Nuclear medicine Competitors or collaborators?

Here in the USA

Nuclear medicine Competitors or collaborators?     

Quantitative differentiation of breast lesions based on three-dimensional morphology from magnetic resonance imaging

OBJECTIVE: The purpose of this study was to develop geometric indices, based on morphologic measurements, of contrast-enhanced breast lesions using three-dimensional magnetic resonance imaging (MRI) that can statistically differentiate between benign and malignant lesions. METHODS: Thirty-three patients with abnormal mammograms were scanned using three-dimensional MRI. The lesion was then extracted from the volume data set using interactive volume-rendering software. From the extracted region of interest, the surface boundary corresponding to the lesion was extracted using an isosurface method. The boundary was represented as a triangular mesh, from which the surface area and volume enclosed by the surface were computed. The following variables were tested for discrimination ability between benign and malignant lesions: 1) the volume-to-surface area (V/S) ratio, 2) spherical shape index (SSI), and 3) resolution reduction for V/S and SSI values (100%, 16%, 8%, 4%, 2%, and 1% resolution). In addition, comparisons were made between the V/S and SSI values at 100% versus their reduced resolutions. RESULTS: Thirty-three subjects (15 malignant tumors and 18 benign tumors) were studied. The SSI index (P = 0.0063) was a significant discriminator for malignancy. The V/S ratio (P = 0.9280) did not seem to be a useful variable in distinguishing benign and malignant masses. The V/S resolution comparisons (P > 0.5897) and the SSI resolution comparisons (P > 0.05) were also not useful discriminating variables. CONCLUSION: The SSI seems to be a useful factor in differentiating between benign and malignant lesions. Current clinical interpretation of breast lesions using MRI may be enhanced by the adjunctive use of this objective postanalysis method.     

MRI detection of myocardial perfusion defects due to coronary artery stenosis with MS-325

PURPOSE: To assess the value of an intravascular, albumin-targeted contrast agent, MS-325, in visualizing myocardial ischemia with magnetic resonance imaging (MRI). MATERIALS and METHODS: Left anterior descending coronary artery (LAD) stenosis was created in 19 pigs using a closed-chest modified angioplasty technique. Myocardial ischemia was detected by first-pass, contrast-enhanced MRI at peak dipyridamole stress and was compared to Technetium-99m (Tc-99m) sestamibi single photon emission computed tomography (SPECT). Regional coronary blood flow was determined using microspheres. RESULTS: Inducible myocardial ischemia with >40% reduction in stress myocardial blood flow was created in eight animals. An MRI defect, classified as > or=75% reduction in peak myocardial signal intensity in the affected territory, was detected in 92.3% of these animals. In the presence of mild coronary stenosis, there was uniform enhancement with MRI and tracer uptake by SPECT. Concordance of MRI and SPECT for detecting perfusion defects was 85%. CONCLUSION: The pattern of prolonged and persistent MR hypoenhancement of the ischemic myocardial bed using MS-325, which is retained primarily in the vascular bed due to its albumin-binding properties, facilitates the detection of myocardial perfusion defects.     

Magnetic resonance imaging in assessment of stress urinary incontinence in women: Parameters differentiating urethral hypermobility and intrinsic sphincter deficiency

AIM: To define the magnetic resonance imaging (MRI) parameters differentiating urethral hypermobility (UH) and intrinsic sphincter deficiency (ISD) in women with stress urinary incontinence (SUI).METHODS: The static and dynamic MR images of 21 patients with SUI were correlated to urodynamic (UD) findings and compared to those of 10 continent controls. For the assessment of the urethra and integrity of the urethral support structures, we applied the high-resolution endocavitary MRI, such as intraurethral MRI, endovaginal or endorectal MRI. For the functional imaging of the urethral support, we performed dynamic MRI with the pelvic phased array coil. We assessed the following MRI parameters in both the patient and the volunteer groups: (1) urethral angle; (2) bladder neck descent; (3) status of the periurethral ligaments, (4) vaginal shape; (5) urethral sphincter integrity, length and muscle thickness at mid urethra; (6) bladder neck funneling; (7) status of the puborectalis muscle; (8) pubo-vaginal distance. UDs parameters were assessed in the patient study group as follows: (1) urethral mobility angle on Q-tip test; (2) Valsalva leak point pressure (VLPP) measured at 250 cc bladder volume; and (3) maximum urethral closure pressure (MUCP). The UH type of SUI was defined with the Q-tip test angle over 30 degrees, and VLPP pressure over 60 cm H₂O. The ISD incontinence was defined with MUCP pressure below 20 cm H₂O, and VLPP pressure less or equal to 60 cm H₂O. We considered the associations between the MRI and clinical data and UDs using a variety of statistical tools to include linear regression, multivariate logistic regression and receiver operating characteristic (ROC) analysis. All statistical analyses were performed using STATA version 9.0 (StataCorp LP, College Station, TX).RESULTS: In the incontinent group, 52% have history of vaginal delivery trauma as compared to none in control group (P < 0.001). There was no difference between the continent volunteers and incontinent patients in body habitus as assessed by the body mass index. Pubovaginal distance and periurethral ligament disruption are significantly associated with incontinence; periurethral ligament symmetricity reduces the odds of incontinence by 87%. Bladder neck funneling and length of the suprapubic urethral sphincter are significantly associated with the type of incontinence on UDs; funneling reduced the odds of pure UH by almost 95%; increasing suprapubic urethral sphincter length at rest is highly associated with UH. Both MRI variables result in a predictive model for UDs diagnosis (area under the ROC = 0.944).CONCLUSION: MRI may play an important role in assessing the contribution of hypermobility and sphincteric dysfunction to the SUI in women when considering treatment options.     

Detection of hepatic lesions in candidates for surgery: comparison of ferumoxides-enhanced MR imaging and dual-phase helical CT

OBJECTIVE: The purpose of this study was to compare the use of phased array MR imaging of the liver at 1.5 T with and without ferumoxides with dual-phase helical CT for the detection of hepatic lesions in candidates for hepatic surgery. SUBJECTS AND METHODS: Patients with known or suspected hepatic lesions who were eligible for surgery underwent dual-phase helical CT at 20 and 70 sec after the start of contrast material injection and phased array MR imaging using fast spin-echo T2-weighted imaging and gradient-echo T1-weighted imaging before and after ferumoxides infusion of 0.56 mg of iron per kilogram of body weight. Three observers who were unaware of the surgical findings separately reviewed the CT scans and unenhanced and enhanced MR images of 24 patients who completed the protocol. The observers' findings were compared with results obtained at surgery using intraoperative sonography and having histopathologic confirmation. Statistical analysis was performed using a segment-by-segment analysis. RESULTS: Eighty-two lesions were found at surgery. The sensitivity of CT, unenhanced MR imaging, and enhanced MR imaging for blinded observers was 60.4%, 62.0%, and 68.2%, respectively. The specificity was 89.2%, 81.9%, and 81.6%, respectively. Five lesions in three patients were not detected preoperatively using any of the techniques. MR imaging found additional lesions not detected on CT in four patients; CT detected one additional lesion not seen on MR imaging. CONCLUSION: Ferumoxides-enhanced MR imaging of the liver shows a trend toward increased sensitivity compared with dual-phase helical CT. Specificity of helical CT was superior to that of enhanced MR imaging for most observers.     

A minimally invasive method for creating coronary stenosis in a swine model for MRI and SPECT imaging

RATIONALE AND OBJECTIVES: To develop a less-invasive method for creating coronary stenosis in an animal model for the study of myocardial perfusion defects by using magnetic resonance imaging (MRI) and single-photon-emission computed tomography (SPECT). METHODS: Eleven farm pigs were instrumented with an MR-compatible coronary flow-reduction fitting in the left anterior descending coronary artery (LAD). These fittings were turned from a nylon rod, tapered from a maximum outer diameter of 3 mm, and drilled to a specified inner diameter (depending on the degree of coronary stenosis desired). The flow-reducing fittings were delivered over a coronary guidewire and advanced to a wedge position in the proximal LAD with an angioplasty catheter via a carotid artery approach. Perfusion determined by contrast-enhanced MRI at peak dipyridamole stress was compared with that obtained by 99mTc sestamibi SPECT. Radiolabeled microspheres were injected at rest, after stenosis implantation, and at peak pharmacological stress to establish the severity of the coronary lesion. RESULTS: Coronary stenosis was successfully created in seven animals. Mild coronary stenoses (<60%) were created in four animals. Significant coronary stenoses (80%-90%) were created in three animals. Thrombosis of the coronary flow-reducing fittings was observed in four animals, leading to sudden death in three animals and myocardial infarction in one animal. CONCLUSIONS: This method of angioplasty-guided, LAD coronary stenosis creation in a swine model presents a less-invasive alternative to open-chest techniques such as hydraulic occluders and ameroid constrictors.