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Dorith Goldsher

Publications and source records attributed to Dorith Goldsher.

6 recordsLinked to original sources
PubMed2006

Segmentation of thin structures in volumetric medical images.

We present a new segmentation method for extracting thin structures embedded in three-dimensional medical images based on modern variational principles. We demonstrate the importance of the edge alignment and homogeneity terms in the segmentation of blood vessels and vascular trees. For that goal, the Chan-Vese minimal variance method is combined with the boundary alignment, and the geodesic active surface models. An efficient numerical scheme is proposed. In order to simultaneously detect a number of different objects in the image, a hierarchal approach is applied.

Algorithms↗
PubMed2006

Magnetic resonance imaging for patients with permanent pacemakers: initial clinical experience.

BACKGROUND: Magnetic resonance imaging is a diagnostic tool of growing importance. Since its introduction, certain medical implants, e.g., pacemakers, were considered an absolute contraindication, mainly due to the presence of ferromagnetic components and the potential for electromagnetic interference. Patients with such implants were therefore prevented from entering MRI systems and not studied by this modality. These devices are now smaller and have improved electromechanical interference protection. Recently in vitro and in vivo data showed that these devices may be scanned safely by MRI. OBJECTIVES: To report our initial experience with three patients with pacemakers who underwent cerebral MRI studies. METHODS: The study included patients with clear clinical indications for MRI examination and who had implanted devices shown to be safe by in vitro and in vivo animal testing. In each patient the pacemaker was programmed to pacing-off. During the scan, continuous electrocardiographic telemetry, breathing rate, pulse oximetry and symptoms were monitored. Specific absorption rate was limited to 4.0 W/kg for all sequences. Device parameters were assessed before, immediately after MRI, and 1 week later. RESULTS: None of the patients was pacemaker dependent. During the MRI study, no device movement was felt by the patients and no episodes of inappropriate inhibition or rapid activation of pacing were observed. At device interrogation there were no significant differences in device parameters pre-, post-, and 1 week after MRI. Image quality was unremarkable in all imaging sequences used and was not influenced by the presence of the pacemaker. CONCLUSION: Given appropriate precautions, MRI can be safely performed in patients with a selected permanent pacemaker. This may have significant implications for current MRI contraindications.

Aged↗
PubMed2004

Method for rapid MRI needle tracking.

A new method for MRI needle tracking within a given two-dimensional (2D) image slice is presented. The method is based on k-space investigation of the difference image between the current dynamic frame and a reference frame. Using only a few central k-lines of the difference image and a nonlinear optimization procedure, one can resolve the parameters that define the 2D sinc function that best characterizes the needle in k-space. The spatial location and orientation of the needle are determined from these parameters. Rapid needle tracking is obtained by repeated acquisitions of the same set of several central k-lines (as in a "keyhole" protocol) and repeated computation of these parameters. The calculated needle tip is depicted on the reference image by means of a graphic overlay. The procedure was tested in computer simulations and in actual MRI scans (the computations were done offline). It was demonstrated that six k-lines out of 128 usually suffice to locate the needle. The refresh rate of the needle location depends on the time required to sample the subset of k-lines, calculate the current needle location, and refresh the reference image.

Brain↗
PubMed2004

Role of multisection CT angiography in the evaluation of vertebrobasilar vasospasm in patients with subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Optimal means for assessing cerebral vasospasm, mainly at the vertebrobasilar system, have not been established. The purpose of this study was to evaluate the role of multisection CT angiography (MCTA) in the detection and quantification of vertebrobasilar vasospasm (VBS) indicated on transcranial Doppler (TCD) imaging in patients with subarachnoid hemorrhage (SAH). METHODS: Forty-three MCTA studies of the vertebrobasilar arteries were performed with a multisection spiral CT scanner in 36 patients with SAH. Parameters used were 1-mm collimation, 0.625Q pitch, 120 kV, and 250 mAs. Contrast material was injected (80-100 mL, 3 mL/s) after a 15-20-second delay. Postprocessing of the vertebrobasilar system was performed by using maximum intensity projection and volume-rendering reconstruction. Vessel diameter was measured at different intracranial locations along the vertebral and basilar arteries perpendicular to their long axis by using curved reformatted multiplanar reformation. TCD imaging of the posterior circulation was performed within 24 hours. RESULTS: MCTA demonstrated narrowed arteries compatible with VBS in 13 patients, consistent with TCD findings. Despite TCD recordings of high flow velocity in three other patients, MCTA did not reveal vasospasm but did show wide arteries feeding arteriovenous malformations in two and normal-sized arteries in one. VBS in two patients was identified on MCTA but overlooked during TCD imaging. Twenty patients had normal findings on both TCD and MCTA studies. CONCLUSION: Cerebral MCTA is recommended as a reliable, rapid, and minimally invasive diagnostic method, one complementary to TCD imaging for assessing VBS in patients with SAH.

Adolescent↗
PubMed2002

Basilar vasospasm diagnosis: investigation of a modified "Lindegaard Index" based on imaging studies and blood velocity measurements of the basilar artery.

BACKGROUND AND PURPOSE: Numerous studies have shown that cerebral vasospasm is one of the leading causes of death and neurological disability after subarachnoid hemorrhage. Most of these studies, however, have focused on anterior circulation vessels. Since the introduction of the transcranial Doppler (TCD), increasing attention has been given to basilar artery (BA) vasospasm, especially in traumatic subarachnoid hemorrhage. As shown for the anterior circulation, however, the significance of elevated flow velocities (FVs) in the posterior vessels may be ambiguous, so vasospasm may not be reliably differentiated from hyperemia. The purpose of the present study was to evaluate the potential additional value of an intracranial/extracranial FV ratio in the posterior circulation to cope with this shortcoming of the TCD in the diagnosis of BA vasospasm. METHODS: FV in the extracranial vertebral artery (VA) was measured in 20 healthy volunteers. Normative values of an intracranial/extracranial VA FV ratio (IVA/EVA) and a BA/extracranial VA FV ratio (BA/EVA) were calculated. Thirty-four patients with subarachnoid hemorrhage were then evaluated with TCD and CT angiography (CTA). The value of the IVA/EVA and BA/EVA ratios in the diagnosis and assessment of vertebrobasilar vasospasm was investigated. RESULTS: The extracranial VA could be insonated in all subjects at depths ranging from 45 to 55 mm. The average FV for the extracranial VA was 26 cm/s. The ratios between intracranial and extracranial VA FVs were 1.6 on both sides, whereas the ratio between the BA FVs and the mean extracranial VA FVs was slightly higher at 1.7. Fourteen patients (41.2%) had CTA evidence of BA vasospasm. Vasospasm was severe in 7 patients, moderate in 1, and mild in the remaining. An FV threshold of 80 cm/s was indicative of BA vasospasm in 92.8% with 3 false-positive results that could be related to vertebrobasilar hyperemia. Comparative analysis between CTA and TCD findings showed that BA/EVA was >2 in all patients with BA vasospasm (100% sensitivity) and < 2 in all but 1 patient without BA vasospasm (95% specificity). Furthermore, the BA/EVA ratio showed a close correlation with BA diameter (r=-0.8139, P<0.0001) and was >3 in all patients with severe vasospasm. CONCLUSIONS: The results of the present study showed that the BA/EVA ratio may contribute to an improved discrimination between BA vasospasm and vertebrobasilar hyperemia and enhance the accuracy and reliability of TCD in the diagnosis of BA vasospasm. Our data further suggest that the BA/EVA ratio may provide an approximation of vasospasm severity and help in identifying patients who are likely to suffer from hemodynamically significant vasospasm.

Adolescent↗