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Inflammatory pseudotumor is a rare benign tumor entity. Because inflammatory pseudotumors mimic malignant tumors both clinically and radiologically, the radiologist should be familiar with this entity. Inflammatory pseudotumor most commonly involves the lung and the orbit, but it has been reported to occur in nearly every site in the body. For making a definite diagnosis a biopsy is often essential. The treatment options are varied and consist of surgery, high-dose steroids, irradiation, and chemotherapeutics.

Primary vascular leiomyosarcomas are very rare tumors, with the venous variety most often arising from the inferior caval vein and the arterial variety from the pulmonary artery. The tumors show either an exclusive intra- or extravascular pattern or a mixed growth pattern. The clinical symptoms depend on tumor location, with intraluminal tumors of the inferior caval vein causing edema or a Budd-Chiari syndrome. Leiomyosarcomas of the pulmonary artery can mimic chronic central or recurrent peripheral pulmonary embolism. Contrast enhanced spiral CT with multiplanar reconstruction is the diagnostic method of choice when a vascular leiomyosarcoma is suspected. MRI with MR-angiography can be added. If a tumor of undetermined origin shows a broad contact with a vessel and/or an intraluminal component, possible primary vascular leiomyosarcoma should be included in the differential diagnosis.

Cystic renal lesions are most often simple or complicated cysts, which can be seen solitary or as part of cystic renal disease. The minority of these lesions are benign or malignant cystic tumors. The classification of cystic renal masses by Bosniak (category l - IV) based on specific ultrasound and CT features is very useful for the characterization of the lesion and for the therapeutic decision. The main objective of this classification is to differentiate nonsurgical (category II) from surgical cystic masses (category III/IV). Ultrasound is the first modality of choice in the diagnostic work-up of cystic renal masses, because an accurate and economically reasonable diagnosis of the frequent simple cyst can be made by maintaining rigid ultrasound criteria of the Bosniak classification. If a complicated cyst or a cystic tumor is suspected a three phasic contrast-enhanced CT of the kidneys should be performed. MRI is superior to CT in the characterization of complex cystic masses.

Purpose: Evaluation of portoportal collateral vessels and associated biliary abnormalities in patients with cavernous transformation of the portal vein by MRI., Material and Methods: Review of 34 MRI examinations performed on patients with angiographically or MR-angiographically proven cavernous transformation. The analysis included the pattern of the portoportal collateral circulation and the abnormalities of the biliary system, such as wall thickening, stenosis, dilations and irregularities of the extra-and intrahepatic bile ducts., Results: 23 (67.6%) of 34 patients with cavernous transformation had paracholedochal portoportal collateral vessels, with 22 (64.7%) showing visible luminal channels. Epicholedochal venous collaterals could be observed in 8 (23.5%) patients. 24 (70.5%) of 34 patients demonstrated biliary abnormalities due to portoportal collaterals, leading to stenosis with dilatation of the proximal bile ducts in 8 (23.5%) patients. The ductal walls were irregular in 7 (20.5%) patients, and thickened in 11 (32.3%). The gallbladder wall was thickened in 4 (12.9%) patients., Conclusion: Portoportal collaterals in patients with cavernous transformation of the portal vein can be identified by MRI. These collaterals frequently alter the biliary system, which must be considered in differential diagnosis of biliary abnormalities observed in the presence of portoportal collaterals.

Purpose: Evaluation of the diagnostic potential of a dynamic MR examination of the pancreas., Material and Methods: Retrospective study on 49 patients who underwent MRI of the pancreas (2 insulinomas, 2 cystadenomas, 19 pancreatic carcinomas, 26 patients with chronic pancreatitis). Interpretation was done in two steps: Initial evaluation of T2-weighted TSE-sequences, T1-weighted gradient echo sequences before and after injection of Gadolinium-DTPA i. v. Afterwards, additional evaluation of a dynamic contrast-enhanced MRI series of the pancreas with four dynamic scans., Result: Dynamic MR examination of the pancreas is useful in case of insulinomas. However, in case of pancreatic cancer an additional dynamic MR examination of the pancreas does not provide further clinically relevant information., Conclusion: In patients with a suspicion of pancreatic cancer, the injection of contrast material should preferably be used for the performance of a contrast-enhanced MR angiography at the expense of a dynamic MR examination.

Background: Aim of this study was to evaluate morphologic criteria for diagnosis of locally recurrent head and neck tumors in helical CT., Methods: Retrospective study, 44 examinations with radiologically abnormal findings were re-read by two radiologists; findings were analysed and correlated with histological diagnosis and clinical findings., Results: 25 cases of local tumor recurrence were confirmed histologically. The accuracy of helical-CT in our preselected examinations for a local tumor recurrence was 93.5 %, the specificity 83.3 %. But 13/44 cases showed radiologically equivocal findings, among them 6 tumor recurrences. The most common characteristics of the 25 proven tumor recurrences were: contrast medium enhancement (96 %), increased volume in comparison to previous examination (92 %), inhomogenity (72 %); however contrast medium-enhancement and increasing volume were also seen in 68.4 % and 63.1 % of the benign changes., Conclusion: Contrast medium enhancement and increasing volume are criteria with a high sensitivity but low specifity in predicting a local tumor recurrence in head and neck cancer.

Purpose: Comparison of anatomical visualisation and diagnostic value of selective MIP reconstructions of respiratory triggered 3D-TSE-MRCP versus standard MIP reconstructions and single-shot MRCP., Material and Methods: 50 patients with pancreaticobiliary disease were examined at 1.5 Tesla (ACS NT II, Philips Medical Systems) using a breath-hold single-shot (SS) and a respiratory triggered 3D-TSE-MRCP technique in 12 standard MIP projections. Additional selective MIP reconstructions with different slice thickness (2, 4, 10 cm) and projections were performed on a workstation. Visualization of the pancreaticobiliary system and the diagnostic value of the examinations were analysed., Results: Single-shot and 3D-TSE in standard projections showed comparable anatomical visualisation. On selective MIP reconstructions the biliary system (SS p < 0.002; 3D-TSE p < 0.000) and the periampullary region (SS p < 0.000; 3D-TSE p < 0.003) were more clearly seen than on SS and standard MIP reconstructions. Furthermore, superior visualisation of the pancreatic duct could be achieved with additional selective MIP reconstructions in contrast to standard MIP (p < 0.003). Sensitivity and diagnostic accuracy showed superior results for selective and standard MIP reconstructions, but no significant differences between the three techniques were found., Conclusion: SS and standard MIP reconstructions showed comparable anatomical visualisation. Selective MIP postprocessing on a workstation offers a better visualisation of the pancreaticobiliary system and is useful for detecting pathological alterations.

Purpose: Analysis of the frequency and significance of small focal liver lesions (< or = 2 cm) detected on MRI in the presence or absence of a history of malignancy., Methods: 628 MRI examinations of the liver performed during 1994-1996 were evaluated. The inclusion criterion into the study was the detection of a focal liver lesion with a size < or = 2 cm. The frequency, the size, the diagnostic proof, and the differential diagnosis of the focal liver lesions were analysed with regard to the patients history of a known malignant tumor., Results: Overall, 179 of the 628 patients (28.5%) had focal liver lesions < or = 2 cm (n = 338). 58.9% of the lesions could be classified based upon follow-up studies by ultrasound, CT or MRI, or by biopsy. The remaining 41.1% of the lesions could not be classified due to the absence of follow-up examinations. 57.3% of all proven lesions were benign and 42.7% were malignant. A history of a malignant tumor was present in 76.7% of all patients with small liver lesions; however, lesions were benign in these patients in 50.6% of the cases. In patients with no known history of a malignancy, 75% of the lesions were benign and 25% were malignant. However, these malignant lesions were in 10/11 cases hepatocellular carcinomas in patients with liver cirrhosis., Conclusion: Even in the presence of a history of a malignant tumor, about 50% of the detected small liver lesions on MRI are benign. In the absence of a tumor history the probability of a small malignant liver lesion is very low, if the patients does not have liver cirrhosis where small hepatocellular carcinomas can be present.

Purpose: The aim of this work was to reduce the influence of motion on diffusion-weighted MR images of the abdomen by pulse triggering of single-shot sequences., Methods: Five healthy volunteers were examined both without and with finger pulse-triggering of a diffusion-weighted single-shot echo planar MR imaging sequence at 1.5 T. Series of diffusion-weighted images were acquired at different phases of the cardiac cycle by varying the time delay between finger pulse and sequence acquisition. The measurements were repeated three times. The diffusion weighted images were analysed by measuring the signal intensities and by determining the ADC values within the spleen, kidney and liver., Results: The magnitude of motion artifacts on diffusion weighted images shows a strong dependence on the trigger delay. The optimum trigger delay is found to be between 500 and 600 ms. For these values the abdominal organs appear homogeneous on all diffusion weighted images and the strongest signal intensities are detected. At optimum triggering the accuracy of the apparent diffusion coefficients is up to 10 times better than without triggering. Moreover, the standard deviation of the repeated measurements is smaller than 12% for all volunteers and for all organs. Without triggering the standard deviation is larger by a factor of 4 on average., Conclusion: Pulse triggering of single-shot sequences leads to significant reduction of motion related artifacts on diffusion weighted images of the abdomen and provides more accurate and reproducible ADC values.

Purpose: Evaluation of malignancy criteria in MRT of kidney tumors in correlation with the histopathological findings., Materials and Methods: 41 patients with suspected malignant kidney tumors were examined using a T1 SE sequence (TR/TE 300/10 ms) before and after i.v. administration of 0.1 mmol/kg Gd-DTPA and a T2 SE sequence (TR/TE 5500/150 ms). The results were correlated with the pathological findings., Results: 38 malignant tumors were found: 29 renal cell carcinomas (RCC), 13 with solid growth, 11 with tubulopapillary growth, and three with mixed growth forms, one cystic RCC, and one chromophobic RCC, in addition, 6 urothelial carcinomas and three other malignomas. Typical MRT criteria for RCC were an inhomogeneity of the tumor with regions of slightly increased signal intensity on the T1-weighted image (59%) and regions with reduced signal intensity on the T2-weighted image (96%) as compared with renal parenchyma; these were due to histomorphological hemorrhage and hemosiderin deposits, respectively. A further criterion for RCC was a hypointense pseudocapsule in the T2 TSE sequence in 79% of the cases., Conclusions: The low-signal nature of RCC in the T2-weighted image correlates with hemorrhage and hemosiderin deposits. The detection of a pseudocapsule is useful in the differential diagnosis of solid tumors in the kidney.

Purpose: To determine the value of a dynamic Gd-enhanced ultrafast T1-weighted 3D-turbo-gradient-echo sequence (3D-TFE) in the detection and characterization of focal liver lesions., Materials and Methods: 51 patients with 124 focal liver lesions (35 hemangiomas, 30 HCC, 24 metastases, 22 cysts, 5 FNH/adenoma, 8 other lesions) were examined using a 1.5 T system. The dynamic 3D-TFE sequence, achieving 40 slices with a thickness of 4.5 mm in a 17-s breath-hold, was compared with a fat-suppressed T2-weighted fast-spin-echo sequence (TSE SPIR), unenhanced and Gd-enhanced T1-weighted spin-echo sequences (SE), and a T1-weighted gradient-echo sequence (FFE)., Results: On 3D-TFE images more lesions (107/124) were identified than on T1-weighted SE (101/124) and T1-weighted FFE images (106/124), but less compared to T2-weighted TSE SPIR images (115/124). The 3D-TFE-sequence provided additional information in 65/107 (61%) detected lesions by delineating the dynamic enhancement pattern, most valuable in patients with HCCs in 90%., Conclusions: On dynamic 3D-TFE images more lesions could be depicted than on conventional T1-weighted SE and T1-weighted FFE images. Visualization of the dynamic enhancement pattern provided additional information for tumor characterization in 61% of the detected lesions on the 3D-TFE images.

Purpose: To determine the value of magnetic resonance imaging (MRI), computed tomography (CT) and CT arterial portography (CTAP) in detecting malignant liver lesions in cirrhosis patients., Materials and Methods: The radiological examinations (CT, MRI and CTAP) of 47 patients suffering from cirrhosis having undergone an orthotopic liver transplantation (OLTX) were analysed retrospectively. The number of detected liver lesions was compared with the results of the histopathological findings after OLTX., Results: 13/21, 11/18 and 7/12 of the malignant lesions were detected by MRI, CT and CTAP respectively. In MRI one false positive case was shown, two in CT and three in CTAP. Almost the same lesions were identified by all three procedures. The examination of the liver with MRI and CT and CTAP did not bring additional information. Most of the lesions that were missed were less than 2 cm in diameter., Conclusions: The rate of detection of HCC in patients with cirrhosis was about 60%. MRI and CT yielded similar results.

Purpose: It has been shown that intravenous administration of contrast media produces an MR arthrographic effect without the need for intraarticular injection. This is the first study evaluating this new technique of indirect MR arthrography in the diagnosis of glenoid labrum tears., Methods: 28 patients with clinically suspected labral injuries were prospectively investigated (1.5 Tesla, flexible surface coil). A plain MR examination of the shoulder (transverse and oblique-coronal orientation, T1-weighted spin- [TE/TR 15/675], proton density- and T2*-weighted gradient echo [TE/TR/Flip 14,32/600/30 degrees] sequences) and indirect MR arthrography (transverse and oblique-coronal orientation, fat-suppressed T1-weighted spin-echo sequences [TE/TR 15/675], intravenous injection of gadopentetate dimeglumine [0.1 mmol/kg], followed by 10-15 min of joint movement) were performed. Results were confirmed by arthroscopy and/or open surgery., Results: Indirect MR arthrography significantly improved delineation of the glenoid labrum and hyaline cartilage (p < 0.05). Sensitivity and specificity of indirect MR arthrography in the diagnosis of labral injuries were 90% and 89%, compared to 79% and 67% of the native MR examination., Conclusion: Indirect MR arthrography is a promising non-invasive technique in the evaluation of the glenoid labrum.

Purpose: Aortic wall thickening due to intramural hemorrhage may be the only sign of aortic dissection. The aim of this study was to evaluate the incidence, imaging features and differential diagnoses of intramural hemorrhage (IMH) of the thoracic aorta., Methods: 98 patients with clinically suspected aortic dissection were investigated via Spiral-CT and MRT. Diagnosis of IMH based on the presence of smooth crescentic or concentric wall thickening over a longer segment of the thoracic aorta without flow visualization and without compression or distortion of the aortic lumen., Results: 69 patients had classic aortic dissections and 7 patients were diagnosed to have IMH of thoracic aorta. One patient with IMH of the ascending aorta died of aortic rupture and subsequent pericardial tamponade 12 hours after onset of symptoms. In one patient with IMH of the descending aorta on initial examination, there was a progression of overt aortic dissection at follow-up after three weeks. In two patients with IMH of the descending aorta, wall thickening decreased in size at follow-up (10-15 weeks), whereas in one patient it remained unchanged., Conclusion: IMH of the aorta should be considered a precursor of aortic dissection. At follow-up IMH may decrease in size, rupture or progress to overt aortic dissection.

Purpose: To evaluate new pulse sequences (turbo-spin-echo [TSE] and turbo-field-echo [TFE] sequences) for study protocol optimisation and to assess the role of MRI in the differential diagnosis of renal tumours., Methods: In six volunteers MRI of the kidney was performed at 0.5 T using a conventional T2 weighted spin-echo (SE) sequence (TR/TE 1800/90 ms) and three different TSE sequences (TR 1800-5000 ms, TE 90-150 ms). Additionally CT and MRI was performed in 34 patients with 41 renal masses. Two readers evaluated both images regarding the differentiation between malignant and benign masses., Results: The pilot study showed that the heavily T2-weighted TSE sequence (TR/TE 5500/150 ms) was superior to other sequences with regard to image quality and differentiation of the corticomedullary junction. In the clinical study malignant tumours were correctly classified with CT and MRI in 86.4% and 95.5% of the cases, whereas the accuracy in the diagnosis of benign lesions of CT and MRI was 73.7% and 89.5%, respectively., Conclusion: Using new puls sequences MRI is superior to CT in the differential diagnosis of renal tumours. MRI is superior to CT in the differentiation between complicated cysts and cystic or hypovascular renal cell carcinomas.

Purpose: To compare five pulse sequences in 60 patients with pancreatic disease by means of MRI at 0.5 T., Methods: T1 weighted Spin-Echo sequences (T1W SE) before and after i.v. contrast medium administration, fat-suppressed T1W SE sequences after i.v. contrast medium administration, T2 weighted Turbo-Spin-Echo sequences (T2W TSE), and fat-suppressed T2W TSE were evaluated within an ROC study., Results: The standard sequences (T1W SE before and after i.v. contrast medium administration, T2W TSE) were superior to the fat-suppressed T1W and T2W (T)SE sequences in delineating the anatomy and for correct diagnosis. The T1W sequence with and without i.v. contrast media detected all anatomic structures best. In most instances the correct diagnosis and coexistent findings in the diseased pancreas were obtained with the T2W sequence., Conclusion: Fat-suppressed sequences are less useful in the diagnosis of pancreatic disease by MRI at medium field strength compared to the standard sequences.

Purpose: To establish the distribution pattern of haematopoietic and fatty bone marrow on MRI of the proximal humerus and the scapula in correlation with age, gender and nutritive factors., Material and Methods: 32 shoulder MR examinations (T1-weighted spin-echo and opposed-phase gradient-echo sequences) from 24 patients and 8 volunteers were analysed retrospectively. The amount of haematopoietic bone marrow within the proximal humerus and scapula was classified into four groups and was correlated with age (H-test), gender (chi 2-Test), and thickness of subcutaneous fat (H-test). The marrow distribution within 10 scapulae of cadavers over 60 years of age at death was studied., Results: With increasing age, the amount of haematopoietic bone marrow in the proximal humeral metaphysis tends to decrease from lateral towards medial (H-test, p = 0.3). Diaphysis and epiphysis did not show haematopoietic marrow. The amount of haematopoietic bone marrow within the paraglenoid region of the scapula also revealed a decrease with increasing age (H-test, p = 0.003). Females had higher amounts of haematopoietic marrow than males (chi 2-test, p = 0.03). The thickness of subcutaneous fat was independent of the marrow distribution., Conclusion: The amount of haematopoietic bone-marrow of the shoulder girdle decreases with increasing age. The knowledge of marrow distribution patterns based upon these changes is important for shoulder MRI interpretation to prevent confusion with infiltrative disease.

Purpose: The value of T2 weighted turbo-spin-echo sequences with selective fat suppression (TSE-SPIR) in the detection and differential diagnosis of focal liver lesions was compared to TSE sequences and conventional T1 weighted spin-echo (T1 SE) sequences at 0.5T., Methods: In 50 patients with focal liver lesions T1 SE-TSE-, and TSE-SPIR sequences were performed. Two independent readers evaluated the sequences with regard to the image quality, fat suppression, and the number and conspicuity of liver lesions. Quantitative analysis was performed by tumour-liver contrast-to-noise (CNR) measurements., Results: From a total of 118 liver lesions the T1 SE sequence, the TSE sequence, and the TSE-SPIR sequence showed 85.6%, 83.9%, and 91.5%, respectively (p < 0.05). The tumour-liver CNR of malignant liver lesions was 30.2-46.6% higher on the TSE-SPIR sequence compared to the TSE sequence (p < 0.01). With the exception of fat-containing lesions there was no significant difference of CNR in benign lesions on both TSE sequences., Conclusion: With regard to lesion detection the TSE-SPIR sequence is superior to the TSE sequence without fat suppression, whereas it is inferior to the TSE sequence in the differential diagnosis of benign and malignant lesions.

Purpose: To evaluate the range of normal contrast enhancement behaviour in dynamic MR mammography of healthy breast parenchyma, and to reduce false-positive results caused by incidental contrast enhancing lesions., Materials and Methods: We performed a prospective two-armed study on 20 healthy premenopausal volunteers who were examined four times within one month (Group 1) or during four consecutive months (Group 2). Incidence, prevalence, morphology, and contrast enhancement pattern of lesions were evaluated., Results: 82% (9/11 of Group 1) and 78% (7/9 of Group 2) showed at least one of a total of 60 contrast enhancing lesions. In 54% or 33% (Group 1 or 2), lesions with enhancement velocity beyond the malignancy threshold were found. 72% or 75% of lesions resolved completely during follow-ups. 69% of lesions were focal with irregular border. Time/signal intensity diagrams were almost always not suspicious; no wash-out phenomenon was seen., Conclusion: In MR mammography of premenopausal breast parenchyma, focal contrast enhancing lesions-even with enhancement beyond the malignancy threshold-may occur without any underlying pathology.

Aim: The value of turbo-spin-echo (TSE) sequences was compared with conventional spin-echo (SE) and inversion-recovery (IR) sequences for cerebral MRT in 70 children at 0.5 T and 1.5 T. In addition we evaluated whether proton weighted sequences (PD) were diagnostically important and in what proportion of cases., Method: Conventional T1 and T2 weighted SE and T2 weighted TSE sequences were used in all children. An IR sequence was performed in 39 patients. The various sequences were analysed semiquantitatively with regard to image quality, artifacts and the demonstration of normal and anatomical structures and pathological findings., Results: By any criteria, TSE sequences were superior to conventional T2 weighted SE sequences at 0.5T and 1.5 T, requiring a shorter examination time (35-53%). In 8.6% the pathological finding was best seen on PD-SE sequences (5 glial scars, 1 tumor)., Conclusion: Although TSE sequences are better than T2 SE sequences with regard to image quality and the demonstration of abnormalities, conventional double-echo SE sequences (with PD and T2 weighted images) cannot be entirely replaced by T2 weighted TSE sequences in children.

Purpose: To determine whether medium field strength (0.5 T) MR mammography is able to differentiate between benign and malignant lesions in the same way as a 1.5 T standard technique., Material: In 40 consecutive female patients with nodular lesions, examinations were carried out at 1.5 T (2D-FFE, TR/TE/FA 200/3.9/80) and 0.5 T (3D-FFE, 24/3.4/40)., Results: There was wide spread of the speed of enhancement of malignant tumours for both techniques (44%-145% with signal increase in the first minute of 42%-189%). In 15 out of 17 carcinomas, the rapidity of uptake and final degree of enhancement after contrast was higher during 0.5 T/3D measurements than it was for 1.5 T/2D images. Fibroadenomas and mastopathies showed similar enhancement characteristics for both techniques. Sharply defined "wash-out" was seen only in malignant lesions; it appeared ten times more frequently in the 0.5 T/3D examinations than at 1.5 T/2D., Conclusions: The distinction between benign and malignant lesions can be made with more certainty using medium field strength and 3D-FFE sequence than using the 2D high-field standard technique.

Purpose: To study the diagnostic value of radiological imaging modalities in patients undergoing endoscopic cholecystectomy., Patients and Methods: In 286 patients with endoscopic cholecystectomy ultrasound and intravenous cholecystography was performed for preoperative work-up. Postoperatively all patients were examined with ultrasound., Results: ERCP showed a stone in the common bile duct in 12 patients with suspected stones on ultrasound, cholecystography or laboratory values. All 12 patients were treated with papillotomy. Postoperative ultrasound detected increasing fluid in the peritoneal cavity in three patients. Laparotomy of one patient showed bleeding from the cystic artery, in the second patient, injury of the right bile duct. One patient showed an accessory hepatic duct, another patient demonstrated pancreatitis., Conclusion: Ultrasound and intravenous cholecystography are suitable for preoperative imaging. Postoperative ultrasound is useful in detecting complications.

Purpose: To determine whether dynamic MR mammography is possible on midfield systems without loss of diagnostic sensitivity when compared to the standard highfield technique., Materials and Methods: 42 consecutive patients were examined twice: Once using the standard dynamic 2D gradient echo technique at 1.5 T; a second examination was performed on a 0.5 T system. For the midfield examinations a 3D sequence with optimized T1 contrast was used to compensate for the shorter T1 relaxation times at 0.5 T. Subtraction images were calculated to improve detectability of enhancing lesions., Results: Image quality was comparable on both systems. Mean enhancement of lesions was higher at 0.5 T/3D as compared to 1.5 T/2D (161% versus 112%). In malignant lesions, enhancement at 0.5 T/3D surpassed that at 1.5 T/2D in 88% of cases; average maximum signal intensity increase of cancers was significantly higher at 0.5 T/3D as compared to 1.5 T/2D (183% versus 108% relative to baseline). One satellite lesion of a recurrent carcinoma was detected on the 0.5 T/3D images only., Conclusion: A 3D gradient echo pulse sequence can be used to compensate for the T1 shortening effect of the lower field strength. With a 3D sequence, sensitivity of MRM at 0.5 T is even superior to that of the standard 2D highfield technique.

Aim: The value of chemical-shift-gradient-echo sequences and turbo-spin-echo sequences with selective fat suppression (SPIR = Spectral Presaturation by Inversion Recovery) in the differentiation of benign and malignant adrenal tumours was investigated., Methods: Both techniques were performed at 1.5 T in 22 patients with 24 tumours. The loss of signal intensity of the tumour or of the signal intensity ratio between tumour and liver or muscle on the opposed phase Fast-Field-Echo (FFE) sequence in comparison to the in phase FFE sequence or on the TSE-SPIR sequence compared to the TSE sequence was the criterion for intratumoral lipid, suggesting a benign mass., Results: The sensitivity and specificity of the chemical shift technique was 62-77 and 100%, respectively. In adrenal tumours larger than 1.5 cm sensitivity of the chemical-shift technique was 89%. On the contrary sensitivity of the TSE-SPIR sequence was only 11-78%. Both techniques had a specificity of 100%., Conclusion: The chemical shift technique is more accurate in the differentiation of adrenal masses than the TSE-SPIR sequence.

Using a spectrometer (n = 60) in vitro and MRT imaging (n = 8) in vivo, we studied the influence of fatty changes of liver cells on the relaxation times of the liver (two animal models of fatty liver disease/orotic acid, L-ethionine). Induction of fatty degeneration of the liver by means of an orotic acid diet resulted in pure deposition of fat in the liver without any histological or serological proof of inflammatory changes. Although accumulation of triglyceride in the liver reduced the T1 relaxation time only relatively slightly (-15%), there was good correlation (r = 0.88) between fat content and T1. There was also good correlation (r = 0.92) between T2 and histological fat content. Inflammatory changes besides fatty deposition were seen both serologically and histologically in the L-ethionine model, so that the fatty content did not correlate with T1. In-vivo MRT imaging showed that spin-echo sequences are inappropriate for diagnosing fatty infiltration of the liver despite the relaxation time changes produced by the fatty deposition. On the other hand, chemical-shift imaging sequences are very sensitive to identify fatty deposits, and are also independent of any additionally existing inflammatory changes.

The value of rapid T1- and T2-weighted fast field (T1-FFE, T2-FFE) gradient-echo sequences and T2 weighted turbo-spin echo (TSE) sequences in the diagnosis of focal liver lesions using 0.5 Tesla was compared with conventional spin-echo sequences (SE). Amongst 88 liver lesions T1-SE sequences showed 98%, T2-TSE sequences showed 92%, T2-SE sequence showed 84%, T1-FFE sequence showed 78% and T2-FFE sequence showed 69%. Direct comparison has shown that TSE sequences are able to demonstrate significantly more lesions (p < 0.05) than T2-SE sequences. Quantitative assessment has shown that the tumor/liver contrast/noise ratio in the T1-SE sequence was 118% higher than in the T1-FFE sequence (p < 0.001). Comparison of T2 weighted sequences has shown that the tumour/liver contrast/noise ratio was 45% higher in the TSE sequence than in the T2-SE and 239% higher than in the T2-FFE sequence (p < 0.001). The results indicate that the TSE sequence should be used instead of the conventional T2-SE sequence because of the reduced time (about 40%), due to improved image quality and increased demonstration rate of liver lesions. Neither T1-FFE nor T2-FFE are suitable, when using moderate field strength, to replace T1-SE or TSE sequences.

Markedly T2-weighted MR images of the pelvis can be obtained with TSE sequences using short acquisition times. In order to determine whether TSE sequences at 0.5 Tesla produce diagnostically valuable images, 9 normals and 53 patients with suspected gynaecological tumours were examined with TSE and SE sequences. Visual comparison showed a considerable superiority of the TSE sequences in most respects. The quality of the TSE images was regarded as very good in 82% and good in 18% (SE sequences: 27% very good, 55% good, 18% moderate), delineation of anatomical structures 81% very good and 19% good (SE sequence: 31% very good, 53% good, 16% moderate). TSE sequences were also superior in the detection of pathological changes (87% very good, 13% good) compared with SE sequences (56% very good, 37% good, 7% moderate). Venous plexuses in the parametrium were better demonstrated by SE sequences. There were significantly higher signal to noise ratios (SNR) with TSE sequences for fat, bone marrow (each p < 0.001), and urine (p < 0.05). Using muscle as reference tissue, there were significantly higher signal-difference to noise ratios (SDR) for fat (p < 0.001), and bone marrow (p < 0.0001), the other pelvic organs and tumours showed no significant differences between the SNR and SDR. TSE sequences are well suited to replace SE sequences in the MR diagnosis of gynaecological tumours.

The qualitative and quantitative MRI findings in 16 patients with focal nodular hyperplasia (FNH) of the liver are described; nine of these were confirmed histologically. A central scar is typical of FNH and provides a reliable diagnosis. This finding was seen in half the cases. If the scar is not demonstrable, the following features suggest the diagnosis: smooth margins, homogeneous signal distribution, increased signal intensity in T2-weighted spin-echo images and reduced signal intensity in inversion-recovery sequences. The T1 and T2 relaxation times in FNH are increased by about 30% compared with normal liver tissue.