Patient safety issues in magnetic resonance imaging: state of the art

The presence of a static magnetic field (Bo), a radiofrequency field (RF), a dynamic gradient which varies in time and loud noises during an MR examination could increase patient risk. Specifically, a magnetic field could interfere with ferromagnetic material leading to one of the following five dangerous interactions: 1) projectile effect, 2) twisting, 3) burning, 4) artefacts and 5) device malfunction. The projectile effect is when an object is attracted by the magnet with the risk, as reported in literature, of hitting the patient, operators and/or the instrument. Objects which typically can undergo this effect are oxygen and helium cylinders, IV stands, cleaning trolleys, chairs, lamp holders, scissors, forceps, clampers, traction weights, monitoring instruments, and especially metallic splinters within the patient. Twisting (torsion) typically occurs with cerebral vascular clamps and cochlear implants. If parts of implants are involved a malfunction may result. Burns can be caused when electrically conductive material is introduced within the magnet, for example, ECG electrodes, monitoring cables and coils which are in contact with the patient's skin, as well as tattoos and eye-liners that contain iron-oxides. Artefacts can be induced by RF emission of implanted devices which can be mistaken for noise of the receiving coil. Implanted devices can induce signal voids which mask or simulate pathologies. Electrical or mechanical malfunction of implanted devices includes pacemakers which can stimulate inappropriately or at an elevated frequency yielding a distorted ECG with altered T-waves. The risk for patients can be reduced by specific educational programs within individual radiology departments which include other specializations and external referring physicians with the aim of developing a standardized safety protocol.

MRI Post-vertebroplasty

PURPOSE

Percutaneous vertebroplasty (PVP), first described by Hervè Deramond in 1984, is an interventional procedure for the treatment of aggressive vertebral angioma. The aim of this study was to evaluate magnetic resonance imaging (MRI) patterns in the affected vertebrae before and after vertebroplasty by determining changes in signal intensity and size and distribution of bone cement within the vertebra at follow-up carried out at 1 week, 6 months and 12 months.

MATERIALS AND METHODS

Fourteen patients were examined using MRI, for a total of 41 treated vertebrae; MRI was performed with a 0.5-Tesla (T) superconductive magnet (SIGNA GE).

RESULTS

MRI patterns following vertebroplasty are mainly characterised by the signal produced by the areas surrounding the cement and by the cement itself. There is little effect on the size of the treated vertebra. Acrylic cement appears as an intraspongy focal area of T1 and T2 hypointensity that is mostly oval (34%) or rounded (26.8%); this appearance tends to become stable 6 months after treatment. The area surrounding the cement appears hypointense on T1 and hyperintense on T2, a likely expression of bone marrow oedema; this signal alteration tends to disappear gradually.

CONCLUSIONS

In pre- and post-vertebroplasty imaging, MRI is regarded as the reference standard for correct evaluation of both container and content. Awareness of cement changes over time and of the reaction of the surrounding bone tissue is crucial for correct assessment of post-vertebroplasty images.

3.0-T morphological and angiographic brain imaging: a 5-years experience

Ever since the introduction of magnetic resonance (MR), imaging with 1.5 Tesla (T) has been considered the gold standard for the study of all areas of the body. Until not long ago, higher-field MR equipment was exclusively employed for research, not for clinical use. More recently, the introduction of 3.0-T MR machines for new and more sophisticated clinical applications has resulted in important benefits, especially in neuroradiology. Indeed, their high gradient power and field intensity (3.0 T) allow adjunctive and more advanced diagnostic methodologies to be performed with excellent resolution in a fraction of the acquisition time required with earlier machines. The purpose of this paper is to illustrate the distinctive semeiological characteristics of 3.0-T morphological and angiographic brain imaging compared with lower-field systems and highlight the respective advantages and drawbacks based on the experience gained in the first 5 years from the installation of a 3.0-T magnet.

Consensus conference on the stapled transanal rectal resection (STARR) for disordered defaecation

An international working party was convened in Rome, Italy on 16-17 June, 2005, with the purpose of developing a consensus on the application of the circular stapling instrument to the treatment of certain rectal conditions, the so-called Stapled Transanal Rectal Resection (STARR). Since the procedure has been submitted to only limited objective analysis it was felt prudent to hold a meeting of interested individuals for the purpose of evaluating the current status and to make conclusions and recommendations concerning the applicability of this new approach.

Magnetic resonance of the breast: correlation between enhancement patterns and microvessel density in malignant tumors

The continuous growth of a solid tumor is contingent upon the induction and formation of new vascular structures (angiogenesis). Several studies have established a close correlation between the microvessel density (MVD) of a tumor and its growth capacity. Therefore, a non-invasive method to accurately assess tumor MVD in vivo would be clinically useful. We studied 20 consecutive patients (age range: from 39 to 78 yrs; average age: 58.9 yrs), with malignant breast neoplasms using dynamic MR examinations with a paramagnetic contrast agent and post-operative pathological evaluation. We found that the differences in dynamic MRI enhancement are a direct consequence of microvascular distribution within the neoplasm. This study did not yield a statistically significant correlation between high microcirculation neo-formation and high aggressiveness of the neoplasm, but did indicate that further studies with a larger study populations are necessary.

Maximum intensity projection analysis in magnetic resonance of the breast

The aim of this study was to determine the sensitivity, specificity and accuracy of vascular asymmetries and vessel location seen using MR Maximum Intensity Projection imaging for malignant and benign lesions. We enrolled 101 women, with an age ranging from 29 to 69 years (mean age of 53.1 years), with a mammary nodule and candidate for surgical intervention. MR was carried out using a 1.5 Tesla superconductive magnet, equipped with a double and bilateral Phased Array dedicated coil. All images obtained were processed using MIP. The relationship between an asymmetry due to a greater amount of vascular structures in the breast with a malignant neoplasm and symmetry with benign neoplasms were statistically significant (p < 0.001): sensitivity of 71.8%, specificity 100% and accuracy 76.2%. The relationship between perilesional or intralesional vessels with malignant versus benign neoplasms were statistically significant (p < 0.001): sensitivity 88.5%, specificity 82.6% and accuracy 87.1%. We concluded that asymmetries between breasts and the presence of perilesional or intralesional vessels seen in MIP images are important signs and, therefore, must be reported.

The Italian multi-centre project on evaluation of MRI and other imaging modalities in early detection of breast cancer in subjects at high genetic risk

This report presents the preliminary results of the first phase (21 months) of a multi-centre, non-randomised, prospective study, aimed at evaluating the effectiveness of contrast-enhanced magnetic resonance imaging (MRI), X-ray mammography (XM) and ultrasound (US) in early diagnosis of breast cancer (BC) in subjects at high genetic risk. This Italian national trial (coordinated by the Istituto Superiore di Sanità, Rome) so far recruited 105 women (mean age 46.0 years; median age 51.0; age range 25-77 years), who were either proven BRCA1 or BRCA2 mutation carriers or had a 1 in 2 probability of being carriers (40/105 with a previous personal history of BC). Eight cases of breast carcinomas were detected in the trial (mean age 55.3 years, median age 52.5; age range 35-70 years; five with previous personal history of BC). All trial-detected BC cases (8/8) were identified by MRI, while XM and US correctly classified only one. MRI had one false positive case, XM and US none. Seven "MRI-only" detected cancers (4 invasive, 3 in situ) occurred in both pre- (n = 2) and post-menopausal (n = 5) women. With respect to the current XM screening programmes addressed to women in the age range 50-69 years, the global incidence of BC in the trial (7.6%) was over ten-fold higher. The cost per "MRI-only" detected cancer in this particular category of subjects at high genetic risk was substantially lower than that of an XM-detected cancer in the general women population. These preliminary results confirmed that MRI is a very useful tool to screen subjects at high genetic risk for breast carcinoma, not only in pre-, but also in post-menopausal age, with a low probability of false positive cases.

Complications after stapled hemorrhoidectomy: can they be prevented?

Stapled hemorrhoidectomy (SH), a new approach to the treatment of hemorrhoids, removes a circumferential strip of mucosa about four centimeters above the dentate line. A review of 1,107 patients treated with SH from twelve Italian coloproctological centers has revealed a 15% (164/1,107) complication rate. Immediate complications (first week) were: severe pain in 5.0% of all patients, bleeding (4.2%), thrombosis (2.3%), urinary retention (1.5%), anastomotic dehiscence (0.5%), fissure (0.2%), perineal intramural hematoma (0.1%), and submucosal abscess (0.1%). Bleeding was treated surgically in 24%, with Foley insertion 15%; and by epinephrine infiltration in 2%; 53% of patients with bleeding received no treatment and 6% needed transfusion. One patient with anastomotic dehiscence needed pelvic drainage and colostomy formation. The most common complication after 1 week was recurrence of hemorrhoids in 2.3% of patients, severe pain (1.7%), stenosis (0.8%), fissure (0.6%), bleeding (0.5%), skin tag (0.5%), thrombosis (0.4%), papillary hypertrophy (0.3%) fecal urency (0.2%), staples problems (0.2%), gas flatus and fecal incontinence (0.2%), intramural abscess, partial dehiscence, mucosal septum and intussusception (each <0.1%). Recurrent hemorrhoids were treated by ligation in 40% and by Milligan-Morgan procedure in 32%. All hemorrhoidal thromboses were excised. Anal stenoses were treated by dilatation in 55% and by anoplasty in 45%. Fissure was treated by dilatation in 57%. Most complications (65%) occurred after the surgeon had more than 25 case experiences of stapled hemorrhoidectomy. The most common complication in the first 25 cases of the surgeon's experience was bleeding (48%). Even though SH appears to be promising, we feel that a multicenter randomized study with a long-term follow-up comparing SH and banding is necessary before recommending the procedure. Most complications can be avoided by respecting the rectal wall anatomy in the execution of the procedure.

Stapled mucosal prolapsectomy for haemorrhoidal prolapse with Lone Star Retractor System

This technical note presents a variation of the stapled mucosal prolapsectomy for haemorrhoidal prolapse using the Lone Star Retractor. Our experience highlights the simplicity and usefulness of the technique which is based on the complete eversion of the prolapse carried out by the Lone Star Retractor, without using any kind of proctoscope and without stretching the anal sphincters. Postoperatively, rectal bleeding occurred in 4.7% of 127 cases, 9.8% of the patients complained of faecal urgency and only 3.9% had severe anal pain. None had faecal incontinence. This method simplifies the making of the purse-string suture as well as the use of the suturing device and achieves satisfactory clinical results.

[Magnetic resonance angiography of the peripheral vessels with automatic moving bed infusion tracking]

PURPOSE

To investigate the actual diagnostic reliability of the Mobitrack technique with a slow intravenous infusion of paramagnetic contrast agent (CA) in MR Angiography of the peripheral arterial district.

MATERIAL AND METHODS

Twelve healthy volunteers (mean age: 34) with no personal or family history of peripheral arterial pathologic conditions, underwent MR Angiography of the peripheral vascular district. A 1.5 T superconductive magnet equipped with automatic table feed was used. In the preliminary phase, the circulation time at the abdominal aorta was optimized and customized for each patient. This was done by performing a pre-targeting Fast Field Echo 2D (FFE 2D) sequence with intravenous administration of 1-2 mL CA by an injector, to evaluate the delay time. A 2D Time of Flight (2D TOF) sequence was then performed for topographic purposes. The partially overlapping volumes were acquired using Fast T1-weighted sequences, intravenous CA administration and an automatic table feed of 10 mm/s. A Fast Field Echo 3D (FFE 3D) T1-weighted sequence with TR/TE/FA: of 6.3/1.6/40 degrees and a slice thickness of 1.5 mm were also performed. Thirty to forty mL CA were slowly administered intravenously at a rate of 0.3-0.6 mL/s. Two blinded readers independently evaluated the images giving one of three diagnostic judgements: 1) arteries were well visualized, 2) heterogeneous arteries with(out) the presence of veins, and 3) arteries seen poorly or not at all. The first two judgements were considered diagnostic. The readers considered 19 different anatomical districts for each patient, giving a total of 190 evaluations.

RESULTS

A blinded evaluation of the readers judgements did not indicate a statistically significant difference (agreement: 100%). Overall, 82% of the images were rated as 1, 8.5% as 2 and 8.4% as 3.

DISCUSSION

In 174/190 judgements the vessels were rated as 1 or 2, that is of diagnostic value. Judgement 3 was always due to the inability to visualize the medial and/or distal third of the arterial circulation of the leg.

CONCLUSIONS

The results of this technique optimization study confirm the overall validity of the Mobitrack technique. However they also indicate that further technical advances are required to ensure maximum diagnostic accuracy in this vascular district.

[NMR cholangiography in the diagnostic algorithm of candidates to video laparocholecystectomy]

BACKGROUND

High resolution magnetic resonance cholangiopancreatography (MRCP) is a non invasive imaging modality for depicting the pancreatobiliary tree. It can demonstrate dilation, stenosis and intraductal filling defects of both the biliary and the pancreatic duct. The imaging quality of high resolution MRCP is excellent. MRCP appears to be more effective and less invasive than endoscopic retrograde cholangiopancreatography (ERCP) to evaluate many pancreatic and biliary diseases as choledocholithiasis, malignant obstruction, incomplete or failed ERCP, postsurgical alterations of the biliary tract (as biliary-enteric anastomoses), sclerosing cholangitis, chronic pancreatitis, and congenital anomalies of the biliary and pancreatic duct.

METHODS

MRCP was performed in 21 non selected patients with suspected choledocholithiasis and demonstrated the presence of stones in the biliary tract in 5 of them. In these 5 patients sequential endoscopic-laparoscopic treatment was performed and confirmed in all cases the presence of stones in the biliary tree. Laparoscopic cholecystectomy (VLC) and transcystic cholangiography was attempted in the restant 16 patients.

RESULTS

Laparoscopic transcystic cholangiography confirmed in all cases the response of MRCP.

CONCLUSIONS

MRCP has the potential to replace ERCP in the management of patients candidate to VLC with suspected choledocholithiasis.

MRI T-staging of laryngeal tumours: role of contrast medium

Our aim was to evaluate the relative diagnostic accuracy of MRI without contrast medium and MRI before and after contrast medium in the assessment of T-staging of laryngeal tumours. We studied 25 men (mean age 51.8, range 41-61) with laryngeal squamous cell carcinomas, using Spin-echo (SE) T1-weighted and fast SE T2-weighted sequences. The T1-weighted sequences were then repeated after gadolinium-diethylene-triaminepenta-acetic acid (Gd DTPA) 0.1 ml/kg. All patients then underwent biopsy and surgery. Two radiologists independently assessed the anonymised images by filling-out two multiple-choice forms, one for each technique, at a 2 week interval. The forms included a judgement concerning tumour identification and infiltration of the anterior commissure, supraglottic region, arytenoid cartilage, Morgagni's ventricle, paraglottic space, thyroid and cricoid cartilages, thyro-hyo-epiglottic space, vocal cords, subglottic region, and epiglottis. Similar forms were filled out by the surgeon and the pathologist after surgery. The sensitivity, specificity and diagnostic accuracy of MRI were unaffected by the use of contrast medium. Since it did not provide additional staging information, its continued routine use in these cases is not justified.

Contrast-enhanced MR angiography (CE MRA) in the study of the carotid stenosis: comparison with digital subtraction angiography (DSA)

PURPOSE

To determine sensitivity, specificity and diagnostic accuracy of contrast-enhanced magnetic resonance angiography (CE MRA) compared to digital subtraction angiography (DSA) in the study of carotid stenosis.

METHODS AND MATERIAL

We studied 23 patients with suspected cerebro-vascular insufficiency by carotid stenosis. Diagnostic examinations by means of CE MRA and DSA were carried out within 24 hours of each other. A 1.5 T superconductive magnet (Signa-General Electric) was used for CE MRA. This technique was performed using a fast spoiled gradient echo recalled (SPGR) sequence acquired in coronal plane 13 sec after injection of contrast medium. Imaging parameters were: TR/TE/FA 8 msec/1 msec/60 degrees, matrix 256 x 128, 1 excitation, FOV 18 x 13 cm, 28 slices per slab, slice thickness of 1 mm, acquisition time of 32 sec. The post-processing was performed using maximum intensity projection (MIP) and targeted MIP. For DSA examinations a Politron 1000 VR unit (Siemens) was used.

RESULTS

In the identification and quantification of lesions, CE MRA showed values of 100%. In particular, in comparison to DSA, CE MRA was accurate in diagnosing all true negative and positive cases. The location of stenosis evaluated with CE MRA agreed in all cases with DSA.

CONCLUSION

In our experience CE MRA proved to be a very valuable technique in diagnosing carotid stenosis, showing the same diagnostic accuracy as DSA. In this way CE MRA appears to be a substantial alternative technique to conventional MRA and other non-invasive diagnostic methods.

High-resolution magnetic resonance angiography of the internal carotid artery: 2D vs 3D TOF in stenotic disease

The aim of this study was to compare high-resolution 2D TOF with high-resolution 3D TOF in the study of internal carotid artery disease. Sixty-four patients with clinical signs of cerebrovascular insufficiency were studied with a superconductive 1.5 T magnet using two techniques: 2D and 3D TOF. Digital subtraction angiography (DSA) was the gold standard. The 2D TOF technique was performed using the following parameters: TR/TE/FA/MA 49 ms/9 ms/60 degrees/512 x 256; the 3D TOF was performed with the following parameters: TR/TE/FA/MA 50 ms/8 ms/20 degrees/512 x 256. The 2D TOF agreed with DSA in 116 of 128 diagnostic judgments (90%) and overestimated seven times. The 3D TOF technique agreed with DSA in 125 of 128 diagnostic judgments (97%) with one overestimation and two underestimations. There was no statistically significant difference (P < 0.05) between the two different techniques. Our study confirms the high reliability of the methodology carried out with the high-resolution 2D and 3D technique.

[Phantom rectum after Miles' operation]

The authors observed symptoms relating to the existence of a phantom rectum, a phenomenon about which little is still known, in 233 cases (32.1%) in a series of 724 patients undergoing amputation of the abdomino perineal rectum due to malignant neoplasm. The genesis of this phenomenon is attributed to an abnormal reactivity of the cortical and thalamic projection areas with greater response to stimuli from the stump or aspecific visceral stimuli, or even stimuli from the adjacent cortical regions. The psychodynamic aspects linked to the patient's need to develop a different body awareness should not be underestimated; this has to integrate a new anatomic reality, such as colostomy in the place of the anorectum, entailing the relinquishment of the previous body scheme. Prevention and treatment of phantom rectum, which is painful in 27% of cases, is essential for a correct operating technique, adequate psychotherapeutic support, the patient's active participation in a reeducation programme for colostomy management. It should not be forgotten that painful phantom rectum, especially with late onset, may be diagnostically significant as an indicator of the recurrence of neoplastic pathology, sometimes allowing diagnosis to be anticipated by several months. This underlines the importance of carrying out a careful postoperative clinical, biohumoral and radiological control in these patients, including pelvic CT. In the authors' experience of 233 patients suffering from phantom rectum, it was possible to document the presence of neoplastic recidivation in 30 cases (12.8%) using pelvic CT. In these cases, symptoms appeared after a disease-free interval of 26.3 months (range 3-75 months), whereas the presence of phantom rectum without recidivation is usually described in the first 2 months after surgery.

MR angiography in carotid stenosis: a comparison of three techniques

PURPOSE

To compare the accuracy of three different magnetic resonance angiography (MRA) techniques for studying steno-occlusive disease of carotid arteries.

METHODS

64 patients were evaluated with three MRA techniques- three-dimensional (3D) time-of-flight (TOF), two-dimensional (2D) TOF, and 3D Phase-Contrast (PC); the acquisition was in the axial plane, the volume included the carotid bifurcation. Digital subtraction angiography (DSA) was considered the 'gold standard'. The MRA images were reprojected with a maximum intensity pixel ray-tracing (MIP) algorithm. The three MRA techniques were blindly graded as normal, mildly stenotic (0-29%), moderately stenotic (30-49%), severely stenotic (70-99%), or occluded.

RESULTS

DSA provided 128 diagnostic judgments: 92 were negatives and 36 positives. 2D TOF was in agreement with angiography in 116 of 128 cases (90%), but overestimated the results in seven cases and underestimated in five cases. 3D TOF agreed with angiography in 125 of 128 cases (97%), with one overestimation and two under estimations. 3D PC was concordant in 116 of 128 cases (90%), overestimating in six cases, underestimating in six cases. The sensitivity, specificity and diagnostic accuracy for 2D TOF was, respectively 84%, 94%, and 92%, while for 3D TOF was 94%, 100%, and 98%, and for 3D PC 86%, 98%, and 95%. The comparison of the three different MRA techniques provided no statistically significant difference (Friedman test P < 0.05).

CONCLUSION

The high degree of diagnostic accuracy of MRA found in the study of the steno-occlusive disease of the carotid arteries confirms the high degree of reliability of this methodology carried out with the 3D TOF technique, compared to 2D TOF and 3D PC.

Pulmonary veins: magnetic resonance angiography anatomy

OBJECTIVE

to optimize magnetic resonance angiography technique for the selective study of the anatomy of pulmonary veins.

MATERIALS AND METHODS

twenty consecutive patients (13 males and seven females; mean age 30.5 years) prospectively studied were enrolled. Magnetic resonance angiography was performed using a 1 T superconductive magnet and three dimensional time of flight technique (3D TOF). Imaging with steady-state free precession sequence during intravenous infusion of contrast medium (Gd DTPA 0.2 mmol kg(-1)) administration was employed using the following parameters: FA 20 degrees, TR 58 ms, TE 6 ms, MA 192 x 256, NEX 1, slice thickness 4 mm and slice orientation on the Z and Y planes.

RESULTS

in the right lung magnetic resonance angiography well visualized 124 venous vessels on the coronal plane versus 106 venous vessels on the sagittal plane, whereas in the left lung magnetic resonance angiography visualized 96 vessels on the coronal plane versus 44 visualized on the sagittal plane. Our data suggest that 3D time of flight with contrast medium is a promising evaluation technique for pulmonary veins, and that combined evaluation of acquisitions on coronal and sagittal planes allows the visualization of a higher number of venous vessels.

CONCLUSION

3D time of flight with contrast medium and without breath-hold permits to visualize a venous vascular map of the lungs.

Vasodilating in MR-angiography: a comparison of techniques

PURPOSE

To verify the hypothesis that a drug that causes vasodilation can contribute to improvement in MRA spatial resolution. To test this hypothesis, a comparison was made between the images obtained using the high resolution time-of-flight (TOF HR 3D) technique and the TOF 3D MTC TONE technique.

METHODS

From November 1993 to December 1994, we studied 40 patients, of which 20 patients (16 males and 4 females; average age of 10 years; range from 3 to 20 years) we examined after they had inhaled Isoflurane (experimental group), and 20 patients (16 males and 4 females; average age 9.7 years; range from 3 to 12 years) were examined with standard MRA (control group).

RESULTS

The vasodilator in both HR MRA and MTC TONE MRA permits a better spatial visualization with respect to the clinical routine MRA. On the other hand, it is true that MTC TONE gives better visualization of the small vessels.

DISCUSSION

In our experience, this preliminary study indicates that with respect to routine MR, the spatial resolution is notably increased when Isoflurane is used. The signal-to-noise ratio is increased but, moreover, the ability to visualize small vessels is increased.

CONCLUSION

The preliminary results obtained in this study indicate that a pharmacological drugs is capable of increasing the vascular detail of MRA images of the intracranial vessels and that continued research this direction is called for.