Jarle Rørvik

Assessment of 3D DCE-MRI of the kidneys using non-rigid image registration and segmentation of voxel time courses.

We have applied automated image analysis methods in the assessment of human kidney perfusion based on 3D dynamic contrast-enhanced MRI data. This approach consists of non-rigid 3D image registration of the moving kidney followed by k-means clustering of the voxel time courses with split between left and right kidney. This method was applied to four data sets acquired from healthy volunteers, using 1.5 T (2 exams) and 3 T scanners (2 exams). The proposed registration method reduced motion artifacts in the image time series and improved further analysis of the DCE-MRI data. The subsequent clustering to segment the kidney compartments was in agreement with manually delineations (similarity score of 0.96) in the same motion corrected images. The resulting mean intensity time curves clearly show the successive transition of contrast agent through kidney compartments (cortex, medulla, and pelvis). The proposed method for motion correction and kidney compartment segmentation might improve the validity and usefulness of further model-based pharmacokinetic analysis of kidney function in patients.

MRI assessment of normal ligamentous structures in the craniovertebral junction

We have established an imaging protocol in order to characterise the normal ligamentous structures in the craniovertebral junction. Thirty volunteers without a history of car accident or head or neck trauma underwent MR imaging with 2-mm-thick proton-density-weighted sections in three orthogonal planes. The alar ligaments were clearly seen in every case and had three different configurations in cross-section: round, ovoid or wing-like. A broadening from lateral to medial in the coronal plane was observed in all cases. The transverse ligament was clearly demonstrated in 26 out of 30 cases. The ligament was flattened where it arched across the dens. Towards the insertions the ligament twisted into an oblique-horizontal orientation. The lower tectorial membrane had a median portion merging with the dura, and a lateral portion separated from it. Between the dens and clivus this membrane either merged totally with dura or was partly separated from it by a thin layer of fat. The posterior atlanto-occipital membrane was clearly demonstrated. It either merged with the dura or was partly or totally separated from it by a fat layer. The anterior atlanto-occipital membrane was inconsistently seen and could not be evaluated. Our refined MR protocol improves the visualisation of the craniovertebral ligamentous structures, and may in the future give new insight into post-traumatic neck disorders up to now poorly understood.

MRI with an endorectal coil for staging of clinically localised prostate cancer prior to radical prostatectomy

Abstract. The purpose of this study was to evaluate the ability of MR imaging with an endorectal coil (erMRI) to predict the local pathological stage of prostatic carcinoma prior to radical prostatectomy. Thirty-one consecutive patients (median age 61 years, range 40–71 years) with clinically localised prostate cancer were assessed preoperatively by endorectal MRI (at 1.0 T). The pulse sequences consisted of fast spin-echo axial and coronal T2-weighted images and inversion recovery with two echoes for axial fat-suppressed images. The assessment of tumour stage and measurement of tumour dimension by erMRI were compared with the corresponding findings on whole-mount step sections of the surgical specimens. Postoperatively, 14 of the 31 patients (45 %) were found to have extracapsular extension, 7 with capsular penetration (CP) only, and 7 had a combination of CP and seminal vesicle invasion (SVI). Capsular penetration was detected by erMRI with a sensitivity of 0.71 and specificity of 0.47, whereas the sensitivity for SVI detection was 0.71 and the specificity 0.83. Endorectal MRI for staging clinically localised prostatic carcinoma gives a good prediction of invasion of the seminal vesicles but is unreliable in predicting capsular penetration.

MR analysis of the transverse ligament in the late stage of whiplash injury.

Purpose: To analyse and classify structural changes in the transverse ligament in the late stage of whiplash injury by use of high-resolution MRI, and to evaluate the reliability of our classification. Material and Methods: Ninety-two whiplash-injured (2–9 years previously, mean 6 years) and 30 non-injured individuals underwent proton-weighted MR imaging of the craniovertebral junction in three orthogonal planes. Structural changes in the transverse ligaments were graded twice (grades 1–3) based on increased signal, independently by 3 radiologists with a 4-month interval. Inter- and intraobserver statistics were calculated by ordinary and weighted kappa (K). Results: Image quality was excellent in 109 cases and slightly reduced in 13. Twenty-two out of 30 ligaments in the control group were classified as normal (73%) compared with only 32 out of 92 in the injured group (36%). Two or all 3 observers agreed in their grading in 101 out of 122 ligaments (83%). Intraobserver agreement (weighted K) was fair to good (0.33–0.73). Pair-wise interobserver agreement was fair (0.24–0.39). Reasons for divergent grading were insufficient knowledge of normal variations, low signal intensity in the peridental soft tissue obscuring the ligament and interpretation flaw. Conclusion:Whiplash trauma can damage the transverse ligament. By use of high-resolution proton-weighted MR images such lesions can be detected and classified. The reliability of this classification still needs improvement.

High frequency of adrenal myelolipomas and testicular adrenal rest tumours in adult Norwegian patients with classical congenital adrenal hyperplasia because of 21‐hydroxylase deficiency

Background  Increased frequencies of adrenal tumours and testicular adrenal rest tumours (TART) have been reported in patients with 21‐hydroxylase deficiency (21OHD).

Comparison of Effective Radiation Doses in Patients Undergoing Unenhanced MDCT and Excretory Urography for Acute Flank Pain

OBJECTIVE The purpose of this study was to measure and compare the effective radiation dose in patients undergoing unenhanced MDCT and excretory urography for acute flank pain, and to explore technical and practical factors affecting the effective dose. SUBJECTS AND METHODS One hundred nineteen patients with acute flank pain were included. All patients were examined using both MDCT and excretory urography. CT involved one acquisition from the upper kidney margin to the symphysis pubis. The only protocol variation was in the tube current (mAs), which was made according to patient body mass. The excretory urography protocol consisted of three images, with more when supplementary images were needed. Effective radiation doses were computer-simulated using dosimetry programs for CT and conventional radiography, based on Norwegian Radiological Protection Board dose data sets. Mean and SDs of measured patient doses were calculated and compared. Further analyses of dose variations in body mass categories (body mass index) were conducted, as were analyses concerning the number of images taken. RESULTS The mean effective doses were 7.7 mSv with MDCT and 3.63 mSv with excretory urography. The effective dose varied both in and between techniques but could be predicted. Radiation risk decreased significantly with increased patient weight. CONCLUSION The average effective dose with MDCT was more than double that with excretory urography. However, the appropriate dose could be strongly predicted by the patients body mass index and by procedure. An optimum low-dose protocol should be considered before initiating unenhanced MDCT for ureteral colic in order to minimize the radiation-induced cancer risk and to secure adequate image quality.

Lymphangiography combined with biopsy and computer tomography to detect lymph node metastases in localized prostate cancer

To evaluate the efficacy of lymphangiography combined with fine needle aspiration biopsy and computer tomography (CT) for lymph node staging in clinically localized prostate cancer. Prospective evaluation of nodal involvement was carried out using standard bipedal lymphangiography combined with fine needle aspiration biopsy (FNAB) in 70 patients (aged 47 to 75 years, mean age 63 years) with apparently locally confined prostate cancer before intended radical prostatectomy. Sixty-four patients also underwent computer tomography. Seventeen withdrew the decision to undergo a radical prostatectomy, leaving 53 patients with pathologic examination of the lymph nodes eligible for analysis. Lymph node metastases were diagnosed in 8 patients (8/53 = 15.1%). Three were diagnosed preoperatively by FNAB, 3 peroperatively by lymph node dissection and frozen section biopsy and an additional 2 at the final pathologic assessment. The sensitivity, specificity, positive and negative predictive values for lymphangiography and lymphangiography combined with FNAB in predicting nodal disease, based on the analysis of the 53 patients with known pathologic results, were 0.63, 0.76, 0.31, 0.92 and 0.38, 1.00, 1.00, 0.90, respectively. The corresponding values for CT staging were 0.25, 0.98, 0.67 and 0.87, respectively. The efficacy of bipedal lymphangiography alone or combined with FNAB or CT alone for assessment of nodal metastases is too low to be worthwhile for lymph node staging in localized prostate cancer patients with expected low or intermediate probability of nodal disease.

Assessment of Kidney Volumes From MRI: Acquisition and Segmentation Techniques

OBJECTIVE The prevalence of chronic kidney disease (CKD) is increasing worldwide. In Europe alone, at least 8% of the population currently has some degree of CKD. CKD is associated with serious comorbidity, reduced life expectancy, and high economic costs; hence, early detection and adequate treatment of kidney disease are important. CONCLUSION We review state-of-the-art MRI acquisition techniques for CKD, with a special focus on image segmentation methods used for the estimation of kidney volume.

1.5-T multiparametric MRI using PI-RADS: a region by region analysis to localize the index-tumor of prostate cancer in patients undergoing prostatectomy

Background The use of multiparametric magnetic resonance imaging (mpMRI) to detect and localize prostate cancer has increased in recent years. In 2010, the European Society of Urogenital Radiology (ESUR) published guidelines for mpMRI and introduced the Prostate Imaging Reporting and Data System (PI-RADS) for scoring the different parameters. Purpose To evaluate the reliability and diagnostic performance of endorectal 1.5-T mpMRI using the PI-RADS to localize the index tumor of prostate cancer in patients undergoing prostatectomy. Material and Methods This institutional review board IRB-approved, retrospective study included 63 patients (mean age, 60.7 years, median PSA, 8.0). Three observers read mpMRI parameters (T2W, DWI, and DCE) using the PI-RADS, which were compared with the results from whole-mount histopathology that analyzed 27 regions of interest. Inter-observer agreement was calculated as well as sensitivity, specificity, positive predictive value (PPV), and negative predicted value (NPV) by dichotomizing the PI-RADS criteria scores ≥3. A receiver-operating curve (ROC) analysis was performed for the different MR parameters and overall score. Results Inter-observer agreement on the overall score was 0.41. The overall score in the peripheral zone achieved sensitivities of 0.41, 0.60, and 0.55 with an NPV of 0.80, 0.84, and 0.83, and in the transitional zone, sensitivities of 0.26, 0.15, and 0.19 with an NPV of 0.92, 0.91, and 0.92 for Observers 1, 2, and 3, respectively. The ROC analysis showed a significantly increased area under the curve (AUC) for the overall score when compared to T2W alone for two of the three observers. Conclusion 1.5 T mpMRI using the PI-RADS to localize the index tumor achieved moderate reliability and diagnostic performance.

Standard 1.5-T MRI of endometrial carcinomas: modest agreement between radiologists

AbstractObjectivesTo evaluate pelvic magnetic resonance imaging (MRI) interobserver agreement for the detection of deep myometrial invasion, cervical stroma invasion and lymph node metastases in endometrial carcinoma patients in relation to surgical staging.MethodsFifty-seven patients with histologically confirmed endometrial carcinoma were prospectively included in a study of preoperative 1.5-T MRI. Four radiologists, blinded to patient data, independently reviewed the images for the presence of deep myometrial invasion, cervical stroma invasion and lymph node metastases. Kappa coefficients for interobserver agreement and diagnostic performances for each observer were calculated using final surgical staging results (FIGO 09) as reference standard.ResultsOverall agreement among all observers was moderate for cervical stroma invasion (κ = 0.50 [95% CI 0.27–0.73]) and lymph node metastases (κ = 0.56 [0.09–0.80]) and fair for deep myometrial invasion (κ = 0.39 [0.26–0.55]). Sensitivity (specificity) values for the four observers were 72–92% (44–63%) for deep myometrial invasion, 38–63% (82–94%) for cervical stroma invasion and 25–38% (90–100%) for lymph node metastases.ConclusionsConventional MRI showed only modest interobserver agreement and diagnostic accuracy for detection of deep myometrial invasion, cervical stroma invasion and lymph node metastases. Improved methods are needed for preoperative imaging in the staging of endometrial carcinomas.Key Points• MRI is an important tool for preoperative endometrial cancer staging. • Staging agreement based on pelvic MRI was modest among different observers. • Preoperative MRI alone was suboptimal in identifying high-risk patients. • Improved imaging and biomarkers may refine preoperative risk stratification in endometrial cancer.