[Modern visualization of the liver with MRT. Current trends and future perspectives]

This contribution provides an overview and imparts basic knowledge on pertinent technical developments in magnetic resonance imaging (MRI) of the liver: 3D sequences, respiratory triggering, parallel imaging, and 3 Tesla (3T). 3D sequences can be used as T1-weighted (T1w) sequences for analyzing dynamics of contrast enhancement or as T2w sequences for MR cholangiography. Consistent improvements in respiratory triggering make it possible to obtain good image quality on T2w scans even in patients unable to hold their breath. Parallel imaging as a universal technique to accelerate image acquisition is particularly appropriate for MRI of the liver, and it has been shown that the reduced acquisition time is not achieved at the expense of image quality. Further progress in MRI of the liver can be expected with use of the 3T systems, but hitherto irrelevant problems must still be solved. Overall the innovations presented here, applied alone or in combination, facilitate rapid, robust, and high-quality MRI diagnostic assessment of the liver.

Potenzial der MRT für die Radiofrequenzablation von Lebertumoren

PURPOSE

To present first results of radiofrequency ablation of liver tumors using a new MR compatible applicator.

MATERIALS AND METHODS

We performed 37 interventions in 20 patients (mean age 58.6 years) with primary intrahepatic malignancies or metastases: colorectal carcinoma n = 6, hepatocellular carcinoma n = 3, pancreatic carcinoma n = 4, sarcoma n = 2, cholangiocellular carcinoma n = 1, carcinoma of the tonsil n = 1, breast carcinoma n = 1, gastric carcinoma n = 1, and gastrointestinal stroma tumor n = 1. Interventions were performed under CT-guidance with CT fluoroscopy (n = 32) and under MR-guidance (n = 5) using fast T1-weighted sequences in breath-hold technique. RFA was performed with the RF-generator (150 W) under local anesthesia and sedation using MR compatible applicators (Starburst XL, Rita Medical Systems, USA) together with the appropriate Soft Tissue Introducer System. Intra-interventional control was performed with intrahepatically or intralesionally placed introducer system or applicator. MRI was performed with plain breath-triggered T2-weighted turbo spin echo sequences (TSE T2) with fat saturation.

RESULTS

All interventions were performed without major events. The mean diameter of induced coagulation was 4.0 (+/- 0.7) cm. Repositioning was necessary in 8 interventions (21 %) after detection of residual tumor on an intra-interventional MRI. After a mean follow-up of 6.5 (+/- 1.2) months, the local tumor control rate was 92 %.

CONCLUSION

MR-compatible RF applicators offer the opportunity for intra-interventional detection of residual tumor during RF ablations by use of sensitive MRI sequences. These procedures may lead to a higher confidence in tumour ablation and may reduce the number of re-interventions and local recurrences of intrahepatic tumors.

[PET-CT interventional tumour therapy]

Multifocal metastatic spread of solid tumours is often a diagnostic and therapeutic challenge. Those patients often cannot undergo curative surgery. Since several years, various types of interventional tumour therapy have been introduced, which may represent a promising option in those cases. In some cases morphological imaging is not able to assess the viability of a previously treated lesion. The combination of computed tomography and positron emission tomography has the potential to ease planning and guiding of interventional procedures and to improve postinterventional control. Due to its higher sensitivity and specificity, PET/CT enables for a more precise selection of patients for interventional tumor therapy. The success of a particular therapy could be assessed with greater accuracy using PET/CT as compared with the separate modalities. PET/CT was also able to improve planning and guiding interventional therapy. As of yet, no data are available concerning the success rate and long-term survival of PET/CT associated interventional procedures.

Are serial CA 19-9 kinetics helpful in predicting survival in patients with advanced or metastatic pancreatic cancer treated with gemcitabine and cisplatin?

BACKGROUND

Serial kinetics of serum CA 19-9 levels have been reported to reflect response and survival in patients with pancreatic cancer undergoing surgery, radiotherapy, and chemotherapy. We prospectively studied serial kinetics of serum CA 19-9 levels of patients with locally advanced or metastatic disease treated with gemcitabine and cisplatin.

PATIENTS AND METHODS

Enrolled in the study were 87 patients (female/male = 26/61; stage III/IV disease = 24/63). Patients received gemcitabine 1,000 mg/m(2) on days 1, 8, and 15 plus cisplatin 50 mg/m(2) on days 1 and 15, every 4 weeks. Serum samples were collected at the onset of chemotherapy and before the start of a new treatment cycle (day 28).

RESULTS

77 of 87 patients (88.5%) with initially elevated CA 19-9 levels were included for evaluation. According to imaging criteria, 4 (5.2%) achieved a complete remission and 11 (14.3%) achieved partial remission, yielding an overall response rate of 19.5%. 43 (55.8%) patients were CA 19-9 responders, defined by a > or = 50% decrease in CA 19-9 serum levels within 2 months after treatment initiation. Except for one, all patients who had responded by imaging criteria (n = 14) fulfilled the criterion of a CA 19-9 responder. Despite being characterized as non-responders by CT-imaging criteria (stable/progressive disease), 29 patients were classified as CA 19-9 responders (positive predictive value 32.5%). Independent of the response evaluation by CT, CA 19-9 responders survived significantly longer than CA 19-9 nonresponders (295 d; 95% CI: 285-445 vs. 174 d; 95% CI: 134-198; p = 0.022).

CONCLUSION

CA 19-9 kinetics in serum serve as an early and reliable indicator of response and help to predict survival in patients with advanced pancreatic cancer receiving effective treatment with gemcitabine and cisplatin.

Leitlinien der Deutschen R�ntgengesellschaft zur Vertebroplastie

In many countries, percutaneous vertebroplasty became a widely accepted therapeutic option in osteoporotic and neoplastic fractures of the vertebral bodies which is employed in more and more patients. Under image guidance the method can be safely performed and provides a high success rate regarding stabilization of vertebral fractures and pain relief. Due to the increasing interest in vertebroplasty in Germany the German Radiological Society-Working Group on Interventional Radiology decided to produce guidelines for percutaneous vertebroplasty. This guidelines are based on the recent standard of knowledge and represent a guide for practical performance of this procedure. Based on the technical development of the method, indications and implementation of the method in multimodal therapy regimens may change over the next years. Therefore, this guidelines are not a rigid body of rules but a basis for an ongoing development adjusted to the scientific progress and the interdisciplinary discussion.

Moving-table MR angiography of the peripheral runoff vessels: comparison of body coil and dedicated phased array coil systems

OBJECTIVE

The aim of our study was to compare the signal-to-noise ratio and the diagnostic accuracy of moving-table MR angiography of the peripheral arteries with body coil and dedicated phased array coil systems.

SUBJECTS AND METHODS

Forty patients were examined with digital subtraction angiography and moving-table MR angiography with a 1.5-T MR imaging system either with a body coil (n = 20) or with a dedicated phased array coil (n = 20). The timing of contrast material was performed with real-time MR fluoroscopy.

RESULTS

For the iliac artery, upper leg, and lower leg, the mean values for signal-to-noise ratios were 56, 51, and 17, respectively, for the body coil, and 54, 74, and 64, respectively, for the dedicated phased array coil. For the body coil, sensitivity and specificity in identifying stenosis greater than 50% and occlusions were 100% and 96%, respectively, for the iliac arteries, and 100% and 96%, respectively, for the upper leg. For the dedicated phased array coil, sensitivity and specificity for stenosis greater than 50% and occlusions were 100% and 96%, respectively, for the iliac arteries, and 100% and 98%, respectively, for the upper leg. Sensitivity and specificity were inferior for the body coil (88% and 85%) compared with the dedicated phased array coil (100% and 96%) in the lower leg. A significant difference of the mean values of contrast-to-noise ratio was found before and after subtraction for the dedicated phased array coil and body-coil techniques (Student's t test, p < 0.01).

CONCLUSION

In comparison with the body coil, the dedicated peripheral phased array surface coil system improves signal-to-noise ratio for the upper and lower leg and diagnostic accuracy in the lower leg.

[Value of various imaging modalities for diagnostic work-up of tumors of the adrenal gland]

OBJECTIVE

This paper describes the value of various imaging modalities for diagnostic work-up of tumors of the adrenal gland.

METHODS

Results of the literature are reviewed. An optimized examination protocol for computed tomography (CT) and magnetic resonance imaging (MRI) is shown for assessment and differentiation of unclear lesions of the adrenal gland.

RESULTS

Measurements of attenuation in the native examination as well as delayed enhancement are the cornerstones in the CT diagnostics of tumors of the adrenal gland. In MRI, chemical-shift imaging and evaluation of signal characteristics in T1- and T2-weighted images are most important for characterization even in unclear cases.

CONCLUSION

CT and MRI play the major role in imaging of adrenal gland tumors. Whereas CT is less expensive and widely available,MRI provides advantages in unclear cases because of the excellent tissue contrast and the superior characterization.

[MRI in Crohn's disease after transduodenal contrast administration using negative oral MRI contrast media]

PURPOSE

To compare the efficacy and quality of conventional and MR enteroclysis with different filling methods regarding the assessment of extension and extraluminal manifestations in Crohn's disease.

MATERIAL AND METHODS

190 patients with known Crohn's disease were studied following small bowel enteroclysis, after oral administration or direct transduodenal filling in the MRI-department.T1- and T2-weighted breathhold MRI-scans w/o spectral fat suppression w/o i.v. Gd-DTPA were applied using negative oral superparamagnetic contrast media.

RESULTS

Typical findings were marked bowel wall thickening with laminated wall contrast enhancement. In 135 patients 98,2% of affected bowel segments, 97,5% of stenoses and all 16 fistulas were detected, when conventional enteroclysis was employed as standard of reference. Additional important extraluminal findings such as ileoileal (n = 18), ileosigmoidal adhesions (n = 12), extraluminal abscesses (n = 35) and pseudotumors (n = 8) were visualized in 73/135 patients. Concerning the distension of jejunum and ileum, oral filling was rated significantly inferior to transduodenal filling in all small bowel segments,whereas filling in the MRI-unit was rated superior to fluoroscopic, mostly due to a mean transport time of 20 min to the MRI-unit.

CONCLUSION

No clinically important findings of enteroclysis were missed when using MRI. Therefore, in patients with Crohn's disease, conventional enteroclysis can be replaced by MRI. For optimal bowel distension oral contrast administration is inferior to transduodenal filling, if a larger time delay between filling and the MRI-scan can be avoided.

Long-term results after posterior fixation of thoraco-lumbar burst fractures

Current concepts of treating thoraco-lumbar burst-compression injuries are based on posterior transpedicular fixation techniques which are angular stable. However, the long-term results of this approach are controversial due to inconsistent reports and due to a paucity of data on late outcome. In the present study we analyzed 50 patients retrospectively who had an unstable burst-compression injury at T 11-L 2 (type A 3 according to Magerl) without a neurological deficit. All fractures were stabilized by an internal fixator either with or without transpedicular spongiosa grafting. Patients were treated between 1991 and 1997. Follow-up times ranged from 36 to 103 months. Follow-up examinations collected occupational, subjective and clinical data (activity score, Hannover spine score) and included radiographic measurements. The latter were used to calculate the sagittal index (SI) which measures deformities of the fractured vertebral body, and the sagittal plane kyphosis (SPK) which additionally describes an eventual destruction of the affected intervertebral disc. Compared with the preinjury status, the percentage of subjects who were able to do physical labor was reduced by half at follow-up, and four times as many patients had a permanent disability. Correspondingly, activity scores and Hannover spine scores declined significantly. After the initial surgical correction SI remained stable until follow-up, whereas SPK decreased again towards pre-operative values indicating a progressive deformity of the intervertebral disc space. Clinical results did not correlate with radiographic results, and neither the time until follow-up nor the type of fracture n or the use of transpedicular bone grafting affected clinical or radiographic results significantly.

[Surgical therapy of locally advanced and primary inoperable pancreatic carcinoma after neoadjuvant preoperative radiochemotherapy]

INTRODUCTION

So far, surgery represents the only prospect for cure in patients with pancreatic cancer. Most patients, however, present with locally advanced pancreatic cancer at primary diagnosis. Recently, novel therapeutic regimens with preoperative radiochemotherapy have been developed that may improve long-term survival and resectability rates of patients with locally advanced pancreatic cancer.

METHODS

This feasibility study evaluates the preliminary results of neoadjuvant therapy with gemcitabine and 5-fluorouracil (5-FU) or cisplatin. Twenty-six patients suffering from locally advanced pancreatic cancer were considered for preoperative radiochemotherapy. They received radiation (45 Gy) and chemotherapy with simultaneous or sequential gemcitabine and 5-FU (n = 15) or gemcitabine and cisplatin (n = 11) administration prior to surgical resection.

RESULTS

Mean patient age was 62.4 +/- 2.6 years and 62% (n = 16) were male. The response rate was 69%, and 11 patients underwent curative surgical resection of the pancreatic cancer. Nine Whipple procedures and two complete pancreatectomies were carried out. In five patients a total of eight surgical complications were observed. Median overall survival was 9.8 months after primary cancer diagnosis (mean 12.0 +/- 1.2). During follow-up no local recurrent disease was detected.

CONCLUSIONS

Our findings lead us to conclude that preoperative chemoradiation with 45 Gy, gemcitabine and 5-FU or cisplatin is a powerful therapeutic tool in patients with locally advanced non-resectable pancreatic cancer. Major resections, including vascular reconstructions, are nonetheless associated with increased mortality. Preoperative chemoradiation contributes to improved survival in patients with primary non-resectable pancreatic cancer.

New contrast agents for imaging the liver

The contrast agents suited for hepatic imaging can be divided into nonspecific, extracellular space- (ECS) directed, reticuloendothelial system- (RES) selective, and hepatocyte-selective compounds. There is a wide variation in regard to biodistribution, pharmacokinetics, contrast behavior, and tissue specificity. The ECS contrast agents provide information on vascularization and perfusion similar to that of X-ray contrast agents. The RES- and hepatocyte-specific contrast agents offer more "functional" information that may enhance tissue characterization; however, the biology of the different hepatocellular and nonhepatocellular tumors is limiting the diagnostic efficacy of the tissue-specific compounds in many respects.

Value of systematic mediastinal lymph node dissection during pulmonary metastasectomy

BACKGROUND

Systematic mediastinal lymph node dissection is the accepted standard when curative resection of bronchial carcinoma is performed. However, mediastinal lymph node dissection is not routinely performed with pulmonary metastasectomy, in which only enlarged or suspicious lymph nodes are removed. The incidence of malignant infiltration of mediastinal lymph nodes in patients with pulmonary metastases is not known.

METHODS

Sixty-three patients who underwent 71 resections through a thoracotomy for pulmonary metastases of different primary tumors were studied prospectively. Selected patients showed no evidence of tumor progression or extrathoracic metastases and pulmonary metastasectomy was planned with curative intent. All patients underwent preoperative helical computed tomography (CT) scanning. Only patients with no evidence of suspicious mediastinal lymph nodes on the CT scan (less than 1 cm in the short axis) were included in this study. A mediastinal lymph node dissection was performed routinely with metastasectomy.

RESULTS

In 9 patients (14.3%) at least one mediastinal lymph node revealed malignant cells in accordance with the resected metastases. When compared with the preoperative CT scan, additional pulmonary metastases were detected in 16.9% of performed operations. There was a trend toward an improved survival rate in patients without involvement of the mediastinal lymph nodes. The number of pulmonary metastases had no influence on survival.

CONCLUSIONS

On a patient-by-patient basis, the frequency of misdiagnosed mediastinal lymph node metastases is about the same as compared with non-small cell bronchial carcinomas. Systematic mediastinal lymph node dissection reveals a significant number of patients, who otherwise are assumed free of residual tumor. The knowledge of metastases to mediastinal lymph nodes after complete resection of pulmonary metastases could influence the decision for adjuvant therapy in selected cases.

[Evaluation of an electromagnetic virtual target system (CT-guide) for CT-guided interventions]

PURPOSE

Evaluation of the accuracy of a new electromagnetic target system for interventional CT-guided procedures with virtual navigation in a previously acquired helical CT.

MATERIAL AND METHODS

The new target system CT-Guide 1010 (Ultraguide, Tirat Hacarmel, Israel) for CT-guided interventions was adapted to the video signal of the Somatom Plus 4 and Volume Zoom (Siemens, Erlangen, Germany). A helical CT-dataset including skin-based sensor cubes was transferred to the integrated navigation system inside the scanner room. 50 image-guided interventions and biopsies were performed outside the gantry using virtual navigation to reach the lesion. The accuracy of the procedures was evaluated using documentation of the needle tip with CT-fluoroscopy, results of histology, and follow-up.

RESULTS

The deviation between planned and documented needle tip was 2.2 +/- 2.1 mm in 50 procedures. Time between the end of planning-CT and needle positioning using the system was 13 minutes. There were no complications due to the use of the system.

CONCLUSION

The CT-Guide allows for virtual real-time navigation with high accuracy. Advantages are the free needle angulation without gantry tilt, use of optimal CT perfusion phase for virtual navigation, and reduction of radiation exposure to the patient and interventionalist.

Acute ischemia of the upper extremity: long-term results following thrombembolectomy with the Fogarty catheter

OBJECTIVE

In 1962, the procedure of arterial thrombembolectomy with the Fogarty catheter was established. Numerous studies have been published studying thrombembolectomies of the lower extremities. Limited information, however, is available following thrombembolectomy of the upper extremity after arterial occlusion. The aim of the present study, therefore, was to determine long-term results (3-5 years after thrombembolectomy) following thrombembolectomy of the upper extremity with the Fogarty catheter in a large retrospective clinical study.

DESIGN

In the present study, 251 patients were encountered. Over a period of 20 years, 283 thrombembolectomies with the Fogarty catheter were performed on the upper extremity at the surgical department of the University of Munich.

MAIN OUTCOME MEASUREMENTS

The appearance of local and general complications in the postoperative phase, as well as long-term results, were evaluated.

RESULTS

The results indicate that general complications - i.e., cardiac insufficiency, cerebral ischemia, etc. - occurred in 18 patients (7.2%). Local complications - i.e., wound infection, persistence of ischemia, or hematoma - were evident in 51 patients (20.3%). Re-occlusion following thrombembolectomy was found in 21 patients (8.8%). The affected extremity had to be amputated in five cases (2.0%), and 14 patients (5.6%) died during the postoperative phase. As a result of multimorbidity of the patients and average age at the time of surgery (73 years), 40% of the patients had died before the date of examination. Nonetheless, 111 patients of the 117 living patients showed no complaints or minor coldness and pain following heavy exercise.

CONCLUSIONS

The results of the present study indicate that, in most cases, thrombembolectomy with the Fogarty catheter represents a successful surgical method for the acute treatment of arterial occlusion of the upper extremity.

Effect of superparamagnetic iron oxide on bone marrow

The goal of this study was to compare the effects of SPIO particles on the signal intensity of the bone marrow of the vertebra spine in patients with and without liver cirrhosis. Forty-eight patients with normal liver tissue and 56 patients with liver cirrhosis were examined before and after intravenous SPIO administration, using a 1.5-T system (Magnetom Vision, Siemens, Erlangen, Germany) with a semiflexible cp-array coil. Three different pulse sequences were applied: a T1-weighted gradient-echo sequence, a T2-weighted fast spin-echo sequence with spectral fat suppression and a T2*-weighted gradient-echo sequence. The signal-to-noise ratio (SNR) of the liver, vertebra bone and paraspinal muscle were obtained. The SNR value change in each patient group and the SNR value difference between the two groups were evaluated. For assessment of statistical significance, Student's t-test with a level of p < 0.05 was applied. No significant differences in the SNR values of the liver and bone marrow between the two groups could be seen with any of the three sequences precontrast. Using the T1-weighted gradient-echo sequence in the noncirrhotic liver group, pre- and postcontrast comparisons of the SNR values of the liver and bone marrow indicated a decrease of approximately -44.3% (p = 0.02) and increase of approximately 15.3% (p = 0.04), respectively. No significant change was seen in the cirrhotic liver group. With the T2-weighted fast spin-echo sequence, a significant decrease of the SNR value of the liver and the bone marrow in both groups was seen. With the T2*-weighted gradient-echo sequence, the signal intensity decrease of the normal liver tissue was approximately -65.6% (p = 0.00), in cirrhotic liver tissue the decrease was -29.9% (p = 0.02). The SNR values of the bone marrow showed a decrease of -27.8% (p = 0.04) in the noncirrhotic liver group, whereas in the cirrhotic liver group it was only -11.3% and statistically not significant. The effect of SPIO particles on the liver and bone marrow is significantly less in patients with liver cirrhosis.

[Improvement in diagnosis of liver metastases with the multi-detector CT]

The introduction of multidetector computed tomography in clinical routine creates a new dimension of increased spatial and temporal resolution in CT scanning. On the basis of the very short acquisition time, the whole liver can now be scanned within one breathhold. Multidetector-CT allows the examination of the liver with nearly isotropic data sets. This is the prerequisite for the optimal assessment of very small liver lesions in all planes and excellent enhancement of liver lesions in defined organic perfusion phases. The speed of multidetector-CT can either be used to reduce the time to cover a given volume, or to use narrower beam collimation to increase the resolution of details along the z-axis and to reduce volume averaging. We report our clinical experiences in hepatic multidetector-CT examinations and optimized examination protocols in the assessment of hepatic metastases. Multidetector-CT and the use of interactive multiplanar reconstructions improve the detection and characterization of liver metastases. However, new problems in data management may arise from the large amount of data generated by multidetector-CT.

[Radiofrequency ablation of liver metastases. Technique and initial results]

Primary and secondary malignant hepatic tumors are the most common tumors with a much more higher incidence of hepatic metastases. Chemotherapy and radiation therapy are in general ineffective. Therefore, surgical resection is considered the method of choice in the treatment of malignant hepatic lesions. Due to systemic disease, general medical or procedure-related reasons hindering surgery, only 25 to 45% of the patients with metastatic disease of the liver are suitable for a curative surgical therapy. In resectable lesions thermoablative methods can offer an alternative to the surgical therapy. The most experience exists in radiofrequency ablation techniques. Technique, indications, contraindications, and limitations of the radiofrequency ablation will be discussed together with a presentation of own cases and a review of the literature. In 37 patients the primary technical success rate of the ablation was 97.3% (72 of 74 lesions). In 4 cases a hematoma of the liver capsule occurred. One of these had to be treated interventionally. During the limited follow-up period of 9 months no local recurrency was seen, however 4 patients developed new hepatic metastases. Beside differences in practicability it is not yet clarified if there are differences in the therapeutic efficacy of the different thermoablation methods. Nevertheless, the results of the ablation therapy may parallel the results of the surgical resection. Interstitial thermotherapy can provide a valuable contribution to local tumor control. However, the final significance of the thermoablation techniques within oncological therapy regimens has to be evaluated in further multidisciplinary studies.

Dynamic contrast-enhanced MR angiography from the distal aorta to the ankle joint with a step-by-step technique

OBJECTIVE

The aim of this study was to visualize the arteries from the distal aorta to the ankle joint and to determine the accuracy of MR angiography for detecting stenoses and occlusions.

SUBJECTS AND METHODS

Twenty-four patients with peripheral arterial occlusive disease underwent digital subtraction angiography and were examined on a 1.5-T MR scanner. The transit time for contrast material was determined with a test bolus injection. A T1-weighted three-dimensional gradient-echo sequence with short TR and TE was used for a dynamic measurement at the level of the iliac arteries, the upper leg, and the lower leg arteries. For each level a single dose of gadolinium was injected into an antecubital vein with an MR power injector. Maximal-intensity-projection reconstructions were calculated after subtraction of the first measurement at each level. Two experienced MR radiologists who were unaware of the digital subtraction angiography results interactively evaluated both the MIP reconstructions and the single slices on a workstation, first independently and then in a consensus interpretation.

RESULTS

With digital subtraction angiography, 80 hemodynamically significant stenoses and 39 occlusions were detected. For the stenoses and occlusions, a sensitivity of 100% was found for MR angiography. The specificity for the assessment of stenoses and occlusions was 98% and 94%, respectively, for the iliac arteries; 98% and 94%, respectively, for the upper leg arteries; and 94% and 95%, respectively, for the lower leg arteries. Most false-positive findings of occlusion were due to metal stents present in the iliac (n = 3) and upper leg (n = 4) arteries.

CONCLUSION

The MR imaging technique that we used revealed the arteries from the distal aorta to the ankle and proved to be reliable at showing arterial stenoses and occlusions.