Transaneurysmal Occlusion of Complicated Common Femoral Artery Pseudoaneurysms Using the Angio-Seal Closure Device-A Promising Technique.

PURPOSE: Pseudoaneurysm (PSA) developing after catheter examinations is one of the most frequent vascular complications and a nonsurgical technique with utmost low risk of complications is warranted. Our aim was to investigate the technical feasibility, success, and safety of transaneurysmal occlusion of complicated post-interventional common femoral artery (CFA) PSA using the Angio-Seal Closure Device (ASCD) and a technique that we describe as the transaneurysmal (TA) maneuver. MATERIAL AND METHODS: We used the Angio-Seal (Terumo, Tokyo, Japan) Closure System to manage complicated PSAs in patients who would otherwise have needed surgery after failure of all conservative therapies. The TA maneuver was performed in 14 consecutive patients from July 2021 to July 2022. After ultrasound-guided puncture of the PSA close to its neck, the CFA was entered radiographically with micro-guidewires, and the neck of the PSA was closed with the ASCD after changing the sheaths and wires. All patient had to wear a pressure dressing until the next day, when successful closure was verified by sonography. RESULTS: All procedures were performed with technical success and without any complications. No patient had to undergo surgery. All sonographies on the next day confirmed complete absence of perfusion within the PSA and normal flow conditions of the CFA and vessels below. CONCLUSION: The TA maneuver a promising minimally invasive procedure for closing complicated PSA of the CFA after catheter examination.

C-Arm Cone Beam CT for Intraprocedural Image Fusion and 3D Guidance in Portal Vein Embolization (PVE).

PURPOSE: Portal vein embolization (PVE) is applied in patients with extended oncologic liver disease to induce hyperplasia of the future liver remnant and make resection feasible. Ultrasound (US) guidance is the gold standard for percutaneous portal vein access. This study evaluated feasibility and safety of C-arm cone beam computed tomography (CBCT) for needle guidance. MATERIALS AND METHODS: In 10 patients, puncture was performed under 3D needle guidance in a CBCT data set. Contrast-enhanced (CE) CBCT was generated (n = 7), or native CBCT was registered to pre-examination CE-CT via image fusion (n = 3). Technical success, number of punctures, puncture time (time between CBCT acquisition and successful portal vein access), dose parameters and safety were evaluated. For comparison, 10 patients with PVE under US guidance were analyzed retrospectively. Study and control group were matched for age, BMI, INR, platelets, portal vein anatomy. RESULTS: All interventions were technically successful without intervention-related complications. In the study group, the mean number of puncture attempts was 3.1 ± 2.5. Mean puncture time was 12 min (±10). Mean total dose area product (DAP) was 288 Gy cm2 (±154). The mean relative share of CBCT-related radiation exposure was 6% (±3). Intervention times and DAP were slightly higher compared to the control group without reaching significance. CONCLUSION: CBCT-guided PVE is feasible and safe. The relative dose of CBCT is low compared to the overall dose of the intervention. This technique may be a promising approach for difficult anatomic situations that limit the use of US for needle guidance.

Intra-arterial ultra low iodine CT angiography of renal transplant arteries.

PURPOSE: This study was designed to evaluate the technical feasibility and the image quality of intra-arterial 320-row CT angiography (ia-CTA) in the detection of transplant renal artery stenosis (TRAS) using a very low dose of contrast agent. METHODS: Evaluation of ia-CTA using a 4F catheter in ten patients with impaired renal transplant function and suspected TRAS. Average amount of contrast agent applied was 10 ± 3.7 ml standard deviation (SD). Patient serum creatinine levels had been monitored for 72 h. TRAS was detected and graded (1: less than 20 %; 2: 20-49 %; 3: 50-74 %; 4: 75-99 %; 5: total occlusion) and presence of kinking was recorded. Attenuation and vessel delineation were parameters for image quality analysis of the renal arterial supply, divided into four segments. Subjective image quality. RESULTS: Ia-CTA of the renal transplant was technically successful in all patients, revealing relevant stenoses in 7 of 10 patients. Serum creatinine levels before and after ia-CTA were 2.71 ± 1.46 and 2.56 ± 1.39 mg/dl, respectively. None of the patients developed signs of contrast-induced nephropathy within 72 h. Subjective image quality was excellent in all four segments, rated by two separate readers. No segment was found to be nondiagnostic. Mean attenuation values in the arterial segments ranged between 754 and 987 Hounsfield units. CONCLUSIONS: Wide detector ia-CTA for the diagnosis of TRAS is feasible using very low doses of contrast agent and results in high image quality.

Simultaneous dual-isotope SPECT/CT with (99m)Tc- and (111)In-labelled albumin microspheres in treatment planning for SIRT.

OBJECTIVES: To investigate simultaneous dual-isotope SPECT/CT with two differently radioisotope-labelled albumin-microsphere fractions for treatment planning of hepatic radioembolisation. METHODS: In addition to (99m)Technetium-labelled albumin microspheres (commercially available), we performed labelling with (111)Indium. Binding stability of (111)Indium-labelled microspheres was tested in vitro and in vivo in mice. Simultaneous dual-isotope SPECT/CT imaging was validated in an anthropomorphic torso phantom; subsequently, dual-isotope SPECT/CT was performed under in-vivo conditions in pigs (n = 3) that underwent transarterial injection of (99m)Technetium- and (111)Indium-labelled microspheres in the liver (right and left hepatic artery, respectively), in both kidneys and in the gluteal musculature. In total, n = 18 transarterial injections were performed. RESULTS: In-vitro testing and in-vivo studies in mice documented high binding stability for both (99m)Technetium-labelled and (111)Indium-labelled microsphere fractions. In phantom studies, simultaneous dual-isotope SPECT/CT enabled reliable separation of both isotopes. In pigs, the identified deposition of both isotopes could be accurately matched with intended injection targets (100 %, 18/18 intended injection sites). Furthermore, an incidental deposition of (99m)Technetium-labelled microspheres in the stomach could be correlated to the test injection into a right hepatic artery. CONCLUSION: Simultaneous dual-isotope SPECT/CT after transarterial injection with (99m)Technetium- and (111)Indium-labelled microspheres is feasible. Thus, it may offer additional, valuable information compared to single (99m)Technetium-labelled albumin examinations. KEY POINTS: • Simultaneous dual-isotope SPECT/CT with (111) In- and (99m) Tc-labelled albumin microspheres is feasible. • Differentiation of two microsphere fractions after transarterial injection is possible. • The origin of an extra-hepatic microsphere deposition can be correlated to the corresponding artery. • This technique could reduce the setup time for selective internal radiation treatment.

Contrast-enhanced MRI predicts local recurrence of osteoid osteoma after radiofrequency ablation.

INTRODUCTION: Osteoid osteoma is a painful benign tumour, which is commonly treated by radiofrequency ablation (RFA). The goal of this study is to assess the value of contrast-enhanced magnetic resonance imaging (MRI) for predicting clinical success after RFA of osteoid osteoma. METHODS: Twenty consecutive patients (14 male, 6 female; mean age 23.3 ± 13.4 years) suffering from osteoid osteoma underwent unenhanced and contrast-enhanced T1-weighted MRI the day after RFA. Post-interventional contrast enhancement of the nidus was analyzed by comparing signal-to-noise ratios (SNR) of the nidus before and after contrast administration. The SNR between pre- and post-contrast scans was computed. RESULTS: There were no significant differences in SNR between pre- and post-contrast scans in the area of ablation (P = 0.1583), while the SNR exceeded one in four patients, indicating residual contrast enhancement. In three of these patients clinical symptoms recurred, requiring re-ablation, while one patient remained free from symptoms during follow-up. In patients with a pre- and post-contrast SNR of ≤ 1.18 no local recurrence was observed. CONCLUSIONS: Contrast enhancement on T1-weighted MRI imaging seems to be predictive of clinically unsuccessful RFA in osteoid osteoma. Patients with a SNR increase of ≥ 20% after contrast administration might be considered for re-ablation to avoid symptomatic tumour recurrence.

High pressure versus standard port system: comparison of implantation and complications.

INTRODUCTION: Completely implantable access ports for high pressure contrast media injection have been in use in clinical routine for a relatively short time. The purpose of our study was to compare a high pressure port system with a standard port system with regard to implantation and complications. METHODS: In 94 oncological patients a completely implantable access port was implanted. Patients (n = 49) planned for oncological follow-up computed tomography (CT) received a high pressure port system. Other patients (n = 45) received a standard port system. Intrainterventional pain perception, postinterventional catheter tip migration and complications were analyzed. RESULTS: No major periinterventional complications occurred. Intrainterventional pain perception was not significantly different between the two groups. A significantly lower rate of tip migration was observed in the high pressure port group (P = 0.03) and when the port system was implanted on the right side (P = 0.03). In the standard port group catheter occlusion occurred in three patients (7%) and a catheter loop in one patient (2%) whereas no such complications occurred within the high pressure port group. Venous thrombosis was detected in one patient (2%) with a high pressure port; this did not occur in the standard port group. CONCLUSIONS: Implantation and use of a high pressure port device is safe and reliable: the complications are comparable to those of a standard port device. High pressure port systems should be considered for implantation, especially in patients who will require frequent CTs.

Bile aspiration and hydrodissection to prevent complications in hepatic RFA close to the gallbladder.

BACKGROUND: Radiofrequency ablation (RFA) of liver tumors is a mainstay of interventional oncology. Its application, however, is limited by tumor size and location with lesions located within 1 cm to the gallbladder being at increased risk for complications. PURPOSE: To evaluate the safety of hepatic RFA after bile aspiration with or without additional hydrodissection for lesions adjacent to the gallbladder. MATERIAL AND METHODS: Six patients undergoing RFA of tumors with a distance of less than 1 cm to the gallbladder were retrospectively identified from a computer database. All patients underwent RFA combined with percutaneous bile aspiration from the gallbladder. In four patients additional hydrodissection was performed. Technical success and post-interventional complications were assessed by reviewing images and patient charts. RESULTS: Ablations were successfully completed in 5/6 patients. In one patient with incomplete ablation re-ablation was performed 2 months after the initial procedure. Minor complications occurred in three patients, including right-sided pleural effusion, hematoma in the gallbladder fossa, and intralesional hemorrhage in one patient each. There were no cases with cholecystitis or damage to the gallbladder during follow-up. CONCLUSION: Bile aspiration with or without additional hydrodissection permits safe RFA of tumors located close to the gallbladder.

Web-based bone age assessment by content-based image retrieval for case-based reasoning.

PURPOSE: Maturity estimation by radiological bone age assessment (BAA) is a frequent task for pediatric radiologists. Following Greulich and Pyle, all hand bones are compared with a standard atlas, or a subset of bones is examined according to Tanner and Whitehouse. We support BAA comparing the epiphyses of a current case to similar cases with validated bone age by content-based image retrieval (CBIR). METHODS: A web-based prototype case-based retrieval system for BAA was developed and is publicly available. Hand radiographs from the USC database or user uploads may be retrieved by image-based query. The ten best matching cases for each epiphysis are retrieved by CBIR and displayed with their BAA, similarity score, and the derived age estimate. The similarity is approximated by cross-correlation. The USC hand database includes 1,101 cases comprising four ethnic groups of both genders between zero and 18 years of chronological age with radiographs and two annotated BAA. The USC image data have been enriched by marking the epiphyseal centers between metacarpals and distal phalanges. RESULTS: Leave-one-out experiments yielded a mean error rate of 0.99 years and a standard deviation of 0.76 years in comparison with the mean USC-BAA. The research prototype enables radiologists to judge their agreement based on similarity of retrieved cases and the derived age. CONCLUSIONS: CBIR provides support to the radiologist with a second opinion for BAA. Self-explanatory web applications can be established to support workflow integration. Enhancements in similarity computation and interface usability may further improve the system.

Functional MR imaging of the eustachian tube in patients with clinically proven dysfunction: correlation with lesions detected on MR images.

OBJECTIVES: To visualise the function of the Eustachian tube by MRI and assess the effect of surrounding lesions. METHODS: Using 1.5 T MRI, 32 Eustachian tubes of 16 patients with clinically proven dysfunction (clinical symptoms, such as autophonia and fullness and non-opening at tympanometry) were investigated. For depiction of the anatomy and associated abnormalities, coronal and axial T2-weighted turbo spin echo sequences and a T1-weighted-2D-gradient echo sequences were acquired. Eustachian tube opening was analysed with real time turbo-gradient echo sequences during a Valsalva manoeuvre. RESULTS: Dysfunction, that is, failure of opening of the Eustachian tube as shown by MRI, correlated in all patients with tympanometry. Lesions detected included nasopharyngeal carcinoma in 4 patients. Mucosal swelling in the paranasal sinus was present in 9 patients. One patient had postoperative defects. In two patients both pharyngotympanic tubes did not open although no structural abnormalities could be depicted. CONCLUSIONS: The opening of the Eustachian tubes during the Valsalva manoeuvre is assessable on MRI. Failure of opening may be due to swelling of the mucosa and may be also associated with tumours. MRI assessment may be helpful in patients with chronic otitis media, where the information about tubal function is important in preoperative planning. KEY POINTS: •Eustachian tube opening during Valsalva manoeuvre can be visualised with MRI •Lesions hampering tubal opening can be delineated at the same MRI examination •Functional MRI of the Eustachian tubes might determine the cause of dysfunction.

Volumetric arterial enhancement fraction predicts tumor recurrence after hepatic radiofrequency ablation of liver metastases: initial results.

OBJECTIVE: The objective of our study was to investigate the diagnostic value of the volumetric arterial enhancement fraction of the liver with color mapping for the early detection of tumor relapse after hepatic radiofrequency ablation (RFA). MATERIALS AND METHODS: Fifty-three patients (24 men, 29 women; mean age ± SD, 65 ± 10 years) with a total of 215 liver metastases treated by RFA and a mean postinterventional follow-up period of 20 ± 15 (SD) months were included in this retrospective study. Quantitative arterial enhancement fraction color maps of the whole liver were computed from triple-phase contrast-enhanced MDCT images. Follow-up examinations served as the standard of reference. The diagnostic performance of the arterial enhancement fraction color maps to predict subsequent tumor occurrence before tumor was visible on routine multiphase CT images was evaluated. RESULTS: The mean arterial enhancement fraction of segments that developed metastases (62% ± 23%) was significantly higher than the mean of segments that did not develop metastases (39% ± 20%) (p < 0.0001). Receiver operating characteristic curve analysis revealed a probability of 77% for arterial enhancement fraction values to be higher in case of subsequent metastases as compared with liver parenchyma without tumor recurrence. CONCLUSION: The arterial enhancement fraction provides incremental value in the imaging surveillance for liver metastases after RFA. Arterial enhancement fraction color maps may be suited to predict tumor recurrence earlier than routine assessment using contrast-enhanced MDCT.

Low-osmolar monomeric versus iso-osmolar dimeric contrast media: an intra-individual comparison in CT angiography using an animal model.

INTRODUCTION: The aim of this study was to compare intra-individual contrast enhancement in multidetector-row computed tomography using the low-osmolar monomeric iopromide 300 and the iso-osmolar dimeric iodixanol 320. METHODS: Repeated computed tomography scanning of the chest of five pigs was performed under standardised conditions using iopromide 300 (300 mg I/mL) and iodixanol 320 (320 mg I/mL) with an identical iodine delivery rate of 1.5 g I/sec and a total iodine dose of 300 mg/kg body weight. Time-enhancement curves were computed, and pulmonary and aortic peak enhancement, time-to-peak and plateau time above 300 Hounsfield units (HU) were analysed. RESULTS: Intra-individual comparison revealed no statistically significant differences in contrast enhancement between the iopromide 300 and iodixanol 320 in the pulmonary artery and the aorta (620 vs 552 HU; P = 0.13). There was no significant difference between the two CM in the plateau time at the pulmonary artery and the aorta (P = 0.75 and P = 0.24, respectively). Aortic peak time was significantly earlier with iopromide 300 than with iodixanol 320 (P = 0.004). CONCLUSIONS: Low-osmolar monomeric and iso-osmolar dimeric CM provide a similar and suitable vascular contrast enhancement.

Free-hand CT-based electromagnetically guided interventions: accuracy, efficiency and dose usage.

The purpose of this paper was to evaluate computed tomography (CT) based electromagnetically tip-tracked (EMT) interventions in various clinical applications. An EMT system was utilized to perform percutaneous interventions based on CT datasets. Procedure times and spatial accuracy of needle placement were analyzed using logging data in combination with periprocedurally acquired CT control scans. Dose estimations in comparison to a set of standard CT-guided interventions were carried out. Reasons for non-completion of planned interventions were analyzed. Twenty-five procedures scheduled for EMT were analyzed, 23 of which were successfully completed using EMT. The average time for performing the procedure was 23.7 ± 17.2 min. Time for preparation was 5.8 ± 7.3 min while the interventional (skin-to-target) time was 2.7 ± 2.4 min. The average puncture length was 7.2 ± 2.5 cm. Spatial accuracy was 3.1 ± 2.1 mm. Non-completed procedures were due to patient movement and reference fixation problems. Radiation doses (dosis-length-product) were significantly lower (p = 0.012) for EMT-based interventions (732 ± 481 mGy x cm) in comparison to the control group of standard CT-guided interventions (1343 ± 1054 mGy x cm). Electromagnetic navigation can accurately guide percutaneous interventions in a variety of indications. Accuracy and time usage permit the routine use of the utilized system. Lower radiation exposure for EMT-based punctures provides a relevant potential for dose saving.

Radiofrequency ablation of osteoid osteoma: initial experience with a new monopolar ablation device.

The purpose of this article is to report our initial experience with the "off-label" use of a new monopolar radiofrequency (RF) probe for percutaneous ablation of osteoid osteomas. Seventeen patients (12 male and 5 female, mean age 24.8 [range 9-49]) with osteoid osteoma were treated by computed tomography (CT)-guided RF ablation (RFA). All procedures were performed with the patient under general aesthesia. After localization of the nidus, a 13G hollow drill was introduced into the nidus through a 7F introducer sheath. A monopolar 16.5G RF probe with a 9-mm active tip (Soloist; Boston Scientific, Natick, MA) was inserted through the introducer sheath and connected to the RF generator. Energy application was started at 2 W and subsequently increased every 2 min by 1 W to a maximum of 8 W. The procedure ended if impedance increased by 500 Ω. Mean duration of energy deposition was 14.2±3.3 min. Fourteen of 17 patients (82%) were free of symptoms at 29.9±14.8 (range 4 to 47) months of follow-up. The primary and secondary success rates were 83% and 100%, respectively. In 3 patients, recurrence of pain at 6 (n=1) and 15 (n=2) months after the initial procedure was successfully treated by reablation. There were no complications. Monopolar RFA using the Soloist probe is effective and safe for the treatment of osteoid osteoma. It results in comparable success rates as other monopolar or bipolar RF systems in the treatment of osteoid osteoma.

Association of aortic valve calcification severity with the degree of aortic regurgitation after transcatheter aortic valve implantation.

BACKGROUND: This study sought to examine a possible relationship between the severity of aortic valve calcification (AVC), the distribution of AVC and the degree of aortic valve regurgitation (AR) after transcatheter aortic valve implantation (TAVI) for severe aortic stenosis (AS). METHODS: 57 patients (22 men, 81 ± 5 years) with symptomatic AS and with a logistic EuroSCORE of 24 ± 12 were included. 38 patients (67%) received a third (18F)-generation CoreValve® aortic valve prosthesis, in 19 patients (33%) an Edwards SAPIEN™ prosthesis was implanted. Prior to TAVI dual-source computed tomography for assessment of AVC was performed. To determine the distribution of AVC the percentage of the calcium load of the most severely calcified cusp was calculated. After TAVI the degree of AR was determined by angiography and echocardiography. The severity of AR after TAVI was related to the severity and distribution of AVC. RESULTS: There was no association between the distribution of AVC and the degree of paravalvular AR after TAVI as assessed by angiography (r = -0.02, p = 0.88). Agatston AVC scores were significantly higher in patients with AR grade ≥ 3 (5055 ± 1753, n = 3) than in patients with AR grade < 3 (1723 ± 967, p = 0.03, n = 54). Agatston AVC scores > 3000 were associated with a relevant paravalvular AR and showed a trend for increased need for second manoeuvres. There was a significant correlation between the severity of AVC and the degree of AR after AVR (r = 0.50, p < 0.001). CONCLUSION: Patients with severe AVC have an increased risk for a relevant AR after TAVI as well as a trend for increased need for additional procedures.

Jugular versus subclavian totally implantable access ports: catheter position, complications and intrainterventional pain perception.

PURPOSE: To determine the safest and most tolerable method for totally implantable access ports (TIAPs) particularly in regard to patient's pain perception and catheter-related complications. MATERIALS AND METHODS: From January 2007 to October 2008 a subcutaneous TIAP (Bardport, Bard Access System, UT, USA) was implanted in 138 oncological patients (60 male, 78 female; 18-85 years old; mean age of 56 ± 6 years) by experienced interventional radiologists. 94 TIAP were implanted through the subclavian vein (subclavian group) and 44 TIAP were implanted through the internal jugular vein (jugular group). Intrainterventional pain perception (visual analogue scale from 1 to 10), postinterventional catheter tip migration and radiation dose were documented for each method and implantation side and differences were compared with Wilcoxon t-test. For ordinal variables, comparison of two groups was performed with the Fisher's exact test. RESULTS: No severe periinterventional complication occurred. Inadvertent arterial punctures without serious consequences were reported in one case for the jugular group versus four cases in the subclavian group. Significantly (p<0.05) lower pain perception, radiation dose and tip migration rate were observed in the jugular group. Catheter occlusions occurred in 4% (n=4) of the subclavian group versus 2% (n=1) of the jugular group. The corresponding values for vein thrombosis and catheter dislocation were 3% (n=3) and 1% (n=1) in the subclavian group, while none of those complications occurred in the jugular group. CONCLUSION: Both techniques, the TIAP implantation via fluoroscopy-guided subclavian vein puncture and via ultrasound-guided jugular vein puncture, are feasible and safe. Regarding intrainterventional pain perception, radiation dose, postinterventional catheter tip position and port function the jugular vein puncture under ultrasound guidance seems to be advantageous.

Pull-through technique for recanalization of occluded portosystemic shunts (TIPS): technical note and review of the literature.

Transjugular intrahepatic portosystemic shunt (TIPS) dysfunction is an important problem after creation of shunts. Most commonly, TIPS recanalization is performed via the jugular vein approach. Occasionally it is difficult to cross the occlusion. We describe a hybrid technique for TIPS revision via a direct transhepatic access combined with a transjugular approach. In two cases, bare metal stents or polytetrafluoroethylene (PTFE)-covered stent grafts had been placed in TIPS tract previously, and they were completely obstructed. The tracts were inaccessible via the jugular vein route alone. In each case, after fluoroscopy or computed tomography-guided transhepatic puncture of the stented segment of the TIPS, a wire was threaded through the shunt and snared into the right jugular vein. The TIPS was revised by balloon angioplasty and additional in-stent placement of PTFE-covered stent grafts. The patients were discharged without any complications. Doppler sonography 6 weeks after TIPS revision confirmed patency in the TIPS tract and the disappearance of ascites. We conclude that this technique is feasible and useful, even in patients with previous PTFE-covered stent graft placement.

Robot arm based flat panel CT-guided electromagnetic tracked spine interventions: phantom and animal model experiments.

PURPOSE: To evaluate accuracy and procedure times of electromagnetic tracking (EMT) in a robotic arm mounted flat panel setting using phantom and animal cadaveric models. METHODS AND MATERIALS: A robotic arm mounted flat panel (RMFP) was used in combination with EMT to perform anthropomorphic phantom (n = 90) and ex vivo pig based punctures (n = 120) of lumbar facet joints (FJ, n = 120) and intervertebral discs (IVD, n = 90). Procedure accuracies and times were assessed and evaluated. RESULTS: FJ punctures were carried out with a spatial accuracy of 0.8 ± 0.9 mm (phantom) and 0.6 ± 0.8 mm (ex vivo) respectively. While IVD punctures showed puncture deviations of 0.6 ± 1.2 mm (phantom) and 0.5 ± 0.6 mm (ex vivo), direct and angulated phantom based punctures had accuracies of 0.8 ± 0.9 mm and 1.0 ± 1.3 mm. Planning took longer for ex vivo IVD punctures compared to phantom model interventions (39.3 ± 17.3 s vs. 20.8 ± 5.0 s, p = 0.001) and for angulated vs. direct phantom FJ punctures (19.7 ± 5.1 s vs. 28.6 ± 7.8 s, p < 0.001). Puncture times were longer for ex vivo procedures when compared to phantom model procedures in both FJ (37.9 ± 9.0 s vs. 23.6 ± 7.2 s, p = 0.001) and IVD punctures (43.9 ± 16.1 s vs. 31.1 ± 6.4 s, p = 0.026). CONCLUSION: The combination of RMFP with EMT provides an accurate method of navigation for spinal interventions such as facet joint punctures and intervertebral disc punctures.

Application of magnetic resonance imaging in transgenic and chemical mouse models of hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. The molecular mechanisms underlying hepatocarcinogenesis are still poorly understood. Genetically modified mice are powerful tools to further investigate the mechanisms of HCC development. However, this approach is limited due to the lack of non-invasive detection methods in small rodents. The aim of this study was to establish a protocol for the non-invasive analysis of hepatocarcinogenesis in transgenic mice using a clinical 1.5 Tesla Magnetic Resonance Imaging scanner. RESULTS: As a model system we used hepatocyte-specific c-myc transgenic mice developing hepatocellular carcinoma at the age of 12-15 months. The scans of the murine livers included axial T2-weighted turbo-spin echo (TSE) images, axial T1-weighted and contrast enhanced T1-weighted gradient echo (fast field echo, FFE) and sagittal true Fast Imaging with Steady state Precession (true-FISP) images. Application of contrast agent was performed via tail vein-catheter and confirmed by evaluation of the altered longitudinal relaxation T1 time before and after application. Through technical adaptation and optimization we could detect murine liver lesions with a minimum diameter of approximately 2 mm and provided histopathological evidence that these MR findings correspond to hepatocellular carcinoma. Tumor growth was repeatedly measured using sequential MRI with intervals of 5 weeks and subsequent volumetric analysis facilitating direct comparison of tumor progression between individual animals. We finally demonstrated that our protocol is also applicable in the widely- used chemical model of N-nitrosodiethylamine-induced hepatocarcinogenesis. CONCLUSION: Our protocol allows the non-invasive, early detection of HCC and the subsequent continuous monitoring of liver tumorgenesis in transgenic mice thereby facilitating future investigations of transgenic tumor mouse models of the liver.

Multi-slice computed tomography: A tool for non-invasive temperature measurement?

PURPOSE: To investigate the potential of multi-slice computed tomography (MSCT) as a tool for non-invasive temperature measurement. MATERIALS AND METHODS: Samples of water, 0.9% saline, sunflower oil and dilutions of (1:32, 1:64, 1:128) contrast agent (Iopromid 370, BayerSchering Pharma, Berlin) were heated in a plexiglass phantom. In a first set-up, samples of 0.9% saline solution were scanned at defined temperatures (25 degrees -75 degrees C; 5 degrees C intervals) using a clinical CT scanner. Scan parameters (tube current-time product, tube voltage, collimation, slice thickness) were systematically varied. In a second set-up samples of the different fluids (water, sunflower oil, contrast agent dilutions) were scanned using the following scan protocol: 250 mAs, 140 kV, 1.2 mm collimation, 9.6 mm slice thickness. CT numbers were measured in reconstructed axial images at the different temperatures. A regression analysis was performed to investigate the relationship between temperature and CT number. RESULTS: Standard deviation of measured CT numbers decreased with increasing tube current-time product, increasing tube voltage, thicker collimation and higher slice thickness. Regression analysis showed an inverse relationship between temperature and CT number for all fluids with regression coefficients of -0.471 (0.9% saline), 0.447 (water), -0.679 (sunflower oil), -0.420 (contrast agent 1:32), -0.414 (contrast agent 1:64) and -0.441 (contrast agent 1:128), respectively. CONCLUSION: Multi-slice computed tomography can depict thermal density expansion of different fluids. Based on these results the implementation of a temperature discrimination of several degrees C at a high spatial resolution is achievable.