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Biomedical subjects

J Kemper

Publications and source records attributed to J Kemper.

At least 19 recordsLinked to original sources
PubMed2006

Detection of small pulmonary nodules in high-field MR at 3 T: evaluation of different pulse sequences using porcine lung explants.

To evaluate two MR imaging sequences for the detection of artificial pulmonary nodules inside porcine lung explants. 67 agarose nodules ranging 3-20 mm were injected into ten porcine lungs within a dedicated chest phantom. The signal on T1-weighted images and radiopacity were adjusted by adding 0.125 mmol/l Gd-DTPA and 1.5 g/l of iodine. A T1-weighted three-dimensional gradient-echo (T1-3D-GRE; TR/TE:3.3/1.1 ms, slice:8 mm, flip-angle:10 degrees ) and a T2-weighted half-Fourier fast-spin echo sequence (T2-HF-FSE; TR/TE:2000/66 ms, slice:7 mm, flip-angle:90 degrees ) were applied in axial orientation using a 3-T system (Intera, Philips Medical Systems, Best, The Netherlands), followed by CT (16x0.5 mm) as reference. Nodule sizes and locations were assessed by three blinded observers. In nodules of >10 mm, sensitivity was 100% using 3D-GRE-MRI and 94% using the HF-FSE sequence. For nodules 6-10 mm, the sensitivity of MRI was lower than with CT (3D-GRE:92%; T2-HF-FSE:83%). In lesions smaller than 5 mm, the sensitivity declined to 80% (3D-GRE) and 53% (HF-FSE). Small lesion diameters were overestimated with both sequences, particularly with HF-FSE. This study confirms the feasibility of 3 T-MRI for lung nodule detection. In lesions greater than 5 mm, the sensitivity of the 3D-GRE sequence approximated CT (>90%), while sensitivity and PPV with the HF-FSE sequence were slightly inferior.

Animals↗
PubMed2006

Orthodontic springs and auxiliary appliances: assessment of magnetic field interactions associated with 1.5 T and 3 T magnetic resonance systems.

The objective of this paper is to evaluate magnetic field interactions at 1.5 and 3 T for 20 orthodontic devices used for fixed orthodontic therapy. Twenty springs and auxiliary parts made from varying ferromagnetic alloys were tested for magnetic field interactions in the static magnetic field at 1.5 and 3 T. Magnetic translational force F(z) (in millinewtons) was evaluated by determining the deflection angle beta [American Society for Testing and Materials (ASTM standard test method)]. Magnetic-field-induced rotational force F(rot) was qualitatively determined using a five-point scale. beta was found to be >45 degrees in 13(15) devices at 1.5(3) T and translational force F(z) exceeded gravitational force F(g) on the particular object [F(z) 10.17-261.4 mN (10.72-566.4 mN) at 1.5(3) T]. F(z) was found to be up to 24.1(47.5)-fold higher than F(g) at 1.5(3) T. Corresponding to this, F(rot) on the objects was shown to be high at both field strengths (> or = +3). Three objects (at 1.5 T) and one object (at 3 T) showed deflection angles <45 degrees , but F(rot) was found to be > or = +3 at both field strengths. For the remaining objects, beta was below 45 degrees and torque measurements ranged from 0 to +2. Of 20 objects investigated for magnetic field interactions at 1.5(3) T, 13(15) were unsafe in magnetic resonance (MR), based on the ASTM criteria of F(z). The implications of these results for orthodontic patients undergoing MRI are discussed.

Electromagnetic Fields↗
PubMed2006

[Multislice CT urography (MSCTU): evaluation of a modified scan protocol for optimized opacification of the collecting system].

PURPOSE: To retrospectively quantify opacification of the urinary tract using a MSCTU protocol based on furosemide and individual adaptation of urographic acquisition delay. MATERIALS AND METHODS: MSCTU examinations obtained from 4-row and 16-row CT scanners in 53 patients (35 men, 18 women, average age 59) were independently reviewed by two radiologists. MSCTUs were performed using a low-dose injection of furosemide. No fixed scan delay for urographic image acquisition was applied. The urographic timing was individually adapted by performing low-dose test images of the distal ureters to display their current opacification. Image analysis included grading of the opacification of the segmented collecting system. The average urographic delay was calculated. Stratified comparisons of mean scores were assessed using the Friedman and Wilcoxon tests. The inter-observer kappa value was calculated. RESULTS: The calculated median scan delay for patients with normal serum-creatinine levels (n = 51) was 418 sec (mean 447 sec; SD, 118 sec). The median number of acquired test images was 2 (range 1 - 6 images). The opacification analysis demonstrated that 98 % of the ICS, 90 % of the proximal, 86 % of the middle, and 83 % of the distal ureteral segments showed opacification greater than 90 %. 9.5 % of the distal ureteral segments could not be visualized. Statistics did not show significant opacification differences between proximal, middle, and distal ureteral segments (p > 0.05). The two observers were largely in agreement (kappa coefficient r = 0.81). CONCLUSION: The analyzed MSCTU technique based on furosemide and scan delay timing by means of test images reliably lead to a homogenous opacification of the entire upper urinary tract. It features the individual adaptation of MSCTU to the excretory rate of the kidneys.

Adolescent↗
PubMed2006

Mycobacterium avium intracellulare otomastoiditis: case report and literature review.

Otomastoiditis caused by Mycobacterium avium intracellulare (MAI) is rare. Sub-optimal management of this condition can lead to significant morbidity and serious damage to the middle ear. Diagnosis is difficult, especially since most physicians are not familiar with the mode of presentation and symptoms. Presented here is a new case, followed by a review of the literature on MAI mastoiditis.

Female↗
PubMed2006

[Modern diagnostic assessment of the upper urinary tract using multislice CT urography].

The advent of Multislice Computed Tomography (MSCT) has made evaluation of the entire urinary tract with high-resolution sections during a single breath-hold a reality. Acquisition of multiple thin overlapping slices provides excellent two-dimensional (2D) and three-dimensional (3D) reformations of the urinary tract. The concept of "Multislice CT Urography (MSCTU)" has emerged from this technical improvement. As a result, a wide range of pathologies inside and outside the urinary tract can be identified. During the last several years, MSCTU has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, MSCT(U) is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The main advantage of IVU has been its ability to offer excellent delineation of pelvicalyceal and ureteral anatomy and to depict subtle uroepithelial abnormalities. MSCTU has already shown promising results for overcoming this challenge. Optimal opacification and distension appear to be an essential requirement for a thorough evaluation of the collecting system. Dedicated preparation strategies have been developed to meet these technical difficulties. The biggest disadvantage of MSCTU is the significant radiation exposure. For broad routine clinical application, there is still a need for dose reduction protocols despite the ongoing technical developments in MSCTU. In this article, we outline the different concepts of technical processing for MSCTU and summarize the current role of MSCTU in the evaluation of the upper urinary tract.

Carcinoma, Transitional Cell↗
PubMed2005

[Multislice CT urography Aspects for technical management and clinical application].

The introduction of multislice computed tomography with its well-known advantages has made it possible to visualize the entire urinary tract with thin collimation during a breath-holding phase. CT data acquisition during urographic contrast enhancement for contiguous imaging of the entire upper urinary tract is termed "multislice CT urography" (MSCTU). Multiplanar reconstructions, maximum intensity projections, and average intensity projections can be rendered from the volume datasets to view the urogenital tract. MSCTU will play an important role in the future of modern uroradiology. This article describes the technical aspects involved in the course of the MSCTU examination and identifies additional potential indications for clinical application.

Anatomy, Cross-Sectional↗
PubMed2005

[Orthodontic brackets in high field MR imaging: experimental evaluation of magnetic field interactions at 3.0 Tesla].

PURPOSE: To evaluate static magnetic field interactions for 32 commonly used orthodontic brackets in a 3.0 T magnetic resonance imaging (MRI) system. MATERIALS AND METHODS: 32 orthodontic brackets consisting of a steel alloy (n = 27), a cobalt-chromium alloy (n = 2), ceramic (n = 1), ceramic with a steel slot (n = 1), and titanium (n = 1) from 13 different manufacturers were tested for magnetic field interactions in a static magnetic field at 3.0 T (Gyroscan Intera 3.0 T, Philips Medical Systems, Best, Netherlands). The magnetic deflection force F (z) [mN] was evaluated by determining the deflection angle beta [ degrees ] using the established deflection angle test according to the ASTM guidelines. The magnetic-field-induced rotational force F (rot) or torque was qualitatively determined using a 5-point grading scale (0: no torque; + 4: very strong torque). RESULTS: In 18 of the 32 brackets, the deflection angle beta was found to be > 45 degrees and the translational force exceeded the gravitational force F (G) on the particular bracket (F (z): 1.2 - 45.7 mN). The translational force F (z) was found to be up to 68.5 times greater than the gravitational force F (G) (F (z)/F (G): 1.4 - 68.5). The rotational force F (rot) was correspondingly high (+ 3/+ 4) for those brackets. For the remaining 14 objects, the deflection angles were < 45 degrees and the torque measurements ranged from 0 to + 2. The static magnetic field did not affect the titanium bracket and the ceramic bracket. No measurable translational and rotational forces were found. CONCLUSION: Of the 32 brackets investigated for magnetic field interactions at 3.0 T, 18 (56.25 %) were unsafe in the MR environment according to the ASTM guidelines. However, the forces measured were minimal compared to the forces generally necessary for dislodging these bonded orthodontic brackets from tooth surfaces. The implications of these results for orthodontic patients undergoing MR examinations at 3 Tesla are discussed.

Humans↗
PubMed2004

[Evaluation of experimental cartilage lesions with ultrahigh-resolution multi-slice-CT in comparison to histology].

PURPOSE: Histologic validation of ultrahigh-resolution multi-slice (MS)-CT for the evaluation of focal, experimental cartilage lesions with special regard to the subchondral bone. Testing of micro-CT ( micro CT) as alternative reference standard. METHODS: 32 experimental cartilage lesions in bovine patellae were imaged surrounded by air (MS-CT-air) and immersed in a contrast material solution (MS-CT-CM) with MS-CT (collimation 2 x 0,5 mm). After the micro CT (8 micro m-voxelsite) examination in three specimen and histologic work-up of 29 specimen two radiologist graded the defects on MS-CT images in consensus (subchondral bone involvement yes or no) and results were compared to the results of histomorphometry and micro CT. RESULTS: The MS-CT-air and -CM had an accuracy of 94 % (30/32) and 88 % (28/32), respectively. MS-CT-air led to one false-positive (remaining cartilage: = 0,1 mm) and false-negative result, each. MS-CT-CM showed false-positive results if the remaining cartilage was < 0,3 mm thick (n = 4), i. e. showed subchondral bone involvement. Contrast-to-noise ratio was significantly higher in MS-CT-air compared to MS-CT-CM. micro CT yielded a clear depiction of cartilage defect depth in the three cases. CONCLUSION: MS-CT-air has a high accuracy in the depiction of focal cartilage defects. MS-CT-CM has a tendency to overestimate cartilage defect depth. micro CT could potentially serve as alternative reference standard to histology.

Animals↗
PubMed2004

MR elastography of the prostate: initial in-vivo application.

PURPOSE: To analyze the initial assessment of the technical feasibility of in-vivo MR elastography (MRE) of the prostate gland in healthy volunteers. MATERIALS AND METHODS: Dynamic sinusoidal MR elastography was performed in 7 healthy volunteers in prone position. The mechanical wave was induced via an external oscillator attached to the pubic bone. A 1.5 Tesla MR system (Philips Medical Systems, Netherland) was used with 4 combined surface coils for signal reception. MRE data acquisition was performed with a motion-sensitive spin-echo MR sequence that was phase-locked to the mechanical oscillation. Subsequently, these images were used to reconstruct the local distribution of elasticity inside the prostate gland. The applied reconstruction algorithm was tested by means of phantom measurements. RESULTS: Sufficient penetration of the mechanical wave into the prostate gland was achieved in all volunteers, allowing the acquisition of utilizable image data sets. The reconstructed distribution of elasticity (shear-modulus) inside the healthy prostate gland correlated with the zonal anatomy of the gland. The elasticity of the central portion (2.2 +/- 0.3 kPa) appeared to be lower than the peripheral prostatic portion (3.3 +/- 0.5 kPa). CONCLUSION: In-vivo MRE of the prostate gland is technically feasible. The proposed experimental set-up allows the efficient insertion of the mechanical wave into the prostate gland and provides a successful MR data acquisition.

Adult↗
PubMed2003

[Comparison of an edema-sensitive HASTE-TIRM sequence with delayed contrast enhancement in acute myocardial infarcts].

GOAL: Comparison between a fluid-sensitive (HASTE-TIRM)-sequence and delayed contrast-enhancement in patients with acute myocardial infarct (AMI) in MRI. MATERIAL AND METHODS: 32 patients with AMI were imaged 7 +/- 4 days after the time of infarction with a 1.5 T unit using a T2 HASTE-TIRM and a contrast-enhanced (CE) T1 turbo FLASH sequence. A threshold method (>2 SD in comparison with normal myocardium) was used to quantify the hyperintense zones in both sequences. The transmurality of the hyperintense regions was measured on a segmental basis. RESULTS: The hyperintense areas were larger on the HASTE-TIRM sequence with 29.6 +/- 13.2 % of the left ventricular (LV) area as compared to the CE-MRI with 19.2 +/- 10 % of the LV area (p < 0.0001). The measured transmurality was higher with the HASTE-TIRM sequence than with the CE-MRI (p < 0.0001). While the correlation between CE-MRI and peak creatine kinase (CK max) was good (r = 0.59, p < 0.001), no correlation was found between the HASTE-TIRM sequence and CK max (r = 0.29, p = ns). CONCLUSIONS: The peri-infarct edema can be depicted with a HASTE-TIRM sequence in addition to the non-viable infarct zone. The HASTE-TIRM sequence shows a higher transmurality of the hyperintense regions than the CE-MRI. The additional area depicted by the HASTE-TIRM sequence could represent functionally impaired but viable myocardium).

Adult↗
PubMed2002

[Evaluation of TSE- and T1-3D-GRE-sequences for focal cartilage lesions in vitro in comparison to ultrahigh resolution multi-slice CT].

PURPOSE: Evaluation of TSE- and T 1 -3D-GRE-sequences for focal cartilage lesions in vitro in comparison to ultrahigh resolution multi-slice CT. MATERIALS AND METHODS: Forty artificial cartilage lesions in ten bovine patellae were immersed in a solution of iodinated contrast medium and assessed with ultrahigh resolution multi-slice CT. Fat-suppressed TSE images with intermediate- and T 2 -weighting at a slice thickness of 2, 3 and 4 mm as well as fat-suppressed T 1 -weighted 3D-FLASH images with an effective slice thickness of 1, 2 and 3 mm were acquired at 1.5 T. After adding Gd-DTPA to the saline solution containing the patellae, the T 1 -weighted 3D-FLASH imaging was repeated. RESULTS: All cartilage lesions were visualised and graded with ultrahigh resolution multi-slice CT. The TSE images had a higher sensitivity and a higher inter- and intraobserver kappa compared to the FLASH-sequences (TSE: 70 - 95 %; 0.82 - 0.83; 0.85 - 0.9; FLASH: 57.5 - 85 %; 0.53 - 0.72; 0.73 - 0.82, respectively). An increase in slice thickness decreased the sensitivity, whereby deep lesions were even reliably depicted on TSE images at a slice thickness of 3 and 4 mm. Adding Gd-DTPA to the saline solution increased the sensitivity by 10 % with no detectable advantage over the T 2 -weighted TSE images. CONCLUSION: TSE sequences and application of Gd-DTPA seemed to be superior to T 1 -weighted 3D-FLASH sequences without Gd-DTPA in the detection of focal cartilage lesions. The ultrahigh resolution multi-slice CT can serve as in vitro reference standard for focal cartilage lesions.

Animals↗
PubMed2001

Radiation dose in dental radiology.

The aim of this study was to compare radiation exposure in panoramic radiography (PR), dental CT, and digital volume tomography (DVT). An anthropomorphic Alderson-Rando phantom and two anatomical head phantoms with thermoluminescent dosimeters fixed at appropriate locations were exposed as in a dental examination. In PR and DVT, standard parameters were used while variables in CT included mA, pitch, and rotation time. Image noise was assessed in dental CT and DVT. Radiation doses to the skin and internal organs within the primary beam and resulting from scatter radiation were measured and expressed as maximum doses in mGy. For PR, DVT, and CT, these maximum doses were 0.65, 4.2, and 23 mGy. In dose-reduced CT protocols, radiation doses ranged from 10.9 to 6.1 mGy. Effective doses calculated on this basis showed values below 0.1 mSv for PR, DVT, and dose-reduced CT. Image noise was similar in DVT and low-dose CT. As radiation exposure and image noise of DVT is similar to low-dose CT, this imaging technique cannot be recommended as a general alternative to replace PR in dental radiology.

Cervical Vertebrae↗
PubMed1998

A follow-up study for estimating the effectiveness of a cross-gender hormone substitution therapy on transsexual patients.

This follow-up study was carried out to validate the effectiveness of cross-gender hormone therapy embedded in a multistep treatment concept for transsexual patients. This therapy described in detail by the authors elsewhere and presented briefly below provides cross-gender hormone substitution to obtain an assimilation of secondary sex characteristics to the desired sex as quickly as possible. Personal and social background data of 46 male-to-female (M-to-F) and 42 female-to-male (F-to-M) patients passing through different stages of the treatment concept were included. In the Endocrinological Outpatient Clinic of the Max-Planck-Institute/Munich the effectiveness of cross-gender hormone replacement therapy as well as frequency and distribution of side effects were examined by follow-up examination of endocrinological parameters. Cross-gender hormones were administered either parenterally or orally. Blood samples were collected routinely after 2 to 6 months depending on the duration of hormone substitution and complication rate. The incidence of hyperprolactinemia in estrogen-treated M-to-F transsexuals lies in the range of studies published before, whereas the number of patients developing galactorrhea is significantly lower in our patients. The incidence of thromboembolic events during the time of cross-gender hormone treatment in our patients is negligible. Changes in hematological parameters are observed under cross-gender hormone therapy. With the cross-gender hormone regimen performed by us it is possible to generate less side effects in the treatment of transsexual patients than described before.

Female↗
PubMed1994

[Protein A immunoadsorption treatment of patients with refractory autoimmune thrombopenia].

Eight patients with chronic immunothrombocytopenia (ITP) who had failed at least one alternative therapy were treated with extracorporeal immunoadsorption. Two of the 8 patients responded to the treatment with a stable increase in platelet counts, but both of them had to be continuously treated with corticosteroids. Side effects of the treatment with extracorporeal immunoadsorption were musculoskeletal pain, nausea, vomiting, tachycardia, purpura, fatigue, and others.

Adrenal Cortex Hormones↗
PubMed1993

Recovery from rhinocerebral mucormycosis in a ketoacidotic diabetic patient: a case report.

An 18-year-old woman with insulin-dependent diabetes mellitus developed an infection of the paranasal sinuses with Rhizopus oryzae resulting in facial swelling, hemiplegia and blindness of the right eye. The therapy of this rhinocerebral mucormycosis consisted of extensive surgical debridement, administration of high-dose amphotericin B, hyperbaric oxygen and control of the underlying predisposing diabetes mellitus. The patient eventually recovered with however, the loss of one eye.

Adolescent↗