Recent topics related to perinatal fetal ultrasound such as fetal intracranial anatomy, fetal circulation, congenital central nervous system anomaly, intrauterine sonographic assessment of the embryo, and three-dimensional ultrasonography are discussed in this review article.

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この研究は脳循環における第2調波造影法を評価した最初のものである.肺の毛細血管を通るUCA (ultrasound contrast agent) はもともと血液の背景反射を増強するよう考案された.椎骨脳底動脈系でのUCAの使用により描出される小脳動脈の数が増える.Harmonic Imaging (第2調波によるtranscranial color-coded sonography, 2ndTCCS) はUCAのガスバブルが超音波診断に使われる周波数で非常によく反響して発振周波数の調波すなわち倍数波を生じる現象を利用したものである.第2調波ドプラシステムは一つの周波数 (fundamental) を送信しその倍の周波数 (second harmonic, 第2調波) を受信する.組織は基礎波の周波数に反応し, UCAのバブルは基礎波の周波数と第2調波の周波数に反応する.このシステムはUCAから基礎波 (ノイズ) を取り除き第2調波の周波数のみを残しsignal to noise比, signal to tissueのアーテイファクトを減少させる.
Duplexシステム (HP SONOS 2500) に1.8/3.6MHz (第2調波) と2.5MHz (通常) のセクタートランスヂューサをつないで用いた.13人の健康なボランティアにLevovist 6.5ml; 400mg/mLを1mL/sの速度で静注し第2調波および通常のカラーduplex imagingを行った.
2ndTCCSと通常TCCSを比較すると前者では空間分解能が著しく改善し, より多くの小脳の動脈 (35対31) , 分枝, 静脈叢が描出され, blooming artifact (カラー信号の過剰な増強) の持続も著明に減少 (7.9対29.9sec) , 診断上有用な信号増強の持続 (248.5対117.4sec) が増加, しかし倍の受診周波数を用いるたあ最大探査深度は減少 (8.4対9.3cm) した.椎骨動脈・脳底動脈の収縮期血流速度はLevovist静注の通常TCCSではartifactのため著明に上昇するが, 2ndTCCSではUCAなしのTCCSと大体同じ速度を示した.
1.8MHzの基礎周波数を用いてLevovistと2ndTCCSを組み合わせると診断上有用な信号増強の持続が長くなり, 空間分解能が改善され, 椎骨動脈系の診断情報が多くなることが示された.

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頸動脈疾患におけるドプラ超音波を用いた無症候性の塞栓シグナル (ES) の検出の頻度は高く, 疾患の活動性のマーカーとなり, 卒中リスクの高い患者の選択を可能にする.しかし報告によって無症候性ESの検出頻度が異なっており, ESの同定に違ったクライテリアが用いられているのではないかという懸念がある.前回の二つのセンターの間の再現性調査では良好な一致を見たが多数のセンター問の調査は行われていない.ES検出について最近報告を出している九つのセンターの間で国際的な再現性調査が行われた.
各センターは症候性頸動脈狭搾のある六人の患者の中大脳動脈TCD記録のオーデイオドプラ信号をブラインドで解析した.ESを検出した正確な時間を記録した.六つのセンターでは各ESの強度の増加も記録した.観察者間の一致は特別な協定に基づく方法で決められた.七つのセンターは39-55の信号を記録した.しかし一つのセンターは142のESを報告した.観察者間の一致確率は.678であるが, 最多のESを報告したセンターを除くと.791であった.デシベル閾値を導入すると一致確率は著明に上昇した.>7dBのデシベル閾値にすると.902の一致確率となった.大概のセンター問での強度測定は良い相関を示したが必ずしも常にそうではない.15の相関のうち3は有意ではなかった.測定された強度の絶対値はセンター間で40%も違っていた.
結論: 研究報告によってESの頻度が違うのは少なくともある程度はESの同定に異なるクライテリアが用いられていることを反映している.以前に提唱されていたES同定のコンセンサスクライテリアは異なるセンターにおけるES同定の再現性には十分に精確とはいえない.デシベル閾値を用いると再現性が向上し観察者間の一致率の著明な改善が得られる.しかし, 一つのセンターで開発された強度閾値をそのまま他の施設で使うことは出来ない.測定方法が違うので同じ装置が用いられていても同じESで違った強度の値が得られるのである.

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We undertook TCD examination combined with transesophageal echocardiography (TEE) and measurements of hematological markers for coagulation, fibrinolysis and platelet function to clarify the clinical significance of micro-embolic signals derived from the heart. We examined nine patients with prosthetic valves including two with cardioembolic stroke (CE) and 11 CE patients without prosthetic valves. All the patients were receiving anticoagulation therapy at the time of the study. TCD study demonstrated 3-54/30 min micro-embolic signals in six of the nine patients with prosthetic valves, but no signal in those without valve replacement. TEE study demonstrated cavitation phenomenon in eight of the nine patients with prosthetic valves, but in none of the patients without valve replacement. No other findings of TEE or hematological examination were correlated with the frequncy of micro-embolic signals. These results indicate a close relationship between cavitation phenomenon and micro-embolic signals in patients with prosthetic valve. Ordinary anticoagulation (INR: international normalized ratio 2.0-3.0) does not reduce the frequency of micro-embolic signals in patients with prosthetic heart valve. However, very high intensity anticoagulation (INR>3.5) might decrease the frequency of micro-embolic signals. Further studies are necessary to clarify the clinical significance of microembolic signals.

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Transcranial Doppler sonography (TCD) for investigation of the vertebro-basilar (VB) system was performed in one patient with left subclavian artery (LSCA) occlusion and the other with LSCA stenosis before and after axial artery to axial artery bypass. Preoperative Doppler waveforms of the left vertebral artery (VA) of the patient with LSCA stenosis showed transient reversal, whereas the patient with LSCA occlusion showed complete reversal. Increased blood flow in the right VA, suggested by an increased flow velocity, apparently compensated for flow in the left VA. TCD done shortly after the operation revealed that the direction of flow in the left VA was still transiently reversed in both cases. Flow reversal continued to be mild and limited to the end-diastolic or presystolic periods in the patient with LSCA stenosis, whereas the patient with LSCA occlusion showed gradually progressive reversal with the last waveforms being completely reversed.

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Transcranial Doppler sonography is frequently used to monitor cerebral blood flow velocities during open heart surgery. There was little information about Doppler findings in patients with congenital heart diseases and valvular heart diseases.
This study included 12 women and six men, with a mean age of 40.6 years. Two patients had ventricular septal defect, four were diagnosed as having atrial septal defect, and one had both defects. Eleven patients underwent surgical replacement of heart valves. Two underwent aortic valve replacements and two underwent surgery on both the aortic and mitral valves. In seven patients, the mitral valve was replaced because of mitral regurgitation. The maximum, mean, and minimum flow velocities of the left middle cerebral artery (MCA) were measured intraoperatively before and after replacement. In the patients with aortic insufficiency and ventricular septal defect, the mean and diastolic flow velocities were markedly reduced on Doppler recordings before valvular replacement. In the patients with aortic insufficiency, a bisferious pulse was found on the Doppler spectra. In contrast, in the patients with mitral regurgitation and atrial septal defect, the Doppler waveforms showed normal findings preoperatively. In the patients with raised intracranial pressure, a high value of PI and low diastolic flow velocities were found on the TCD spectra. The same findings were sometimes seen in the patients with aortic insufficiency or ventricular septal defect. In patients with mitral insufficiency or atrial septal defect, the Doppler spectra showed no change on the TCD records postoperatively. Spiky contours were detected by Doppler in the patients with valvular heart disease secondary to subacute endocarditis.
It is concluded that TCD could provide an approximation of changes in cerebral blood flow velocity in patients with valvular heart disease and ventricular septal defect.

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Transcranial Doppler (TCD) findings in a neonatal girl with a scalp arteriovenous malformation (AVM) are reported. She was born with a large scalp AVM in the left temporal region, which caused uncontrollable cardiac failure. Preoperative color Doppler showed that the AVM was fed only by the external carotid artery, and that the flow velocity in the left middle cerebral artery (MCA) was lower than that in the right MCA. The left superficial temporal artery was ligated, followed by surgical resection of the AVM 37 days after birth. TCD findings demonstrated a transient rise in the left MCA flow velocity immediately after resection and its subsequent normalization. The pulsatility index of the straight sinus was preoperatively high and became normal after resection. These TCD findings suggested improvement of both the blood flow in the left MCA region and intracranial venous circulation after resection of the AVM. TCD proved to be a noninvasive and useful monitor of neonatal and infantile vascular disorders.

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