A multipurpose phantom for quality assurance of contrast-enhanced MR imaging of the breast

A phantom consisting of four components was developed to simulate contrast-enhanced MR imaging of the breast. These components included the correlation between the signal intensity and the contrast medium concentration, the uniformity of signals within surface coils, artefacts due to opposed-phase imaging effects, spatial resolution and the acquisition of relevant signal-to-time curves. Repetitive measurements demonstrated an excellent reproduction of phantom imaging with a deviation in signal intensity of approximately 5 %. The presented phantom allows the optimization of examination protocols as well as the comparison of different examination techniques. Furthermore, it enables the routine quality monitoring of contrast-enhanced MR imaging of the breast.

Investigation of the imaging properties of an X-ray film scanner

In this note, the imaging properties of a CCD x-ray film scanner were investigated. The relationship between optical density and the logarithm of output pixel value provides information on the linearity of the system. The resolution properties of the scanner can be characterized by the presampling modulation transfer function which was calculated from a set of line spread functions with various alignments relative to the sampling grid. Our results show that the scanner is linear up to 2.0 optical density units, which leads to restrictions in digitizing x-ray films with higher optical density. The measured MTF shows the good spatial resolution of the CCD scanner which is demonstrated on an example.

Compression device to reduce motion artifacts at contrast-enhanced MR imaging in the breast

A prototype compression device for a bilateral breast surface coil was manufactured. It was tested in clinical practice (157 patients), and resultant images were compared with those obtained with simple ventral stuffing of the bottom of the coil (181 patients). Compression resulted in reduction of magnetic resonance (MR) examinations with severe motion artifacts from 20 (11%) of 181 examinations to three (2%) of 157 examinations (P = .001). Use of this compression device allowed the subtraction technique at MR imaging in the breast to become an effective method for ensuring more lesion conspicuity.

[MRI-assisted biopsy and localization of the breast]

If suspicious lesions found with MR imaging cannot be visualized by either mammography or ultrasound, MR imaging--based guidance systems are needed to guide needle biopsy or to allow localization of the lesion before surgery. The authors give an overview of the advantages and disadvantages of biopsy devices presented by different working groups. Furthermore, MR-compatible needle equipment for interventions of the breast is demonstrated. The angulation of the needle and the type of sequence are the most important factors for signal loss due to susceptibility. The strategy in special problem cases (multicentricity, bilateral lesions) is discussed. Control MR imaging within the first week after open biopsy is the best way to document the complete excision of a suspicious hypervascularized lesion after MR-guided wire localization. At our institute, percutaneous biopsy (36 interventions) revealed benign findings in 67% and malignant lesions in 25% of cases. Three biopsies were insufficient. Histology after MR-guided wire localization (136 interventions) showed benign findings in 51% and malignancy in 49% of cases. The suspicious lesion was missed by the surgeon in three cases. We perform MR-guided interventions of the breast routinely in indicated cases.

Stereotaxic add-on device for MR-guided biopsy of breast lesions

Breast biopsy and lesion localization were performed with gadolinium-enhanced magnetic resonance (MR) imaging guidance, with use of a stereotaxic biopsy system consisting of a flexible circular surface coil with an acrylic cylinder as an add-on guidance device. Twenty-five procedures (23 localizations, two core biopsies) were performed in lesions depicted at diagnostic MR imaging, without technical failure. The guidance system permitted easy, precise, and flexible biopsy and localization of all breast lesions.

MR imaging-guided breast intervention: experience with two systems

PURPOSE

To evaluate two different systems for magnetic resonance (MR) imaging-guided breast intervention.

MATERIALS AND METHODS

Thirty-four patients with 34 lesions detected exclusively with contrast material-enhanced MR imaging underwent 51 interventional procedures (23 needle biopsies and 28 preoperative wire localizations) with two different systems. An add-on device for surface coils was used in 25 cases, and a dedicated single breast biopsy coil was used in 26. For needle biopsies, material was aspirated with nonmagnetic 19.5-gauge needles. For preoperative localizations, nonmagnetic hook wires were used.

RESULTS

Surgical excision or follow-up verified the cytologic findings in 19 of the 23 cases sampled for biopsy. Cytologic diagnosis was impossible in three of the 23 cases. One technical failure occurred with the biopsy coil. Open biopsy performed after MR imaging-guided localization successfully removed 26 of the 28 lesions. One missed carcinoma was found at repeat localization and removed. One technical failure occurred with the biopsy coil. In that case, the lesion was close to the chest wall.

CONCLUSION

Both systems are suitable for fine-needle biopsy and preoperative localization of lesions seen exclusively on MR images.

MR-guided biopsy of suspect breast lesions with a simple stereotaxic add-on-device for surface coils

A guiding attachment is described that transforms a conventional magnetic resonance (MR) imaging surface coil into a stereotaxic biopsy unit. Eight patients, aged 38-66 years (mean, 54 years), with suspect breast lesions detected exclusively at contrast material-enhanced MR imaging underwent MR-guided needle biopsy with this unit. Diagnostic material was successfully aspirated in all patients (four carcinomas, three fibroadenomas, and one intraductal hyperplasia), and the diagnosis was subsequently confirmed at surgical biopsy. This technique promises to increase the diagnostic specificity for lesions seen solely at MR imaging.

[A comparative consideration of para-aortic fields within the framework of the German Hodgkin's Disease Study]

In 33 patients of the multicenter German Hodgkin's Lymphoma Study Group the field borders of the paraaortic field were compared computer-assisted. It was seen that fields are chosen often too small or too large, though precise description of the fields is given in the protocol. In these patients the para-aortics were irradiated exclusively as extended field region. In addition to the above observation the clipping of the spleen pedicle provides the optimal help for correct positioning of this field. Overall a very low frequency of lymphatic clipping is observed, though clinical needs are obvious.

[The use of the RACE technique for quantitative flow measurements. Evaluation using a clinically relevant flow model]

A phantom has been designed for measuring flow velocities; using pipes of specified diameter and selectable pulse rates, flow rates varying from 0-250 cm/s can be determined. The measurements are made in a superconductive magnet with a field strength of 1.5 Tesla, employing a RACE technique. The reference technique was electromagnetic flow measurement. There was good linear correlation between the electromagnetic and the MRT results with a correlation coefficient of 0.98. It is necessary in the first place to estimate flow speed; if flow velocity is unknown initially, there is no correlation. Hence, in everyday use erroneous results may be obtained, particularly since one cannot always demonstrate vessels in all parts of the body without superimposition. Further clinical studies are required in various vascular territories to evaluate the usefulness of the RACE technique for flow measurements.

Digital image processing techniques for cephalometric analysis

This paper describes the application of digital image processing methods for better landmark identification in cephalometric analysis. Conventionally taken radiographs are captured by a video camera and processed by the IPS system (KONTRON). After a detailed analysis of the transfer characteristics of the image acquisition system, the algorithms for enhancing digitized cephalograms are described. The improvement of image quality is demonstrated by several examples. The limitations of video acquisition systems are discussed and possibilities for further development are indicated.

[An Axicon lens for the focusing of ultrasound fields]

In this paper the properties of an ultrasonic axicon lens of 10 cm diameter are investigated. This device generates a narrow ultrasonic beam in a range of 20 cm. The beam width varies from 1.7 to 0.5 mm in the frequency range from 1.7 to 5.5 megahertz. For practical applications a water path is necessary.

[An axicon lens for focussing ultrasound fields]

In this paper the properties of an ultrasonic axicon lens of 10 cm diameter are Investigated. This device generates a narrow ultrasonic beam in a range of 20 cm. The beam width varies from 1.7 to 0.5 mm in the frequency range from 1.7 to 5.5 megahertz. For practical applications a water path is necessary.