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Biomedical subjects

J T Tans

Publications and source records attributed to J T Tans.

34 records · Page 2Linked to original sources
PubMed1986

The role of digital subtraction angiography in neuroradiology. An evaluation of intravenous and intra-arterial digital subtraction angiography.

A few years after the introduction of intravenous digital subtraction angiography (DSA) in clinical practice it became clear that, although the method had been developed as an alternative to arterial angiography, especially for the analysis of cerebral ischemia, its application was not as successful as the earlier reports had indicated. Based on the results of a study comparing intravenous DSA, intra-arterial DSA, and the Doppler examination, in 168 consecutive patients, a diagnostic algorithm for the management of these patients is proposed. A second and more important application of digital subtraction is its use with arterial angiography, especially with a high resolution system configuration.

Angiography, Digital Subtraction↗
PubMed1985

CSF outflow resistance and pressure-volume index determined by steady-state and bolus infusions.

Intraventricular or lumbar CSF pressure was measured in 58 adult hydrocephalic patients. CSF outflow resistance (Rcsf) and pressure-volume index (PVI) were determined by steady-state and bolus infusion techniques, using mathematical models with and without a constant term. Comparison of the various Rcsf and PVI values indicates that the most reliable Rcsf is obtained by steady-state infusion. The best approximation of the PVI is obtained by bolus infusions, provided the pressure decay curve is excluded. Mathematically a model with a constant term is to be preferred.

Biomechanical Phenomena↗
PubMed1984

Comparison of ventricular steady-state infusion with bolus infusion and pressure recording for differentiating between arrested and non-arrested hydrocephalus.

In 6 years 26 adult patients with chronic communicating or non-communicating hydrocephalus underwent ventricular fluid pressure (VFP) recording, including intraventricular steady-state and bolus infusion tests. Patients were treated with a shunt when steady-state infusion yielded a csf outflow resistance (Rcsfs) greater than 10 mm Hg/ml/min; the success rate was 83%. The main purpose of the study was to compare Rcsfs with outflow resistance obtained by bolus infusions (Rcsfb), pressure-volume index (PVI) and VFP. Rcsfs was higher than Rcsfb, particularly when resistance was high and the degree of disturbance of csf dynamics was reflected by Rcsfs better than by Rcsfb. The PVI showed a roughly inverse relationship with the Rcsfs but was not helpful in differentiating arrested from non-arrested hydrocephalus. Rcsfs and VFP correlated better than expected. A high Rcsfs was associated with an elevated VFP and a normal Rcsfs with a normal VFP. VFP only varied when Rcsfs exhibited a mild to moderate increase. It is concluded that steady-state infusion remains the most reliable method for the prediction of the result of shunting. We recommend shunting when Rcsfs is greater than 10 mm Hg/ml/min. Bolus infusions provide valuable data on brain elastance and additional information on csf outflow resistance. VFP recording is certainly worthwhile because infusion tests can be omitted when VFP is clearly elevated and useful information is obtained when Rcsf is borderline.

Adolescent↗
PubMed1983

Intracranial volume-pressure relationship in man. Part 2: Clinical significance of the pressure-volume index.

Pressure-volume indices (PVI's) were determined for a heterogeneous group of 40 patients who underwent continuous monitoring of ventricular fluid pressure (VFP). The main purpose was to investigate the relationship between VFP and PVI and to establish the significance of the measured PVI values. Determinations of PVI appear to be useful only when baseline VFP is under 20 mm Hg, maximum VFP is under 30 mm Hg, A-waves are absent, and B-waves do not occur numerously. The authors advocate starting with 1-ml bolus infusions, and then, when the resulting pressure rise exceeds 4 mm Hg, additional bolus infusions can be omitted. Results indicate that 13 ml and 10 ml are the key values for the PVI. A PVI of less than 13 ml indicates the need for either reduction of VFP and improvement of compliance or intensive monitoring of both the VFP and the volume-pressure relationship; if the PVI is below 10 ml, anti-hypertensive treatment is almost always necessary. Values of PVI's between 13 and 18 ml, although pathological, usually have no therapeutic consequences.

Brain Injuries↗
PubMed1980

Angiographical findings and risk factors in cerebral ischaemia. A retrospective study.

Reviewing the angiograms of 100 patients with RIA or stroke we found intracranial lesions in 67%, extracranial lesions in 64%, and normal angiograms in 13% of the cases. Risk factors occurred more often as the angiographic lesions were more extensive. These findings confirm the importance of angiographic examination of the intracranial vessels in patients with cerebral ischaemia.

Adult↗
PubMed1979

Differentiation of normal pressure hydrocephalus and cerebral atrophy by computed tomography and spinal infusion test.

The diagnostic value of computed tomography (CT) and spinal infusion test (SIT) was investigated in 27 patients with normal pressure hydrocephalus (NPH) and 35 patients with cerebral atrophy. The most consistent CT finding of NPH was dilatation of the temporal horns, that of cerebral atrophy widening of the convexity sulci. However, 43% of patients with cerebral atrophy demonstrated no cortical atrophy. The SIT showed an excellent relation with isotope cisternography and continuous intracranial pressure recording. NPH and cerebral atrophy were correctly differentiated in 71% by CT and SIT. A normal SIT and a CT scan without the typical features of NPH exclude impairment of cerebrospinal fluid absorption. An abnormal SIT and a CT scan showing ventricular enlargement without dilatation of convexity sulci, require isotope cisternography and possibly intracranial pressure recording to determine the degree of the absorption deficit.

Atrophy↗
PubMed1978

Doppler flow velocity measurements in patients with intracranial hypertension.

In patients with severe brain lesions monitoring of the intracranial pressure as well as monitoring of cerebral blood flow can be of clinical value. While at the moment there is no atraumatic method for measuring cerebral blood flow in man, it is recommended to measure blood flow velocity with the ultrasound Doppler technic in the common carotid artery. On theoretical grounds a positive correlation between cerebral blood flow and blood flow velocity can be expected and the observations presented show that such a correlation exists in normal controls and in neurological patients. In many neurological patients the flow velocity in the common carotid artery decreases with increasing intracranial pressure. This suggests that the autoregulation is disturbed. The demonstration of such a disturbance can have clinical implications.

Blood Flow Velocity↗
PubMed1978

Computed tomography of supratentorial astrocytoma.

In a group of 40 astrocytomas the C.T. appearance was correlated with the grade of malignancy. On the plain scan the majority presented an irregular, nonhomogeneous low density lesion, better demarcatable in high than in low grade astrocytomas. Contrast enhancement was seen in 28 of the 32 high grade astrocytomas, 50% of the annular, 25% of the nodular and 25% of the mixed type. Six of the 8 low grade astrocytomas showed no contrast enhancement and 1 showed an annular type lesion. A relationship was found between the degree of contrast enhancement and the vascularity. Mass effect was observed in all but 1 patient, but more pronounced in high grade astrocytomas. At the first interpretation 98% were recognized as a lesion, 93% as a tumor and 68% as an astrocytoma. One false negative and no false postive C.T.scans were obtained. In review, high and low grade malignancies were correctly differentiated in 90%. As a screening method, the combination of EEG and echo equalled C.T.; in establishing a definite diagnosis angiography was inferior to C.T. Solely on the basis of the C.T. appearance, astrocytomas can hardly be differentiated from the other malignant brain tumors, but the grade of malignancy can be predicted reliably.

Astrocytoma↗
PubMed1977

Computed tomography of intracerebral hematoma.

The C.T. findings of 33 intracerebral hematomas are described. During the first week intracerebral hematomas were visible as a sharply demarcated lesion with markedly increased density without contrast enhancement. Thereafter the density decreased gradually and after 30 days the density was always lower than that of cerebral tissue. Depending on the etiology of the hemorrhage, differences were found in the localization, shape and density of the lesion on the C.T. scan. Secondary mass effects could be evaluated precisely. On first interpretation, 94% of the hematomas were recognized as focal lesions (2 false negative) and 85% as intracerebral hematomas (2 false negative and 3 incorrect). False positives were absent. The review C.T. diagnosis was correct in 94%. In the diagnosis of intracerebral hematomas, C.T. was found to be superior to all other investigations both quantitatively and qualitatively. C.T. also has therapeutic consequences since the operability can be much better judged than before.

Adult↗
PubMed1977

Computed tomography of extracerebral hematoma.

The appearance on C.T. of 30 extracerebral hematomas is described. Acute subdural hematomas were seen as bandlike lesions with markedly increased, homogenous density. Epidural hematomas demonstrated a high density and a biconvex, lenticular shape. During the process of liquefaction the density decreases and three hematomas appeared as isodense lesions. The majority of chronic subdural hematomas presented a mildly to moderately decreased, nonhomogenous density, the clearly identifiable inner wall of the lesion being either convex or concave. Subdural hygromas showed a homogeneous, markedly decreased density. Almost all the hematomas caused compression of the homolateral lateral ventricle and displacement of midline structures, particularly of the septum pellucidum. In 60% of the hematomas a dilatation of the contralateral lateral ventricle, predominantly of the posterior part was seen. Acute hematomas presented oedema in varying degrees, in chronic hematomas oedema was usually absent. In the original interpretation extracerebral hematomas were recognized as a lesion on C.T. in 97% (1 false negative result), in 90%, the lesion was correctly diagnosed as an extracerebral hematoma (1 false negative and 2 incorrect). The series contained one false positive C.T. scan and 2 intracerebral hematomas were interpreted incorrectly as subdural hematomas. The review C.T. diagnosis proved to be correct in 100%. C.T. and angiography appeared to have about the same diagnostic accuracy. However, C.T. is a non invasive investigation and it provides valuable additional information with regard to all the intracranial contents. Therefore C.T. should be the method of first choice in the diagnosis of extracerebral hematomas.

Adult↗
PubMed1977

Computed tomography of supratentorial meningioma.

The appearance on C.T. of 28 meningiomas is described. On the plain scan they presented as a rounded, well defined lesion with a high density in 18 cases and a density equal to or lower than brain tissue in 10 cases. The density could be related to certain histologic features as the amount of connective tissue and extracellular water and the presence of psammoma bodies or lipid storage cells. After administration of contrast a homogeneous, markedly increased, sharply marginated density was seen in most meningiomas. Contrast enhancement appeared to be dependent on the vascularity of the tumour. +/- 50% of the cases demonstrated edema grade II or III. On first interpretation 93% of the meningiomas were recognized as a lesion and a tumour (2 false negative) and 79% as a meningioma (2 false negative and 4 incorrect). Only one false positive C.T. scan was encountered. As a screening method R.N. scanning has about the same accuracy as C.T.; in establishing a definite diagnosis angiography equals C.T.; but C.T. is superior as it combines the diagnostic qualities of both methods.

Adult↗
PubMedDate not supplied

The role of venous digital subtraction angiography of the carotid bifurcation in the evaluation of patients with reversible ischemic attacks or stroke.

The diagnostic value of venous digital subtraction angiography (VDSA) was evaluated in 168 consecutive patients with suspected or known atherosclerotic lesions of the internal carotid artery. The VDSA findings were correlated with that of arterial angiography (AA) in 50 patients, yielding a sensitivity of 84%, a specificity of 93% and an accuracy of 89%. Correlation of the results of Doppler with that of AA and VDSA provided support for the reliability of VDSA. Clinical data relevant to the selection of angiographic technique was collected, comparing patients who underwent only VDSA, only AA and VDSA followed by AA. The conclusions of our study are: If the image quality is good a normal VDSA practically excludes the presence of surgical lesions in the internal carotid artery and obviates the need for AA. The presence of therapeutically relevant obstructive disease is reliably detected by VDSA, but the degree of obstruction cannot be determined accurately enough to proceed with cerebrovascular surgery without AA. Patients with ischemic events in the carotid territory who are potential candidates for surgery should undergo VDSA when the non-invasive tests are normal and AA when these tests indicate the presence of a stenosis or occlusion.

Angiography↗