Radiologische Diagnostik des Rektumkarzinoms: Nachsorge und Rezidivdiagnostik

Rectal carcinoma is one of the most frequent malignant tumors in adulthood. Not only after total resection but also after partial resection of the tumor with postoperative radiochemotherapy a sufficient follow-up is necessary to diagnose recurrent rectal cancer as early as possible. Various guidelines suggest different intervals for physical examinations and diagnostic methods depending on the initial tumor stage. In addition to routine examinations, the physician can choose between CT, MRI, endosonography and functional imaging techniques such as PET and immunoscintigraphy for further evaluation if a recurrent rectal cancer is suspected. Multiple studies and meta-analyses show the differences in the specificity and sensitivity of the diagnostic methods in the detection of lymph nodes, metastases, and local tumor infiltration. Endosonography and endorectal MRI show very good results in staging local tumor infiltration. However, obstructive lesions can inhibit an adequate examination. CT provides prompt and convincing results in the evaluation of the metastases. Most of the time the tumor can be identified but the lack of detailed imaging makes it hard to perform sufficient staging. Additionally image-guided biopsy can be performed. Immunoscintigraphy and PET have a high specificity because they take advantage of the tumor's metabolism. The introduction of the PET-CT has eliminated the disadvantage of low image resolution. In addition to the detection of small nodular pulmonary metastases, MRI with its "phased-array" coils is another excellent tool for the diagnosis of recurrent rectal cancer and search for metastases. This review shows the advantages and disadvantages of each diagnostic method in the visualization of recurrent rectal cancer.

Kernspintomographisches Staging des Prostatakarzinoms mittels kombinierter Endorektal-Body-Phased-Array-Spule und histopathologische Korrelation

PURPOSE

Evaluation of the diagnostic value of the combined endorectal body-phased array technique regarding the staging of prostate cancers, especially in the differentiation between stages T2 and T3.

MATERIALS AND METHODS

Forty-two patients with biopsy-proven or clinically suspected prostate cancer were examined on a 1.5 T scanner (Siemens, Symphony) prior to radical prostatectomy. T (2)-weighted TSE (axial, coronal) and T (2)-weighted FSE (axial) sequences were obtained with and without fat suppression. After application of 0.2 mmol/kg body-weight Gd-DTPA, T (1)-weighted GRE sequences were obtained using dynamic MRI. All images were prospectively interpreted by two observers. The MR images were correlated with the histopathological findings of wide-area sections of prostatectomy specimens.

RESULTS

For the detection of extracapsular growth and seminal vesicle infiltration (T2 versus T3) the accuracy was between 94 % and 97 % (sensitivity 100 %, specificity between 87 % and 93 %, observer 1 and 2). In two cases with a histologically proven stadium pT2b, observer 1 had diagnosed stadium pT3a. The results of observer 2 were marginally better in only one case, which was histologically proven to be pT2b and overstaged as pT3a. MRI did not lead to under-staging of a single tumor with regard to the differentiation between T2 and T3. Overall, the staging of the tumor stages (T1 - T4) was correct in 25 of 33 cases (75 %). The dynamic MRI showed no improvement regarding sensitivity (100 %) and specificity (62 %) and achieved a staging accuracy of only 75 %.

CONCLUSION

MRI performed with a combination of a pelvic phased-array coil (PPA) and integrated endorectal coil plays a significant role in the preoperative staging of prostate cancer. However, differentiation between capsular infiltration (T2) and penetration (T3) as well as evaluation of the seminal bladder (T3b) seem to be difficult.

[Diagnosis of colorectal tumors]

With the introduction of multislice CT extensive volumetric data sets can be quickly acquired in high spatial resolution. The high spatial resolution reduces partial volume effects and enables multiplanar reconstructions. Regarding the colorectum this means that the colon can be assessed if the colon is sufficiently cleaned and distended, and that transmural infiltration of colorectal carcinoma and liver metastases can be better detected. T-staging of colon cancer is less important than T-staging of rectal cancer. Based on the higher contrast MRI is superior to CT in T-staging of rectal cancer and in the differentiation between scarring tissue and recurrence of carcinoma.

[Comparison between endorectal MRI (EMRTI) and endorectal sonography (ES) after surgery or therapy for rectal tumors to exclude recurrent or residual tumor]

PURPOSE

This study was designed to evaluate the accuracy and limitations for staging of contrast-enhanced endorectal MR imaging comparing with transrectal US for restaging of rectal lesions after surgery or after therapeutic radiation. Both methods were correlated with histologic findings.

METHOD/MATERIALS

The efficacy of these both methods was evaluated in 30 patients with supposed residual or recurrent rectal neoplasms. Contrast enhanced (bolus injection of 0.1 mmol/kg b.w. Gd-DTPA) endorectal MR imaging was performed using a 1.5 Tesla Magnetom. In addition endosonography (7.5 x or 10-MHz transducer) was used.

RESULTS

In 8 patients with rectal adenoma after electro-laser resection, 8 patients with rectal carcinoma stage pT1 after transanal resection, 8 patients with rectal carcinoma stage pT2 and 6 patients with rectal carcinoma stage pT3 after regional hyperthermia with radiochemo-therapy, the following results were obtained during the postsurgical or posttherapeutical follow-up with respect to histopathological evaluation: exact staging in 86.6 % with EMRI and 63.3 % in ES, overstaging in 8 % (EMRI) and 23 % (ES), understaging in 0 % (EMRI) and 7 % (ES). The highest diagnostic accuracy was shown in EMRT in patients with rectal adenoma and rectal carcinoma (pT1) and after electro-laser resection or transanal resection during follow-up.

CONCLUSIONS

Contrast enhanced endorectal MR imaging appears to be very promising for accurate posttherapeutical staging of rectal cancer and helpful in the diagnosis of recurrence or the differentiation between scar tissue and residual rectal tumor.

MRI and color-coded duplex sonography: diagnosis of partial priapism

A case of partial priapism is reported diagnosed by contrast-enhanced MR imaging and color-coded duplex sonography. Follow-up examinations after 4 weeks and 3 months were performed. According to the results of color-coded duplex sonography and MRI, a partial priapism with development from the subacute stage to a fibrous residuum after spontaneous lysis was diagnosed. There are only very few cases of partial priapism reported in the literature and this is the first case report that demonstrates diagnosis and follow-up both by color-coded duplex sonography and contrast-enhanced MR imaging.

[Arterial steal syndrome in patients after liver transplantation: transarterial embolization of the splenic and gastroduodenal arteries]

Arterial steal syndrome in patients after liver transplantation: transarterial embolization of the splenic and gastroduodenal arteries.

PURPOSE

To evaluate transarterial embolization of splenohepatic and gastroduodenal steal syndrome in patients with impaired liver function tests after liver transplantation.

METHODS AND MATERIAL

In a prospective study 22 patients (10 male, 12 female; mean age 49.5 years) with unexplained elevation of hepatic enzymes after liver transplantation underwent transcatheter arterial embolization of splenohepatic (n = 18) and gastroduodenal (n = 4) steal syndrome with use of Gianturco coils or microcoils. Liver and spleen parenchyma were surveyed and evaluated before and after embolization with plain helical CT, including volumetry of liver and spleen.

RESULTS

DSA examinations revealed a dilated splenic artery (n = 18) or gastroduodenal artery (n = 4) combined with a slightly decreased perfusion of the hepatic arteries, while immediately after successful embolization a normal perfusion of the hepatic arteries could be noted. Volumetric measurements before and after embolization showed no significant changes in liver parenchyma (x = + 7 % +/- 2), and variable changes in splenic volume of -5 % to + 28 % (mean, + 11 %), with initial measurements. Clinical follow-up examinations revealed a normalization of the previously elevated hepatic enzymes and a normalization of liver function tests after successful embolization. Complications were observed in 4 patients (infarction of the spleen).

CONCLUSIONS

The preliminary results reveal that in liver transplant candidates with splenohepatic and gastroduodenal steal syndrome successful embolization results in an improvement of organ perfusion with normalization of function tests.

Prospective comparison of endorectal ultrasound, three-dimensional endorectal ultrasound, and endorectal MRI in the preoperative evaluation of rectal tumors. Preliminary results

BACKGROUND

The aim of this study was to compare the value of endorectal ultrasound (EUS), three-dimensional (3D) EUS, and endorectal MRI in the preoperative staging of rectal neoplasms.

METHODS

Thirty consecutive patients with rectal tumors were assessed by EUS and endorectal MRI. Additionally, three-dimensional ultrasound was performed in a subgroup of 25 patients. EUS data were obtained with a bifocal multiplane transducer (10 MHz) and processed on a 3D ultrasound workstation. MR imaging was carried out with a 1. 5 T superconducting unit using an endorectal surface coil.

RESULTS

EUS was carried out successfully in all 30 patients, whereas endorectal MRI was not feasible in two patients. Compared with the histopathological classification, EUS and endorectal MRI correctly determined the tumor infiltration depth in 25 of 30 and 28 patients, respectively. The comparative accuracy of EUS, 3D EUS, and endorectal MRI in predicting tumor invasion was 84%, 88%, and 91%, respectively. EUS, three-dimensional EUS, and endorectal MRI enabled us to assess the lymph node status correctly in 25, 25, and 24 patients, respectively. Both three-dimensional EUS and endorectal MRI combined high-resolution imaging and multiplanar display options. Assessment of additional scan planes facilitated the interpretation of the findings and improved the understanding of the three-dimensional anatomy.

CONCLUSION

The accuracy of three-dimensional EUS and endorectal MRI in the assessment of the infiltration depth of rectal cancer is comparable to conventional EUS. One advantage of both methods is the ability to obtain multiplanar images, which may be helpful for the planning of surgery in the future.

Detection of focal liver lesions at biphasic spiral CT: randomized double-blind study of the effect of iodine concentration in contrast materials

PURPOSE

To evaluate the effect of iodine concentration on the detection of focal liver lesions at biphasic spiral computed tomography (CT).

MATERIALS AND METHODS

One hundred two patients (64 men, 38 women) with neoplastic (n = 85) and nonneoplastic focal lesions (n = 17) were prospectively assigned to biphasic injection group A or B and received 180 mL of iopromide containing 370 or 300 mg of iodine per milliliter, respectively, during spiral CT. Comparison included assessment of quantitative and qualitative parameters.

RESULTS

Hepatic time-attenuation curves and mean hepatic enhancement in the portal venous phase and aortic time-attenuation curves in both arterial and portal venous phases were statistically superior in group A compared with group B. There was no significant difference in the mean enhancement in all lesions in either group. In contrast, among patients with hepatocellular carcinoma, mean contrast enhancement in lesions in the arterial phase was significantly superior in group A compared with group B. Blinded readers classified hepatic attenuation and lesion visibility as very good and as improved significantly more often in group A than in group B.

CONCLUSION

A decrease in iodine concentration significantly affects aortic and hepatic contrast enhancement and may impair the detectability of focal liver lesions during biphasic spiral CT.

Initially unresectable hilar cholangiocarcinoma: hepatic regeneration after transarterial embolization

PURPOSE

To assess with volumetric computed tomography (CT) the pattern and extent of hepatic regeneration induced with transarterial embolization of initially unresectable hilar cholangiocarcinoma (Klatskin tumor).

MATERIALS AND METHODS

In this prospective study, 13 patients (four men, nine women) with hilar cholangiocarcinoma, aged 43-74 years (mean +/- 1 standard deviation, 59.9 years +/- 9.6), underwent preoperative embolization of the right hepatic lobe. Embolization was performed transarterially by using four to 15 embolization coils. Volumetric measurements of the entire liver, left hepatic lobe, and spleen were performed with contrast material-enhanced and unenhanced helical CT before and after embolization in all patients.

RESULTS

After right lobe embolization, volumetric helical CT measurements revealed a 2%-33% decrease (mean, 10%) in the volume of the affected right hepatic lobe, an 11%-68% increase (mean, 37%) in the volume of left hepatic lobe parenchyma, and variations in splenic volume of -5% to +28% (mean, +11%). Nine patients underwent extended hepatectomy 27-75 days (mean, 44 days) after embolization. No patient had severe complications due to embolization.

CONCLUSION

In patients with an initially unresectable bilateral Klatskin tumor, right lobar arterial coil embolization results in enlargement of the left hepatic lobe (as verified with volumetric helical CT), thus allowing right hemihepatectomy.

Radiochemotherapy and hyperthermia in the treatment of rectal cancer

We evaluated the use of regional hyperthermia with radio-chemotherapy in a phase I/II study on locally advanced rectal carcinomas. Thirty-four patients with primary advanced (stage T3/T4) rectal carcinomas (24 patients) or recurring rectal carcinomas (6 patients) were treated using preoperative radiochemo-thermotherapy. Initial tumour staging was carried out clinically (degree of fixation) and using endorectal ultrasonography and CT. Radiotherapy was carried out with the patient prone (on a belly board) at 5 x 1.8 Gy per week up to 45 Gy at the reference point. 5-Fluorouracil (300-500 mg/m2) was administered with low-dose leucovorin (50 mg) on days 1-5 and 22-26. Patients were treated with regional hyperthermia each week prior to radiotherapy, using the Sigma-60 ring of the BSD-2000 system. Temperature/position curves and temperature/time curves were recorded via endocavitary catheters (tumour contact, bladder, vagina). Following endosonographic and clinical restaging, the operation was carried out 4-6 weeks after the end of preoperative therapy. In cases where tumours were unresectable, a boost of up to 60 Gy was given. Twenty-three of the 34 patients (68%) proved to be curatively resectable. Of these patients, 70% were downstaged endosonographically during preoperative therapy. The actuarial survival rates among these patients were 85% (primary rectal cancer) and 60% (recurrences) at 30 months. All in all, the preoperative multimodal therapy was well tolerated, and premature termination was necessary in only two cases. The quality of temperature distribution (T90, cum min T90 > 40.5 degrees C) depends on the power level and relative power density. The response (particularly downstaging) correlates significantly with the quality parameters of the temperature distributions. This regimen proved practical and effective, with encouraging downstaging rates and local control rates.

Hepatocellular carcinoma: evaluation with dynamic and static gadobenate dimeglumine-enhanced MR imaging and histopathologic correlation

PURPOSE

To analyze the potential of gadobenate dimeglumine-enhanced magnetic resonance (MR) imaging for the characterization and diagnosis of hepatocellular carcinoma (HCC) by using static and dynamic sequences.

MATERIALS AND METHODS

Twenty-eight patients with histopathologically proved HCC were evaluated with T1- and T2-weighted spin-echo and static and dynamic gradient-echo sequences before, during, and after intravenous administration of 0.1 mmol/kg gadobenate dimeglumine (0.5 mol/L).

RESULTS

During the perfusion phase of the dynamic sequence, all 16 nodular well-differentiated HCC lesions showed a rapid increase in signal intensity 10-30 seconds after injection followed by a progressive decrease in signal intensity. The nine poorly differentiated HCC lesions showed no rapid increase in signal intensity. All eight large (> 3 cm), nodular, well-differentiated HCC lesions showed a hypointense rim before injection and both hypo- and hyperintense rims (double-ring sign) immediately after injection, compared with normal liver parenchyma. About 55 seconds after injection, substantial single-rim enhancement was detected in 21 of the 28 HCC lesions.

CONCLUSION

Dynamic gadobenate dimeglumine-enhanced MR imaging allows improved characterization of HCC lesions, which show rapid increase in signal intensity during the early, arterial phase in well-differentiated HCC lesions and a double-ring sign in large well-differentiated nodular HCC lesions.

[Volumetric and morphological CT parameters for assessing prognosis and treatment control in hepatocellular carcinoma undergoing arterial chemoembolization]

PURPOSE

To evaluate volumetric CT data as a guide for indication and assessment of prognosis for transarterial chemo-embolisation (TAE) of hepatocellular carcinomas (HCC).

MATERIAL AND METHOD

74 patients with HCC were treated with repeated TAE. 50 mg Adriblastin/m2 body surface, 50 mg cisplatin/m2 body surface and 10 ml lipiodol were combined with 2-10 ml Spherex and injected selectively (25 cases) or superselectively (49 cases); in 28 patients a single injection and in 46 patients multiple injections were used.

RESULTS

CT findings before and after the procedure showed a solitary lesion in 17 patients, two lesions in 18 patients and in 39 patients there were three or more lesions. Mean expectation of life was 523 days (median = 372 days; 57% of one year survival probability). In 29 patients with > 75% lipiodol retention, mean survival was 819 days; in 17 patients with < 75% lipiodol retention it was 382 days; lower lipiodol retention of < 50% it was 231 days (< 25% 192 and < 10% 152 days). A statistically significant relationship (p < 0.0001) could be established between survival time and tumour volume, relationship of tumour to liver volume, intratumoral lipiodol retention, the type of tumour growth and the number of liver segments involved.

CONCLUSION

TAE provides best survival rates after repeated injections of solitary HCC with tumour volumes < 50 ml and > 75% intra-tumoral lipiodol retention.

Accuracy of staging rectal tumors with contrast-enhanced transrectal MR imaging

OBJECTIVE

Our objective was to evaluate the accuracy of contrast-enhanced transrectal MR imaging in staging rectal adenoma and carcinoma by correlating with histopathologic findings.

SUBJECTS AND METHODS

Thirty-five patients underwent transrectal MR imaging on a 1.5-T superconducting unit using unenhanced T1-weighted and T2-weighted spin-echo and turbo spin-echo sequences, a dynamic gadopentetate dimeglumine-enhanced turbo fast low-angle shot sequence, and enhanced T1-weighted spin-echo sequences. For all patients, histopathologic correlation was available from biopsy (n = 15) or surgical resection (n = 20). Two radiologists unaware of each other's interpretations of the scans interpreted each case from which we evaluated qualitative and quantitative data.

RESULTS

Rectal adenomas (n = 15) were identified when imaging revealed an intact muscularis mucosae, a homogeneous internal structure, and high contrast enhancement of the lesion. Carcinomas staged as T1 by TNM criteria (n = 6) were best revealed by dynamic turbo fast low-angle shot sequences, in which an intact muscularis propria could be seen. Visualization of enhancing tumor tissue in the muscularis propria indicated T2 carcinoma (n = 5). All T3 (n = 5) and T4 (n = 4) carcinomas were correctly staged with dynamic and static MR imaging. The stage revealed by MR imaging correlated well with histologic staging results in 89% (observer 1) and 86% (observer 2) of interpretations. However, when interpreting MR imaging, observers tended to overstage and never understaged.

CONCLUSION

Transrectal surface-coil MR imaging provided reliable information in staging patients before surgery and in evaluating rectal adenoma and carcinoma.

[Magnetic resonance tomography and endosonography in the preoperative staging of advanced rectal carcinomas after hyperthermoradiochemotherapy]

PURPOSE

Comparison of diagnostic accuracy of staging of endorectal sonography (ES) and body coil MRI after preoperative hyperthermoradiochemotherapy in patients with advanced rectal cancer.

METHODS

Prospective analysis of MRI and ES in 30 patients after hyperthermoradiochemotherapy and correlation with histopathological patterns.

RESULTS

T-staging by MRI was correct in 47% and by ES in 53% of the cases. Despite similar accuracy of staging in T0- and T1-tumours, we found different accuracies concerning T2-tumour staging about 63% versus 73% (MRI/ES), concerning perirectal infiltration 70% for both techniques, concerning invasion of adjacent organs 90% versus 87%, and concerning lymph node metastases without respect to the N-stage 63% versus 63%.

CONCLUSION

Both imaging modalities provide useful information for operation planning despite limited accuracy after hyperthermoradiochemotherapy. The body coil MRI does not seem to be severely inferior to ES in post-therapeutic staging, despite better contour line imaging by ES. With respect to the determination of invasion of other organs, MRI seems to be more useful.

Superparamagnetic iron oxide--enhanced versus gadolinium-enhanced MR imaging for differential diagnosis of focal liver lesions

PURPOSE

To assess AMI-25- versus gadolinium-enhanced magnetic resonance (MR) imaging in the differential diagnosis of liver tumors.

MATERIALS AND METHODS

Twenty-nine patients with liver tumors underwent unenhanced, AMI-25-enhanced (15 micromol/kg), and gadolinium-enhanced(0.1 mmol/kg) imaging within 2 weeks.

RESULTS

A significant (P< .05) difference in percentage signal intensity loss (PSIL) was seen in benign tumors on AMI-25-enhanced proton-density-weighted images (nine focal nodular hyperplasia [FNH], 41%; one adenoma, 32.4%) versus malignant tumors. Gadolinium-enhanced T1-weighted gradient-echo images showed strong enhancement in benign lesions (seven FNH, 147.5%; one adenoma, 91.3%) and moderate enhancement in malignant tumors (eight hepatocellular carcinomas, 116.2%, 11 metastases, 39.7%). Receiver operating characteristic analysis revealed a threshold PSIL of 10% on AMI-25-enhanced images as the most essential criteria to distinguish benign from malignant lesions (sensitivity, 88%; specificity. 89%). Interobserver analysis for two observers revealed specificity of 93% for AMI-25-enhanced imaging versus 81.5% for gadolinium-enhanced MR imaging.

CONCLUSION

AMI-25 decreased the SI of benign tumors and helped differentiate benign from malignant tumors.

[High-resolution magnetic resonance tomography by means of an endorectal coil--the results in rectal tumors]

PURPOSE

To assess the value of high-resolution MRI of the rectum using an endorectal coil.

METHODS

10 volunteers and in 31 patients with suspected rectal tumors were examined. In 17 patients (n = 17) with rectal carcinoma, of which 15 subsequently underwent radical surgery, the preoperatively obtained tumor stage was compared with histology. In 12 patients (n = 12) with rectal adenoma (severe and medium graded epithelial dysplasias according to the WHO) who underwent endoscopy the results of the endorectal surface coil examination were compared with endoscopy and histology. In 4 patients (n = 4) with large rectal adenomas the surface coil was used before and as follow-up after endoscopic electro laser resection and the absence of adenoma after therapy also in the deeper layers of the rectal wall could be confirmed.

RESULTS

Visualization of anatomical structures of rectum and adjacent structures is improved by the use of the endorectal surface coil. The diagnosis of carcinoma and adenoma of the rectum and the documentation of the exact extension can be reached with high accuracy (85%).

CONCLUSION

MRI with an endorectal surface coil may play an important role in the preoperative diagnosis of rectal carcinoma. This method is useful for primary diagnosis and follow-up of large rectal adenoma after endoscopic electro laser resection.

Radiological modalities in the staging of colorectal tumors: new perspectives for increasing accuracy

The purpose of this study was to evaluate the diagnostic accuracy of contrast-enhanced endorectal MRI for the staging of rectal adenoma versus rectal carcinoma in correlation to findings from biopsy and histopathology. Ten volunteers and 20 patients underwent body-coil and endorectal MRI (1.5T supraconducting unit) using plain, T1-weighted (w) T2-w SE and TSE-w sequences, a dynamic Gd-DTPA enhanced protocol (turboFLASH), and postcontrast T1-w-SE sequences. Histopathological correlation via biopsy (n = 10) and surgical resection (n = 19) were conducted for all patients. An independent, two-observer, reader evaluation was performed and qualitative and quantitative data calculated. In volunteers and all patients endorectal MRI reliably delineated normal wall layers. Rectal adenomas (n = 7) were identified by a visualization of an intact muscularis mucosae, a homogeneous inner structure, and a significant contrast enhancement. T1 carcinomas (n = 4) were best identified in dynamic turboFLASH sequences by delineation of an intact muscularis propria. The visualization of contrast-enhancing tumor tissue was indicative of a T2 carcinoma (n = 4). All T3 (n = 3) and T4 (n = 2) carcinomas were correctly staged on dynamic and static MRI. The endorectal MRI stage agreed with the staging results from pathological study in 16 of 20 (80%) patients. Endorectal surface coil MRI provides reliable data for the preoperative staging and evaluation of rectal lesions.

[Spiral-CT of the liver: optimizing contrast medium administration and examination technique]

AIM OF STUDY

To analyze different protocols for spiral-CT with regard to the enhancement of liver parenchyma and vessels of the upper abdomen. To compare the achieved density values with those obtained by conventional CT.

METHODS

30 CT-examinations of the abdomen of different patients with normal findings of the liver were selected. In all examinations the upper abdomen was scanned before injection of contrast agent in conventional technique. In 10 patients spiral-CT of the liver was performed in the arterial phase at a delay of 15 sec and a flow of 4 ml/sec with 100 ml contrast agent, in 10 other patients in the portal-venous phase at a delay of 35 sec and a flow of 4 ml/sec with 100 ml contrast agent, followed by a spiral-CT of the upper abdomen in the arterial-venous phase at a delay of 70 sec and a flow of 1 ml/sec with 85 ml contrast agent. In 10 patients conventional CT of the upper abdomen was performed at a delay of 30 sec and a flow of 1 ml/sec with 200 ml contrast agent.

RESULTS

The highest density of the aorta was achieved by the arterial spiral-CT (p < 0.001). In the portal-venous spiral-CT the density of liver parenchyma was lower than in the arterial-venous spiral-CT and conventional CT (p < 0.001). Both arterial-venous spiral-CT and conventional CT achieved the same contrast in the aorta (216 +/- 10 vs. 217 +/- 23 HE) and in liver parenchyma (110 +/- 3 vs. 112 +/- 16 HE), but arterial-venous spiral-CT showed a lower density in the inferior vena cava than conventional CT (138 +/- 9 vs. 162 +/- 21 HE) (p < 0.002).

CONCLUSIONS

The spiral-CT-protocol for the examination of the liver in arterial and arterial-venous phase enables a reliable and adequate enhancement of liver parenchyma and all vessels of the upper abdomen with a lower dose of contrast agent than is possible with conventional CT. Together with unenhanced CT, this protocol promises a better detection of focal lesions of the liver with different enhancement modes in the arterial and venous phases.

[Diagnostic results of abdominal computerized tomography in HIV-infected patients]

The exact frequency of pathologic findings in abdominal computed tomograms of HIV-infected patients is not yet known. To analyse such findings, CT scans of 339 HIV-infected patients were reviewed. While over four fifths of patients displayed abnormal findings; hepatosplenomegaly, lymphadenopathy, pathologically enlarged lymph nodes, and bowel wall thickening were the most common signs of disease. Only for enlarged lymph nodes could a dependency on clinical stage of the infection be demonstrated. As a conclusion, abdominal computed tomography reveals pathologic findings in the vast majority of HIV-infected patients, almost independent of clinical stage. Specifically, CT provides well documented lymph node staging. There are practically no age-or sex-dependent disease patterns in abdominal CT scans.

[Diagnosis of cerebral metastasis with standard dose gadobutrol vs. a high dose protocol. Intraindividual evaluation of a phase II high dose study]

PURPOSE

To assess the effectiveness and safety of normal and high doses of Gadobutrol versus a standard dose of Gadolinium DTPA in the MR evaluation of patients with brain metastases.

MATERIAL AND METHODS

In a clinical phase-II study 20 patients who had been diagnosed as having brain metastases with CT or MRT were studied prospectively with Gadobutrol, a new nonionic, low osmolality contrast agent. Each patient received an initial injection of 0.1 mmol/kg body weight and an additional dose of 0.2 mmol/kg Gadobutrol 10 min later. Spin-echo images were obtained before and after the two applications of Gadobutrol. Dynamic scanning (Turbo-FLASH) was performed for 3 min after each injection of the contrast agent. Both quantitative and qualitative data were intraindividually evaluated. The primary tumor was a bronchial carcinoma in 11 cases; in 9 other cases there were different primary tumors.

RESULTS

Forty-eight hours after the use of Gadobutrol there were no adverse signs in the clinical examination, vital signs or blood and urine chemistry. Statistical analysis (Friedman test and Wilcoxon test) of the C/N ratios between tumor and white matter, percentage enhancement, and visual assessment rating revealed statistically significant superiority of high-dose Gadobutrol injection in comparison to the standard dose. The percentage enhancement increased on average from 104% after 0.1 mmol/kg to 162% after 0.3 mmol/kg Gadobutrol. Qualitative delineation and contrast of the lesions increased significantly. The use of high-dose Gadobutrol improved the detection of 36 additional lesions in 6 patients.

CONCLUSION

The first in vivo results prove the excellent contrast capacity of the nonionic contrast agent Gadobutrol for the diagnosis of intracerebral metastases.

Malignant liver tumors treated with MR imaging-guided laser-induced thermotherapy: technique and prospective results

PURPOSE

To evaluate magnetic resonance (MR) imaging-guided laser-induced thermotherapy (LITT) of liver metastases.

MATERIALS AND METHODS

In a phase II study, 20 patients with 33 metastases from colorectal carcinoma (75%) or other primary tumors (25%) underwent LITT. MR thermometry performed with fast low-angle shot sequences was used to monitor therapy on-line, and dynamic and static contrast material-enhanced MR images enabled estimation of the degree of resultant necrosis. Follow-up studies were performed 3 months after thermotherapy.

RESULTS

The thermosequences enabled accurate on-line monitoring in 85% of lesions. In 69% of lesions 20 mm in diameter or smaller, contrast-enhanced MR images depicted substantial necrosis, with a local tumor control rate of 69% after 6 months and 44% after 12 months. Among lesions larger than 20 mm, necrosis was frequently incomplete, with a local control rate of only 41% after 6 months and 27% after 12 months.

CONCLUSION

MR imaging-guided LITT of liver metastases is a safe and promising therapy for liver metastases.

[CT angiography in carotid stenosis. Diagnostic value compared to color-coded duplex ultrasonography and MR angiography]

PURPOSE

To evaluate the accuracy of different diagnostic methods for the visualization of the carotid arteries and their pathological changes in order to avoid invasive angiography whenever surgery was considered.

MATERIAL AND METHODS

24 patients with clinically suspected stenosis or occlusion of the carotid arteries were prospectively examined via CT angiography. MR angiography and colour-coded duplex sonography (ccds) to evaluate the degree of stenosis and the extent of calcification.

RESULTS

In 36 cases stenoses of different extent could be documented with CT angiography, 33 cases were found using colour-coded duplex sonography and MRA. Sonography could not prove mild stenoses (< 30%), and in two patients with sonographically suspected total occlusion vessel perfusion was documented via CT angiography. MR angiography led to a overestimation in patients with high-grade stenosis compared to the degree of stenosis obtained via ccds and CTA. With regard to the diagnosis of calcification MIP, reconstructions after CT examination showed best correlation to the plain CT slices referring to length (94.6%) and thickness (89.2%).

CONCLUSION

CTA with MIP reconstructions is an excellent screening method and, in combination with ccds, CT angiography may replace DSA before surgery or intervention.

Cervical lymphadenopathy: ratio of long- to short-axis diameter as a predictor of malignancy

The purpose of this study was to evaluate short- and long-axis diameters of enlarged cervical lymph nodes with ultrasonography and to determine whether the long-to-short axis (l/s) ratio is a valid diagnostic parameter in the differentiation between benign and malignant nodal disease. 730 enlarged cervical lymph nodes in 285 patients were examined with ultrasound. The short- and the long-axis diameters of each enlarged node were measured and the l/s ratio calculated. Definite diagnoses of the nodes were obtained by histological examination following neck dissection. 95% of enlarged cervical nodes shown on ultrasound to have a l/s ratio of more than 2 were correctly diagnosed as benign. Nodes presenting with a more circular shape and a l/s ratio of less than 2 were diagnosed correctly as metastases with 95% accuracy. The l/s ratio of lymph nodes thus provides an excellent criterion for differentiation between benign and malignant enlargement in cervical lymphadenopathy.

MR diagnosis of head and neck tumors: comparison of contrast enhancement with triple-dose gadodiamide and standard-dose gadopentetate dimeglumine in the same patients

OBJECTIVE

The purpose of this study was to compare the relative values of MR images obtained with a triple dose of gadodiamide and MR images obtained with the standard dose of gadopentetate dimeglumine for the detection and determination of the extent of tumors of the head and neck.

MATERIALS AND METHODS

Forty-two patients with benign and malignant tumors of the head and neck were examined with contrast-enhanced MR imaging in a comparison of a triple dose of gadodiamide (0.3 mmol per kilogram body weight) and a standard dose (0.1 mmol per kilogram body weight) of gadopentetate dimeglumine. All patients underwent MR imaging with both doses of contrast material. Contrast-to-noise ratios and the percentage enhancement of normal and abnormal structures were calculated, and delineation of the lesion and the contrast between tumor and surrounding tissue were evaluated visually.

RESULTS

Statistical analysis (Friedman test and Wilcoxon test) of the contrast-to-noise ratios between tumor and white matter, the percentage enhancement, and the visual assessment rating revealed a statistically significant superiority of the triple dose of gadodiamide over the standard dose of gadopentetate dimeglumine. Tumor/muscle contrast-to-noise ratios were not significantly different with the two doses. The detection rate for tumors was no better with the triple dose of gadodiamide than with the standard dose of gadopentetate dimeglumine.

CONCLUSION

Use of the triple dose of gadodiamide results in a statistically significant improvement in the visual assessment rating, but it does not increase the number of tumors detected on MR images over the number detected with the standard dose of gadopentetate dimeglumine and does not appear to alter the differential diagnosis.

[MR-angiography in diagnosis and follow-up of therapy: arteria lusoria]

Diagnostic and therapeutic procedures are presented in a 29-year-old female patient who suffered from severe dysphagia and rapid loss in weight. In the conventional X-ray examination and barium swallow an aberrant right subclavian artery was suspected. MR imaging (MRI) and MR angiography (MRA) were done to plan the surgical correction. Postoperative MRA documented exactly the complex topography after surgical correction and the flow pattern in the implanted Gore-Tex stretch graft prosthesis. Non-invasive MR angiography renders possible the concrete planning of complex corrections of thoracic vessels replacing invasive catheter angiography.

[The value of the liver-specific superparamagnetic contrast medium AMI-25 for the detection and differential diagnosis of primary liver tumors versus metastases]

The value of the superparamagnetic contrast medium AMI-25 and its clinical acceptability was investigated in a phase-III-multicenter study. 18 patients with primary and secondary hepatic tumours were studied using T2- and T1-weighted spin-echo sequences, FATSAT sequences and FLASH-2-D-breathold sequences, both before and after intravenous application of AMI-25 (0.2 mmol GE/ml 15 mmol/kg KG in 100 ml 5% glucose infusion), using a 1.5 Tesla MRT (Magnetom 63 SP, Siemens). In 6 patients the MRT findings could be correlated with in vitro results within 30 minutes following surgical resection. In 8 patients a diagnosis of metastases was made. Amongst patients with primary liver tumours (FNH 6 cases, HCC 3 cases, adenomatosis 1 case) 3 of the 10 patients showed more lesions following the injection of contrast; similarly, in 4 patients of the 8 with secondary tumours contrast increased the number of visible lesions. The absence of contrast enhancement separated primary from secondary lesions. Amongst the patients with secondary liver tumours, in vitro correlation always showed more tumours than had been visualised whereas there was exact in vivo/in vitro correlation amongst patients with primary liver tumours.

[NMR tomography of the liver with the new contrast agent Gd-BOPTA. The results of an in-vivo phase-I test]

A phase 1 study on 8 normals has been carried out to determine the effectiveness and safety during MRI of a new hepatobiliary contrast medium Gd-BOPTA for causing enhancement of the upper abdominal organs. Gradient echo sequences (flash), T1 and T2-weighted spin echo sequences and turbo-flash sequences were used. The contrast medium was given as a single infusion in various concentrations (0.005, 0.05, 0.1, and 0.2 mmol/kg body weight). Optimal contrast of liver parenchyma was obtained with a dose of 0.05-0.1 mmol/kg body weight, resulting in contrast increase of 149.1% during gradient echo sequences and 107.8% during T1 spin echo sequences. In general, the increased contrast lasted for about two hours. Because of the biliary and renal excretion there was an enormous increase in signal intensity of the bile ducts and a significant increase in the kidneys and ureters. The results of the first in-vivo trial of Gd-BOPTA encourages the performance of further clinical studies of this new hepatobiliary contrast medium.

Gadobenate dimeglumine--a new contrast agent for MR imaging: preliminary evaluation in healthy volunteers

Gadobenate dimeglumine (formerly known as Gd-BOPTA) is a recently developed paramagnetic contrast agent that undergoes biliary as well as renal excretion. It may, therefore, be useful in MR imaging of the liver. Its safety, tolerance, and usefulness in visualizing hepatobiliary structures were studied in eight healthy subjects. Axial abdominal images were obtained with T1-weighted spin-echo and gradient-echo sequences at 1.5 T before and after IV administration of gadobenate dimeglumine in doses of 0.005, 0.05, 0.1, and 0.2 mmol/kg body weight. Two subjects received each dose. Administration of 0.1 mmol/kg resulted in a maximum liver enhancement of 149% on the gradient-echo sequence and of 90% on the T1-weighted spin-echo sequence 60 min after injection. The contrast enhancement of the liver remained virtually constant for 2 hr. The signal-to-noise ratio of the biliary tract increased from 38 to 121 after 2 hr on gradient-echo images. In addition, there was significant contrast enhancement of the kidneys. Optimal visualization of the liver parenchyma was achieved with doses of 0.05 and 0.1 mmol gadobenate dimeglumine/kg. Mild to moderate side effects such as nausea and retching, a sense of warmth at the infusion site, and transient pruritus lasting 1 min were reported by three (38%) of the subjects. The initial results of the first application of gadobenate dimeglumine in humans are encouraging because the contrast agent appears to be reasonably well tolerated at the doses appropriate for hepatobiliary imaging. Further clinical studies of this contrast agent are warranted to assess its effect on liver lesion conspicuity and the frequency with which side effects occur.