Assessment of hepatic function employing hepatocyte specific contrast agent concentrations to multifactorially evaluate fibrotic remodeling

Background

Diffuse parenchymal liver diseases are contributing substantially to global morbidity and represent major causes of deaths worldwide. The aim of our study is to assess whether established hepatic fat and iron quantitation and relaxometry-based quantification of hepatocyte-specific contrast material as surrogate for liver function estimation allows to evaluate liver fibrosis.

Methods

Retrospective consecutive study. Seventy-two healthy patients (mean age: 53 years) without known liver disease, 21 patients with temporary elevated liver enzymes (mean: 65 years) and 109 patients with biopsy proven liver fibrosis or cirrhosis (mean: 61 years), who underwent liver magnetic resonance imaging (MRI) with a hepatocyte-specific contrast agent [gadoxetate disodium, gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA), 0.25 mmol/mL Primovist, Bayer AG, Leverkusen, Germany] at 1.5 T (n=133) and at 3 T (n=69), were included. Fibrosis was classified using the histopathological meta-analysis of histological data in viral hepatitis (METAVIR) and the clinical Child-Pugh scores. Gd-concentration were quantified using T1 map-based calculations. Gd-concentration mapping was performed by using a Look-Locker approach prior to and 912±159 s after intravenous administration of hepatocyte specific contrast agent. Additionally, parenchymal fat fraction, R2*, bilirubin, gender and age were defined as predicting factors. Diagnostic accuracy was calculated in a monoparametric (linear regression, predictor: Gd-concentration) and multiparametric model (predictors: age, bilirubin level, iron overload, liver fat fraction, Gd concentration in the left and right liver lobe).

Results

Mean Gd-concentration in the liver parenchyma was significantly higher for healthy patients ([Gd] =0.51 µmol/L) than for those with liver fibrosis or cirrhosis ([Gd] =0.31 µmol/L; P<0.0001) and with acute liver disease ([Gd] =0.28 µmol/L), though there were no significant differences for the latter two groups. There was a significant moderate negative correlation for the mean Gd-concentration and the METAVIR score (ρ=-0.44, P<0.0001) as well as for the Child-Pugh stage (ρ=-0.35, P<0.0001). There was a significant strong correlation between the bilirubin concentration and the Gd-concentration (ρ=-0.61, P<0.0001). The diagnostic accuracy for the discrimination of healthy patients and patients with known fibrosis or cirrhosis was 0.74 (0.71/0.60 sensitivity/specificity) in a monoparametric and 0.76 (0.85/0.61 sensitivity/specificity) in a machine learning based multiparametric model.

Conclusions

T1 mapping-based quantification of hepatic Gd-EOB-DTPA concentrations performed in a multiparametric model shows promising diagnostic accuracy for the detection of fibrotic changes. Liver biopsy might be replaced by imaging examinations.

Respiratory anomalies associated with gadoxetate disodium and gadoterate meglumine: compressed sensing MRI revealing physiologic phenomena during the entire injection cycle

OBJECTIVES

The goal of this study was to investigate the precise timeline of respiratory events occurring after the administration of two gadolinium-based contrast agents, gadoxetate disodium and gadoterate meglumine.

MATERIALS AND METHODS

This retrospective study examined 497 patients subject to hepatobiliary imaging using the GRASP MRI technique (TR/TE = 4/2 ms; ST = 2.5 mm; 384 × 384 mm). Imaging was performed after administration of gadoxetate (N = 338) and gadoterate (N = 159). All GRASP datasets were reconstructed using a temporal resolution of 1 s. Four regions-of-interest (ROIs) were placed in the liver dome, the right and left cardiac ventricle, and abdominal aorta detecting liver displacement and increasing vascular signal intensities over time. Changes in hepatic intensity reflected respiratory dynamics in temporal correlation to the vascular contrast bolus.

RESULTS

In total, 216 (67%) and 41 (28%) patients presented with transient respiratory motion after administration of gadoxetate and gadoterate, respectively. The mean duration from start to acme of the respiratory episode was similar (p = 0.4) between gadoxetate (6.0 s) and gadoterate (5.6 s). Its mean onset in reference to contrast arrival in the right ventricle differed significantly (p < 0.001) between gadoxetate (15.3s) and gadoterate (1.8 s), analogously to peak inspiration timepoint in reference to the aortic enhancement arrival (gadoxetate: 0.9s after, gadoterate: 11.2 s before aortic enhancement, p < 0.001).

CONCLUSIONS

The timepoint of occurrence of transient respiratory anomalies associated with gadoxetate disodium and gadoterate meglumine differs significantly between both contrast agents while the duration of the event remains similar.

KEY POINTS

• Transient respiratory anomalies following the administration of gadoterate meglumine occurred during a time period usually not acquired in MR imaging. • Transient respiratory anomalies following the administration of gadoxetate disodium occurred around the initiation of arterial phase imaging. • The estimated duration of respiratory events was similar between both contrast agents.

ESGAR consensus statement on liver MR imaging and clinical use of liver-specific contrast agents

Objectives

To develop a consensus and provide updated recommendations on liver MR imaging and the clinical use of liver-specific contrast agents.

Methods

The European Society of Gastrointestinal and Abdominal Radiology (ESGAR) formed a multinational European panel of experts, selected on the basis of a literature review and their leadership in the field of liver MR imaging. A modified Delphi process was adopted to draft a list of statements. Descriptive and Cronbach’s statistics were used to rate levels of agreement and internal reliability of the consensus.

Results

Three Delphi rounds were conducted and 76 statements composed on MR technique (n = 17), clinical application of liver-specific contrast agents in benign, focal liver lesions (n = 7), malignant liver lesions in non-cirrhotic (n = 9) and in cirrhotic patients (n = 18), diffuse and vascular liver diseases (n = 12), and bile ducts (n = 13). The overall mean score of agreement was 4.84 (SD ±0.17). Full consensus was reached in 22 % of all statements in all working groups, with no full consensus reached on diffuse and vascular diseases.

Conclusions

The consensus provided updated recommendations on the methodology, and clinical indications, of MRI with liver specific contrast agents in the study of liver diseases.

Key points

• Liver-specific contrast agents are recommended in MRI of the liver.

• The hepatobiliary phase improves the detection and characterization of hepatocellular lesions.

• Liver-specific contrast agents can improve the detection of HCC.

[Rational imaging of hepatocellular carcinoma. The challenge of multimodal diagnostic criteria]

CLINICAL/METHODICAL ISSUE

Both computed tomography (CT) and magnetic resonance imaging (MRI) constitute the gold standard in radiological imaging of hepatocellular carcinoma (HCC). In cases of typical contrast behavior each modality as a single dynamic technique allows the diagnosis of HCC. There is still a challenge in detection of small HCCs < 2 cm, in differentiating HCC and high-grade dysplasia from other benign liver lesions as well as the evaluation of hypovascular liver lesions in the cirrhotic liver.

PERFORMANCE

Nowadays, both modalities achieve high detection rates of 90-100 % for lesions > 2 cm. Regarding lesions between 1 and 2 cm there is a higher sensitivity for MRI ranging between 80 and 90 % compared to 60-75 % with CT. Besides the multimodal diagnostic criteria, MRI provides significant benefits with the use of hepatobiliary contrast. Especially in combination with diffusion- weighted imaging (DWI) increased sensitivity and diagnostic accuracy compared to CT has been described for lesions sized < 2 cm. Regarding the differentiation from other hepatic nodules in the cirrhotic liver there is strong evidence that the coexistence of arterial enhancement and hypointensity on hepatobiliary imaging is specific for HCC. Moreover, hypointensity on hepatobiliary imaging is associated with a high positive predictive value (PPV) of up to 100 % for the presence of high-grade dysplasia and HCC.

ACHIEVEMENTS

The use of MRI including hepatobiliary imaging and DWI has to be regarded as the best non-invasive imaging modality for the detection of HCC and for the characterization of nodules in patients with liver cirrhosis. In comparison to CT there are benefits regarding detection of small lesions < 2 cm and evaluation of hypovascular liver lesions in the context of the hepatocarcinogenesis including prognostic values of premalignant lesions.

PRACTICAL RECOMMENDATIONS

Both MRI and CT provide a high diagnostic performance in evaluation of HCC in liver cirrhosis. With MRI there are considerable advantages regarding the detection rate and specificity. For daily clinical routine, CT offers a fast, reliable and easy available modality with benefits for patients in reduced general state of health and restricted compliance.

Case report. Spontaneous cholecystocolic fistula and locoregional liver tumour ablation: a cautionary tale

A liver abscess is a feared and potentially fatal complication following transarterial chemoembolisation (TACE) and radiofrequency ablation (RFA) of liver tumours. Iatrogenic bilio-enteric communications, such as bilio-enteric anastomosis, sphincterotomy and biliary stents, are considered major risk factors and are due to bacterial colonisation of the biliary tree with enteric flora. Naturally occurring spontaneous cholecysto-enteric fistula poses a similar risk as its iatrogenic counterparts but is rarely described in the literature. We present a case where abscess formation complicated a combined TACE and RFA in an unrecognised cholecystocolic fistula.

Gain in signal-to-noise for first-pass contrast-enhanced abdominal MR angiography at 3 Tesla over standard 1.5 Tesla: prediction with a computer model

RATIONALE AND OBJECTIVES

To estimate the gain in signal-to-noise ratio (SNR) in first-pass contrast-enhanced (CE) abdominal magnetic resonance angiography (MRA) at 3.0 T compared with 1.5 T.

MATERIALS AND METHODS

Three protocols were simulated using six contrast agents: gadopentetate dimeglumine (Magnevist, Berlex, Wayne, NJ), gadoteridol (Prohance, Bracco, Princeton, NJ), gadobenate dimeglumine (Multihance, Bracco, Princeton, NJ), gadodiamide (Omniscan, Amersham Health, Princeton, NJ), gadoversetamide (Optimark, Mallinckrodt, St. Louis, MO), and gadofosveset trisodium (MS-325, EPIX Medical, Cambridge, MA). Contrast concentrations were calculated for five abdominal vessels. Based on these data, the gain in SNR during CE abdominal MRA at 3.0 T over 1.5 T was estimated.

RESULTS

In these simulations, peak concentrations in all five target vessels were about 5 mM, 10 mM, and 0.7 mM for protocol 1, protocol 2, and protocol 3, respectively. A gain in SNR at 3 T over 1.5 T during CE abdominal MRA of at least 94% in all five target vessels could be achieved by applying protocol 1 or protocol 2, whereas protocol 3 provided a gain in SNR of 70%.

CONCLUSIONS

Although five of the contrast agents studied fulfill the expectation of providing approximately twice the SNR at 3.0 T versus 1.5 T during CE abdominal MRA, MS-325 offers a gain in SNR of 70% only.

3.0- Versus 1.5-T MR Cholangiography: A Pilot Study

OBJECTIVE

The purpose of our study was to evaluate quantitative and qualitative image quality of MR cholangiography at a field strength of 3.0 T compared with the standard field strength of 1.5 T.

MATERIALS AND METHODS

A standardized MR cholangiography sequence protocol was used for 15 healthy male volunteers (mean age +/- SD, 32.4 +/- 4.3 years) who underwent both 1.5- and 3.0-T MRI within 2 hr in an alternating fashion. Dedicated circular polarized torso coils (1.5 and 3.0 T) were used. The sequence protocol included breath-hold single-slice rapid acquisition with relaxation enhancement (slice thickness, 50 mm; orientation, coronal and +/- 20 degrees oblique coronal); breath-hold multislice HASTE (slice thickness, 3 mm; coronal only); and a non-breath-hold, respiratory-triggered 3D turbo spin-echo (TSE) T2-weighted sequence (slice thickness, 1 mm; 60 slices per slab; coronal only). Maximum intensity projections were generated from each multislice data set. Bile duct (common bile duct, right posterior segmental branch, and left hepatic duct) to periductal tissue contrast-to-noise ratios were compared at 1.5 and 3.0 T. Qualitative image analysis was performed by three independent reviewers. Qualitative analysis included delineation of the extra- and intrahepatic biliary anatomy, with specific attention given to the presence (or absence) of cystic or intrahepatic ductal variants, using a 4-point confidence scale. Statistical analysis consisted of the paired Student's t test and the signed rank test.

RESULTS

Contrast-to-noise ratios between the bile duct and the periductal tissue were higher at 3.0 T in all three locations (common bile duct, right posterior segmental branch, and left hepatic duct). In each magnet class, the 3D TSE sequence offered the best contrast-to-noise ratio and qualitative analysis. Superiority of the 3D TSE sequence was statistically significant in all analyses. Five of the 15 volunteers had intrahepatic biliary variants that were detected with a higher level of confidence (p < 0.01) on the 3.0-T system than on the 1.5-T system.

CONCLUSION

Compared with MR cholangiography at 1.5 T, MR cholangiography at 3.0 T offers improved contrast-to-noise ratio and a higher level of confidence for depicting intrahepatic variants.

Effect of iodine concentration of contrast media on contrast enhancement in multislice CT of the pancreas

The purpose of this study was to determine the influence of two different iodine concentrations of the non-ionic contrast agent, Iomeprol, on contrast enhancement in multislice CT (MSCT) of the pancreas. To achieve this MSCT of the pancreas was performed in 50 patients (mean age 57+/-14 years) with suspected or known pancreatic tumours. The patients were randomly assigned to group A (n=25 patients) or group B (n=25 patients). There were no statistically significant differences in age, height or weight between the patients of the two groups. The contrast agent, Iomeprol, was injected with iodine concentrations of 300 mg ml(-1) in group A (130 ml, injection rate 5 ml s(-1)) and 400 mg ml(-1) in group B (98 ml, injection rate 5 ml s(-1)). Arterial and portal venous phase contrast enhancement (HU) of the vessels, organs, and pancreatic masses were measured and a qualitative image assessment was performed by two independent readers. In the arterial phase, Iomeprol 400 led to a significantly greater enhancement in the aorta, superior mesenteric artery, coeliac trunk, pancreas, pancreatic carcinomas, kidneys, spleen and wall of the small intestine than Iomeprol 300. Portal venous phase enhancement was significantly greater in the pancreas, pancreatic carcinomas, wall of the small intestine and portal vein with Iomeprol 400. The two independent readers considered Iomeprol 400 superior over Iomeprol 300 concerning technical quality, contribution of the contrast agent to the diagnostic value, and evaluability of vessels in the arterial phase. No differences were found for tumour delineation and evaluability of infiltration of organs adjacent to the pancreas between the two iodine concentrations. In conclusion the higher iodine concentration leads to a higher arterial phase contrast enhancement of large and small arteries in MSCT of the pancreas and therefore improves the evaluability of vessels in the arterial phase.

MR imaging-guided radiofrequency thermal ablation in the porcine brain at 0.2 T

The aim of this study was to test the hypotheses that (a) MR imaging-guided radiofrequency (RF) thermal ablation is safe and feasible in porcine brain using an open C-arm-shaped low-field MR system, and that (b) induced thermal lesion size can be predicted using low-field MR imaging. Magnetic resonance-guided RF ablation was performed in the cerebral frontal lobes of six pigs. An 18-G monopolar RF electrode was inserted into the porcine brain using MR image guidance and RF was then applied for 10 min. After post-procedure imaging (T2-weighted, T1-weighted before and after gadodiamide administration), the pigs were killed and the brains were used for pathologic examination. Successful RF electrode placement was accomplished in all cases without complications; total magnet time ranged from 73 to 189 min. The thermal lesion size varied from 10 to 12 mm perpendicular to the electrode track and was easily visualized on T2-weighted and enhanced T1-weighted images. Enhanced T1-weighted imaging demonstrated the highest brain-to-RF thermal lesion contrast-to-noise ratio with an average of 1.5 +/- 1.6. Enhanced T1-weighted imaging never underestimated pathologic lesion diameter with a mean difference of 2.3 +/- 1.0 mm and a radiologic/pathologic correlation of 0.69. Magnetic resonance imaging-guided RF thermal ablation is feasible and safe in the porcine brain using an open MR low-field system. Induced-thermal lesion size can best be monitored using enhanced T1-weighted images. In the future, RF ablation under low-field MR guidance may offer an alternative treatment option for primary and secondary brain tumors.

Diagnosis of papillomas of the breast: value of magnetic resonance mammography in comparison with galactography

The aim of this study was evaluation of MRI alone and in combination with mammography and galactography in the diagnosis of intraductal papillomas. From 1994 to 1998, a total of 48 women presenting with pathologic mammary secretion underwent galactography and magnetic resonance mammography (MRM). Thirty-five patients aged 16-71 years (average age 46 years) subsequently underwent surgery or diagnostic puncture and the histologic findings were compared with the results of the radiologic examination. Histology revealed papillomas in 16 cases. In 6 of these patients, there was associated malignant degeneration. Malignancy without associated papilloma was observed in 3 cases. Galactography displayed a sensitivity of 94% and a specificity of 79% with five false-positive findings and one false-negative finding in the recognition of intraductal papillomas. Malignant processes were detected by mammography/galactography in only one instance. Magnetic resonance mammography visualized pathologic contrast medium uptake in 8 of 9 cases of malignant disease (sensitivity 89%). One patient with in situ ductal carcinoma escaped detection with MRM. Papillomas showed no or below-the-threshold-lying contrast uptakes with no specific sign suggestive of papilloma. Galactography in combination with mammography remains the primary diagnostic procedure in cases of pathologic mammary secretion or suspected papilloma. The addition of MRI permits exclusion of malignant disease with a high degree of certainty; thus, expectant management in individual cases with negative findings appears justified.

Ability of MR cholangiography to reveal stent position and luminal diameter in patients with biliary endoprostheses: in vitro measurements and in vivo results in 30 patients

OBJECTIVE

Our goal was to evaluate the ability of MR cholangiography to show stent position and luminal diameter in patients with biliary endoprostheses.

MATERIALS AND METHODS

Susceptibility artifacts were evaluated in vitro in three different stent systems (cobalt alloy-based, nitinol-based, and polyethylene) using two breath-hold sequences (rapid acquisition with relaxation enhancement, half-Fourier acquisition single-shot turbo spin echo) on a 1.5-T MR imaging system. The size of the stent-related artifact was measured, and the relative stent lumen was calculated. In vivo stent position and patency were determined in 30 patients (10 cobalt alloy-based stents, five nitinol-based stents, and 15 polyethylene stents).

RESULTS

In vitro, the susceptibility artifact of the cobalt stent caused complete obliteration of the stent lumen. The relative stent lumens of the nitinol-based and polyethylene stents were 38-50% and 67-100%, respectively. In vivo, all stents were patent at the time of imaging. The position of the cobalt alloy-based stent could be determined in nine of 10 patients, but stent patency could not be evaluated. Stent position of nitinol stents could not be adequately evaluated in any of the five patients, and internal stent diameter could be visualized in only one patient. In nine of 15 patients, the fluid column within the implanted polyethylene stent was seen on MR cholangiography.

CONCLUSION

The internal stent lumen could be visualized in most patients with an indwelling polyethylene stent, but not in patients with cobalt alloy- or nitinol-based stents.

[Comparison of susceptibility artefacts of different radiofrequency electrodes at O.2 T. Influence of electrode positioning, pulse sequence and image reconstruction methods]

PURPOSE

Interventional MRI procedure monitoring requires small but accurate susceptibility artifacts of the instruments used. In this investigation, susceptibility artifacts of different RF-electrode designs were compared using a variety of pulse sequences and k-space acquisition methods.

METHODS

4 different 18-gauge RF-electrodes (with three single electrodes made of stainless steel, copper, inconal, and a triple-clustered electrode configuration made of inconal) were placed in a 0.2 T MR-scanner perpendicular to the main magnetic field. Pulse sequences used included: TSE T2, FISP, true-FISP, PSIF, and a temperature sensitive ES-GRE sequence. In addition to the 2D Cartesian k-space trajectory with Fourier transformation (2DFT), projection reconstruction (PR) was used with the FISP, true-FISP and PSIF sequences.

RESULTS

The best tip accuracy was achieved with the combination of inconal electrodes and TSE T2. The usefulness of the tested sequences was found to be: TSE T2 > PSIF > FISP/true-FISP > ES-GRE. In general 2DFT provided better or equal tip accuracy than PR. The apparent shaft width was smaller using the copper electrode compared to the inconal electrode. However, the "match shaped" tip artifact of the copper probe led to a higher error in tip accuracy.

CONCLUSIONS

TSE-T2 sequences and Cartesian 2DFT acquisitions should be used for accurate tip positioning at 0.2 T. Further, artifact size of the electrode shaft prevents the use of inconal for temperature sensitive sequences. Copper electrodes can be used for these purposes, although copper is not considered to be biocompatible at present.

How does alteration of hepatic blood flow affect liver perfusion and radiofrequency-induced thermal lesion size in rabbit liver?

The purpose of this study was to test the hypothesis that decreasing liver perfusion in rabbits results in an increase in thermal lesion size and that these effects can be accurately monitored using magnetic resonance imaging (MRI). We additionally tested the hypothesis that the increase in thermal lesion size would depend on the particular vessel or vessels occluded (hepatic artery, portal vein, or both). Using an Institutional Animal Care and Use Committee approved protocol, 20 New Zealand white rabbits were randomly assigned to four treatment groups (five in each group): control and ligation of portal vein (PV), hepatic artery (HA), or both PV and HA (HAPV). Surgical ligation of the appropriate vessel was performed under general anesthesia. Immediately after ligation, the rabbits were placed in a 0.2-T open MR system, and an 18-G copper radiofrequency (RF) electrode with a 2-cm exposed tip was inserted into the liver. RF was applied for 10 minutes with the tip temperature maintained at 90 degrees +/- 2 degrees C. Before and after ablation, perfusion data were obtained for 90 seconds using 30 3-second sequential single oblique-slice fast imaging with steady-state progression (FISP) acquisitions after injection of gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) via the inferior vena cava. Postablation scanning included axial and oblique turbo spin-echo (TSE) T2-weighted (T2w), STIR, and Gd-enhanced T1w sequences. Lesion size was determined perpendicular to the RF electrode using software calipers on the imager. The rabbits were sacrificed after completion of the post-therapy scans, and their livers were harvested for histologic analysis. The liver showed a mean increase in signal amplitude (SA) of 76% 24 seconds after Gd contrast injection in the control group. After contrast injection, the SA increased to a mean of only 66% in the group with ligated hepatic arteries, with no difference in the time to peak compared with the control group. No significant SA increase over baseline could be found in the groups with ligated PV or ligated PV and HA. T2-weighted images demonstrated the highest lesion-to-liver contrast-to-noise ratios (CNRs; mean -5.5) on postprocedure images, followed by STIR images (mean -2.2) in the control group. The lesions were poorly delineated on the Gd-enhanced images. Average maximum lesion sizes (mean +/- 95% confidence interval) were 22 +/- 4.3 mm after ligation of PV, 22 +/- 2.6 mm after ligation of both PV and HA, 14 +/- 2.0 mm after ligation of HA, and 13 +/- 1.9 mm in the control group. We accept the hypothesis that the diameter of the region of coagulation necrosis achieved by standardized RF ablation in the liver increases with reduced organ perfusion and that this effect can be accurately monitored using MRI. The major factor influencing the size of the coagulation area is the portal venous flow. Occlusion of the hepatic artery alone does not significantly increase lesion size. T2w sequences are best suited for postprocedure imaging due to the high lesion-to-liver CNR in rabbits with normal hepatic perfusion. J. Magn. Reson. Imaging 2001;13:57-63.

Imaging findings in pancreatic lymphoma: differential aspects

When the radiologist is faced with a well-circumscribed tumoral mass in the pancreas, knowing when to direct the patient toward nonsurgical biopsy instead of surgical biopsy and staging is critical. Lymphoma does not require surgical staging or a palliative Whipple's procedure before chemotherapy or radiation therapy. A better overall prognosis with nonsurgical treatment is additional impetus to search for secondary signs of primary pancreatic lymphoma. In patients with primary pancreatic lymphoma, no marked pancreatic ductal dilatation is present even with ductal invasion. Adenocarcinoma commonly dilates the more distal pancreatic duct when more proximal ductal invasion has taken place. Lymph node involvement below the level of the renal veins was another finding not seen with adenocarcinoma. Clinical and imaging findings are otherwise not specific in the differentiation of pancreatic lymphoma and pancreatic cancer, but a bulky homogeneous tumoral mass without alteration of Wirsung's duct or the peripancreatic vessels should suggest the diagnosis. In patients with diffuse infiltration of the pancreatic gland without clinical signs of pancreatitis, the radiologist should be alert to the possibility of pancreatic lymphoma.

Percutaneous magnetic resonance image-guided biopsy and aspiration in the head and neck

OBJECTIVE/HYPOTHESIS

To test the hypotheses that 1) magnetic resonance imaging (MRI)-guided biopsy and aspiration with an open 0.2-T system (Magnetom Open, Siemens, Erlangen, Germany) in the head and neck is feasible and successful and 2) procedure times can be sufficiently short to be well tolerated by the patient.

METHODS

Sixty-one MRI-guided procedures were performed in 47 patients (ages, 6 mo-88 y) in the head and neck, including the mucosal sites and masticator and parapharyngeal spaces (n = 23), parotid space (n = 6), submandibular space (n = 2), cervical vertebral column/paraspinal tissues (n = 8), skull base (n = 3), larynx or hypopharynx (n = 3), and infrahyoid nodal chains and surrounding tissues (n = 16). A clinical C-arm imaging system was used, supplemented by an in-room radiofrequency-shielded liquid crystal monitor, rapid gradient echo sequences for needle guidance, and MRI-compatible anesthesia, monitoring, and surgical lighting equipment. Tissue sampling included fine-needle aspiration (n = 58) and cutting-needle core biopsy (n = 27), with 24 patients undergoing both procedures. Procedures were evaluated for success of needle placement, procedure time, and complications.

RESULTS

Successful needle placement was accomplished in all cases without complication, with tissue sufficient for pathological diagnosis obtained for all but five patients with an average of 2.1 passes per patient. For fine-needle aspiration, average instrument time was 7.8 minutes per pass, and average cutting-needle core biopsy time was 9.2 minutes.

CONCLUSIONS

Interactive MRI guidance for needle biopsy and aspiration of deep head and neck lesions is feasible, successful, and safe. Procedure times are sufficiently short to be well tolerated by the patient.

Reduction of aseptic measures in gynecologic endoscopy: a comparative clinical trial

OBJECTIVE

A prospective comparative clinical study was conducted on 200 patients to evaluate the consequences of minimizing the following standard hygienic measures in gynecologic laparoscopy: surgical scrub, patient draping, surgical gowns.

STUDY DESIGN

A group of 100 patients treated according to maximum hygienic protocol was compared to a group of 100 patients undergoing laparoscopic procedures with only limited aseptic precautions. Clinical control parameters were perioperative temperature and white blood cell count up to the 4th postoperative day. Furthermore, patients and their gynecologists were interviewed 2-4 weeks after surgery to rule out any delayed manifestation of an infection.

RESULTS

Perioperative infection was low in both groups.

CONCLUSION

As we found no significant difference between the two collectives' control parameters, we conclude that a reduction in perioperative hygiene seems feasible for certain laparoscopic procedures. However, a larger collective should be studied in order to confirm this action.

MR imaging-guided radio-frequency thermal ablation in the pancreas in a porcine model with a modified clinical C-arm system

PURPOSE

To test the hypotheses that (a) magnetic resonance (MR) imaging-guided radio-frequency (RF) thermal ablation in the pancreas is safe and feasible in a porcine model and (b) induced thermal lesion size can be predicted with MR imaging monitoring.

MATERIALS AND METHODS

MR imaging-guided RF ablation was performed in the pancreas of six pigs. A 17-gauge monopolar RF probe was inserted into the pancreas with MR imaging guidance, and RF was applied for 10 minutes. After postprocedural imaging (T2-weighted, short inversion time inversion-recovery [STIR], and T1-weighted imaging before and after intravenous administration of gadodiamide), the pigs were observed for 7 days and follow-up MR images were acquired. The pigs were sacrificed, and pathologic examination was performed.

RESULTS

Successful RF probe placement was accomplished in all pigs; the interventional procedure took 46-80 minutes. Thermal lesions were 12-15 mm perpendicular to the probe track and were best seen on STIR and contrast material-enhanced T1-weighted images with a radiologic and/or pathologic mean difference in RF lesion diameter of 1.7 mm +/- 1.0 (SD) and 0.8 mm +/- 1.2, respectively. Diarrhea was the only side effect during the 1-week follow-up; no clinical signs of pancreatitis occurred.

CONCLUSION

MR imaging-guided RF thermal ablation in the pancreas is feasible and safe. Induced thermal lesion size can best be monitored with STIR and contrast-enhanced T1-weighted images. In the future, RF ablation may offer an alternative treatment option for pancreatic cancer.

MRI-guided radiofrequency thermal ablation of implanted VX2 liver tumors in a rabbit model: demonstration of feasibility at 0.2 T

Successful radiofrequency (RF) thermal ablation was performed on VX2 tumors implanted in 23 rabbit livers under magnetic resonance (MR) guidance using a C-arm-shaped low-field 0.2 T system. RF application and immediate postprocedure MRI of all animals was performed [T2-weighted, turbo short tau inversion recovery (STIR), T1-weighted before and after gadopentetate dimeglumine administration). Follow-up MRI with a superparamagnetic iron oxide (SPIO) contrast medium was performed in nine rabbits at 2 weeks and in four rabbits at 1 month post RF ablation. All livers were harvested for pathologic examination. T2-weighted and turbo-STIR images demonstrated the highest tumor-to-RF-thermal lesion contrast-to-noise ratios (CNRs; means 4.5 and 3.8, respectively) on postprocedure images; this was redemonstrated at 2- and 4-week follow-up imaging. T2-weighted imaging never overestimated pathologic lesion size by more than 2 mm, and the radiologic-pathologic correlation coefficient was not less than 0.90. In conclusion, MRI-guided RF thermal ablation in implanted liver tumor is feasible using a C-arm-shaped low-field 0.2 T system. The thermal lesion size can be most accurately monitored with T2-weighted and turbo-STIR images.

MR-guided RF thermal ablation of the kidney in a porcine model

OBJECTIVE

The purpose of the study was to evaluate the ability of MR imaging to reveal RF interstitial thermotherapy in the porcine kidney, as a model for future human trials, and to provide guidance for RF probe insertion.

SUBJECTS AND METHODS

Ten MR-guided RF ablations were performed in the kidneys of three pigs. A 17-gauge monopolar RF probe electrode was inserted into the renal cortex using MR guidance, and RF was applied for 10 min. After postprocedure imaging (T2-weighted, turbo short inversion time inversion recovery [STIR], and T1-weighted sequences), the kidneys were harvested for pathologic examination.

RESULTS

Successful RF probe placement was accomplished in all cases; the interventional procedure time for probe insertion ranged from 4 to 15 min. The thermal lesion size varied from 7 to 14 mm perpendicular to the probe track and was best seen on turbo STIR images. Turbo STIR had the highest renal cortex-to-RF thermal lesion contrast-to-noise ratio with an average of 4.4 +/- 3.5. Turbo STIR imaging never overestimated pathologic lesion diameter with a mean difference of 1.5 +/- 1.4 mm. Three subcapsular hematomas occurred. which could be detected immediately on postprocedure imaging.

CONCLUSION

MR-guided RF thermal ablation in the porcine kidney was found to be feasible, but minor complications occurred. Induced thermal lesion size was best monitored using turbo STIR images. In the future, RF ablation may offer an alternative treatment option for renal cancer.

Effects of superparamagnetic iron oxide on radio-frequency-induced temperature distribution: in vitro measurements in polyacrylamide phantoms and in vivo results in a rabbit liver model

PURPOSE

To determine whether contrast medium containing superparamagnetic iron oxide (SPIO) alters radio-frequency (RF)-related temperature distribution in acrylamide phantoms and in an in vivo model.

MATERIALS AND METHODS

In nine acrylamide phantoms with increasing SPIO content, RF was applied with simultaneous measurement of temperature profile along the probe track. Additionally, magnetic resonance imaging-guided RF ablation was performed in the liver of six rabbits after the intravenous administration of SPIO (0.05 mL per kilogram of body weight) 40 minutes prior to ablation (SPIO group) and in another six rabbits without prior SPIO administration (control group). Coagulation diameter was evaluated on the basis of postprocedural imaging and subsequent gross pathologic findings. Statistical analysis was performed with the Student t test.

RESULTS

In the phantoms, progressive increases in iron content resulted in higher temperatures along the RF electrode track (P < .05). In the in vivo model, however, SPIO at physiologic concentrations did not significantly increase the diameter of coagulation on the basis of either postprocedural imaging or subsequent gross pathologic findings. Additionally, no significant differences were seen in other RF-related parameters including impedance, voltage, current, and grounding pad temperature.

CONCLUSION

Administration of SPIO in conjunction with RF ablation of focal liver lesions is feasible and safe, but no significant difference in the extent of induced coagulation can be expected.

Fast T(2)-weighted imaging by PSIF at 0.2 T for interventional MRI

Rapid T(2) weighted (T(2)W) images would facilitate physicians being able to distinguish normal tissues, vessels, tumors, and thermal lesions from therapeutic devices throughout interventional MRI procedures commonly performed in open low-field scanners (e.g., 0.2 T). Conventional diagnostic MRI techniques have not been successful at low-field strength for fast T(2)W imaging during the guidance phase of interventional MRI (I-MRI) procedures. FISP and true-FISP methods yield T(1)/T(2)-weighted images and do not always provide sufficient contrast for device guidance or lesion assessment. As such, a variant of PSIF (a gradient reversed form of FISP) which collects the T(2)-weighted spin echo of the SSFP signal was developed and implemented at 0.2 T for use in I-MRI procedures. The sequence has a balanced readout gradient to reduce motion sensitivity. Asymmetric sampling toward the end of the TR cycle reduces T(2)* decay of the spin echo component in the SSFP signal. The sequence gives one image in 5-7 s in vivo with adequate SNR and T(2) contrast for interventional applications. Patient studies showed that the PSIF sequence variant demarcates many tumors not detectable by either FISP or true-FISP. Results from animal experiments suggested that it has potential to monitor thermal lesions during interstitial thermal ablation procedures. Magn Reson Med 42:335-344, 1999.

Temperature Measurement Using Echo-Shifted FLASH at Low Field for Interventional MRI

Temperature Measurement Using Echo-Shifted FLASH at Low Field for Interventional MRI. Yiu-Cho Chung, Jeffrey L. Duerk, Ajit Shankaranarayanan, Monika Hampke, Elmar M. Merkle, and Jonathan S. Lewin. (Article was originally published in the Journal of Magnetic Resonance Imaging, Volume 9, No. 1, 1999). In this article, some of the references were printed with the incorrect journal name. Here is the corrected list of references for this article.

MRI-guided radiofrequency thermal ablation of implanted VX2 liver tumors in a rabbit model: demonstration of feasibility at 0.2 T

Successful radiofrequency (RF) thermal ablation was performed on VX2 tumors implanted in 23 rabbit livers under magnetic resonance (MR) guidance using a C-arm-shaped low-field 0.2 T system. RF application and immediate postprocedure MRI of all animals was performed [T2-weighted, turbo short tau inversion recovery (STIR), T1-weighted before and after gadopentetate dimeglumine administration). Follow-up MRI with a superparamagnetic iron oxide (SPIO) contrast medium was performed in nine rabbits at 2 weeks and in four rabbits at 1 month post RF ablation. All livers were harvested for pathologic examination. T2-weighted and turbo-STIR images demonstrated the highest tumor-to-RF-thermal lesion contrast-to-noise ratios (CNRs; means 4.5 and 3.8, respectively) on postprocedure images; this was redemonstrated at 2- and 4-week follow-up imaging. T2-weighted imaging never overestimated pathologic lesion size by more than 2 mm, and the radiologic-pathologic correlation coefficient was not less than 0.90. In conclusion, MRI-guided RF thermal ablation in implanted liver tumor is feasible using a C-arm-shaped low-field 0.2 T system. The thermal lesion size can be most accurately monitored with T2-weighted and turbo-STIR images.

MR-guided percutaneous nephrostomy of the nondilated upper urinary tract in a porcine model

OBJECTIVE

The purpose of this study was to assess the safety and feasibility of MR-guided percutaneous nephrostomy of the nondilated contrast-enhanced upper urinary tract in a porcine model.

SUBJECTS AND METHODS

Six MR-guided percutaneous nephrostomies of the nondilated upper urinary tract were performed in four domestic farm pigs (body weight range, 20-25 kg) using a 0.2-T system. Ten minutes after IV administration of 0.2 mmol/kg of gadodiamide and 0.4 mg/kg of furosemide, a fast T1-weighted sequence was used to guide insertion of an 18-gauge MR-compatible needle into a predetermined calix. After confirmation of needle position using a turbo spin-echo T1-weighted sequence, a 0.035-inch catheter coated with superparamagnetic iron oxide was inserted during MR monitoring. Insertion was followed by tract dilatation and insertion of a 4-French sheath. The final position of the sheath was confirmed by injection of diluted superparamagnetic iron oxide into the collecting system.

RESULTS

Needle insertion was successful for all six procedures, with no complications. Instrumentation time ranged from 4 to 13 min (mean, 6+/-4 min). Sheath placement was successful in five of six kidneys. Placement time ranged from 6 to 28 min (mean, 16+/-9 min).

CONCLUSION

MR-guided percutaneous nephrostomy of the nondilated contrast-enhanced upper urinary tract in a porcine model is feasible and safe.

Low-flow vascular malformations in the head and neck: safety and feasibility of MR imaging-guided percutaneous sclerotherapy--preliminary experience with 14 procedures in three patients

Fourteen percutaneous sclerotherapy procedures with magnetic resonance (MR) imaging guidance were performed in three patients with low-flow vascular malformations. All targeted vascular malformation compartments were filled with sclerosing agent without complications in a mean procedural time of 29 minutes. Follow-up imaging demonstrated reduction in size of the treated portions in all patients. In conclusion, sclerotherapy with MR imaging guidance can be performed safely and allows monitoring of injection.

Temperature measurement using echo-shifted FLASH at low field for interventional MRI

We investigated the feasibility of using echo-shifted fast low-angle shot (FLASH) for temperature-monitored thermo-therapeutic procedures in a 0.2 T interventional magnetic resonance (MR) scanner. Based on the proton resonance frequency shift technique, modified echo-shifted FLASH has sufficiently high signal-to-noise ratio to provide accurate temperature maps with short scan times, i.e., 5 seconds in phantoms (TR = 20.5 msec; effective TE = 30 msec; one echo shift; NSA = 2) and ex vivo experiments (TR = 19.4 msec; effective TE = 28.9 msec; one echo shift; NSA = 2) and 3 seconds (TR = 19.4 msec; effective TE = 28.9 msec, one echo shift; NSA 1) for an in vivo case. The proton resonance frequency shifts with temperature observed in a 0.2 T MR scanner using this sequence were -0.0072 ppm/degrees C (temperature uncertainty = +/-2.5 degrees C) for polyacrylamide phantoins and -0.0086 ppm/degrees C (temperature uncertainty = +/- 1 degrees C) for ex vivo bovine liver. These experiments demonstrated that echo-shifted FLASH is a viable method for low-field temperature monitoring despite the decreased signal and decreased phase sensitivity compared with its counterpart in a 1.5 T MR imaging system. The improved temporal resolution of temperature images, now possible in low-field interventional MR systems using echo-shifted FLASH, will allow clinicians more accurate monitoring of interstitial ablation in MR-guided interventional procedures.

Metastases to the pancreas

Disparity in prognosis and management between primary and secondary pancreatic tumours makes recognition of metastases to the pancreas on CT and MRI an important goal. Three different patterns of secondary pancreatic tumours may be seen: localized, multifocal, or diffuse enlargement. CT findings include hypodense lesions, which show rim enhancement following intravenous contrast medium. On MR examination, the lesions are usually hypointense on T1 weighted and hyperintense on T2 weighted images.

[High-resolution virtual laryngoscopy based on spiral CT data]

This pilot study investigated the feasibility and clinical value of high-resolution virtual real-time laryngoscopy based on helical CT data sets. Nine patients with laryngeal pathology (three with tumors of the vocal cords, two laryngeal carcinomas, one with invasion of the larynx by thyroid carcinoma and six subglottic stenoses) underwent examination by helical CT at a collimation of 1 mm. Following acquisition, the images were processed at a workstation with standard visualization software, such that virtual endoscopy (VE) in real time was possible. The images were then compared with the findings of conventional endoscopy. Because of swallowing artifacts, reconstruction failed in 2 of 12 patients. None of the carcinomas of the vocal cords was recognized at VE or in the cross-sectional CT images. VE provided the correct diagnosis in 8 of 12 cases (laryngeal tumors, subglottic stenoses). Virtual laryngoscopy is capable of simulating the visual findings of endoscopy in cases of laryngeal tumors and subglottic stenoses. Small tumors of the vocal cords are not adequately visualized. The major problem affecting results is motion artifacts resulting from involuntary swallowing.

[Diagnosis of gallstone ileus]

Gallstone ileus is a rare disorder, which, because it is often misdiagnosed preoperatively, may become life-threatening. The classic triad of Rigler (aerobilia, small bowel ileus and a calcified, dystopic stone) is visualized on abdominal plain films in only 14-35% of cases. Further work-up includes ultrasound, upper gastrointestinal series with water soluble contrast medium and computed tomography (CT). CT is especially reliable in demonstrating all three criteria.

[MRCP (magnetic resonance cholangiopancreatography)--an assessment of current status]

For the first time, magnetic resonance cholangiopancretography (MRCP) provides images of the biliary and pancreatic ducts based on 3D data similar to those we are used to from endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic cholangiography (PTC). Extraordinarily impressing is the fact that no contrast media have to be applied. The following manuscript shows technical basics and the development of this technique from gradient echo sequences to the recent single-shot techniques. Furthermore possibilities and limitations of MRCP will be discussed with respect to certain illnesses.

Computed tomographic measurements of the nasal sinuses and frontal bone in mummy-heads artificially deformed in infancy

The purpose of the present study was to ascertain whether artificial skull deformation, carried out during infancy, has an effect on the pneumatization of the frontal and maxillary sinuses and on the osseous structure of the frontal bone. Thus, two normal and 12 artificially deformed adult human skulls (12 males, two females) from the collection of pre-Columbian Peruvian skeletons and mummies in the Institute of Anthropology and Human Genetics (University of Munich) were investigated by computed tomography. These skulls had been excavated from four sites on the Peruvian coast: Las Trancas, Cahuachi. Pacatnamu, and Estaqueria. The volumes of the maxillary sinuses varied from 5.18 mL to 17.19 mL. Those of the frontal sinuses varied from zero to 6.21 mL. The artificial deformation of the skull, which occurred during infancy, had no influence on the size of the maxillary and frontal sinuses. There was also no difference in the average bone thickness of the os frontale; however, artificial deformation in infancy had an influence on the bone structure, resulting in a tremendous rarefication of the diploe of the frontal bones. Based on these findings we conclude that the various types of skull deformation instituted in infancy seem to exert no inhibitory effect on the pneumatization of either the frontal or maxillary sinuses.

Virtual cystoscopy based on helical CT scan datasets: perspectives and limitations

The purpose of the study was to simulate cystoscopy based on three-dimensional helical CT scan datasets in real-time in patients with tumours of the urinary bladder. A helical CT scan with double detector technology was carried out pre-operatively in 11 patients with histologically confirmed carcinoma of the urinary bladder and one patient with chronic cystitis. A non-enhanced scan was first performed, followed by an examination in the early phase of contrast medium enhancement. Further images were acquired after adequate filling of the bladder with contrast medium, approximately 30 min after injection. These data were transferred to a separate graphic computer workstation and reconstructed. The results were then compared with the cystoscopic and histopathological findings. All tumours of the urinary bladder identified at fibreoptic cystoscopy were shown on virtual cystoscopy. The best reconstruction results were obtained from data acquired 30 min after injection of contrast medium. The ureteric orifices were not visualized at virtual cystoscopy. These data lead us to conclude that, at present, virtual cystoscopy has not reached the quality of fibreoptic examination and remains restricted to use in specific cases, for example patients with urethral strictures.

[Pulse sequences and visualization of instruments]

While initially advocated primarily for intrasurgical visualization (e.g., craniotomy), interventional MRI rapidly evolved into roles in image-guided localization for needle-based procedures, and thermal ablation of cancer. In this contest, MRI pulse sequences and scanning methods serve one of four primary roles: (1) speed improvement, (2) device localization, (3) anatomy/lesion differentiation and (4) temperature sensitivity. The first part of this manuscript deals with passive visualization of MR-compatible needles and the effects of field strength, sequence design, and orientation of the needle relative to the static magnetic field of the scanner. Issues and recommendations are given for low-field as well as high-field scanners. The second part contains methods reported to achieve improved acquisition efficiency over conventional phase encoding (wavelets, locally focused imaging, singular value decomposition and keyhole imaging). Finally, the last part of the manuscript reports the current status of thermosensitive sequences and their dependence on spinlattice relaxation time (T1), were diffusion coefficient (D) and proton chemical shift (delta).

Comparison of real-time virtual and fiberoptic bronchoscopy in patients with bronchial carcinoma: opportunities and limitations

OBJECTIVE

Both helical CT and fiberoptic bronchoscopy are used in the staging of pulmonary tumors for therapeutic decision making. The improved resolution offered by helical CT has led to the clinical use of three-dimensional reconstruction techniques such as virtual bronchoscopy. We tested this new simulated endoscopic view of inner organ surfaces and compared it with corresponding fiberoptic examinations of the tracheobronchial system.

SUBJECTS AND METHODS

Twenty patients with malignancies of the lung and mediastinum were examined with both virtual bronchoscopy and fiberoptic bronchoscopy. Both examinations were reviewed by radiologists and surgeons familiar with fiberoptic bronchoscopy. Virtual bronchoscopy was calculated and reconstructed from the cross-sectional images on a separate workstation. Stenoses and tumor infiltration were classified from the fiberoptic examination. These results were compared with the virtual bronchoscopy findings.

RESULTS

Virtual bronchoscopy of diagnostic quality was achieved in 19 of 20 patients. High-grade stenoses were revealed equally well with virtual and fiberoptic techniques. Virtual bronchoscopy offered the advantage of being able to visualize areas beyond even high-grade stenoses. However, on virtual bronchoscopy discrete infiltration or extraluminal impression was not visible in five patients. In another patient, strong heart pulsation produced motion artifacts that prevented evaluation of the reconstruction.

CONCLUSION

Virtual bronchoscopy represents a new noninvasive method for evaluating helical CT findings. In comparison with fiberoptic bronchoscopy, virtual bronchoscopy offers the advantage of being able to visualize areas beyond even high-grade stenoses. In addition to the limited view of fiberoptic bronchoscopy, extraluminal causes of lumen compressions can be analyzed in the cross-sectional images and evaluated together with the virtual representation. However, it was not possible to detect small infiltrations with virtual bronchoscopy. This new representation of helical CT data might be helpful for postoperative follow-up examinations, such as after stent implantation, and can be carried out without additional risk to the patient. Radiologists do need special fiberoptic bronchoscopy knowledge and experience with three-dimensional-reconstructions to differentiate between real stenoses and artificial stenoses that might be caused by pulsation artifacts.

[MR enteroclysis for nuclear spin tomographic diagnosis of inflammatory bowel diseases with contrast enhancement]

PURPOSE

To evaluate MRI for effectiveness in assessment of intra- and extramural changes in the small intestine.

METHODS

40 patients with known or suspected small bowel disease underwent MR imaging immediately after conventional enteroclysis with barium and a mixture of methyl cellulose and gadolinium-DTPA.

RESULTS

In 6 of 24 patients with no pathological findings in conventional enteroclysis, intraabdominal pathology such as thickening of the intestinal wall and an abscess were identified. In the remaining patients, MRI showed good correlation with conventionally obtained data and provided important additional information regarding extraluminal involvement such as enlargement of mesenterial lymph nodes and fistulas as well as abscesses.

CONCLUSIONS

MRI, carried out using this technique, provides important additional information regarding intra- and extraluminal changes with good image quality.

Musculoskeletal involvement in cystic echinococcosis: report of eight cases and review of the literature

OBJECTIVE

Our purpose was to describe the morphologic appearance of musculoskeletal lesions in patients with cystic echinococcosis shown by CT and MR imaging.

CONCLUSION

Patients with musculoskeletal lesions of cystic echinococcosis typically have cystic structures in adjacent soft tissues. These cysts morphologically resemble abscesses, with peripheral uptake of contrast medium and variable signal intensities on T1-weighted MR images. The absence of calcifications or endovesicular daughter cysts does not exclude the diagnosis of cystic echinococcosis.

Bone and soft tissue manifestations of alveolar echinococcosis

OBJECTIVE

The present study demonstrates the osseous and soft tissue manifestations of alveolar echinococcosis (AE).

PATIENTS

We report on eight patients with AE with bone or soft tissue involvement confirmed at biopsy or needle cytology.

RESULTS

All eight patients showed hepatic involvement. Four exhibited infiltration of the spine as a result of direct spread of the hepatic primary lesion; distant metastases were observed in only three of these patients. Calcifications, which are typical for hepatic manifestations of the disease, were observed in soft tissue in only two of eight cases (25%); we observed no instances of endovesicular daughter cysts.

CONCLUSIONS

AE manifests itself in the vertebral column as a form of spondylitis and in soft tissue presents similar to an abscess. Since in most of these cases spread of the disease per continuitatem from the liver is present, the diagnosis is easily made from the characteristic hepatic findings.

[Radiation exposure in digital micturition cystourethrography in children. How much exposure by fluoroscopy?]

OBJECTIVE

Determination of the proportion of the dose-area product caused by fluoroscopy at voiding cystourethrography in children, using digital image intensifier technology.

PATIENTS AND METHODS

Using computer-assisted dosimetry, we determined the dose-area product and the respective proportions of the dose-area product caused by fluoroscopy and radiography as well as the number of radiographs taken at a given examination of 40 children (8 children less than 2 years old, 15 children between 2 and 6 years old and 17 children between 6 and 15 years old).

RESULTS

The computer software program correctly differentiated between fluoroscopy and radiography in 80% of cases. Incorrect results were primarily observed in newborns and young children. The total radiation dose ranged in relation to patient age from 22 to 651 cGy x cm2. Fluoroscopy was responsible for an average 78% of the applied radiation dose.

CONCLUSION

Computer-assisted dosimetry is useful in determining the proportion of the dose-area product caused by fluoroscopy in older children undergoing voiding cystourethrography. When image intensifier technology is used, this accounts for more than 75% of the total radiation dose. The method is not suitable for use in small children.

[Virtual cystoscopy based on spiral CT data]

Simulation of three-dimensional cystoscopy based on helical CT scan data in real-time in patients with tumours of the urinary bladder. In three patients with histologically confirmed carcinoma of the urinary bladder, a helical CT scan with double detector technology was carried out preoperatively. A native scan was first performed, followed by an examination in the early contrast medium enhanced phase. After adequate contrasting of the urinary bladder (30 minutes latency), further images were acquired. These data were transferred to a separate graphic computer workstation and reconstructed. The results were then compared with the cystoscopic and pathohistological findings. All tumours of the urinary bladder identified at fiberoptic cystoscopy were also visualised by virtual cystoscopy. The best reconstruction results were obtained from data acquired after the 30-minute latency period. Virtual cystoscopy represents an interesting option in helical CT scanning, which is able to visualise polypoid tumours of the urinary bladder. Its clinical relevance, however, must be demonstrated in studies with a larger number of patients examined.

Papillary cystic and solid tumor of the pancreas

The papillary cystic and solid tumor of the pancrease (PCSTP) is a primary pancreatic neoplasm of unknown etiology occurring most commonly in young women and regularly containing hemorrhagic areas. Clinical symptoms are non-specific. Although these tumors reach an average diameter of 10 cm, they are often discovered by accident. Because patients with surgically resected PCSTP have very good prognoses, it is important to distinguish these tumors from other growths in the pancreas, for example mucinous cystadenoma. Whereas, due to the variable proportion of fluid components, these tumors offer non-characteristic structure at ultrasonography, computed tomography (CT) possesses high specificity for PCSTP, particularly when calcifications are present. Angiography distinguishes these tumors from hypervascular neoplasms, such as the endocrinologically inactive islet cell tumor. Magnetic resonance tomography (MRT) is especially suited for imaging the hemorrhagic areas in solid tumor formations, as well as hemorrhagic debris in the fluid portions and layer phenomena are frequently observed.