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Fig. 17.4. Baseline SPECT imaging in a patient with bilateral carotid occlusions and symptomatic left hemispheric ischemic spells, demonstrating normal and symmetric uptake bilaterally. SPECT imaging in the same patient after acetazolamide administration, demonstrating decreased left hemispheric uptake. The patient was treated with left-sided STA-MCA bypass surgery. SPECT, single photon emission computed tomography; STA, superficial temporal artery; MCA, middle cerebral artery.

Fig. 17.4. Baseline SPECT imaging in a patient with bilateral carotid occlusions and symptomatic left hemispheric ischemic spells, demonstrating normal and symmetric uptake bilaterally. SPECT imaging in the same patient after acetazolamide administration, demonstrating decreased left hemispheric uptake. The patient was treated with left-sided STA-MCA bypass surgery. SPECT, single photon emission computed tomography; STA, superficial temporal artery; MCA, middle cerebral artery.

sacrifice, such as the repair of giant aneurysms of the cavernous internal carotid artery. In these instances, pre-operative trial balloon occlusion is a useful qualitative tool in assessment of adequacy of collateral cerebral blood flow. We perform trial balloon occlusion in the interven-tional neuroradiology suite, according to the following protocol: A baseline activated clotting time (ACT) is determined, and the patient receives 5,000-8,000 units of intravenously administered heparin. Serial ACTs are obtained throughout the procedure, and additional heparin is given as needed to maintain the ACT approximately two-and-a-half times the baseline value. A 5.0 French double lumen balloon catheter is placed in the cervical segment of the internal carotid artery and slowly inflated until the artery is occluded. Occlusion is maintained for 30 minutes, during which time the patient is closely monitored for any change in neurologic function. During the period of trial occlusion, the patient's blood pressure is lowered pharmacologically to decrease the mean arterial pressure 20 mmHg from baseline. The collateral circulation through the circle of Willis to the vascular territory to be occluded is assessed during the period of balloon occlusion by obtaining digital subtraction angiograms of the contralateral carotid artery, the ipsilateral external carotid artery and the dominant vertebral artery. Pre- and post-balloon occlusion radioactive xenon CBF measurements are also obtained

(see details below in section on 133Xe intraoperative monitoring). In addition, 99Tc-ECD is injected intravenously during the period of trial occlusion, and a cerebral perfusion SPECT scan is obtained after the patient leaves the angiography suite. Development of a neurological deficit, a CBF decline of approximately 30%, or a CBF measurement of less than 25 ml/ 100 g/min is considered a failed trial balloon occlusion.

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The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

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