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SummaryAim - To correlate the magnetic resonance imaging signal changes observed during interstitial laser photocoagulation (ILP) therapy with histopatho-logical analysis of tissue necrosis. A 1.5T MR system was used. Lesions were produced with a diode laser (805 nm) in the liver of normal Wistar rats at laparotomy under general anaesthesia and imaged during treatment. Seventeen lesions were monitored with a T1-weighted spin echo (T1WSE) sequence, and 15 with a FLASH sequence. Treated tissue was removed and stained for NADPH-diaphorase to determine the extent of devitalization. Per-procedural T1WSE showed an expanding area of low signal which developed a high signal rim as ILP progressed. FLASH imaging showed an expanding area of low intensity which was replaced by a complex region of signal change as treatment progressed. Good imaging-histopathological correlation was shown: for T1WSE, r2=0.88 (P < 0.001) and for FLASH, r2=0.95 (P < 0.001). MR imaging during hepatic ILP accurately shows the extent of tis...

SummaryInterstitial laser photocoagulation (ILP) is currently limited by deficient per-procedural monitoring. The purpose of this study was to evaluate MR control of ILP of hepatic metastases. Twenty-two laser activations were used to treat eight metastases in seven patients under local anaesthesia and sedation. Laser energy was delivered via optical fibres positioned in the tumour under ultrasound guidance. T1-weighted FLASH and spin-echo sequences were used to monitor the procedure. Enhanced CT was performed at 24 h to assess thermal necrosis. FLASH imaging showed an enlarging area of signal change during ILP. The final extent of this correlated closely with the extent of tissue necrosis on CT. Spin-echo imaging was disappointing because of poor contrast between the treated tissue and normal liver/untreated tumour. Per-procedural MR imaging accurately and reliably depicts ILP-induced necrosis. MR control may permit more widespread application of ILP to the treatment of hepatic tumours.

Magnetic resonance imaging (MRI) is showing considerable promise as a monitor for interventional procedures. Laser surgery is “MRI compatible, ” and temperature-sensitive imaging techniques can be usefully applied to these procedures. We have been investigatingT1derived temperature-dependent imaging as a monitor for interstitial laser photocoagulation (ILP) in rat liver.In vitro experiments suggested that temperature calibration may be achieved. We have investigated ILPin vivo using short TR spin-echo imaging sequences taking one set of images every 30 s during and after the procedure. Our resultsin vivo suggest that this simple model may be inadequate for temperature mapping as the biological reaction to the ILP is on a similar time scale to that of the procedure. Nonetheless, MRI shows well-defined, repeatable signal changes that can be related to histological borders.

Background—An obstructive defect is usual in bronchiectasis, but the pathophysiological basis of airflow obstruction remains uncertain. High resolution computed tomographic (CT) scanning now allows quantitation of static morphological abnormalities, as well as dynamic changes shown on expiratory CT scans. The aim of this study was to determine which static and dynamic structural abnormalities on the CT scan are associated with airflow obstruction in bronchiectasis. Methods—The inspiratory and expiratory features on the CT scan of 100 patients with bronchiectasis undergoing concurrent lung function tests were scored semiquantitatively by three observers. Results—On univariate analysis the extent and severity of bronchiectasis, the severity of bronchial wall thickening, and the extent of decreased attenuation on the expiratory CT scan correlated strongly with the severity of airflow obstruction; the closest relationship was seen between decreased forced expiratory volume in one second (FEV1) and the extent of decreased attenuation on the expiratory CT scan (Rs = ‐0.55, p