBs and 48 PCCs, representing an estimated prevalence of IPNBs among biliary neoplasms of 4%. Approximately one half of IPNBs were incidentally found on imaging conducted for other purposes. In terms of tumor location, 15/19 IPNBs (79%) developed in intrahepatic bile ducts, and 41/48 PCCs (85%) in the distal bile duct. Cystic appearance was highly suggestive for IPNBs (p < 0.001). Using these two parameters, 78% of papillary bile duct neoplasms could be classified into IPNBs or PCCs. Other imaging findings favoring IPNBs included frond-like mural nodule, downstream bile duct dilatation, and the lack of abnormal enhancement in the adjacent bile duct. Interestingly, two patients with non-invasive or microinvasive IPNB had undergone abdominal imaging studies > 3 years before, and a retrospective review of the previous images identified small nodular or cystic lesions, suggesting a less progressive nature of IPNBs than currently thought. CONCLUSIONS: Imaging findings useful for discriminating IPNBs from PCCs appear to be tumor location, shape of tumor, appearance of mural nodules, duct dilatation at unaffected duct, and abnormal enhancement of the adjacent bile duct. KEY POINTS: • Intrahepatic location and cystic dilatation of the affected bile duct are the strong discriminators between IPNBs and PCCs. • The shape of the mural nodule and appearance of the neighboring bile duct are helpful for distinguishing IPNBs and PCCs. • The less aggressive behavior of IPNBs compared with PCCs may facilitate less invasive management in patients with IPNB.

Excretion of necrotic hepatocellular carcinoma tissues into the biliary system after transcatheter arterial chemoembolization.

AIM: To evaluate the incidence and condition of necrotic tumor excretion into the biliary system in patients with hepatocellular carcinoma (HCC) >5 cm treated with conventional transcatheter arterial chemoembolization (TACE). METHODS: Eighty-three patients who underwent TACE for newly developed HCC >5 cm without an intraductal tumor thrombus and were followed-up by computed tomography for longer than 6 months were eligible. According to the location, the maximum tumors were divided into central (in contact with the left or right hepatic duct, n = 39) or peripheral (not in contact with them, n = 44). When high-density material in the biliary system that was not seen on pretreatment computed tomography was identified, it was determined as excreted necrotic tumor tissue containing iodized oil. The incidence, interval between TACE and occurrence of the necrotic tumor excretion, and clinical course were evaluated. RESULTS: Tumor excretion into the biliary system was identified in nine (10.8%) patients with a central tumor (mean diameter, 85.0 ± 29.6 mm) 28-433 days (mean, 219.3 ± 128.2) after the initial TACE. In one patient, the necrotic tumor cast caused cholangitis 1203 days after the initial TACE, and was endoscopically removed. Infection of the embolized tumor developed in two cases and percutaneous drainage was carried out 105 and 158 days later, respectively. CONCLUSIONS: Excretion of necrotic tumors into the biliary system after TACE was not rare in patients with centrally located HCC >5 cm. The detached tumor rarely caused symptoms and the communication between the tumor and bile duct caused the infection of tumors.

Performance of novel virtual parenchymal perfusion software visualizing embolized areas of transcatheter arterial chemoembolization for hepatocellular carcinoma.

AIM: To evaluate the performance of novel virtual parenchymal perfusion (VPP) software in conventional transcatheter arterial chemoembolization (cTACE) for hepatocellular carcinoma. METHODS: VPP was retrospectively applied to 43 hepatocellular carcinomas treated with cTACE. The virtual embolized area (VEA) was estimated after positioning a virtual injection point on images of non-selective cone-beam computed tomography during hepatic arteriography, at the same position in superselective cTACE. The real embolized area (REA) was defined as the area where iodized oil was retained on 1-week computed tomography after cTACE. Three dimensions across the tumor (maximum [a] and minimum [b] in the axial and craniocaudal [c]) directions, and the volume of the VEA and REA were compared using linear regression analysis. It was also evaluated whether an adequate safety margin ≥5 mm could be predicted by VPP. RESULTS: The mean lengths of a, b, and c of the VEA and REA were 54.6 ± 15.9 mm (range 24.9-91.0 mm) and 55.0 ± 15.7 mm (range 23.9-92.8 mm; r = 0.9448, P < 0.001), 35.4 ± 11.7 mm (range 16.1-66.0 mm) and 35.4 ± 13.2 mm (range 12.2-69.2 mm; r = 0.9369, P < 0.001), and 42.1 ± 11.6 mm (range 25.0-75.7 mm) and 42.9 ± 11.7 mm (range 25.7-78.7 mm; r = 0.9092, P < 0.001), respectively. The mean volume of the VEA and REA was 71.8 ± 44.8 mL and 75.5 ± 46.9 mL, respectively (r = 0.9913, P < 0.0001). VPP showed no safety margins in seven tumors, including all three actually embolized without safety margins. CONCLUSION: The VEA estimated using VPP showed a good correlation with the REA of cTACE.