Kjell‐Inge Gjesdal

MR urography: the future gold standard in paediatric urogenital imaging?

Background. Examination of the paediatric urogenital tract is traditionally performed using methods that utilise ionising radiation, such as intravenous urography (IVU), computerised tomography (CT), voiding cystourethrography (VCU), and scintigraphy, in addition to ultrasound (US). Objective. To determine the potential and effectiveness of MR urography (MRU) in infants and children. Materials and methods. 44 MRU examinations were prospectively performed in 39 patients (21 infants, mean age 3.5 months, and 18 children, mean age 6 years 2 months) with known or suspected pathology of the urinary tract. Non-enhanced, fast spin-echo sequences (TSE) were performed in all patients. In 70 % of the patients a contrast-enhanced, fast gradient-echo sequence (TFE) was included. The dynamic sequence was prolonged and supplemented with furosemide provocation in some patients with suspected urinary-tract obstruction. Results. Nine percent of examinations were non-diagnostic or interrupted due to movement. MRU contributed additional information in 66 %. Nine patients with suspected urinary-tract obstruction were examined with both contrast-enhanced MRU and scintigraphy. Three MRU examinations were less informative and one equal to scintigraphy when obstruction was the diagnosis. When using a technique with a prolonged dynamic sequence, including frusemide provocation, four MRU examinations were equal and one was superior to scintigraphy. Conclusions. MRU has the potential to replace traditional diagnostic methods which use ionising radiation in paediatric patients. Further studies are needed before definite conclusions can be drawn.

Prostate magnetic resonance imaging: Multiexponential T2 decay in prostate tissue

To investigate the T2 decay in prostate tissue for multiexponentiality and to assess how the biexponential model relates to established T2W contrast.

Visualization of deep veins and detection of deep vein thrombosis (DVT) with balanced turbo field echo (b-TFE) and contrast-enhanced T1 fast field echo (CE-FFE) using a blood pool agent (BPA).

To assess image quality, vessel visualization, preliminary diagnostic properties, and interobserver variability of a novel balanced turbo field echo (b‐TFE) sequence and contrast‐enhanced T1 fast field echo (CE‐FFE) sequence with blood pool agent (BPA).

Functional Magnetic Resonance Imaging of Primary Visual Processing Using a 1.0 Tesla Scanner

Recent advances in functional magnetic resonance imaging (fMRI) at > or = 1.5 T magnetic field strength and with high speed single-shot echo planar imaging techniques have made it possible to monitor local changes in cerebral blood volume, cerebral blood flow, and blood oxygenation level in response to sensory stimulation, simple motor activity, and possibly also to more complex cognitive processing. However, fMRI has also been accomplished on conventional MR scanners of medium field strength (approximately 1.0 T) using special pulse sequences and appropriate methods for image analysis. We present results from six subjects on photic stimulation using a standard 1.0 T MR scanner together with special software for off-line image analysis. Continuous serial T2-weighted imaging were performed for 6 minutes in the plane of the calcarine fissure. There were 3 repetitions of 1 minute resting state of darkness (OFF) and 1 minute activated state (ON) with 8 Hz flicker stimulation. To directly map these functional images to the underlying anatomy we also acquired a high resolution T1-weighted image from the same axial slice. The results demonstrated that stimulus-related signals can be obtained from primary visual cortex with a conventional 1.0 T MR scanner. Further methodological improvements are discussed and related to present and future possibilities for the use of fMRI within psychophysiology.

A noncontrast-enhanced pulse sequence optimized to visualize human peripheral vessels

The purpose of this paper is to present a pulse sequence optimized to visualize human peripheral vessels. The optimized MR technique is a 3D multi-shot balanced non-SSFP gradient echo pulse sequence with fat suppression. Several imaging parameters were adjusted to find the best compromise between the contrast of vascular structures and muscle, fat, and bone. Most of the optimization was performed in the knee and calf regions using multi-channel SENSE coils. To verify potential clinical use, images of both healthy volunteers and volunteers with varicose veins were produced. The balanced non-SSFP sequence can produce high-spatial-resolution images of the human peripheral vessels without the need for an intravenous contrast agent. Both arteries and veins are displayed along with other body fluids. Due to the high spatial resolution of the axial plane source or reconstructed images, the need for procedures to separate arteries from veins is limited. We demonstrate that high signals from synovial joint fluid and cystic structures can be suppressed by applying an inversion prepulse but at the expense of reduced image signal-to-noise and overall image quality.

Dynamic First Pass 3D EPI of the Prostate: Accuracy in Tumor Location

Purpose: To evaluate the potential of dynamic contrast enhanced (DCE) 3D EPI in the location of prostate cancer. Material and Methods: A DCE 3D EPI scan was included in the magnetic resonance imaging protocol for prostate examination. Twenty‐eight patients who subsequently underwent radical prostatectomy were included in the study. T2‐weighted (T2W) Turbo Spin Echo (TSE) images were initially evaluated by two radiologists. Parametric images reflecting contrast enhancement were added and new evaluations performed. The results were compared with histology from resected specimens. Accuracies and interobserver agreements were calculated. Results: Interobserver agreement was κw =49±3% for the T2W technique and κw =30±3% for the combined techniques. No statistically significant advantages were found for location of tumor in the prostate or in the seminal vesicles by adding the DCE information. Conclusion: DCE 3D EPI did not improve tumor location compared with that of T2W TSE images. Further investigation is needed on how best to exploit the DCE technique.

Split dynamic MRI: Single bolus high spatial–temporal resolution and multi contrast evaluation of breast lesions

To test the feasibility of a novel “split dynamic” method in which high temporal and high spatial resolution dynamic MR images are acquired during a single bolus injection.

Three-dimensional balanced steady state free precession imaging of the prostate: flip angle dependency of the signal based on a two component T2-decay model.

To investigate the contrast of three‐dimensional balanced steady state free precession (3D bSSFP) in the two component T2 model and to apply the results to optimize 3D bSSFP for prostate imaging at 1.5 Tesla.

Magnetic Resonance-Assisted Imaging of Slow Flow in the Pancreatic and Common Bile Duct in Healthy Volunteers

Background: Magnetic resonance cholangiopancreaticography (MRCP) is commonly used to evaluate the pancreatic (PD) and common bile duct (CBD), and the addition of secretin is used to obtain functional information (S-MRCP). Neither method gives any information on flow velocities within the ducts. Purpose: To evaluate a new, MRI diffusion-based, slow-flow-sensitive sequence for the detection of slow flow changes in the PD and CBD. Material and Methods: Seven healthy volunteers were examined. A modified single-shot turbo spin-echo sequence was used to detect slow flow changes. Three b factors (0, 6, and 12 s/mm2) were used. The flow sensitivity was applied in two directions, vertically and horizontally. Scanning was performed before and after glucagon was given, and again after an intravenous injection of secretin. The sequence gives signal loss from a duct when flow increases, and such changes were recorded. Results: All images showed the PD with b = 0 (no flow sensitization). After administration of glucagon, artifacts from bowel movements were reduced and visibility of the PD was improved at both b = 6 and b = 12. Significant reduction of the visibility of the PD, indicating increased flow, was recorded both at b = 6 and b = 12 after the administration of secretin. There were no changes in the visibility of the CBD. Conclusion: This study shows that MRI-based detection of slow flow changes inside the PD is possible. Due to the sequence’s high sensitivity to any motion, further studies are required before adopting the method for clinical use.

Single bolus split dynamic MRI: Is the combination of high spatial and dual‐echo high temporal resolution interleaved sequences useful in the differential diagnosis of breast masses?

To test the split dynamic magnetic resonance imaging (MRI) technique in the assessment of breast masses in which high spatial resolution and dual‐echo high temporal resolution data are acquired during a single bolus injection.