The introduction of transpulmonary stable echoenhancing agents offer new perspectives for transcranial ultrasound. Improving signal intensity and therefore signal to noise ratio enables to perform Doppler sonography according to established clinical criteria in patients with insufficient acoustic bone window. The complete asessment of the circle of Willis is achievable and the number of non-diagnostic scans is reduced. Echoenhancement also offers new perspectives, increasing the sensitivity of ultrasound scanning for low volume flow as in high grade stenosis, and for low velocity flow as in the cerebral venous system. These improvements support the analysis of vascular pathologies such as stenosis, occlusion, AV malformations, aneurysms and cavernomas. The vascularity of tumors, with low velocity and low flow volume, can be assessed, and new diagnostic opportunities arise from the transcranial analysis of the venous system for thrombosis. Additionally, new approches such as three-dimensional vascular imaging are enabled by the iv. application of echoenhancers. With an excellent safety profile, echoenhancers add to diagnostic capabilities of transcranial Doppler ultrasound, resulting in less non-diagnostic scans, improved accuracy of diagnosis and novel diagnostic opportunities.

抄録全体を表示

The present study was performed to examine the influence of head-up postural change on cerebral circulation in patients with internal carotid artery occlusion (ICAO) . Duplex ultrasonography was used to measure blood flow velocity (FV) and pulsatility index (PI) of the common carotid artery (CCA) in 11 men with unilateral ICAO (aged 63.0±7.2 yr) while they were lying flat, as well as standing up. In addition, the change in cerebral blood flow (CBF) after becoming upright was evaluated using SPECT. No patient showed any sign of orthostatic hypotension. FVs and PI on the nonoccluded side and systolic FV on the occluded side remained unchanged, while mean, end-diastolic (ED) FVs on the occluded side decreased, and the PI on the occluded side increased. Thus, the side-to-side ratio of EDFV (ED ratio) increased in all cases. A decrease in CBF was observed in 7 out of 9 patients when they were standing upright. The degree of the increase in the ED ratio was associated with worsening of hypoperfusion in upright SPECT. Our results suggest that head-up postural change increases the relative resistance of the CCA against the decrease in carotid arterial pressure due to gravity in carotid occlusive disease, and that cerebral dysautoregulation might then occur. Duplex ultrasonography and SPECT are both safe and useful methods for evaluating the hemodynamic influence of head-up postural change on cerebral circulation in such patients, and the upright test is helpful in diagnosing ICAO using Doppler sonography because of the conspicuous laterality of the FVs.

抄録全体を表示

1990年に人工弁患者でmicroembolic signals (MES) が検出されて以来, その臨床的意義については多くの研究がなされてきたが, 未だに結論が得られていない.そこで, 筆者らは多数例で検討するため4施設の人工弁患者580例におけるMESの意義について再解析を試みた.
MESの定義は特徴的な音を呈し, 心周期にランダムに出現し, 背景より3dB以上のintensityを有し, ドプラスペクトラムの一側に出現するものとした.対象患者の1時間あたり一側中大脳動脈で検出されるMESの個数と検出頻度を明らかにするとともに, 年齢, 弁置換後の期間, 弁の種類とサイズ, 心調律, 抗凝血薬療法, および弁置換術3ヵ月以後の神経合併症発現の有無を調査した.
MESの個数と検出頻度を機械弁 (median0個と70.3％) と豚生体弁 (medianO個と26.2％) で比較すると, 機械弁であきらかに高い値を示した (両項目ともp<0.01, Mann-Whitney U test and Chi square test) .とりわけ, Bijork-Shiley monostrut弁 (median133個と92％) とCarbomedics弁 (median8個と81％) が高値を示した.全体として僧帽弁と大動脈弁の二弁置換例の方が一弁置換例よりMESの個数が多く, 一部の弁で僧帽弁置換例と大動脈弁置換例でMESの個数に差があった.しかし, 弁のサイズ, 神経合併症の有無, 心調律, 年齢及び弁置換後の期間とMESの個数や検出頻度には関連性を見いだせなかった.
これらの結果から筆者らは人工弁で見られるMESは人工弁のタイプや部位と関連しており, 直接的な臨床的意義を有さないと結論している.人工弁で見られるMESの本体についてはcavitation bubblesを反映している可能性を考察している.本研究は多数例で人工弁のタイプや部位とMESとの関連性を示した点で優れているが, 多施設で機種の異なる装置を使用し神経症候の責任血管で, もしくは神経合併症出現時にTCD検査が行われていないことと, 抗凝血薬療法の程度とMESとの検討が十分になされていないという問題点も有している.

抄録全体を表示

Activation studies of cerebral circulation are important for evaluation of cerebrovascular reactivity (CVR) . In this study, CVR was investigated in 52 healthy subjects, 25 patients with chronic severe hypertension and 16 patients with hyperlipidemia. All the patients had normal findings of neurological studies, brain CT and neck vessel echo-Doppler. The CVR was assessed by TCD recording of blood flow velocity in the middle cerebral artery (MCAFV) under resting conditions and at 5, 10, 15 and 20 min after i.v. injection of 1g Acz. Additionally, we performed an Acz-activated ¹³³Xe-CT study in 8 healthy patients (16 hemispheres) who had mild carotid stenosis on MR-angiography. The regional cerebral blood flow (rCBF) in the MCA territory was measured and the CVR was also analyzed. MCAFV and CVR determined by TCD study showed a non-significant tendency to be reduced in the group aged over 60 yr. The MCAFV under resting conditions was nearly the same in the normal controls and in the patients with hypertension, but the CVR was decreased in patients even without stroke. The normal value of CVR seemed to be 40-50% in this study. When planning surgical treatment for asymptomatic patients (e.g.; those with occlusive cerebrovascular disease and unruptured cerebral aneurysm) with decreased CVR, they should be treated carefully using prophylaxis for ischemic complications.

抄録全体を表示

剖検や経食道心エコー図検査 (TEE) で大動脈における動脈硬化病変と虚血性脳血管障害との関連性が指摘されて以来, TEEが大動脈における動脈硬化病変の評価に利用されている.しかし, TEEは侵襲的検査法であり, 全ての患者で探触子が挿入できるわけではない.さらに, 上行大動脈の遠位側は気管の走行によりTEEによる評価が困難である.そこで, 筆者らは右鎖骨上窩からBモード法で大動脈における動脈硬化の評価を試み, その所見をTEEと比較した.
右鎖骨上窩からのBモード検査には7.5MHzの周波数を有するlinear型の探触子を, TEEには5-7MHzの可変周波数を有するmultiplane探触子を用いた.お互いの検査所見を知らない異なる検者が20症例で二つの検査を行い, 上行大動脈と大動脈弓部をそれぞれ近位部と遠位部に分けて, 各部位における単純動脈硬化病変 (4mm未満) と複合動脈硬化病変 (4mmを越える) の有無を調べた.
近位上行大動脈ではTEEで8個の単純動脈硬化病変を検出したが, 右鎖骨上窩からのBモード検査ではいずれも検出できなかった.遠位上行大動脈では1つの複合動脈硬化病変が両検査でみられ, 右鎖骨上窩からのBモード検査は単純と複合動脈硬化病変をさらに1ずつ検出した.近位大動脈弓部では両検査で6つの複合動脈硬化病変と5つの単純動脈硬化病変がみられ, さらにTEEはもう1つの複合動脈硬化病変を検出した.遠位大動脈弓部ではTEEが2ずつの単純と複合動脈硬化病変を見いだし, 右鎖骨上窩からのBモード検査が3つの複合動脈硬化病変を見いだした.
以上の結果から, TEEは近位上行大動脈の評価に, 右鎖骨上窩からのBモード検査は遠位上行大動脈の評価に優れており, 右鎖骨上窩からのBモード検査は上行大動脈と大動脈弓部の評価におけるTEEの所見を補う検査法といえるであろうと結論している.

抄録全体を表示

Transcranial Doppler sonography is frequently used to monitor cerebral blood flow during open heart surgery. However, there is little information about cerebral blood flow velocity in patients under hypothermia.
In this study, mean flow velocities (FVs) in the middle cerebral artery (MCA) during the rewarming period were studied in 67 patients. In all cases, cardiac operations were performed with mild hypothermia and non-pulsatile cardiopulmonary bypass. The pump flow was fixed at 2.6 L/m²/min in all patients. MCA blood flow velocity changes on TCD records were compared with nasopharyngeal temperature (NPT) during the rewarming period. At first the patients were divided into two groups; 1) those with occlusive cerebrovascular attacks (CVA) (53 patients), and 2) those without occlusive CVA (14 patients) . In the patients without occlusive CVA, linear regression analysis demonstrated a relationship between NPT and FV of MCA (mean FV=-1.78+1.23 (NPT), R²=0.278) . There were no significant correlations between NPT and mean FV in patients with occlusive CVA. The patients without occlusive CVA were subdivided into two groups according to age (cut-off value, 70 years) . In the patients aged under 70 years (40 patients), there was a close correlation between NPT and mean FV (mean FV=0.211+1.33 (NPT), R² =0.278), whereas in the patients aged over 70 years (13 patients), there was a relationship between them (mean FV=10.80+0.649 (NPT), R² =0.114) . In the patients under 70 years old, there were 21 patients who received coronary artery bypass grafts (CABG group) and 19 who underwent closure of septal defects or replacement of heart valves (non-CABG group) . As in the CABG group, there was a linear correlation between NPT and mean FV (mean FV=5.77+0.911 (NPT), R² =0.290) . Non-CABG patients showed the strongest correlations between these parameters (mean FV= -2.73 + 1.38 (NPT), R²=0.357) .
It is concluded that flow velocity is reduced under hypothermia in proportion to the reduced NPT in patients aged under 70 years. TCD can provide an approximation of changes in cerebral circulation during mild hypothermia.

抄録全体を表示

We have developed a prototype second harmonic/flash echo imaging system for visualizing tissue perfusion. Second harmonic imaging is a new method that exploits the nonlinear properties of microbubble-containing ultrasound contrast agent. In phantom experiments, we obtained excellent harmonic images by eliminating the echoes from tissue-mimicking materials. The hepatic parenchyma was clearly enhanced in animal studies, and myocardial perfusion was visualized in studies using dogs.
Flash echo imaging (FEI) is a new contrast echo imaging technique. In FEI, the strong echoes that are momentarily induced by intermittent ultrasound transmission are detected. The results of our studies indicate that the harmonic mode of FEI is able to visualize microvessels which perfuse organ parenchyma.
The target blood flow can be changed by varying the suspension time for ultrasound transmission. FEI will be expected to visualize the flow rate of perfusion.
Second harmonic imaging and flash echo imaging are expected to expand the capabilities of diagnostic ultrasound systems for visualizing tissue perfusion.

抄録全体を表示