T1-weighted SE Research Articles

Bone marrow lesions: evaluation with fat-suppression turbo spin echo MR imaging at 0.5 T.

The purpose of this study was the assessment of the diagnostic value of fat-suppression T2-weighted images for a variety of bone marrow lesions. We performed 40 studies of the axial or appendicular skeleton in 33 patients (age range 4-80 years) with neoplastic, inflammatory or traumatic lesions with a 0.5 T system (Gyroscan T5, Philips Medical Systems, Best, The Netherlands). Fat-suppression T2-weighted images [turbo spin echo (TSE) with spectral presaturation with inversion recovery (SPIR)] were obtained in addition to the routine T1-weighted SE and T2-weighted TSE sequences. Fat-suppression TSE T2-weighted images were better than standard TSE T2-weighted images in 25 studies. In 11 of them demonstration and characterization of the lesions (known from T1-weighted images) was possible only after fat suppression. In the other 14 patients demonstration of the full extent of the lesion especially to the nearby soft tissues was possible only after fat suppression. In 13 studies no advantage was conferred by SPIR, whereas in two instances T2-weighted images were better. Fat-suppression T2-weighted images are diagnostically useful in a variety of lesions of the musculoskeletal system, but their limitations should be known.

MRI of bowel obstruction using the HASTE sequence.

High quality MR images of the gastrointestinal tract are now obtainable using a T2-weighted fast SE MR sequence with half-Fourier acquisition of data (the HASTE sequence). This fast sequence can acquire a set of images in a single breath hold and is insensitive to peristalsis-related artifact. It can be used with other imaging modalities in defining bowel obstruction and is accurate in determining the presence of bowel dilation and level of obstruction and in differentiating obstructing tumor from other causes of obstruction.

MR imaging in gout

The appearance of gouty tophus in magnetic resonance imaging (MRI) is characteristic. On T1- and T2-weighted SE images, the signal intensity of tophaceous lesions is similar to that of muscles. According to the histology, T2-weighted SE images demonstrate extremely hyperintense signals, which reflect the high protein content in the amorphous center of the tophus. The microscopic urate crystals deposited there have no MRI signal and are of no further diagnostic impact. Vascularized granulation tissue surrounding the tophus center enhance after intervenous application of contrast agents (Gadolinium). The inflamed tophus is associated with local edema, causing high signal intensity. MRI is superior to plain radiography for early detection of intraosseous tophi. Involvement of anatomical structures such as ligaments and tendons can be evaluated sufficiently. For peripheral joints, axial slice orientation is most helpful.

Hepatocellular carcinoma: MR imaging with mangafodipir trisodium (Mn-DPDP).

To determine the efficacy of manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate) (DPDP) at magnetic resonance (MR) imaging for evaluation of hepatocellular carcinoma (HCC). MR imaging at 1.5 T was performed in 20 patients with 65 HCC nodules. T1- and T2-weighted spin-echo and T1-weighted gradient-recalled-echo images were obtained before and after administration of 5 mumol/kg Mn-DPDP. Readers individually evaluated the pre- and postcontrast images for detection of tumor nodules, with subsequent consensus reading for interpretation discrepancies. Quantitative measurements of tumor-liver contrast-to-noise ratio (C/N) were also performed. Enhancement characteristics were correlated with histologic tumor differentiation. Precontrast images depicted 50 lesions in 17 patients, and postcontrast images depicted 49 lesions in 20 patients. Combination of pre- and postcontrast images enabled detection of 53 lesions in 20 patients. Three lesions (three patients) were seen only on postcontrast images. Four lesions (three patients) were seen only on precontrast images. Reader evaluation of tumor conspicuity showed a significant preference for precontrast T2-weighted SE images (P < .01). Quantitative evaluation showed a significant increase in C/N on postcontrast T1-weighted images (P < .01). Well-differentiated lesions showed significantly greater enhancement than that of poorly differentiated lesions (P < .05). Mn-DPDP-enhanced MR imaging depicts HCC tumors not visualized with unenhanced studies. The degree of tumor enhancement correlates with histologic differentiation.

Macroscopic and microscopic assessments of disease burden by MRI in multiple sclerosis: relationship to clinical parameters.

We have evaluated macroscopic white matter abnormalities (visible lesions) together with microscopic abnormalities in the normal appearing white matter (NAWM) of patients with multiple sclerosis (MS) to determine their relative contributions to the development of disability. The total visible lesion volume (TLV) was computed as a measure macroscopic changes, whereas both texture analysis and T2 were used as possible indicators of diffuse disease in the NAWM. Dual echo T2-weighted SE images were obtained from 41 patients with definite MS: 10 primary progressive (PP), 11 secondary progressive (SP), 10 benign (BE), 10 early relapsing remitting (ERR), as well as from 10 healthy controls. Calculation of T2 and texture parameters were performed in a region of frontal NAWM of patients and controls. The TLV of each patient was measured using a semiautomated lesion detection program. No significant differences were found between the controls and the patients for all texture parameters examined. However, NAWM T2 was longer in the patients than in the controls (P = .02). Mean TLV was highest for SP and lowest for BE and ERR patients. A significant correlation was found between TLV and EDSS (P < .01) but not between NAWM T2 or texture and expanded disability status score (EDSS). Our study suggest that: (a) diffuse changes are present in NAWM, (b) texture analysis is unable to detect any subtle structure in the NAWM abnormalities, possibly because of the limited image resolution; (c) in the development of disability in MS, macroscopic lesions are more important than microscopic abnormalities in the NAWM.

Differentiation between multiple liver hemangiomas and liver metastases of gastrinomas: value of enhanced MRI.

Hepatic metastases of neuroendocrine tumors are known to mimic hemangiomas on nonenhanced SE MR sequences. The usefulness of MR examination with gadolinium injection to identify lesions was prospectively evaluated. Nine patients with multiple liver metastases of gastrinomas were compared with six patients showing multiple liver hemangiomas. Patients underwent unenhanced T2-weighted SE, T1-weighted SE, and FLASH sequences, followed by enhanced sequential FLASH sequences and a 5 min delayed T1-weighted SE sequence. On T2-weighted SE sequence, all hemangiomas displayed the same typical morphology as a sharply defined, homogeneous, high signal intensity lesion, but this pattern was also observed for some or all of the lesions in seven of nine patients with gastrinoma metastases. Dynamic FLASH sequences were accurate for lesions larger than 2 cm, hemangiomas displaying a nodular peripheral enhancement with centripetal filling in, and metastases displaying either an initial homogeneous or a regular peripheral enhancement. Precise assessment of lesions smaller than 2 cm remained equivocal. Delayed T1-weighted. SE sequence (performed at least 5 min after Gd-chelate injection) was the most accurate technique to identify metastases by showing hypo- or isointensity signal, whereas all hemangiomas were hyperintense. Postcontrast delayed T1-weighted sequence is the primary technique to differentiate equivocal cases of hemangiomas from metastases of gastrinoma.

Gadolinium-DTPA-enhanced MR imaging in asymptomatic knees.

To evaluate the occurrence and extent of Gd-DTPA-enhanced synovial structures in asymptomatic knee joints of middle-aged healthy individuals. MR imaging of the knee joint was performed in 10 healthy subjects aged 40-61 years. The study included a sagittal T1-weighted SE sequence before and after i.v. injection of 0.1 mmol Gd-DTPA/kg b.w. Contrast-enhanced synovial structures were found in all knees. The extent of the synovial structures was usually not uniform within the examined joint. In the intercondylar fossa, the thickness of synovial structures was more often pronounced. In the suprapatellar recess, synovial thickness was constant and minimal. The presence and the varying extent and thickness of synovial structures in asymptomatic knees in middle-aged individuals must be considered in the evaluation of early and mild synovitis of the knee joint with Gd-enhanced MR imaging in this age group.

Das Meningeale Zeichen: eine Neubewertung

To evaluate the occurrence of the meningeal sign in meningiomas and metastases. We studied 20 patients with meningiomas and 17 patients with cerebral metastases adjacent to the dura. MRI studies (Siemens, Magnetom 1,5) included axial T1-weighted and T2-weighted unenhanced as well as gadolinium-DTPA enhanced T1-weighted (axial, coronal, sagittal) SE imaging. In all patients the tumours were resected with the attached dura mater. Histopathological examinations were done, which corresponded to the area of marked enhancement by gadolinium-DTPA. There was no correlation between the occurrence of the meningeal sign and the histopathological examinations. In 20 patients with meningiomas adjacent to the dura we found the meningeal sign in 11 cases. Histologically we observed an increase of collagen fibres and fibrocytes. In 5 of 17 cases with superficial cerebral metastases the meningeal sign was seen, histologically as dura infiltrations and microbleedings. The meningeal sign is not specific for meningiomas and can be observed in a wide variety of pathological entities.

MRI of pancreatic metastases from renal cancer.

Our goal was to describe the MR features of pancreatic metastases from renal cancer. Five patients with pancreatic metastases from renal cancer were imaged with MR. Imaging was performed on a 1.5 T MR imager using excitation-spoiled fat-suppressed T1-weighted SE images (all patients), T1-weighted spoiled GE images (all patients), T2-weighted fast SE (one patient) and excitation-spoiled fat-suppressed T2-weighted fast SE (one patient) images, serial postgadolinium spoiled GE images (all patients), and postcontrast excitation-spoiled fat-suppressed T1-weighted SE images (two patients). Multiple pancreatic lesions (n = 6) were present in two patients, solitary tumors in two patients, and diffuse micronodular pancreatic enlargement in one patient. All lesions were hypointense compared to normal pancreas on T1-weighted fat-suppressed SE images. Lesions were high in SI on T2-weighted images in two of two patients. All lesions demonstrated enhancement on the immediate postgadolinium spoiled GE images with the smaller tumors (<1.5 cm, three individual and the micronodular tumors) showing diffuse enhancement and the larger tumors (>1.5 cm, five tumors) showing predominantly rim enhancement. Pancreatic metastases from renal cell carcinoma have distinctive MR features that include diffuse enhancement in small lesions and rim enhancement in large lesions on immediate postgadolinium images and high SI on T2-weighted images.

Value of fat signal suppression MRI pulse sequences for diagnosis of malignant tumors in the area of the head-neck

Evaluation of frequency-selective fat saturation (FS) and short-tau inversion recovery (STIR) fat suppression (FU) in MRI of patients with malignant head and neck tumors. Forty-five patients with biopsy-proven carcinomas of the extracranial head and neck were examined with MRI at 1.0 T. A T2-weighted TSE sequence with and without STIR-FU and a T1-weighted SE sequence with and without FS were compared in axial slices. STIR-FU was successful in all and FS in 85-88% of the head examinations (nasopharynx, sinuses, oropharynx, and oral cavity) and 33-46% of the neck examinations (hypopharynx and larynx). When visualization and delineation of tumors were ranked on a four-point scale (0-3), respective mean values for images with/without FU or FS were 2.6/1.9 for T2-TSE in all examinations, 2.2/1.7 (nasopharynx and sinuses) and 1.3/1.4-1.6 (oropharynx, oral cavity, hypopharynx, and larynx) for T1-SE without contrast media administration (CM) and 2.3/2.1 (nasopharynx and sinuses) and 2.4-2.5/1.9-2.0 (oropharynx, oral cavity, hypopharynx, and larynx) with CM. STIR-T2-TSE was a technically reliable pathfinder for localization and extension of both tumors and lymph nodes. FS-T1-SE was technically unreliable in examinations of the hypopharynx and larynx. With CM, FS-T1-SE was most useful for MRI of carcinomas of the oral cavity and oropharynx. In the nasopharynx and sinuses, T1-SE with CM and FS-T1-SE with or without CM were equal for tumor visualization and delineation.

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

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

MRI of the anal sphincter.

The anal sphincter was imaged with MR using an internal coil to demonstrate its anatomy, contrast enhancement patterns, and appearance in disease. A cylindrical saddle geometry coil was placed in the anal canal. Sixteen volunteers and 18 patients were examined. Imaging was performed on a 0.5 T Picker Asset MRI scanner in all the volunteers and nine patients and on a 1.0 T Picker HPQ Vista in nine patients. Then T1- and T2-weighted SE, T1-weighted GE and STIR images transverse to the sphincter, and T1-weighted SE images parallel to the sphincter in the coronal oblique plane were obtained. Intravenous gadopentetate dimeglumine (0.1 mmol/kg) was given to 2 normal subjects for dynamic studies and 10 patients for conventional postcontrast imaging. The coils were easy to insert and well tolerated and provided high spatial resolution. The internal sphincter had a higher signal intensity than the external sphincter on all sequences but particularly on STIR images. Brisk contrast enhancement of the internal sphincter was seen. Sphincteric abscesses and fistulous tracks were identified in three patients and confirmed at surgery. Sphincter defects were seen in three patients with past obstetric trauma, and these were also confirmed at surgery. Sphincter atrophy was seen in three patients with idiopathic fecal soiling. MRI of the anal sphincter with an internal coil provides excellent visualization of normal anatomy and may be of considerable value in diagnosis.

MRT fokaler Leberläsionen bei 1,5 T Turbo-Spinecho- im Vergleich mit der Spinecho-Technik

The aim of our study was to evaluate a T2-weighted turbo-spinecho sequence in comparison to a T2-weighted spinecho sequence in imaging focal liver lesions. In our study 35 patients with suspected focal liver lesions were examined. Standardised imaging protocol included a conventional T2-weighted SE sequence (TR/TE = 2000/90/45, acquisition time = 10.20) as well as a T2-weighted TSE sequence (TR/TE = 4700/90, acquisition time = 6.33). Calculation of S/N and C/N ratio as a basis of quantitative evaluation was done using standard methods. A diagnostic score was implemented to enable qualitative assessment. In 7% (n = 2) the TSE sequence enabled detection of further liver lesions showing a size of less than 1 cm in diameter. Comparing anatomical details the TSE sequence was superior. S/N and C/N ratio of anatomic and pathologic structures of the TSE sequence were higher compared to results of the SE sequence. Our results indicate that the T2-weighted turbo-spinecho sequence is well appropriate for imaging focal liver lesions, and leads to reduction of imaging time.

MRI of placental polyps.

Placental polyp is intrauterine polypoid placental tissue retained after delivery or abortion and may cause life-threatening bleeding. We studied the value of MRI in diagnosing placental polyps. Two women, 26 and 32 years old, with histologically proven placental polyp were included in this study. These patients were treated with local injections of methotrexate or transcatheter arterial embolization. The MR images before and after these treatments were studied retrospectively. High intensity pedunculated masses of 3-4 cm in size were observed in the expanded uterine cavity on T2-weighted and contrast-enhanced T1-weighted SE images. Bloody contents were observed around the masses. Placental polyps were more intensely enhanced than the myometrium by the contrast media, and the enhanced T1-weighted images indicated the retained placental tissues with an adherent part to the myometrium. Magnetic resonance imaging was also useful in following up the reduction in the size of the lesions and in the blood flow after the treatments. Magnetic resonance imaging may be useful in diagnosing and following up placental polyps.

Benign Hepatocellular Tumors

Our goal was to describe the features of benign hepatocellular tumors on superparamagnetic iron oxide (SPIO)-enhanced MR images and to evaluate the potential role of SPIO administration in the diagnosis of these tumors. The T1- and T2-weighted SE images were performed before and after SPIO administration in 19 patients with focal nodular hyperplasia (FNH) or adenomas. The lesions were counted and qualitatively assessed. In 32 tumors with a diameter of > 10 mm, the contrast-to-noise ratio (CNR) and the liver and tumor enhancement were calculated. Thirty-seven tumors were detected on MR images: 29 before and 36 after SPIO administration (p < 0.05). The SPIO-enhanced T1-weighted images provided the highest detection rate and CNR. The central scar was most conspicuous on SPIO-enhanced T2-weighted images. Most FNHs and adenomas lost less signal than the liver, three tumors did not lose signal, and four FNHs showed a signal loss equal to or greater than that of the liver. The SPIO-enhanced T1-weighted images increased the CNR and the detection rate of benign hepatocellular tumors. On T2-weighted images, most benign hepatocellular tumors showed a signal decrease after SPIO administration. No significant difference in signal loss was observed between FNH and adenomas.

Vegetable oil as an MR contrast agent for rectal applications

The purpose of this study was to evaluate the feasibility of pure vegetable oil as an MR contrast agent for rectal applications. The hypothesis was that vegetable oil highlights the lumen of the rectum after rectal application as a positive contrast medium and offers additional contrast qualities using fat suppression techniques. Eleven MRI examinations were performed on 11 subjects (five healthy volunteers, all males, mean age 35 yr; and six patients, three males, three females, mean age 49 yr). Peanut oil, 200 ml, was applied rectally. In addition, 0.1 mmol/kg GD-DTPA was administered intravenously to the six patients only. Conventional T1-weighted SE sequences and T1-weighted SE images with fat suppression were obtained. Criteria for image evaluation were: overall image quality; uniformity of contrast distribution; chemical shift artifact; and delineation of the rectal wall. Side effects were assessed. There were no complaints reported by the 11 subjects. The image quality was sufficient in all studies. In all five of the volunteers and five of the six patients, the distribution of oil was uniform. Chemical shift artifacts did not deteriorate image quality. After rectal application of vegetable oil, the delineation of the rectal wall was sufficient with and without fat suppression techniques. Vegetable oil highlights the lumen of the rectum in MRI studies and offers additional contrast qualities with fat suppression techniques, acting as a positive as well as a negative contrast agent, depending on the chosen sequence.

Artifacts in MR Imaging Caused by Small Quantities of Powdered Iron

The MR image artifacts caused by minute metallic particles were investigated by imaging small powdered iron quantities from 0.01 mg to 1.7 mg in water phantoms. Images with T1-weighted GRE 3-D and T2-weighted SE 2-D sequences were reconstructed with 5 MR imagers: at 0.04 T, 0.1 T (2 scanners), 1.0 T and 1.5 T. In GRE 3-D images the artifacts were round, clearly demarcated black areas, whereas in SE 2-D images artifact areas were elliptic and surrounded by a bright irregular rim with ghost veils in the direction of frequency encoding. The area of the artifact increased slightly up to 0.1 mg of iron, but grew clearly with larger samples. It appeared to behave independently on the MR imager system for all iron samples. This study shows that even microscopic magnetic particles cause a notable distortion in the MR image independently of the MR equipment used.

Artifacts in MR Imaging Caused by Small Quantities of Powdered Iron

The MR image artifacts caused by minute metallic particles were investigated by imaging small powdered iron quantities from 0.01 mg to 1.7 mg in water phantoms. Images with T1-weighted GRE 3-D and T2-weighted SE 2-D sequences were reconstructed with 5 MR imagers: at 0.04 T., 0.1 T (2 scanners), 1.0 T and 1.5 T. In GRE 3-D images the artifacts were round, clearly demarcated black areas, whereas in SE 2-D images artifact areas were elliptic and surrounded by a bright irregular rim with ghost veils in the direction of frequency encoding. The area of the artifact increased slightly up to 0.1 mg of iron, but grew clearly with larger samples. It appeared to behave independently on the MR imager system for all iron samples. This study shows that even microscopic magnetic particles cause a notable distortion in the MR image independently of the MR equipment used.

Detection of focal liver lesions with superparamagnetic iron oxide: value of STIR and SE imaging.

We assessed the value of superparamagnetic iron oxide (SPIO) particles on the detection of focal liver lesions by MRI. Twenty patients with one to five focal liver lesions, primarily detected with ultrasonography and/or contrast-enhanced CT, were evaluated further with unenhanced and iron oxide-enhanced MRI at 1.0 T. Superparamagnetic iron oxide particles were administered intravenously as a slow infusion. Then T1-, T2-, and proton density-weighted SE images were obtained. In addition, the performance of a short TI inversion recovery (STIR) sequence was evaluated. The iron oxide contrast medium had marked effects on liver signal-to-noise (S/N) and tumor-to-liver contrast-to-noise (C/N) ratios but only minimal effects on tumor S/N ratios in cases of malignant tumor foci. Lesion-to-liver contrast, expressed as differences between the tumor and liver S/N ratios, improved very significantly after SPIO infusion with all four pulse sequences. Contrast enhancement of the liver parenchyma was best in T2-weighted SE images, but the tumor-to-liver C/N values were highest with the postcontrast STIR sequence. The SPIO enhancement revealed a number of additional focal lesions (31%), also foci under 1 cm in diameter. In three benign focal lesions, SPIO infusion produced a definite reduction in the S/N ratio of the lesions in contrast to the minimal change measured in malignant foci. The favorable performance of the STIR sequence contradicts the disappointing results previously obtained at 0.6 T. Superparamagnetic iron oxide is a promising new contrast medium for MR examinations of the liver, increasing the conspicuity and reducing the detectability threshold of focal hepatic lesions.

Pituitary microadenomas: diagnosis with dynamic serial CT, conventional CT and T1-weighted MR imaging before and after injection of gadolinium

Purpose: The few studies comparing CT and MR in the diagnosis of pituitary microadenomas give discordant results. This prospective study compares the value of dynamic serial CT (DSCT), conventional CT (CCT), pre-Gd T1-weighted spin echo (T1SE-Gd) and post-Gd T1-weighted SE (T1SE+Gd) in the detection of pituitary microadenomas. Methods: The value of CT and MR was assessed in 17 cases, with the surgical confirmation as reference. The CTs and MRs were independently and blindly evaluated by two neuroradiologists. Because the finding at MR and/or CT influenced the selection of patients for surgery, the positive predictive value was calculated. The sensitivity calculation applies only for a specific group of postsurgical patients with positive CT and/or MR (marked with an asterisk for these reasons). Results: In this study, the highest sensitivity ∗ (88% and 82%, respectively, for observes I and II) was achieved by DSCT. The T1SE-Gd and T1SE+Gd (evaluated separately) were slightly inferior (sensitivity ∗ of 76% for observer I). The combination of T1SE-Gd with T1SE+Gd improved the sensitivity ∗ to 94% and 82%, respectively, for observers I and II. There was also moderate improvement of sensitivity ∗ by combination of DSCT with conventional CT (94% for observer I). Conclusion: These results suggest that rapid injection of a large amount of contrast conjointly with a fast scanning through the pituitary is crucial for the confident detection of microprolactinomas. Taking into account the similar results of the comination DSCT + CT and T1SE-Gd + T1SE+Gd in the detection of microprolactinomas, high field MRI is the first step modality in the evaluation of presumed hypophyseal hyperprolactinemia.