Biomedical subjects

J Gieseke

Publications and source records attributed to J Gieseke.

At least 37 records · Page 2Linked to original sources

PubMed2000

MR imaging of pneumonia in immunocompromised patients: comparison with helical CT.

OBJECTIVE: A T2-weighted turbo spin-echo sequence was compared with CT in immunocompromised patients with opportunistic pneumonia. SUBJECTS AND METHODS: Sixteen patients with pneumonia shown on helical CT were examined using MR imaging within 2 days. MR examinations were performed on a 1.5-T system with a transversal T2-weighted ultrashort turbo spin-echo sequence using expiratory gating and diastolic triggering. Two radiologists reviewed the MR and CT images independently. The number, localization, and morphology of lesions were noted. MR image quality was rated using a 4-point scale. RESULTS: The results of the CT and MR examinations concerning the number and morphology of pulmonary lesions caused by pneumonia were identical in 75% of the patients (n = 12). MR imaging was able to depict all typical features of pneumonia including different stages of parenchymal infiltration (ground-glass versus consolidation). MR imaging depicted early necrotizing pneumonia not shown on contrast-enhanced CT in 25% of the patients (n = 4); 82% of the MR examinations were rated as excellent (1 point) or good (2 points). CONCLUSION: T2-weighted turbo spin-echo imaging is able to depict characteristic features of pneumonia and shows excellent results compared with CT. This MR technique offers advantages in patients with pneumonia because of its higher sensitivity for necrotizing pneumonia.

Adolescent↗

PubMed1999

Do T2-weighted pulse sequences help with the differential diagnosis of enhancing lesions in dynamic breast MRI?

In this study, our purpose was to determine whether T2-weighted images are a useful diagnostic adjunct for lesion characterization in dynamic breast MRI. On a 1.5-T system, 205 enhancing benign and malignant breast tumors were examined. The standardized protocol consisted of a T2-weighted turbo spin echo (TSE) pulse sequence with and without spectral fat suppression (SPIR), followed by a two-dimensional dynamic series with subtraction postprocessing. In 59 cases, T2*-weighted gradient-echo images also were obtained. Two independent radiologists visually rated the lesions (101 malignant, 104 benign) as having either a low or a high signal with respect to the adjacent glandular tissue. To assess age dependency of lesion enhancement velocities and T2-TSE signal intensities, we compared the results for patients at or below the age of 50 (group A), between 40 and 50 (group B), and beyond the age of 50 (group C). In T2-weighted TSE images, breast cancers were iso- or hypointense with respect to breast parenchyma in 87% of cases, whereas fibroadenomas were hyperintense in 71%. Visual assessment of lesion appearance in T2-weighted TSE images allowed to distinguish between fibroadenomas and breast cancers, with a respective sensitivity, specificity, positive predictive value, and negative predictive value of 72%, 75%, 46%, and 90% for young patients; 94%, 66%, 78%, and 89% for the patients between 40 and 50; and 89%, 62%, 85%, and 68% for the patients over 50 years of age. No significant difference was found for the distribution of signal intensities of lesions in T2*-weighted images or in fat-suppressed images. In a contrast-enhancing breast lesion, careful analysis of T2-weighted TSE images can improve differential diagnosis. The accuracy of this criterion varies with age.

Adult↗

PubMed1999

[The quantification of the magnetization transfer contrast (MTC) effect by calculating MT quotients: does it yield additional information for the differentiation of benign and malignant diseases of the locomotor apparatus?].

PURPOSE: To investigate the potential information of the amount of magnetization-transfer effect in musculoskeletal lesions and to compare MT ratios from benign and malignant musculoskeletal lesions. MATERIAL AND METHOD: 49 patients with malignant tumors (3 osteosarcoma, 3 malignant fibrous histiocytoma, 4 chondrosarcoma, 2 Ewing sarcomas) and benign lesions (8 chondroma, 2 fibrous dysplasia, 3 osteoid-osteoma, 6 ganglion cyst, 3 cyst, 3 osteomyelitis, 4 tendinitis, 3 rotator cuff tear, 5 scar tissue) were scanned using routine MRI protocols including T1- and T2-weighted spin echo as well as T2*-weighted gradient echo (FFE) sequences at 1.5 Tesla (ACS II, Philips Medical). Additionally MTC images were generated by combining the FFE sequence and the off-resonance MT technique (-1500 Hz off-resonance frequency, 1770 degrees flip angle and 50 ms pulse duration). MT ratios were calculated as Slo-Slm/Slo. RESULTS: The MT ratio of benign lesions was 26 +/- 15%, that of malignant lesions was 22 +/- 6%. The difference was statistically not significant. As expected muscle showed a high MT ratio of 50 +/- 8%. Scar tissue demonstrated an MT ratio of 39 +/- 16% which was significantly higher than the tumor MT ratios. CONCLUSION: MTC (MT ratios) failed to show significant differences between benign and malignant lesions as was expected due to basic differences in cellularity, rate of mitosis and chromatin content. MTC might however gain more importance in separating scar tissue from recurrent tumor in the future.

Adolescent↗

PubMed1999

[MR whole-spine recording: computer-assisted simulation of the conventional x-ray technic].

PURPOSE: Development of an MR-based imaging technique for the spine allowing reduction of frequency of conventional Nadiographs in the monitoring of juvenile scoliosis. PATIENTS AND METHODS: 25 patients between the ages of 6 to 36 years were examined in supine position. Two examinations of the cervical and upper thoracic spine and of the lower thoracic and lumbar spine were performed with a 1.5 T Gyroscan ACS-NT Powertrak 6000 system with body coil employing 3D EPI-sequence (TR 17 ms, TE 9 ms, flip angle 20 degrees, field of view 450 mm) or 3D FFE sequences (TR 9 ms, TE 4.5 ms, flip angle 20 degrees, field of view 450 mm) and pulse-oximetry gating. 64 coronal slices were acquired with reconstructed slice thickness of 2 mm. Image processing was performed with an algorithm merging acquisition results into two single images in the coronal and sagittal orientations allowing measurement of the Cobb angle. RESULTS: Mean examination time was 14 minutes per patient. Mean data processing time was seven minutes. Interobserver variance of determination of the Cobb angle was 1.8 degrees. CONCLUSIONS: It is to be hoped that MR whole spine projection will allow a reduction of the frequency of conventional projection in the monitoring of juvenile scoliosis.

Adolescent↗

PubMed1999

[The temporal changes in the diffusion coefficients in stroke].

PURPOSE: Analysis of temporal changes of ADC values at different stages after stroke. MATERIALS AND METHODS: The original images of all scans were evaluated and a region of interest analysis was performed on ADC (apparent diffusion coefficient) maps. 92 patients with symptoms of ischemic stroke were examined at 1.5 Tesla (ACS-NT, Philips Medical Systems). The study protocol included a navigated multishot SE-EPI DWI (b = 0, 189, 750 s/mm-2, TE = 120/140 ms, delta/delta = 49/60 ms), a GraSE (TR/TE = 3500/90 ms) and a FLAIR-TSE (TR/TE/TI = 6000/150/2000 ms) sequence. 8 patients had regular follow-ups. All patients had an additional CT scan. RESULTS: In hyperacute stroke (< 6 h, n = 10) the relative ADC of the infarct core dropped to about 50% and reached a minimum in the acute state (6-48 h, n = 14) during the next few hours. In subacute stroke (< 3 weeks, n = 29) the ADC began to rise significantly (p = 0.001) back to normal values and reached (p < 10(-4)) values similar to cerebrospinal fluid in the chronic state (> 3 weeks, n = 20). The combined use of DWI and conventional MRI improved the diagnostic information in 16% of all MR examination beyond the hyperacute assessment. CONCLUSION: By means of the ADC-values the age of stroke can be determined. Infarcts at different stages can be readily diagnosed with the combined use of DWI, FLAIR-TSE and GraSE. Pitfalls of DWI and conventional imaging can be avoided.

Adult↗

PubMed1999

[The MRT of focal liver lesions: the value of gadolinium-enhanced dynamic studies of the whole organ with a fast 3D-turbo-gradient echo sequence].

PURPOSE: To determine the value of a dynamic Gd-enhanced ultrafast T1-weighted 3D-turbo-gradient-echo sequence (3D-TFE) in the detection and characterization of focal liver lesions. MATERIALS AND METHODS: 51 patients with 124 focal liver lesions (35 hemangiomas, 30 HCC, 24 metastases, 22 cysts, 5 FNH/adenoma, 8 other lesions) were examined using a 1.5 T system. The dynamic 3D-TFE sequence, achieving 40 slices with a thickness of 4.5 mm in a 17-s breath-hold, was compared with a fat-suppressed T2-weighted fast-spin-echo sequence (TSE SPIR), unenhanced and Gd-enhanced T1-weighted spin-echo sequences (SE), and a T1-weighted gradient-echo sequence (FFE). RESULTS: On 3D-TFE images more lesions (107/124) were identified than on T1-weighted SE (101/124) and T1-weighted FFE images (106/124), but less compared to T2-weighted TSE SPIR images (115/124). The 3D-TFE-sequence provided additional information in 65/107 (61%) detected lesions by delineating the dynamic enhancement pattern, most valuable in patients with HCCs in 90%. CONCLUSIONS: On dynamic 3D-TFE images more lesions could be depicted than on conventional T1-weighted SE and T1-weighted FFE images. Visualization of the dynamic enhancement pattern provided additional information for tumor characterization in 61% of the detected lesions on the 3D-TFE images.

Artifacts↗

PubMed1999

[MRT versus CT in the diagnosis of pneumonias: an evaluation of a T2-weighted ultrafast turbo-spin-echo sequence (UTSE)].

PURPOSE: To evaluate a T2-weighted URSE sequence for the assessment of pulmonary infiltrations in comparison to CT. METHODS: 28 MRT scans of 22 patients with confirmed pneumonia were recorded on a 1.5 Tesla apparatus with an expiratory and diastolic triggered, T2-weighted ultrafast-spin-echo sequence in axial slice mode with the following parameters: TReff/TE/Turbo-factor 2000-4000/90 ms/21-23; slice thickness/separation 6/0.6 mm; FOV 360 mm; 24 slices. 24 spiral CTs (since thickness/table advance: 1-2 mm/10mm) were available for comparison. The separate evaluation of MRTs and CTs was performed by three radiologists in a consensus procedure with regard to pulmonary lesions (e.g., infiltration, round foci, net patterns) and image quality of the MRTs (4-step scale). RESULTS: In 71% of the cases the CTs and MRTs agreed with the diagnosis and representation of the lesions, in 25% MRT was superior. MRT was better for the detection of pulmonary abscesses. In 93% the image quality of the MRT was very good to good. CONCLUSIONS: MRT in the technique presented here is in most cases equal to CT for the detection of pneumonia. Diagnosis of pulmonary abscesses seems to be better with MRT.

Adult↗

PubMed1999

[3D-TSE MR cholangiopancreatography with breath triggering to clarify unclear hepatopathies in children].

PURPOSE: Evaluation of 3D-TSE MR-cholangiography with respiratory triggering in the work up of hepatopathies in infants and young children. PATIENTS AND METHOD: 16 infants (4-16 years) with increased transaminases, two with recurrent pancreatitis, were examined at 1.5 T (ACS-NT II, Philips Medical Systems) using a 3D-TSE MRCP with respiratory triggering in addition to a regular MRI of the liver. The MRCP was compared to ERCP. Two radiologists and one gastroenterologist evaluated the technical quality, visualization of the pancreaticobiliary system, and the diagnostic value of the examinations. RESULTS: Technically feasible were 14/16 MRCPs and 13/16 ERCPs. Two MRCP were not of diagnostic value due to motion artifacts and in three ERCP cannulation of the papilla was not possible. 14/16 ERCP required general anaesthesia, while MRCP needed i.v. sedation in two patients only. Extrahepatic ducts/cystic duct/pancreatic duct were visualized in 14/12/8 patients using MRCP, and in 13/10/3 patients using ERCP, both without adverse effects or complications. Intrahepatic ducts were better delineated with MRCP. In 10 patients with histologically proven periportal fibrosis (n = 7) and liver fibrosis (n = 1) or antineutrophil cytoplasmatic antibodies and associated inflammatory bowel disease, MRCP and ERCP revealed pathological results. CONCLUSION: MRCP using a 3D-TSE sequence with respiratory triggering is a good non-invasive technique for delineation of the biliary tract in infants and young children for the work up to hepatopathies.

Adolescent↗

PubMed1999

Dynamic breast MR imaging: are signal intensity time course data useful for differential diagnosis of enhancing lesions?

PURPOSE: To assess the relevance of the signal intensity time course for the differential diagnosis of enhancing lesions in dynamic magnetic resonance (MR) imaging of the breast. MATERIALS AND METHODS: Two hundred sixty-six breast lesions were examined with a two-dimensional dynamic MR imaging series and subtraction postprocessing. Time-signal intensity curves of the lesions were obtained and classified according to their shapes as type I, which was steady enhancement; type II, plateau of signal intensity; or type III, washout of signal intensity. Enhancement rates and curve types of benign and malignant lesions were compared. RESULTS: There were 101 malignant and 165 benign lesions. The distribution of curve types for breast cancers was type I, 8.9%; type II, 33.6%; and type III, 57.4%. The distribution of curve types for benign lesions was type I, 83.0%; type II, 11.5%; and type III, 5.5%. The distributions proved significantly different (chi 2 = 139.6; P < .001). The diagnostic indices for signal intensity time course were sensitivity, 91%; specificity, 83%; and diagnostic accuracy, 86%. The diagnostic indices for the enhancement rate were sensitivity, 91%; specificity, 37%; and diagnostic accuracy, 58%. CONCLUSION: The shape of the time-signal intensity curve is an important criterion in differentiating benign and malignant enhancing lesions in dynamic breast MR imaging. A type III time course is a strong indicator of malignancy and is independent of other criteria.

Breast↗

PubMed1998

[A rational study of the great abdominal veins using 2D-TOF- and turbo-spin-echo sequences].

PURPOSE: Development of a fast and reliable protocol for the detection and exclusion of abdominal venous thrombosis with an optimised T2-TSE- and 2D-TOF sequence. MATERIAL AND METHOD: Evaluation of the flow-void phenomenon with a flow phantom on a 1.5 and 0.5 Tesla system using different echo times. Examination of 22 patients with suspected abdominal shunt- or abdominal vein-thrombosis with a optimum T2-TSE- and 2D-TOF sequence with a 1.5 or 0.5 Tesla system. Confirmation of thrombosis with contrast-enhanced computed tomography or digital subtraction angiography. RESULTS: The most effective combination of strong flow-void phenomena, signal/noise ratio and scan time was found with the following parameters: TE 120 ms, TR 2000 ms, 5 mm slice gap. In the patient group two complete and two partial thromboses were diagnosed with both sequences. One wrong positive thrombosis occurred in a stenotic anastomosis with the 2D-inflow sequence. CONCLUSION: With optimum parameters the T2-TSE sequence produces a strong "flow-void" phenomenon suitable for "black-blood"-MRA. The use of this sequence alone or in combination with 2D-inflow MRA, if "bright-blood" MRA is recommended, allows a reliable evaluation of thrombosis in abdominal veins without high-tech MRA equipment and contrast media.

Abdomen↗

PubMed1998

[Magnetization transfer contrast (MTC)--which is the most MTC-sensitive MRI sequence?].

PURPOSE: This study aimed at evaluating MTC-sensitivity of frequently used MR-sequences. MATERIAL AND METHODS: 7 sequences (T1-, T2-, PD-weighted SE, four gradient-echo sequences) were combined with a 4 element on-resonance MT-Pulse at 0.5 Tesla (T5, Philips medical systems). The measurements were performed at a knee joint and MT-ratios of cartilage, muscle, fat and a copper sulfate phantom were calculated. RESULTS: Proton density weighted gradient and to a lesser degree spin-echo sequences were superior to T1- and T2-weighted sequences in visualising the MT effects. CONCLUSION: It is important to choose an appropriate MR-sequence for MTC experiments. Proton-density gradient echo sequences are recommended for that purpose. T1- and T2-weighted SE sequences should be avoided.

Adipose Tissue↗

PubMed1998

[Improved diagnosis of early cerebral infarct by the combined use of diffusion and perfusion].

PURPOSE: To evaluate the feasibility and the diagnostic efficacy of multislice diffusion-weighted and perfusion imaging in addition to FLAIR-TSE, T2w-GraSE and MR-angiography in the diagnosis of acute stroke. METHODS: 18 patients with acute stroke were examined at 1.5 Tesla (Gyroscan ACS-NT, Philips Medical Systems) within 6 (n = 9) and 6-48 (n = 9) hours, respectively, and followed at regular intervals. For diffusion imaging we used a multislice multishot EPI-SE sequence with navigator echo correction and cardiac gating. Perfusion imaging was done by means of a FFE-EPI sequence after bolus injection of Gd-DTPA. RESULTS: The diagnostic value of diffusion-weighted and perfusion imaging was significantly higher compared with FLAIR-TSE (p = 0.0023) and GraSE (p = 0.0012) during the first 6 hours. With FLAIR-TSE and GraSE first pathologic changes were seen after 4 hours. We detected perfusion deficit (rCBV < 10%) and a corresponding drop of the ADC in all infarcts larger than 1 cm in diameter. Within the area of low rCBV the combined analysis of diffusion and perfusion imaging allows to identify an infarct region with characteristics of a penumbra and one with characteristics of the infarct core. TTP was increased in the surrounding tissue. However, parts of this area were rarely included in the infarct. The final extension of the untreated infarct, as revealed by computed tomography, corresponded well to the perfusion deficit. CONCLUSIONS: Early ischaemic cerebral infarcts can be diagnosed with diffusion and perfusion imaging before pathological changes are visualized with other imaging modalities. The combined use may allow to distinguish the infarct core from surrounding, potentially salvageable tissue.

Adult↗

PubMed1998

[MRI in patients with cardiac pacemakers: in vitro and in vivo evaluation at 0.5 tesla].

PURPOSE: MRI is currently regarded as absolutely contraindicated in patients with implanted cardiac pacemakers. In this prospective study safety and feasibility of MRI in patients with new generation pacemakers (PM) was evaluated in vitro and in vivo. METHODS: 14 PM models in vitro and 18 patients with implanted new generation PM underwent a MRI exam at 0.5 Tesla with standard spin, turbo spin, and gradient echo (FFE) sequences under continuous ECG-monitoring. PM inquiry was performed before and after the MRI exam, including assessment of stimulation thresholds. RESULTS: In the static magnetic field all PM switched to the asynchronous mode due to activation of the Reed switch, resulting in continuous pacing at a fixed rate. In three PM models in vitro, however, after activation of the Reed switch, there was a software-induced switch back to the demand mode. In these PM inhibition and triggering were observed after starting the MRI scan due to influence of the pulsed magnetic fields. PM program changes, damage of PM components, dislocation/torque of the PM and rapid pacing of the PM were observed neither in vitro nor in vivo. Atrial and ventricular stimulation thresholds remained unchanged. CONCLUSION: MRI at 0.5 Tesla should not be regarded as absolutely contraindicated in patients with implanted new generation PM. However, knowledge of the behaviour of the specific PM model in static and pulsed magnetic fields is required, if necessary also changes of the PM program prior to the MRI exam, continuous ECG monitoring and cardiological stand-by.

Contraindications↗

PubMed1998

[Diffusion-weighted MR tomography: navigated multi-shot SE-EPI technique for clinical use].

PURPOSE: Evaluation of a navigated multi-shot SE EPI sequence for routine clinical use in MR diffusion imaging. METHODS: We compared a multi-shot SE EPI sequence with the conventional SE sequence as well as with a single-shot SE EPI sequence on a standard 1.5 Tesla MR-scanner (ACS-NT, Philips Medical Systems) with a conventional gradient system (10 mT/m). Image quality and the reproducibility of the apparent diffusion coefficient were analysed with phantoms and with healthy volunteers. The diffusion coefficients of different brain areas were determined in a group of twenty volunteers. RESULTS: The multi-shot SE EPI sequence showed considerably shorter measurement times and smaller motion artifacts than the SE sequence and was less sensitive to susceptibility artifacts than the single-shot version. The reproducibility of the diffusion coefficients was better than 10%. CONCLUSION: The navigated multi-shot SE technique is more practicable and meaningful than the SE and the single-shot SE EPI techniques on a standard 1.5 Tesla MR-scanner with a conventional gradient system. In our opinion it is now the best method for diffusion imaging and should be preferred in clinical use. The determination of diffusion coefficients yields reliable results and characteristic values for different tissue can be obtained.

Adult↗

PubMed1998

[Detection of focal lung lesions with magnetic resonance tomography using T2-weighted ultrashort turbo-spin-echo-sequence in comparison with spiral computerized tomography].

PURPOSE: To compare spiral CT and MRT for the detection of focal pulmonary lesions. PATIENTS AND METHODS: 50 patients with focal pulmonary lesions confirmed by spiral CT were examined using a T2-weighted UTSE sequence (TE: 90 ms, TR: 1500-3000 ms, echo interval 9 ms, 8 mm slice thickness, diastolic triggering, expiratory breath gating). Image quality was compared using a 4-stage scale. Lesions with a minimum size of 2 mm were counted and measured in the CT image. The results were compared with the MRT images. RESULTS: The image quality in CT examinations with an average value of 1.22 better than that in MRT (1.78). In total 163 pulmonary lesions with a size of 2-115 mm were found by CT. MRT found 151/163 lesions (92.6%). Of the 12 lesions not detected, 9 were smaller than 4 mm, 1 corresponded to a 12 mm large, completely calcified granuloma. In 2 cases there was a 4 or 5 mm large unspecific scar. Thus, 160/163 (98.1%) of all lesions larger than 3 mm were detected. CONCLUSIONS: MRT with use of a suitable UTSE sequence is an alternative to CT for the detection of focal pulmonary lesions with a size larger than 3 mm.

Adolescent↗

PubMed1998

High-resolution MR imaging of the cutis and subcutis. Histological correlation.

OBJECTIVE: To determine whether the spatial resolution that can be achieved with currently available MR devices is adequate for the evaluation of skin disease. MATERIAL AND METHODS: We correlated high-resolution MR images of the skin with dermatohistopathology in 26 patients. The examinations were carried out on a 1.0 T imager using a commercially available surface coil (ID 7.5 cm) and optimized SE and GE sequences. Image quality was assessed by four readers on a questionnaire. RESULTS: The visualization of the dermis, subcutaneous tissue, and muscle fascia allowed a pattern analysis that gave findings identical to those at dermatohistopathology. It was possible to distinguish septal from lobular panniculitis, and lipatrophia from sclerodermia. Images with contrast media infusion were useful in the differential diagnosis. CONCLUSION: High-resolution MR imaging may narrow down the differential diagnosis of various skin diseases and may help to reduce the number of skin biopsies on certain indications.

Adolescent↗

PubMed1998

Detection of focal hepatic lesions: effects of superparamagnetic iron oxide (AMI-25) on magnetic resonance imaging of the liver using T2-weighted fast spin-echo sequences and gradient-and-spin-echo sequences at 1.0 tesla.

RATIONALE AND OBJECTIVES: The authors evaluate the value of two fast spin-echo sequences (FSE) with different T2-weighting (repetition time [TR]/echo time [TE] = 2000/90 mseconds and TR/TE = 2000/40 mseconds) and combined gradient-and-spin-echo sequences (TR/TE = 2000/90 mseconds) for contrast-enhanced liver imaging with superparamagnetic iron oxide (AMI-25). METHODS: Forty-seven patients with focal liver lesions underwent magnetic resonance imaging at 1.0 tesla. AMI-25 was administered intravenously at a dose of 15 micromol iron/kg. RESULTS: Administration of AMI-25 resulted in a significant increase of lesion/liver contrast-to-noise ratio (C/N) for all T2-weighted sequences (P < 0.001). On the precontrast images, the FSE sequence with a TE of 90 mseconds had the highest C/N (16.0 +/- 4.5) whereas the best postcontrast C/N (27.9 +/- 7.6) was obtained with the mild T2-weighted FSE sequence with a TE of 40 mseconds. CONCLUSIONS: Fast spin-echo sequences are valuable sequences for imaging of the liver at 1.0 tesla. For AMI-25-enhanced magnetic resonance imaging, a mild T2-weighted FSE sequence is recommended.

Adult↗

PubMed1997

[Localization of puncture needles in MRI: experimental studies on precision using spin-echo sequences at 1.0 T].

PURPOSE: To evaluate accuracy of needle localisation using and signal enhancement on a 1.OT MR imager for various needles for MR-guided biopsy. METHODS: The differences between actual and virtual needle position of needles with different orientations were evaluated in a phantom for spin-echo including turbo-spin-echo sequences. RESULTS: Artifacts depended on the orientation of the needle relative to the field B0, frequency-encoding gradients (Gf) and slice orientation. This resulted in different artifact shapes and sizes for left or right and cranial or caudal biopsy access routes. Applying turbo spin echo sequences feasible for biopsy, the signal void of a 18 G needle (Cook) parallel to Gf reached between 0.3 and. 4.6 mm further into the medium than the real needle tip, depending on needle orientation relative to B0. The diameter of the signal void around the needle varied, the needle shaft was right in the centre of the signal void. With Gf orthogonal to the needle the offset of signal void to needle tip ranged from 2.7 to 3.3 mm, while the actual position of the needle shaft was up to 3.3 mm lateral of the signal void center. While nominal echo times did not influence the size of the artifact in turbo-spin-echo sequences, the artifacts increased with smaller matrix and larger water-fat shift. Material and mass of the needle determined the size of the artifacts as well. CONCLUSION: Localisation accuracy of the needle can be optimised by choosing optimal gradient directions depending on whether needle tip or shaft position should be displayed.

Artifacts↗