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M P Marks

Publications and source records attributed to M P Marks.

At least 73 records · Page 4Linked to original sources
PubMed1994

A mechanically detachable coil for the treatment of aneurysms and occlusion of blood vessels.

PURPOSE: To evaluate mechanically detachable coil designs capable of controlled and instantaneous release within an aneurysm or vascular space. METHODS: Three mechanically detachable coil designs, clamped ball, looped ribbon, and interlocking cylinder, were evaluated using in vitro and in vivo testing to study reliability of coil release, retractability, and coil behavior in a microcatheters. In vitro tests were performed using a glass side-wall aneurysm model and conventional microcatheters. In vivo experiments in rabbits included aneurysm models (side-wall and bifurcation) and arterial occlusions (carotid and renal). RESULTS: All three designs deployed coils easily and were able to retract coils after partial deployment. Motion was seen in previously released coils and in the catheter when using the clamped ball and looped ribbon designs. The interlocking cylinder design did not cause similar motion. When compared with the other two designs, the interlocking cylinder had significantly greater separation forces between coil pusher and coil while in the catheter. Frictional forces within the catheter were lower for the interlocking cylinder mechanically detachable coil design than for a commercially available conventional coil and coil pusher system. During in vivo testing, the mechanically detachable coil design operated smoothly in the catheter, providing good release and retraction in aneurysms and straight vessels. CONCLUSION: The interlocking cylinder mechanically detachable coil design is superior to the other two tested designs. The mechanically detachable coil was reliably delivered and detached in in vivo testing for the treatment of aneurysms and for the occlusion of blood vessels.

Animals↗
PubMed1994

Blood flow in major cerebral arteries measured by phase-contrast cine MR.

PURPOSE: To measure mean blood flow in individual cerebral arteries (carotid, basilar, anterior cerebral, middle cerebral, and posterior cerebral) using a cine phase contrast MR pulse sequence. METHODS: Ten healthy volunteers (22 to 38 years of age) were studied. The cine phase-contrast section was positioned perpendicular to the vessel of interest using oblique scanning planes. This pulse sequence used a velocity encoding range of 60 to 250 cm/sec. From the velocity and area measurements on the cine images, mean blood flow was calculated in milliliters per minute and milliliters per cardiac cycle. In the same subjects, transcranial Doppler measurements of blood velocity in these same vessels were also obtained. RESULTS: There was no difference in blood flow in the paired cerebral arteries. Carotid arteries had mean blood flow in the range of 4.8 +/- 0.4 ml/cycle, the basilar artery 2.4 +/- 0.2 ml/cycle, the middle cerebral artery 1.8 +/- 0.2 ml/cycle, the distal anterior cerebral artery 0.6 +/- 0.1 ml/cycle, and the posterior cerebral artery 0.8 +/- 0.1 ml/cycle. Overall, there was poor correlation between MR-measured and transcranial Doppler-measured peak velocity. CONCLUSION: Although careful attention to technical detail is required, mean blood flow measurements in individual cerebral vessels is feasible using a cine phase-contrast MR pulse sequence.

Adult↗
PubMed1993

Diagnosis of carotid artery disease: preliminary experience with maximum-intensity-projection spiral CT angiography.

OBJECTIVE: Spiral CT allows continuous data to be acquired rapidly, and if a correctly timed IV bolus of contrast material is given, spiral CT angiography can be performed. This study was designed to evaluate spiral CT angiography with maximum-intensity-projection reconstructions for assessing the degree of carotid artery stenosis. SUBJECTS AND METHODS: Spiral CT angiography (of 28 carotid bifurcations in 14 patients) was compared in a blinded fashion with conventional angiography (of 28 bifurcations) and with two-dimensional time-of-flight MR angiography (of 12 bifurcations) to assess degree of stenosis. A nonblinded comparison of the contour of the lumen at the site of stenosis was then made between conventional angiography, spiral CT angiography, and MR angiography. The degree of stenosis was measured in each internal carotid artery and categorized as mild (< 30%), moderate (30-69%), or severe (70-99%) stenosis or as occlusion. Maximum-intensity-projection images were used for the evaluations; however, if calcification was circumferential and the lumen of the carotid artery could not be analyzed in the area of the calcification, the axial source images were used. RESULTS: The results of CT angiography and conventional angiography agreed overall in 25 (89%) of 28 cases (r = .921, p = .05, Spearman rank correlation). The presence of severe stenosis or occlusion was correctly identified in seven of seven cases. In the moderate and mild stenosis categories, 18 (86%) of 21 were correctly identified (r = .802, p = .122). Three internal carotid arteries (11%) had circumferential calcification that necessitated evaluation of the axial source images, and the measurements obtained from the axial images agreed well with angiographic findings. MR angiography correlated well with the various categories of stenosis. However, when we compared MR angiography directly with CT angiography and conventional angiography, we found that the degree of stenosis was overestimated when MR angiography was used. CONCLUSION: Our results show that spiral CT angiography shows normal and abnormal carotid anatomy well when compared with conventional angiography. The short examination time and clear depiction of arterial caliber in areas of stenosis are significant advantages of spiral CT angiography compared with MR angiography.

Aged↗
PubMed1992

Determination of cerebral blood flow with a phase-contrast cine MR imaging technique: evaluation of normal subjects and patients with arteriovenous malformations.

This study evaluated a phase-contrast cine magnetic resonance (MR) imaging technique capable of simultaneously allowing determination of velocity and volume flow rate (VFR) in both carotid arteries and the basilar artery. Forty patients were studied; 24 were neurologically normal, and 16 had intracerebral arteriovenous malformations (AVMs). In the normal group, mean basilar flow was significantly less than mean carotid flow. Mean velocity and VFR showed a significant decline with age in the basilar artery. Carotid artery flow and total cerebral blood flow did not decline with age. In the AVM patients, flow and velocity measurements were significantly elevated in all three arteries. Flow in the carotid artery ipsilateral to the AVM was significantly greater than flow in the contralateral carotid artery. VFR increased in all three arteries with increasing AVM volume. Four patients underwent partial embolization, and a corresponding decrease in flow was observed. Phase-contrast cine MR imaging provides rapid, simultaneous, noninvasive velocity and VFR measurement in the major intracranial arteries.

Adolescent↗
PubMed1992

Intranidal aneurysms in cerebral arteriovenous malformations: evaluation and endovascular treatment.

Patients with cerebral arteriovenous malformations (AVMs) have an increased risk of hemorrhage if an intranidal aneurysm is present. Angiograms from 125 patients with cerebral AVMs were evaluated, and 15 (12%) had intranidal aneurysms. All 15 patients had a history of bleeding. Five patients underwent particulate or liquid embolization before surgical excision of or radiation therapy for the AVM. All aneurysms were thrombosed at the time of embolization. Ten patients underwent radio-surgery alone. Eight of the 10 underwent angiographic follow-up (mean, 33 months); seven patients showed complete obliteration of the AVM without residual aneurysm. Histologic evaluation showed intranidal aneurysms to be thin-walled vascular structures, and they are the likely site for AVM hemorrhage. Embolization is an effective method for achieving thrombosis of the intranidal aneurysm and may be beneficial in patients undergoing radiation therapy because of a long latency period between treatment and thrombosis of the AVM.

Adolescent↗
PubMed1992

Clinically documented hemorrhage in cerebral arteriovenous malformations: MR characteristics.

This study assessed the ability of magnetic resonance (MR) imaging to identify vascular characteristics of cerebral arteriovenous malformations (AVMs) which are predictive of hemorrhage. The study also evaluated the sensitivity and specificity of spin-echo (SE) and gradient-recalled-echo (GRE) imaging in the detection of prior clinical hemorrhage on the basis of location of the hemorrhage (parenchymal, intraventricular, or subarachnoid). Fifty patients with high-flow AVMs were evaluated. Twenty-four (48%) patients had prior clinical hemorrhage documented at computed tomography or MR imaging at the time of bleeding. Central venous drainage (P less than .001), central AVM location (P less than .001), and peri- or intraventricular AVM location (P less than .01) correlated positively with prior clinical hemorrhage. Intranidus aneurysms and angiomatous change could not be detected with MR. Nineteen of the 24 patients with prior hemorrhage underwent both SE and GRE imaging. Hypointensity, indicating the presence of iron from prior hemorrhage, was demonstrated in 14 of 19 T2-weighted SE images (sensitivity, 74%) and in 18 of 19 GRE images (sensitivity, 95%). No patient without a prior episode of clinical bleeding demonstrated evidence of iron deposition at MR imaging (specificity, 100%).

Adolescent↗
PubMed1992

CT angiography with spiral CT and maximum intensity projection.

The authors describe a technique for obtaining angiographic images by means of spiral computed tomography (CT), preprocessing of reconstructed three-dimensional sections to suppress bone, and maximum intensity projection. The technique has some limitations, but preliminary results in 48 patients have shown excellent anatomic correlation with conventional angiography in studies of the abdomen, the circle of Willis in the brain, and the extracranial carotid arteries. With continued development and evaluation, CT angiography may prove useful as a screening tool or replacement for conventional angiography in some patients.

Abdomen↗
PubMed1992

Charged-particle radiosurgery for intracranial vascular malformations.

Heavy charged-particle radiation has unique physical characteristics that offer several advantages over photons and protons for stereotactic radiosurgery of intracranial AVMs. These include improved dose distributions with depth in tissue, small angle of lateral scattering, and sharp distal fall-off of dose in the Bragg ionization peak. Under multi-institutionally approved clinical trials, we have used stereotactic helium-ion Bragg peak radiosurgery to treat approximately 400 patients with symptomatic, surgically inaccessible vascular malformations at the UCB-LBL 184-in synchrocyclotron and bevatron. Treatment planning for stereotactic heavy charged-particle radiosurgery for intracranial vascular disorders integrates anatomic and physical information from the stereotactic cerebral angiogram and stereotactic CT and MR imaging scans for each patient, using computerized treatment-planning calculations for optimal isodose contour distribution. The shape of an intracranial AVM is associated strongly with its treatability and potential clinical outcome. In this respect, heavy charged-particle radiosurgery has distinct advantages over other radiosurgical methods; the unique physical properties allow the shaping of individual beams to encompass the contours of large and complexly shaped AVMs, while sparing important adjacent neural structures. We have had a long-term dose-searching clinical protocol in collaboration with SUMC and UCSF and have followed up over 300 patients for more than 2 years. Initially, treatment doses ranged from 45 GyE to 35 GyE. Currently, total doses up to 25 GyE are delivered to treatment volumes ranging from 0.1 cm3 to 70 cm3. This represents a relatively homogeneous dose distribution, with the 90% isodose surface contoured to the periphery of the lesion; there is considerable protection of normal adjacent brain tissues, and most of the brain receives no radiation exposure. Dose selection depends on the volume, shape, and location of the AVM and several other factors, including the volume of normal brain that must be traversed by the plateau portion of the charged-particle beam. The first 230 patients have been evaluated clinically to the end of 1989. Using the clinical grading of Drake, about 90% of the patients had an excellent or good neurologic grade, about 5% had a poor grade, and about 5% had progression of disease and died, or died as a result of unrelated intercurrent illness. Neuroradiologic follow-up to the end of 1989 indicated the following rates of complete angiographic obliteration 3 years after treatment: 90% to 95% for AVM treatment volumes less than 4 cm3, 90% to 95% for volumes 4 to 14 cm3, and 60% to 70% for volumes greater than 14 cm3.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Physiologic imaging of the brain.

Advances in imaging hardware for positron emission tomography and single-photon emission CT, coupled with a wide variety of radiopharmaceutical agents, have allowed these techniques to be used in the evaluation of neoplasm, stroke, epilepsy, and dementia. Cerebral perfusion agents continue to be the mainstay of single-photon emission CT imaging but, in addition to the evaluation of ischemia, it has seen an increasing role in the study of dementia, neuropsychiatric disorders, and seizures. Positron emission tomography scanning has had similar applications but it is playing a greater part in the evaluation of neoplasms, including primary gliomas and pituitary adenomas. Stable-xenon CT has shown value in the study of ischemia associated with meningitis, sickle cell disease, chronic subdural hematomas, and cerebral arteriovenous malformations. MR diffusion imaging shows promise in the evaluation of white matter pathology and some tumors.

Brain↗
PubMed1991

Stereotactic helium ion Bragg peak radiosurgery for intracranial arteriovenous malformations. Detailed clinical and neuroradiologic outcome.

89 patients with angiographically documented arteriovenous malformations were treated with helium ion Bragg peak radiation. The rate of complete angiographic obliteration 2 years after radiation was 94% in those lesions smaller than 4 cm3 (2.0 cm in diameter), 75% for those 4-25 cm3 and 39% for those larger than 25 cm3 (3.7 cm in diameter); at 3 years after radiation, the corresponding obliteration rates were 100, 95 and 70%. Major clinical complications occurred in 10 patients (8 permanent, 2 transient) between 3 and 21 months after treatment; all were in the initial stage of the protocol (higher radiation doses). 10 patients bled from residual malformation between 4 and 34 months after treatment. Seizures were improved in 63% and headaches in 68% of patients. Excellent or good clinical outcome was achieved in 94% of patients. Compared to the natural history and risks of surgery for these difficult malformations, we consider these results encouraging. Heavy-charged-particle radiation is a valuable therapy for surgically inaccessible symptomatic cerebral arteriovenous malformations. The current procedure has two disadvantages: the prolonged latent period before complete obliteration and the small risk of serious neurological complications.

Adolescent↗
PubMed1991

Stereotactic helium ion Bragg peak radiosurgery for angiographically occult intracranial vascular malformations.

Between July 1983 and July 1989, we treated 35 patients with surgically inaccessible, symptomatic angiographically occult vascular malformations (AOVMs) using stereotactic heavy-charged-particle radiosurgery. AOVMs were located in the brainstem (19), thalamus or internal capsule (9), basal ganglia (3), deep cerebral hemisphere and motor area (3), or cerebellopontine angle (1). All patients presented with clinical and radiological evidence of previous hemorrhage, usually with multiple episodes of hemorrhage. Treatment volumes ranged from 80 to 15,200 mm3 and treatment doses from 7.7 to 34.6 Gy. Mean follow-up was 40 months, with 31 patients followed for at least 2 years. Clinical outcome was excellent in 46%, good in 34% and poor in 14%; 6% died. Twenty-seven patients in excellent and good condition prior to treatment remained stable or improved neurologically. Two patients initially in poor condition, who had previously received conventional radiotherapy, died at 9 and 14 months after treatment, respectively. Six patients experienced recurrent hemorrhage 2-60 months following treatment. Three of these patients made a complete recovery. Although a larger number of treated patients must be followed over longer periods of time, stereotactic heavy-particle radiotherapy may be a valuable treatment modality for surgically inaccessible intracranial AOVMs.

Adolescent↗
PubMed1990

Stereotactic heavy-charged-particle Bragg-peak radiation for intracranial arteriovenous malformations.

BACKGROUND: Heavy-charged-particle radiation has several advantages over protons and photons for the treatment of intracranial lesions; it has an improved physical distribution of the dose deep in tissue, a small angle of lateral scattering, and a sharp distal falloff of the dose. METHODS: We present detailed clinical and radiologic follow-up in 86 patients with symptomatic but surgically inaccessible cerebral arteriovenous malformations that were treated with stereotactic helium-ion Bragg-peak radiation. The doses ranged from 8.8 to 34.6 Gy delivered to volumes of tissue of 0.3 to 70 cm3. RESULTS: Two years after radiation treatment, the rate of complete obliteration of the lesions, as detected angiographically, was 94 percent for lesions smaller than 4 cm3, 75 percent for those of 4 to 25 cm3, and 39 percent for those larger than 25 cm3. After three years, the rates of obliteration were 100, 95, and 70 percent, respectively. Major neurologic complications occurred in 10 patients (12 percent), of whom 8 had permanent deficits. All these complications occurred in the initial stage of the protocol, before the maximal dose of radiation was reduced to 19.2 Gy. In addition, hemorrhage occurred in 10 patients from residual malformations between 4 and 34 months after treatment. Seizures and headaches were less severe in 63 percent of the 35 and 68 percent of the 40 patients, respectively, who had them initially. CONCLUSIONS: Given the natural history of these inaccessible lesions and the high risks of surgery, we conclude that heavy-charged-particle radiation is an effective therapy for symptomatic, surgically inaccessible intracranial arteriovenous malformations. The current procedure has two disadvantages: a prolonged latency period before complete obliteration of the vascular lesion and a small risk of serious neurologic complications.

Adolescent↗
PubMed1990

Combination treatment for massive cavernous hemangioma of the face: YAG laser photocoagulation plus direct steroid injection followed by YAG laser resection with sapphire scalpel tips, aided by superselective embolization.

A massive cavernous hemangioma of the face in an 11 month old child has been successfully resected utilizing a combination of laser and non-laser techniques. The hemangioma was initially treated twice with YAG laser photocoagulation plus direct injection of steroids. This treatment promptly stopped the rapid growth and induced blanching as well as a 25% shrinkage with each treatment. Arteriogram with superselective embolization produced a further shrinkage of the hemangioma. Finally, the contact YAG laser with sapphire scalpel tips was utilized for complete and cosmetically satisfactory hemangioma resection. The treatment of a massive cavernous hemangioma by a combination of modalities is discussed.

Combined Modality Therapy↗
PubMed1990

Benefits of contact and noncontact YAG laser for periorbital hemangiomas.

Twenty patients with capillary/cavernous hemangiomas of the periorbital area (eyelid, eyebrow, nose extending to canthus) have been treated with a variety of techniques. Six patients were treated by yttrium-aluminum-garnet (YAG) laser photocoagulation and direct injection of steroids. Rapid shrinkage of the hemangiomas occurred in all patients, and 2 infants whose eye was totally occluded by the hemangioma had their eyes rapidly opened. YAG laser excision with or without previous photocoagulation plus injection and with arteriogram plus superselective embolization was performed in the other 14 patients. Results were satisfactory in all patients.

Adrenal Cortex Hormones↗
PubMed1990

Hemorrhage in intracerebral arteriovenous malformations: angiographic determinants.

The most serious and frequent complication of intracranial arteriovenous malformations (AVMs) is intracranial hemorrhage. Identification of patients at greatest risk for intracranial bleeding would be beneficial. Detailed analysis of vascular architecture was performed in 65 patients with intracranial AVMs to identify the vascular characteristics that correlated with hemorrhage. Fifteen characteristics were assessed. Hemorrhage was present in 45 patients (69%). The following characteristics correlated positively with hemorrhage (Fisher-Irwin exact test): central venous drainage (P less than .0001), periventricular or intraventricular location of the AVM (P = .0002), and intranidal aneurysm (P = .028). The following characteristics correlated negatively with hemorrhage: angiomatous change (P = .0005), peripheral venous drainage (P = .005), and mixed venous drainage (P = .021). Multivariate linear discriminant analysis demonstrated that central venous drainage, angiomatous change (negatively predictive), intranidal aneurysm, and periventricular or intraventricular location of the AVM were the most discriminating or predictive characteristics of hemorrhage. Detailed analysis of the vascular architecture of intracranial AVMs helped identify features that strongly correlate with clinical hemorrhage and have important prognostic implications for the treatment of patients with these lesions.

Adult↗