Biomedical subjects
Publications and source records attributed to J M Hawnaur.
Sacrocolpopexy is a surgical procedure that provides effective treatment for pelvic prolapse. The surgical technique and complications of laproscopic sacrocolpopexy are described. This review presents experience of MRI for postoperative assessment and illustrates normal and abnormal findings.
Explore the source record for details and available documents.
AIM: Magnetic Resonance Imaging (MRI) has the potential to assess inguinal lymph nodes more accurately than palpation and less invasively than surgical exploration. The objective of this study was to measure the accuracy of MRI in identifying inguinal metastases by demonstrating abnormal lymph node morphology. MATERIALS AND METHODS: 10 women with vulval malignancy underwent T1- and fat-suppressed T2-weighted surface coil MRI of both groins before surgery. Each groin was prospectively categorised as normal or as having metastatic lymphadenopathy using criteria established in normal volunteers. Histopathological findings in patients undergoing groin dissection for invasive vulval carcinoma were used as validation. RESULTS: MRI had a positive predictive value of 89%, negative predictive value of 91%, sensitivity of 89%, specificity of 91% and accuracy of 90%. The most useful observations on MRI to identify metastatic lymphadenopathy were those of lymph node contour irregularity, cystic change in a lymph node, short axis diameter exceeding 10mm and abnormal long: short axis diameter ratio. CONCLUSION: High resolution MRI of the inguinal regions has potential to screen for lymph node metastases in patients with vulval cancer, with the aim of reducing the number of women who have to undergo groin dissection.
AIM: To evaluate the role of dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) in distinguishing residual or recurrent tumour from radiation change in patients with bladder carcinoma. MATERIALS AND METHODS: Forty patients with biopsy proven bladder carcinoma were imaged before and at 4 and 12 months after radiotherapy (XRT) using conventional and dynamic contrast-enhanced magnetic resonance imaging at 0.5 Tesla. An enhancement of >1.54 times above baseline at 80 s post-contrast injection proved a reliable indicator of tumour before radiotherapy and was therefore applied to the assessment of patients after XRT. Conventional MR images and dynamic enhancement profiles (DEPs) from the site of previous tumour were scored by three radiologists for the presence of tumour at 4 and 12 months after XRT. Findings were compared with cystoscopic biopsy. RESULTS: Dynamic contrast-enhanced magnetic resonance imaging had negative predictive values of 100% and 93% for tumour recurrence at 4 and 12 months, respectively. The positive predictive values, sensitivity and specificity were 48, 100 and 48% at 4 months and 50, 80 and +76% at 12 months post XRT, respectively. CONCLUSION: Dynamic contrast-enhanced magnetic resonance imaging may prove reliable in excluding the presence of persistent or recurrent tumour up to 12 months after XRT.
Pelvic actinomycosis is associated with long-standing use of an intrauterine contraceptive device and may present with clinical signs and symptoms of pelvic malignancy. Diagnostic imaging can confirm the presence of a pelvic mass and tissue infiltration but findings are often non-specific. We present a case of pelvic actinomycosis with tubo-ovarian abscess in which magnetic resonance imaging demonstrated lower signal intensity tissue on T2 weighted sequences than would be typical for pelvic malignancy or infection and was useful in confirming regression of pelvic disease in response to antibiotic therapy.
Endometriosis is a relatively common condition in pre-menopausal women. Rarely, endometrial malignancy may arise in and co-exist with endometriosis. In this case report, the findings on CT and MRI which indicated this development are described. Multiple image-guided biopsies showed features consistent with endometriosis and the diagnosis was not confirmed histopathologically until formal laparotomy and open biopsy.
The objectives of this study were to compare tumour staging and volume assessment by examination under anaesthesia (EUA), transrectal ultrasound (TRU) and magnetic resonance imaging (MRI) in patients with invasive carcinoma of the cervix, and to correlate findings with long-term outcome following treatment by radiotherapy. Tumour staging was performed on 60 patients immediately before starting radiotherapy. Clinicians and radiologists performing EUA, TRU or MRI were blinded to the results of other investigations. Tumour stage and dimensions were recorded prospectively for each technique, and analysed for concordance. The relationship between pre-treatment stage, size of tumour and patient outcome after radiotherapy was assessed, using clinical status 5 years after treatment as the truth measure. EUA, TRU and MRI assigned the same tumour stage in only 30% of patients and EUA and MRI agreed tumour stage in a further 27%. In cases of disagreement, the MRI stage correlated better with outcome than the TRU or EUA stage. There was a significant difference between tumour volume obtained from measurements made on MRI and those from TRU. 62% of patients with enlarged lymph nodes on pre-treatment MRI either died, or developed tumour recurrence or metastases. The ability of MRI to assess the full extent of bulky tumours and the presence of lymph node enlargement was an advantage over both EUA and TRU in identifying patients with a poor prognosis.
Recurrent tumour and post-treatment inflammatory masses may be difficult to differentiate on T2 weighted and post-contrast T1 weighted MR sequences. The purpose of this study was to assess the value of quantitative analysis of enhancement patterns in improving the separation of tumour recurrence from benign post-treatment masses in the pelvis. 32 patients with a total of 44 benign or malignant pelvic masses arising more than 6 months after treatment by surgery and/or radiotherapy were studied. After localizing the lesion on T1 and T2 weighted sequences, sequential T1 weighted spoiled gradient recalled echo (SPGR) images were obtained through the mass during bolus intravenous injection of 0.1 mmol kg-1 of Gd-chelate. Analysis of the maximum enhancement and proportion of maximum enhancement by 30, 60 and 90 s after onset of injection was performed prospectively by radiologists using standard manufacturer's software. Semi-automated analyses using software to provide irregular regions of interest and automated signal intensity measurements were also performed. Maximum enhancement was significantly greater in tumour recurrence than fibrosis following surgery, with better separation between the two groups using computer assisted analysis (p < 0.001) than manual analysis (p < 0.05). Separation between post-radiotherapy tumour recurrence and benign post-radiotherapy masses reached statistical significance for manual measurements of maximum enhancement (p < 0.05) but not for computer assisted analysis. There was no significant difference in enhancement rates between benign and malignant masses in post-radiotherapy patients. Measurement of the maximum enhancement of a mass alone does not reliably separate lesions in the post-radiotherapy patient but may be helpful when considered together with signal intensity and morphology on conventional MRI sequences.
The use of on-resonance 121 binomial composite pulses in two- or three-dimensional magnetization-prepared gradient-recalled echo magnetic resonance imaging experiments generates rotary echoes, leading to an increase in contrast range that is, in part, determined by the ratio of T2 to T1. In comparison with other fast gradient-recalled echo imaging techniques designed for enhanced T2 contrast, this method is more robust with respect to radiofrequency field inhomogeneity and less sensitive with respect to motion artifacts. Three-dimensional parametric images may be calculated using least-squares fitting based on a simple model for steady-state longitudinal magnetization during the imaging sequences.
PURPOSE: To define the appearance of peripheral vascular malformations at magnetic resonance angiography (MRA) and assess the role of magnetic resonance imaging (MRI) and MRA in the investigation of these lesions. PATIENTS AND METHODS: Fourteen patients (aged 8-51 years) with clinical evidence of a vascular malformation were referred for MRI and MRA, performed on a 0.5T GE Vectra superconducting system (International General Electric, Slough, UK). Multisection T1-weighted spin-echo and T2-weighted fast spin-echo pulse sequences were performed, with an inversion recovery fast spin-echo sequence in two cases. Two-dimensional time of flight (2-D TOF) and/or 2-D phase contrast (PC) MRA was performed in 13 cases. Eleven patients had digital subtraction angiography (DSA) using a Phillips Integris V3000 digital angiographic unit. The findings at MRA and MRI were compared with the catheter angiograms, and the effective diagnostic input of MRA and MRI was determined. RESULTS: MRA demonstrated major feeding vessels and multiple intra-lesional vessels in relation to the high flow lesions, features absent in the low flow lesions. However, small feeding vessels to the AVMs were not clearly identified. MRI gave a clear demonstration of the anatomical extent of all lesions. AVMs (n = 6) and venous malformations (n = 6) were reliably distinguished, the former containing multiple serpentine signal voids on T1- and T2-weighted imaging, the latter being hyperintense to fat on T2-weighted images. Two other high-flow lesions diagnosed clinically as vascular malformations appeared solid on MRI, and were diagnosed histologically as a carotid body tumour and an angiomyolipoma. CONCLUSION: Although 2-D TOF MRA can distinguish AVMs from venous malformations, the technique adds little extra practical information to the diagnostic process, and cannot compete with catheter angiography for the detailed demonstration of AVM feeding vessels. These lesions can also be characterized using spin-echo sequences, though the primary role of MRI is to demonstrate their anatomical extent.
Explore the source record for details and available documents.
Skin tumors were staged at magnetic resonance (MR) imaging on a 0.5-T (middle-field-strength) system, with use of a 2-cm-diameter receive-only surface coil. T1- and T2-weighted spin-echo (SE), fast SE, or three-dimensional (3D) spoiled gradient-recalled imaging were performed in three volunteers and in 13 patients with skin tumors (nine, basal cell carcinoma). MR findings correlated well with histologic findings in the patients (epidermis, relatively hyper-intense on all images; dermis, hypo-intense with irregular interface with subdermal fat). 3D images had the optimal combination of tissue contrast, signal-to-noise ratio, and spatial resolution. MR imaging depicts depth of skin tumor invasion, and findings are complementary to clinical staging.
The use of iron oxide as a superparamagnetic contrast agent for magnetic resonance imaging of the liver has been described previously. When administered intravenously, superparamagnetic iron oxide (SPIO) is sequestered by the reticuloendothelial system causing significant shortening of the T2-relaxation time. The majority of the contrast is taken up by the reticuloendothelial tissue of the liver. Since tumours have reduced or absent reticuloendothelial tissue the effect on relaxation time is minimal and signal intensity differences between tumour and liver are increased. AMI 25 (Laboratoire Guerbet, Paris) is a colloidal solution of ferrous and ferric oxides. We have performed MR examination of the liver in 16 patients with focal liver lesions using AMI 25 as a superparamagnetic contrast agent. Our results indicate that SPIO significantly increases the conspicuity of focal lesions and the effect is greatest in malignant tumours. We observed no adverse reaction to this contrast agent.
A new method of acquiring two-dimensional (2D) and three-dimensional (3D) fat/water decomposed images on a 0.5 T magnetic resonance (MR) imaging system is described. The method uses a gradient-recalled echo (GRE) sequence incorporating a composite 121 pulse, originally used for magnetization transfer contrast (MTC) experiments, for frequency-selective pre-saturation. By applying the 121 pulse off resonance, a sharp discrimination between the chemically shifted water and fat signals may be obtained using a composite pulse as short as 4 ms. Phantom studies demonstrate that suppression ratios as high as 50:1 are achievable. The new method has been applied to volunteers and patients, and good fat/water images of limb, abdomen, head and neck obtained. The new method can be incorporated into other pulse sequences related to GRE, such as phase contrast (PC) and time-of-flight (TOF), and represents the first practical (i.e. rapid) method for 3D fat/water imaging at an operating field as low as 0.5 T.
Pre-operative magnetic resonance imaging (MRI) was carried out in 50 women scheduled for operative treatment of invasive carcinoma of the cervix. The extent of the primary tumour (stage), its dimensions and the presence of lymph node enlargement were assessed and compared with findings at surgery and/or histopathological examination of the resected uterus. In 45 patients undergoing radical hysterectomy, accuracy of MRI staging of the primary tumour was 84.4%. In the group as a whole, including four patients with inoperable disease, staging accuracy was 84%. Most errors were due to difficulty in identifying early vaginal or parametrial invasion by tumour. There was close correlation between the volume of tumour measured from pre-operative MRI scans and measurements made on the hysterectomy specimen (r = 0.95). MRI had a sensitivity of 75% and a specificity of 88% in predicting metastatic lymphadenopathy, based solely on the criterion of enlargement of any pelvic or para-aortic nodes to 1.5 cm or greater. However, retrospective analysis of the presence or absence of metastases by site in 49 patients undergoing lymphadenectomy or lymph node sampling at laparotomy showed that true sensitivity to be 57.1% and the specificity 96.8%. Differentiation between malignant and reactive lymphadenopathy was not reliably achieved on MRI, and in several patients, metastases were present in normal-sized lymph nodes.
Fast spin echo (FSE) sequences enable T2-weighted MR scans to be obtained in a fraction of the time necessary for conventional SE sequences with long TR and long TE. Comparison has been made of a FSE sequence (TR = 4000 ms, effective TE = 100 ms, 2 NEX) with the T2-weighted SE sequence (TR = 2000 ms, TE = 90 ms, 1-2 NEX) normally used in 35 patients referred for cranial MRI. Contrast-to-noise ratios (CNR) for grey:white matter and brain:CSF on the FSE sequence compared favourably with variable echo (VE) sequences which take up to three times as long to acquire. Although the conspicuity of some pathological lesions such as multiple sclerosis plaques was inferior to that of conventional T2-weighted SE scans, no lesions were missed on FSE scans. The FSE sequence was more prone to movement artefacts. The benefit of the markedly increased patient throughput made possible by using the FSE sequence outweighs the slight reduction in sensitivity for small lesions.
Image synthesis methods are based on the hypothesis that a magnetic resonance (MR) image with optimized contrast can be reproduced by synthesis from three calculated basic images of T1, T2 and spin density. This method, however, is limited by noise due to uncertainties in the initial measurements. The principal component analysis (PCA) method is based on an information theory approach that decomposes MR images into a small set of characteristic feature images. PCA images, or eigenimages, show morphology by condensing the structural information from the source images. Eigenimages have also been shown to improve contrast-to-noise ratio (CNR) compared with source images. In this study we have developed a method of synthesizing MR images using a flexible model, comprising a set of eigenimages derived from PCA. A matching process has been carried out to find the best fit between the model and a synthetic image calculated from the Bloch equations. The method has been applied to MR images obtained from a group of patients with intracranial lesions. The images derived from the flexible model show increased lesion conspicuity, reduced artefact and comparable CNR to the directly acquired images while maintaining the MR characteristic information for diagnosis.
Explore the source record for details and available documents.