Biomedical subjects

J Oellinger

Publications and source records attributed to J Oellinger.

10 recordsLinked to original sources

PubMed2000

CSF flow studies of intracranial cysts and cyst-like lesions achieved using reversed fast imaging with steady-state precession MR sequences.

BACKGROUND AND PURPOSE: Differentiating between intracranial cysts or cyst-like structures and communicating or noncommunicating cysts is often not possible with cranial CT or nonfunctional MR imaging. We evaluated a retrospective ECG-gated fast imaging with steady-state precession (PSIF) MR sequence with optional cine mode to differentiate cystic masses from enlarged CSF spaces and to determine the accuracy of detecting communication between cysts and neighboring CSF spaces. METHODS: Fourteen patients with intracranial cystic masses underwent CSF flow studies with an ungated and a retrospective ECG-gated cine-mode PSIF sequence in addition to spin-echo imaging. Findings were evaluated retrospectively by using a five-point rating scale and without knowledge of clinical or other imaging findings. Results were compared with intraoperative findings or with results of intrathecal contrast studies. RESULTS: Eighteen arachnoid cysts and one enlarged cisterna magna were diagnosed. Improved differentiation between cysts and enlarged CSF spaces was obtained with cine-mode PSIF imaging in six lesions (six patients). Increased diagnostic certainty as to communication between cysts and CSF spaces was obtained in 18 cysts (13 patients). Diagnoses were verified by membranectomy in five lesions, by CT cisternography in five lesions, and indirectly by shunting in one cystic lesion. In one case, MR diagnosis was not confirmed by CT cisternography. CONCLUSION: Cine-mode MR imaging with a retrospective ECG-gated flow-sensitive PSIF sequence contributed to the certainty of communication between arachnoid cysts and neighboring CSF spaces with an accuracy of 90%, using surgical findings or intrathecal contrast studies as reference. Differentiation between intracranial cysts and enlargement of CSF spaces and other cystic masses was improved in 25% of cases.

Adolescent↗

PubMed1999

[Malignant lymphoma: magnetic resonance tomography findings in residual supradiaphragmatic space-occupying lesions].

PURPOSE: Evaluation of MR imaging in patients with Hodgkin's lymphoma and high grade non-Hodgkin's-lymphoma and mediastinal residual mass after first line chemotherapy. MATERIALS AND METHODS: MR imaging (1.5 T) was performed in 36 patients (Hodgkin's lymphoma n = 26, NHL n = 10) after first line chemotherapy). Twenty patients had inactive residual mass, 16 patients had residual lymphoproliferative lesions. T1- and T2-weighted spin echo images were visually analysed by a score index (range 1-5) as well as quantification of enhancement by signal-intensity-ratios SImax/SIplain). RESULTS: For the differentiation between residual lymphoproliferative activity and inactive residual mass, the highest accuracy was obtained for the signal intensity of residual mass on T2-w-SE compared to pectoralis muscle (94% sensitivity, 80% specificity, likelihood ratios: 4.0 [LR+]; 0.3 [LR-]). The cut-off value of the SI ratio was calculated retrospectively at 1.96 (p > 0.05). CONCLUSIONS: Differentiation between inactive (fibrotic) and lymphoproliferative (active) residual mediastinal mass is possible by MR imaging using as parameter the size reduction after therapy and the signal intensity on T2-w-SE in comparison to pectoralis muscle. Thus study suggests an additional value using the SI ratio for the differentiation.

Adult↗

PubMed1999

1H and 31P NMR characterisation of a double breast coil for spectroscopic measurements and imaging.

For the first time a double turn breast coil has been described which can be used for 1H imaging, 1H spectroscopy and 31P spectroscopy. The paper describes basic technical features of the coil, coil design, B1 field/excitation field distribution for 1H and 31P, sensitivity, and feasibility for 31P spectroscopic in vivo studies. The main advantage of the double frequency tuneable coil is that 1H imaging for tumor localization and 31P spectroscopy for response control can be done without an additional repositioning of the patient.

Breast Neoplasms↗

PubMed1999

Staging and monitoring of malignant lymphoma of the bone: comparison of 67Ga scintigraphy and MRI.

UNLABELLED: The aim of this study was two-fold: to compare 67Ga scintigraphy with MRI (a) for the staging of malignant lymphoma of the bone and (b) with regard to accuracy in detecting residual disease after first-line chemotherapy for restaging. METHODS: Twenty-one patients with 36 malignant osseous lesions were examined, including 7 patients with primary or multifocal osseous lymphoma and 14 patients with malignant lymphoma and simultaneous or secondary involvement of the bone. After first-line therapy, MRI and 67Ga scintigraphy were performed on 13 patients. The remission status based on all clinical and radiological findings during the follow-up was used as the gold standard. RESULTS: The osseous lesions were located on the axial skeleton in 64% of patients and on the appendicular skeleton in 36%. 67Ga scintigraphy detected 77% of the osseous lesions examined by MRI. For restaging after first-line therapy, MRI had a sensitivity of 90% and a specificity of 80% when dynamic MRI information was included. There were several false-positive results as a result of the pathologic increase in signal intensity ratios of reactive hematopoietic regions after chemotherapy. For 67Ga scintigraphy, a sensitivity of 70% and a specificity of 93% were calculated. CONCLUSION: These data show that monitoring malignant lymphoma of the bone still presents diagnostic problems. Given the high sensitivity of MRI and the high specificity of 67Ga scintigraphy but the limited specificity of MRI and sensitivity of 67Ga scintigraphy, both methods are valuable but should be used as complementary diagnostic tools.

Adolescent↗

PubMed1997

Imaging of the orifice of the left ventricular outflow tract: technique and initial results.

The mechanism of left ventricular outflow tract (LVOT) obstruction in the patient after mitral valve replacement or repair was examined with the aid of 2D echocardiography. For the interpretation of the spatial relationship between the aortic root and mitral annulus, however, the 2D display is sometimes inadequate since it may not simultaneously capture these structures in each center. We developed a method to clarify this relationship in 3D based on magnetic resonance images. We defined the office of the left ventricular outflow tract (LVOT orifice), consisting of, in turn, a muscular region, i.e., edge of the interventricular septum, and an annular region, i.e., the annulus of the anterior mitral leaflet. In this paper we present image data obtained from one of eight normal subjects examined and compare this with data of one of two patients who preoperatively suffered degenerative mitral regurgitation and subsequently underwent chordal-preserving mitral valve replacement, in which anterior chordae were reattached to the anterior annulus. In the normal subject, the mitral annulus exhibited a flexible change in shape during the systole, maintaining sufficient LVOT orifice size. In the patient, the prosthetic valve exhibited translational motion during systole, resulting in dynamic LVOT obstruction. This phenomenon was also observed in one other case. Furthermore, the lateral view of the LVOT orifice revealed a projection of the prosthetic valve into the LVOT, causing mechanical LVOT obstruction. The finding that translational motion of the prosthetic valve with an inflexible mitral annulus results in dynamic LVOT obstruction may support the hypothesis that annular rigidity causes dynamic LVOT obstruction after mitral valve repair with a rigid prosthetic ring.

Adult↗

PubMedDate not supplied

The inflexible mitral annulus after valve prosthesis. Inherent risk of dynamic left ventricular outflow tract obstruction.

Although chordal preserving mitral valve replacement is beneficial to cardiac function, the loss of flexibility of the annulus and consequent translational motion of the valve prosthesis during systole may cause potential left ventricular outflow tract (LVOT) obstruction after surgery. The extent of the flexibility of the mitral valve annulus (MVA) necessary for the prosthetic valve to prevent potential LVOT obstruction was determined. The three dimensional images of the MVA at 0, 100, 200, and 300 msec delay from the electrocardiogram R wave were reconstructed from cine-mode magnetic resonance images in eight normal subjects. In the lateral view of the MVA, the dorsal flexion angle (DFA) was defined. This angle implies the extent of the flexion of the anterior half of the MVA in relation to the posterior half. The data (mean +/- SD) for the DFA were 31.7 +/- 5.4 degrees (0 msec), 36.4 +/- 4.5 degrees (100 msec), 39.0 +/- 3.8 degrees (200 msec), and 43.6 +/- 2.6 degrees (300 msec), whereas the systolic increase in DFA was 11.9 +/- 3.2 degrees. The flexibility observed in normal mitral annuli is relevant to prosthetic mitral valves.

Adult↗

PubMedDate not supplied

The relationship between the mitral annulus and left ventricular outflow tract.

Mitral annular inflexibility due to rigid prostheses (ring or valve) has long been considered to contribute to the mechanism of dynamic left ventricular outflow tract (LVOT) obstruction after mitral repair or replacement. In clarifying the geometric relationship between LVOT orifice and mitral valve annulus (MVA) in eight normal subjects, the authors have endeavored to show how that a rigid mitral prosthesis might obstruct the LVOT based on the assumption that any rigid prosthesis necessarily follows the motion of the posterior half of the MVA (MVApost) in the course of every heart beat. During systole, the relationship between the MVApost and the approximated plane of the LVOT orifice was constant. However, with the respect to the relationship between the LVOT orifice and the approximated plane of the MVApost (PI-MVApost), the intersection between the two shifted toward the apex during systole. Assuming the prosthesis is aligned on the MVApost with the same orientation as the PI-MvApost, this shift implies a reduction in the effective size of the LVOT orifice due to the prosthesis. The calculated obstruction rate was 24.9% (0 ms), 30.9% (100 ms), 35.5% (200 ms), and 45.4% (300 ms). These results indicate the importance of maintaining the flexibility of the MVA after mitral valve surgery.

Adult↗

PubMedDate not supplied

Mitral annular flexibility.

An analysis of three-dimensional movement of the mitral valve annulus (MVA) may address the question of geometrical change after mitral valve repair to preserve mitral annular function. Conventionally, annular contraction has been studied for this purpose. We investigated this geometrical change occurring in the anterior half of the MVA and discuss its clinical significance. Three-dimensional images of the MVA during systole were reconstructed from magnetic resonance images of eight normal subjects. The posterior half of the MVA exhibited translational motion. We assume that this portion, exhibiting translational motion as well as contraction, purely follows the motion of the left ventricular contraction. Compensating for the discrepancy between the motion of the aortic root and that of the posterior half of the MVA, the anterior half exhibited a flexible change in shape during systole, thus maintaining a sufficient left ventricular outflow tract (LVOT). The increase in the extent of displacement of the anterior MVA from the posterior half of the MVA during systole, which was 3.6 +/- 1.0 mm (mean +/- SD), indicates the annular flexibility. The preservation of annular flexibility may prevent LVOT obstruction. Further geometrical analysis of patients after mitral repair will clarify annular function as presented in this article.

Adult↗

PubMedDate not supplied

The effects of the use of piezoelectric motors in a 1.5-Tesla high-field magnetic resonance imaging system (MRI).

PURPOSE: This paper presents the results of an experimental investigation with two different rotatory piezomotors in a closed 1.5 Tesla high-field MRI. The focus of the investigation was on testing the functionality of these motors within the MRI and to determining the image interference they caused. MATERIALS AND METHODS: To obtain a differentiated estimate of the interference the motors were tested in both the passive (turned off, i.e. without current flow) and active (turned on, i.e. with current flow) state during MRI scanning. Three different types of sequences were used for the test: Spin-Echo (SE), Gradient-Echo (GE) and Echo-Planar Imaging (EPI). A plastic container filled with a gadolinium-manganese solution was used for representation of the artefacts. The motors investigated were placed parallel to the container at predetermined distances during the experiment. RESULTS AND CONCLUSIONS: The results show that the motors investigated suffered no functional limitations in the magnetic field of the MRI but, depending on the type of motor, the measurement distance and the state of the motor, the motors had different effects on the sequence images. A motor in the off-state placed immediately next to the object to be measured mainly causes artefacts because of its material properties. If, on the other hand, the piezomotor is in the on-state images with strong noise result when the motor is immediately next to the object being measured. The images regain their normal quality when the motor is approximately at a distance of 1 m from the object being investigated. Driving the motor inside the MRI, therefore, is only to be recommended during the pauses in scanning: this delivers artefact-free images if minimal, motor-specific distances are kept to. With regard to the three different types of sequences it was determined that the SE sequence was the least sensitive and the EPI sequence the most sensitive to disturbance. The GE sequence showed only minimal differences to the SE sequence with regard to signal-to-noise ratios. Since it requires considerably shorter scan-times it can be considered to be the most effective type of sequence under these conditions.

Artifacts↗

PubMedDate not supplied

Dynamic change in the left ventricular base with or without a rigid mitral valve prosthesis.

To evaluate the narrowing of the left ventricular outflow tract (LVOT) during systole caused by a rigid mitral prosthesis, the geometric relationship between the prosthesis (or the mitral annulus) and the left ventricular base (LVB) was studied in five patients with mechanical mitral valve prostheses and eight normal subjects. The images of the mitral valve annulus (MVA) and the LVOT orifice reconstructed in three dimensions were projected on the plane of the LV base. Calculating the areas of these projected images (i.e., those for MVA [Sm], LVOT orifice [So], the LVB [Sb; Sb = Sm + So]), the MVA-LVB ratio (Sm/Sb) was determined. In the normal subject, the MVA-LVB ratio was nearly constant during systole (59 +/- 5% at 0 msec and 62 +/- 7% at 300 msec, respectively), whereas in the patients with prostheses, the ratio increased from 61 +/- 4% (0 msec) to 69 +/- 4% (300 msec). The increase in MVA-LVB ratio reduces the proportionate share of LVOT orifice in relation to the total LVB. The ideal mitral valve prosthesis should be flexible at the annulus to attain good performance in LVB dynamics.

Adult↗