Fast T2*-weighted MRI of the prostate at 3 Tesla

Purpose:

To describe a rapid T2*‐weighted (T2*W), three‐dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1‐weighted turbo‐spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS).

Materials and Methods:

B₀ susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k‐space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six‐channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed.

Results:

Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W‐positive areas. Post‐biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS.

Conclusion:

The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T. J. Magn. Reson. Imaging 2011;33:902–907. © 2011 Wiley‐Liss, Inc.     

Snapshot MRI with T2*-weighted magnetization preparation

A method for encoding T₂*-dependent contrasts into the preparation period of magnetization-prepared uitrafast MRI sequences is demonstrated and validated. The preparation block consists of a 90°—T—90°_p sequence, where p is shifted by 90° for successive images. By adding two such successive images in quadrature, a combined image is obtained, in which the pixel intensities depend on the incoherent intravoxel dephasing that occurred during T in a way that is similar to the dependence on TE in a gradient-echo sequence. The method could therefore be useful for applications that require very short repetition times for good temporal resolution, together with detection of T₂*-weighted contrasts, such as functional MRI in the brain.     

Evaluation of peri-infarcted hypoperfusion with T2*-weighted dynamic MRI

The purpose of this study was to evaluate cerebral perfusion with T2*-weighted dynamic MRI in the area around the infarcted core. We examined seven patients with subacute cerebral infarction. After bolus injection of gadopentetate dimeglumine, a series of gradient-echo images were recorded in a selected slice. From these images, concentration-time curves were created on a region-of-interest (ROI) basis around infarction for calculating relative regional cerebral blood volume (rrCBV). Brain perfusion single photon emission computed tomography (SPECT) study also was performed with intravenous injection of ¹²³I-labeled N-isopropyl-p-iodoamphetamine (¹²³I-IMP). All patients showed prolonged signal decrease in the area around the infarcted core. ROI analysis showed significantly increased rrCBV compared to the normal side (P < .01, paired t test). The ¹²³I-IMP SPECT study showed that these areas had decreased cerebral blood flow. These findings suggest compensatory vascular dilatation due to decreased perfusion pressure. T2*-weighted dynamic MRI is a useful method for detecting compensatory vasodilatation of ischemic insult in the peri-infarcted area.     

MRI of the female pelvis at 3T compared to 1.5T: evaluation on high-resolution T2-weighted and HASTE images

Purpose

To evaluate the feasibility of MRI of the female pelvis using high‐resolution T2‐weighted imaging (T2WI) and the half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) technique at 3 Tesla (T) compared to 1.5T, while focusing on the uterine body and cervical anatomy.

Materials and Methods

A total of 19 healthy women underwent pelvic MR scans on 3T and 1.5T scanners. Axial and sagittal T2W (voxel size of 0.6 × 0.8 × 2 mm) and sagittal HASTE images were obtained. The images were evaluated qualitatively for overall image quality, contrast in the uterine zonal appearance and cervical structure, image inhomogeneity, and artifacts. A quantitative evaluation was performed regarding zonal contrast and image inhomogeneity.

Results

On T2WI, the image contrast in the uterine cervix and vagina were significantly higher at 3T than at 1.5T, although there was no significant difference in the overall image quality or contrast in the uterine zonal appearance. Image inhomogeneity was more prominent at 3T, and motion artifact was more severe at 1.5T.

Conclusion

Our results suggest that MRI of the female pelvis at 3T may potentially provide excellent images of the uterine cervix on high‐resolution T2WI. New techniques to reduce inhomogeneity are thus called for. J. Magn. Reson. Imaging 2007;25:527–534. © 2007 Wiley‐Liss, Inc.     

Evaluation of T2-weighted and dynamic contrast-enhanced MRI in localizing prostate cancer before repeat biopsy

We assessed the accuracy of T2-weighted (T2w) and dynamic contrast-enhanced (DCE) 1.5-T magnetic resonance imaging (MRI) in localizing prostate cancer before transrectal ultrasound-guided repeat biopsy. Ninety-three patients with abnormal PSA level and negative prostate biopsy underwent T2w and DCE prostate MRI using pelvic coil before repeat biopsy. T2w and DCE images were interpreted using visual criteria only. MR results were correlated with repeat biopsy findings in ten prostate sectors. Repeat biopsy found prostate cancer in 23 patients (24.7%) and 44 sectors (6.6%). At per patient analysis, the sensitivity, specificity, positive and negative predictive values were 47.8%, 44.3%, 20.4% and 79.5% for T2w imaging and 82.6%, 20%, 24.4% and 93.3% for DCE imaging. When all suspicious areas (on T2w or DCE imaging) were taken into account, a sensitivity of 82.6% and a negative predictive value of 100% could be achieved. At per sector analysis, DCE imaging was significantly less specific (83.5% vs. 89.7%, p < 0.002) than T2w imaging; it was more sensitive (52.4% vs. 32.1%), but the difference was hardly significant (p = 0.09). T2w and DCE MRI using pelvic coil and visual diagnostic criteria can guide prostate repeat biopsy, with a good sensitivity and NPV.     

Comparison of special interest computed tomography, endosonography and histopathological stage of oesophageal cancer

AIMS: To assess the strength of agreement between the perceived pre-operative stage of oesophageal tumours as determined by spiral computed tomography (CT) and endoscopic ultrasound (EUS), both alone and in combination, with the histopathological stage. METHODS: Sixty patients with oesophageal cancer underwent both pre-operative CT and EUS performed by two consultant radiologists with a special interest in upper gastrointestinal radiology. The strength of the agreement between the radiological stage and the histopathological stage was determined by means of the weighted Kappa statistic (Kw). RESULTS: Sensitivity for T and N stages was 58% and 79% for CT, and 72% and 91% for EUS. Specificity for T and N stages was 80% and 84% for CT, and 85% and 68% for EUS. Kw for T and N stages was 0.455 (p=0.0001) and 0.603 (p=0.0001) for CT compared with 0.604 (p=0.0001) and 0.610 (p=0.0001) for EUS. In patients when CT and EUS agreed regarding the T and N stages, the strength of agreement between the radiological and the histopathological stage was greater (Kw T 0.613 (p=0.0001), Kw N 0.781 (p=0.0001)).CONCLUSION: CT and EUS are complimentary techniques for the staging of oesophageal tumours, and these results reinforce the importance of specialist radiology in stage directed management.     

Fat-suppressed MRI of musculoskeletal infection: fast T2-weighted techniques versus gadolinium-enhanced T1-weighted images

 Purpose. To investigate gadolinium’s role in imaging musculoskeletal infection by comparing the conspicuity and extent of inflammatory changes demonstrated on gadolinium-enhanced fat-suppressed T1-weighted images versus fat-suppressed fast T2-weighted sequences. Design. Eighteen patients with infection were imaged in a 1.5-T unit, using frequency-selective and/or inversion recovery fat-suppressed fast T2-weighted images (T2WI) and gadolinium-enhanced frequency-selective fat-suppressed T1-weighted images (T1WI). Thirty-four imaging planes with both a fat-suppressed gadolinium-enhanced T1-weighted sequence and a fat-suppressed T2-weighted sequence were obtained. Comparison of the extent and conspicuity of signal intensity changes was made for both bone and soft tissue in each plane. Results. In bone, inflammatory change was equal in extent and conspicuity on fat-suppressed T2WI and fat-suppressed T1WI with gadolinium in 19 planes, more extensive or conspicuous on T2WI in three planes, and less so on T2WI in two planes. Marrow was normal on all three sequences in 10 cases. In soft tissue, inflammatory change was seen equally well in 20 instances, more extensively or conspicuously on the T2WI in 11 instances, and less so on T2WI in 2 instances. One case had no soft tissue involvement on any of the sequences. Five abscesses and three joint effusions were present, all more conspicuously delineated from surrounding inflammatory change on the fat-saturated T1WI with gadolinium. The average imaging time for the fat-saturated T1WI with gadolinium was 6.75 min, while that of the T2-weighted sequences was 5.75 min. Conclusion. Routine use of gadolinium is not warranted. Instead, gadolinium should be reserved for clinically suspected infection in or around a joint, and in cases refractory to medical or surgical treatment due to possible abscess formation.     

Analysis of artefacts and detail resolution of lung MRI with breath-hold T1-weighted gradient-echo and T2-weighted fast spin-echo sequences with respiratory triggering

The aim of this study was to evaluate feasibility and limitations of two MR sequences for imaging of the lung using a semi-quantitative rating scale. Ten healthy volunteers were assessed with a breath-hold T1-weighted gradient-recalled-echo (TR/TE=129/2.2 ms, matrix 173 x 256) and a T2-weighted turbo spin-echo (TSE) sequence with respiratory triggering (TR/TE=3000-5000/120 ms, matrix 270 x 512) in axial 6-mm slices. The T1-weighted GRE protocol included a pre-saturation pulse over the mediastinal structures. Artefacts and resolution of vessel/airway structures in each lung segment were evaluated by two observers (10 volunteers, 180 segments). Cardiac and vessel pulsation artefacts predominated on T1-weighted GRE, respiration artefacts on T2-weighted TSE (lingula and middle lobe). Pre-saturation of the mediastinum reduced pulsation artefacts on T1-weighted GRE. T1-weighted GRE images were improved by bright flow signal of vessels, whereas image quality of T2-weighted TSE was reduced by black-blood effects in central parts of the lung. Delineation of lung periphery and the mediastinum was superior with T2-weighted TSE. Segmental/sub-segmental vessels (up to fourth/fifth order) and bronchi (up to third order) were identified. All 180 lung segments were imaged in diagnostic quality with at least one of the two sequences (T1-weighted GRE not diagnostic in 9 of 180, T2-weighted TSE in 4 of 180). Both sequences were found to be complementary: superior identification of gross lung anatomy with T1-weighted GRE and higher detail resolution in the periphery and the mediastinum with T2--weighted TSE.     

Dynamic contrast-enhanced T2*-weighted MRI in patients with cerebrovascular disease

Our purpose was to investigate the potential of dynamic susceptibility contrast-enhanced MRI in assessing regional haemodynamics in patients with cerebrovascular disease. T2^*-weighted FLASH sequences were performed on a control group of 10 healthy subjects, 13 patients with unilateral stenosis or occlusion of the internal carotid artery and 6 patients with acute onset of neurological symptoms, the observed signal intensities being converted into concentration-time curves. A gamma-variate function was fitted to the measured concentration-time curves to eliminate effects of tracer recirculation. In each patient the two cerebral hemispheres were compared and the difference between the mean transit times and the percental change of the regional cerebral blood volume, calculated for each side. Patients with haemodynamically significant unilateral carotid obstruction can be divided into two subgroups: those with good and those with poor collateral supply. Patients with good collateral supply had a slight but not statistically significant increase in mean transit time and cerebral blood volume on the diseased side, whereas those with poor collaterals had a significant increase compared with the control group. In patients with acute onset of neurological symptoms perfusion maps clearly demonstrated the disturbed perfusion at a time when T2-weighted images were still normal. Perfusion imaging is a reliable and noninvasive method of assessing changes in cerebral perfusion in patients with unilateral carotid stenosis. This MR technique permits monitoring of haemodynamic changes during therapy and thus may become an alternative to SPECT and PET scanning. In patients with acute occlusion of a cerebral artery, perfusion imaging reveals the entire perfusion deficit before conventional MRI and thus allows early intervention. Received: 10 April 1996 Accepted: 14 June 1996     

Assessment of relative brain iron concentrations using T2-weighted and T2*-weighted MRI at 3 Tesla

In this paper a new method is presented for the relative assessment of brain iron concentrations based on the evaluation of T₂ and T₂* -weighted images. A multiecho sequence is employed for rapid measurement of T₂ and T₂*, enabling calculation of the line broadening effect ( T₂′). Several groups have failed to show a correlation between T₂ and brain iron content. However, quantification of T₂′, and the associated relaxation rate R₂′, may provide a more specific relative measure of brain iron concentration. This may find application in the study of brain diseases, which cause associated changes in brain iron levels. A new method of field inhomogeneity correction is presented that allows the separation of global and local field inhomogeneities, leading to more accurate T₂* measurements and hence, T₂′ values. The combination of T₂*, and T₂-weighted MRI methods enables the differentiation of Parlkinson's disease patients from normal age-matched controls based on differences in iron content within the substantia nigra.     

Assessment of the diagnostic accuracy of T2*-weighted MR imaging for identifying hepatocellular carcinoma with liver explant correlation

Background

T2*-weighted MRI may represent a novel method for identifying hepatocellular carcinoma (HCC). The goal of this study was to assess the diagnostic accuracy of T2*-weighted MRI for HCC with liver explant correlation.

Materials and methods

A retrospective review identified 25 patients who had undergone liver transplantation with pre-operative T2*-weighted MRI. All patients had Child's-Pugh A (9), B (9), or C (7) liver disease with 13 transplanted for liver dysfunction and 12 for HCC. The T2*-weighted images were interpreted by 2 blinded, independent observers and the results compared with the explanted specimens. Sensitivity and specificity of T2*-weighted MRI for the identification of HCC was assessed.

Results

By pathology, 16 HCC (mean largest diameter 2.1 cm; range 0.9–3.6 cm) were identified in 14 patients. Reader 1 had a sensitivity of 69% (95% confidence interval 41–88%) and a specificity of 100% (68–100%). Reader 2 had a sensitivity of 56% (31–79%) and a specificity of 100% (68–100%). There was a very good inter-observer agreement (kappa = 0.84).

Conclusion

T2*-weighted MRI had a moderate sensitivity for identifying HCC but had an excellent specificity. A T2*-weighted MR sequence may be a useful component of a liver MRI protocol due to its high specificity for HCC, and may be particularly useful in patients unable to undergo gadolinium enhanced MRI.     

Chondroid lipoma: MRI appearances with clinical and histologic correlation

 Chondroid lipoma is a recently described benign tumor of adipose origin which, pathologically, mimics myxoid liposarcoma and myxoid chondrosarcoma. This tumor typically presents as a well-defined mass in the superficial tissues of the extremities. In this report, we present the magnetic resonance imaging (MRI) appearances of a pathologically proven chondroid lipoma. To our knowledge, this is the first report of any imaging findings associated with this tumor.     

Differential diagnosis of intracranial lesions with high signal on T1 or low signal on T2-weighted MRI

Magnetic resonance imaging (MRI) is the preferred technique for examining intracranial pathology in the non-acute setting in most cases. The aim of this review is to demonstrate the imaging appearances on unenhanced spin-echo MRI of lesions that show characteristic, unusual signal changes, which occur due to the presence of fat, cholesterol, paramagnetic substances, rapidly flowing fluids, air, cortical bone or calcification. The nature of the MRI signal, together with the anatomical location of the lesion should allow the provision of a narrow differential diagnosis, before the use of intravenous contrast medium or additional imaging sequences.     

3D T2-weighted fast spin-echo MRI sialography of the parotid gland

The diagnostic value of 3D T2-weighted MRI sialography and 2D T2-weighted fast spin-echo (FSE) images for delineation of the normal duct system and characterisation of parotid gland duct pathology was compared in a prospective study. We studied eight healthy volunteers and 18 patients with pathology of the parotid gland (tumours in 3, sialolithiasis in 6, Sjögren's disease in 4, recurrent or chronic parotitis in 4, post-traumatic stricture of the main parotid duct in 1). A heavily T2-weighted 3D FSE sequence was compared with a conventional 2D T2-weighted FSE sequence. The normal main parotid duct was always visible on 3D sialography and seen in 68 % of the 2D T2-weighted FSE studies. The diagnostic reliability of both sequences for diagnosis of luminal concretions in sialolithiasis and dilatation of the duct in duct stricture or chronic parotitis was equal, although slight intraglandular dilatation was appreciated only on 3D sialography. Extraductal pathology resulting in obstruction or displacement of ducts was better characterised on 2D T2-weighted images. However, 3D MRI sialography offered the advantage of postprocessing with overview images and multiple maximum-intensity projection images in any plane.     

0.5 T MRI of small renal masses: value of T2-weighted and Gd-DOTA-enhanced images

We compared the value of T2-weighted and Gd-DOTA-enhanced T1-weighted images for the detection and characterisation of 33 small renal masses (14 clear cell carcinomas, 6 angiomyolipomas, 3 angiomyomas, 4 adenomas, 3 papillary carcinomas, 3 oncocytomas, 1 haemorrhagic cyst). Dynamic enhanced MRI was performed to study the tumoral vascular supply (19 cases). MRI depicted all the masses more than 1 cm in diameter, but missed all the lesions less than 1 cm (4 false-negative). The results of T2-weighted images and Gd-DOTA-enhanced images were similar as regards detection; however, Gd-DOTA-enhanced images depicted more clearly the tumours smaller than 2 cm (11 cases). MRI enabled the characterisation of only 3 masses (2 angiomyolipomas, 1 haemorrhagic cyst). New MRI features are described for oncocytomas (low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, early and marked enhancement on dynamic enhanced MRI). Dynamic enhanced MRI did not contribute to the differentiation of benign from malignant tumours. Correspondence to: O. Hélénon     

Multimodal imaging findings including high-resolution 3D T2-weighted imaging for COVID-19 vaccine-associated axillary lymphadenopathy in a patient with breast cancer

COVID-19 vaccines have received authorization worldwide. Vaccines are typically administered to the deltoid muscle, and axillary swelling/tenderness at the first dose (11.6%) and the second dose (16%) have been reported as secondary effects. Regional lymphadenopathy in the axilla and supraclavicular region has also been reported with a prevalence of 1.1% and is referred to as COVID-19 vaccine-associated lymphadenopathy (VAL). COVID-19 VAL mimics lymph node (LN) metastases on magnetic resonance imaging, ultrasound, and 18F-fluoro-2-deoxy-Dglucose positron emission tomography. Although several specific findings of VAL on clinical imaging have been reported, the difficulty in differentiating between VAL and LN metastases could lead to false-positive or -negative diagnoses. Here, we report a case of breast cancer with ipsilateral VAL with multimodal imaging including 3D T2-weighted imaging, a new magnetic resonance imaging technique, and discuss the future perspective for differentiating between VAL and LN metastases.     

Rectal tumour volume (GTV) delineation using T2-weighted and diffusion-weighted MRI: Implications for radiotherapy planning

Purpose

To compare the rectal tumour gross target volume (GTV) delineated on T2 weighted (T2W MRI) and diffusion weighted MRI (DWI) images by two different observers and to assess if agreement is improved by DWI.

Material and methods

27 consecutive patients (15 male, range 27.1–88.8 years, mean 66.9 years) underwent 1.5 T MRI prior to chemoradiation (45 Gy in 25 fractions; oral capecitabine 850 mg/m²), including axial T2W MRI (TR = 6600 ms, TE = 90 ms) and DWI (TR = 3000 ms, TE = 77 ms, b = 0, 100, 800 s/mm²). 3D tumour volume (cm³) was measured by volume of interest (VOI) analysis by two independent readers for the T2W MRI and b800 DWI axial images, and the T2W MRI and DWI volumes compared using Mann–Whitney test. Observer agreement was assessed using Bland–Altman statistics. Significance was at 5%.

Results

Artefacts precluded DWI analysis in 1 patient. In the remaining 26 patients evaluated, median (range) T2W MRI MRI and DWI (b = 800 s/mm²) 3D GTVin cm³ were 33.97 (4.44–199.8) and 31.38 (2.43–228), respectively, for Reader One and 43.78 (7.57–267.7) and 42.45 (3.68–251) for Reader Two. T2W MRI GTVs were slightly larger but not statistically different from DWI volumes: p = 0.52 Reader One; p = 0.92 Reader Two. Interobserver mean difference (95% limits of agreement) for T2W MRI and DWI GTVs were −9.84 (−54.96 to +35.28) cm³ and −14.79 (−54.01 to +24.43) cm³ respectively.

Conclusion

Smaller DWI volumes may result from better tumour conspicuity but overall observer agreement is not improved by DWI.     

Comparison of breath-hold multishot echo-planar and respiratory triggered fast-spin-echo sequences for T2-weighted MRI of liver lesions

The purpose of this study was to evaluate the usefulness of multishot echo-planar imaging in detecting liver tumors in comparison with respiratory triggered T2-weighted fast-spin-echo (FSE) imaging. Thirty-two patients with 70 focal liver lesions were imaged using a 1.5-T high speed MR imager. Eight-shot echo-planar images covering the whole liver were acquired during a single breath-hold period. FSE images were acquired with respiratory triggering in approximately 4 minutes. Lesion detectability and image quality of the two pulse sequences were analyzed qualitatively. Quantitative analysis was performed by means of signal-to-noise and tumor-liver contrast-to-noise analysis. Lesion detectability was comparable in both solid (86.3% vs 90.2%: .3 < P < .5) and nonsolid lesions (89.5% vs 100%: .3 < P < .5) between echo-planar and FSE images. Echo-planar imaging provided significantly reduced image artifact, better lesion conspicuity, and anatomic detail compared with FSE imaging. The signal-to-noise and contrast-to-noise ratios of echo-planar images were significantly higher than those of FSE images. Breath-hold eight-shot echo-planar imaging can be an alternative to T2-weighted FSE imaging because it can provide comparable image quality in a substantially decreased acquisition time.     

MRI of acute post-ischemic cerebral hemorrhage in stroke patients: diagnosis with T2*-weighted gradient-echo sequences

The use of T2^*-weighted sequences has been advocated for early differentiation between hematoma and ischemia in patients with acute stroke. Early hemorrhagic transformation of ischemic stroke is an adverse event which may occur under treatment and may impair the prognosis: our aim is to evaluate the ability of T2*-weighted gradient-echo sequence (T2^* GRE) to detect post-ischemic cerebral hemorrhage. The imaging procedure included: (1) baseline CT scan at admission. (2) MRI performed within 24 h of therapy onset including: (a) dual fast spin echo T2 sequence, (b) axial isotropic echoplanar diffusion-weighted imaging sequence, (c) conventional T2* GRE, and (d) 3D TOF turbo MRA. Post-ischemic cerebral hemorrhage was diagnosed if T2^* GRE detected a focal intraparenchymal area of signal loss. The diameter of this lesion had to be more than 5 mm in order to eliminate past microbleeds. (3) Patients who showed an early suspicion of bleeding on MRI promptly had a second CT scan, and, if this one was negative for bleeding, another CT scan was performed 1 day later. All the other patients had a control CT scan during the first week. Forty-five consecutive patients have been included. T2* GRE showed intracranial bleeding in seven. The diagnosis of post-ischemic cerebral bleeding was confirmed by CT in all patients. Control CT scans did not reveal any post-ischemic cerebral hemorrhage in patients with negative MRI. In one case, hemorrhage was seen earlier on MRI than on CT scan. In conclusion, T2^* GRE appeared to be at least as efficient as CT scan in the detection of early post-ischemic cerebral hemorrhage. Received: 30 October 2000/Accepted: 23 March 2001