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M Cohnen

Publications and source records attributed to M Cohnen.

At least 37 records · Page 2Linked to original sources
PubMed2002

[Imaging of supradiaphragmatic manifestations of extranodal non-Hodgkin's lymphoma].

Malignant lymphomas are differentiated into Hodgkin's and non-Hodgkin's-lymphoma (NHL). The following article discusses the imaging of extranodal NHL in supradiaphragmatic localizations. Lymphoma can affect nearly all tissues, and represent a rare entity as primary extranodal NHL. A secondary involvement of non-nodal tissue as consequence of a generalized lymphoproliferative disease is more common,and may be seen as well in HIV-positive patients defining AIDS. As extranodal lymphoma mimic the radiologic appearance of other malignant tumors, direct diagnosis without histologic analysis is often impossible. The article describes typical manifestations of lymphoma of the lungs, the head and neck area including the large glands, and rare localizations as the heart or the breast.

Head and Neck Neoplasms↗
PubMed2002

[Modern diagnostic imaging: MR urography].

MR-urography presents a new diagnostic approach to the urinary system, resulting in images comparable to those known from i.v.-urography. T2-weighted MR-urograms demonstrate static fluid without ionizing radiation or nephrotoxic contrast media. The excretory renal function can be examined by the use of gadolinium-enhanced T1-urography. The degree and cause of ureteric obstruction can be diagnosed with high sensitivity and specificity. On the other hand, urolithiasis is frequently misdiagnosed by MR-urography and, in this case, spiral CT should be used. Pediatric or pregnant patients can be examined as well as donors before and patients after renal transplantation. Furthermore, in case of a tumor MR-imaging, including MR-angiography, is a potential diagnostic "all-in-one" approach.

Adult↗
PubMed2002

A comparison of conventional panoramic radiographs with volumetric computed tomography images in the preoperative assessment of impacted mandibular third molars.

PURPOSE: In the present study, we evaluated the geometric, topographic, and anatomic reliability of volumetric computed tomography (VCT) images by comparing conventional panoramic radiographs with reconstructed VCT panoramic and paraxial images before performing third molar surgery. PATIENTS AND METHODS: A total of 6 anatomic sites on 10 patients who showed a topographic relationship between the apices of the third molar root and the mandibular canal were preoperatively assessed by 5 oral surgeons using conventional panoramic radiographs; these were complemented and compared with secondary reconstructed paraxial and panoramic VCT images. RESULTS: The position of the apices in relation to the mandibular canal could be revealed on 94% of VCT reconstructed paraxial images. Assessment of VCT paraxial images could be facilitated by using a toolbar marker in 70% of the paraxial images. In 90% of the paraxial images, it was possible to assess the relationship of the mandibular canal and its adjacent anatomy. The visual grading scores for conventional panoramic images were significantly better on all 7 assessed anatomic sites compared with the reconstructed VCT panoramic images. CONCLUSION: The results showed that the VCT paraxial images gave a significantly clearer perception of the mandibular nerve than conventional panoramic radiographs. However, conventional panoramic radiographs were shown to be better than the VCT reconstructed panoramic images and were therefore an invaluable tool in the "expert-derived" assessment and posed the potential for identifying the need for further VCT diagnostic procedures.

Adult↗
PubMed2002

Differential diagnosis of hyperthyroidism: Doppler sonographic quantification of thyroid blood flow distinguishes between Graves' disease and diffuse toxic goiter.

The aim of our study was to evaluate the usefulness of color duplex sonography to distinguish Graves' disease from diffuse toxic goiter. 24 patients with Graves' disease and 13 patients with diffuse toxic goiter underwent B-mode- and color duplex sonography of the thyroid gland. All patients had hyperthyroidism and elevated (99m)Tc-uptake. Spectral Doppler recordings were obtained at all thyroid arteries. Representative color flow maps of the thyroid gland were analyzed, calculating the percentage area of the thyroid gland, occupied by color pixels (color pixel density). The B-mode ultrasound pattern was subjectively assessed on a 4-point rating scale. In patients with Graves' disease the mean peak systolic velocity (PSV) (SD) was 110 (+/- 49) cm/s, the mean volume flow rate (VFR) was 123 ( +/- 67) ml/min and the mean color pixel density (CPD) was 33 (+/- 12) %. For patients with diffuse toxic goiter mean PSV (SD) was 43 ( +/- 9) cm/s (p < 0.001), mean VFR was 23 (+/- 10) ml/min (p < 0.001) and mean CPD was 9 (+/- 6) % (p = 0.007). CPD and spectral duplex recordings were positively correlated (CPD/PSV: rs = 0.77, CPD/VFR: rs = 0.75; p < 0.0001). No significant differences were observed concerning RI values. Sensitivity was 87% and specificity 92% for CPD and VFR and 87% and 100% for PSV. We conclude, that color duplex sonography can reliably distinguish diffuse toxic goiter from Graves' disease and therefore contributes significantly to the differential diagnosis of hyperthyroidism in diffuse thyroid disease.

Adult↗
PubMed2002

Multi-slice CT-colonography in low-dose technique--Preliminary results.

PURPOSE: Assessment of Multi-Slice CT-colonography (MSCTC) with standard and low-dose technique in comparison to conventional colonoscopy (CC). MATERIALS AND METHODS: After standardized bowel cleansing, 28 men and 24 women (mean age 60,3 years) underwent CC within two hours after MSCTC had been performed (4 x 2.5 mm collimation, 3 mm slice width, 17.5 mm table feed, 120 kVp). In 19 patients, MSCTC was performed with 120 mAs (CTDI w, eff : 11.28 mGy), and in 33 patients with 10 mAs (CTDI w, eff : 0.94 mGy), respectively. After noise reduction using mathematical algorithms by a dedicated software (ECCET), images were analyzed by two blinded readers in simultaneously displayed 2D- and 3D-modes. Findings in MSCTC were compared to the results obtained with CC. RESULTS: Calculated effective doses ranged between 9 and 12 mSv for 120 mAs, and between 0.75 and 1 mSv for the low-dose technique. In standard dose MSCTC, 20 of 25 lesions (80 %) were found: all 7 tumors (100 %), one large polyp (> 10 mm; 100 %), 6 of 7 medium sized polyps (9.9 to 5 mm; 86 %) and 6 of 10 small polyps (< 5 mm; 60 %). In low-dose MSCTC, 32 of 44 lesions (73 %) were seen: all three large polyps (100 %), 13 of 14 medium sized polyps (93 %) and 16 of 27 small polyps (59 %). An overall sensitivity of 78 % with a specificity of 68 % was calculated. False positive findings were seen mostly for small lesions (12 for standard dose, 11 for low-dose). CONCLUSION: Despite a 12-fold reduction of radiation exposure, MSCTC in low-dose technique performs comparably well to standard dose MSCTC. After mathematical noise reduction, more than 90 % of polyps larger than 5 mm can be detected.

Algorithms↗
PubMed2002

Dose reduction in multi-slice CT of the heart by use of ECG-controlled tube current modulation ("ECG pulsing"): phantom measurements.

PURPOSE: To evaluate the effect of ECG-controlled tube current modulation on radiation exposure in retrospectively-ECG-gated multislice CT (MSCT) of the heart. MATERIAL AND METHODS: Three different cardiac MSCT protocols with different slice collimation (4 x 1, and 4 x 2.5mm), and a pitch-factor of 1.5 and 1.8 were investigated at a multi-slice CT scanner Somatom Volume Zoom, Siemens. An anthropomorphic Alderson-Rando phantom was equipped with LiF-thermoluminescence dosimeters at several organ sites, and effective doses were calculated using ICRP-weighting factors. Scan protocols were performed with ECG-controlled tube current modulation ("ECG pulsing") at two different heart rates (60 and 80 bpm). These data were compared to previous data from MSCT of the heart without use of "ECG pulsing". RESULTS: Radiation exposure with (60 bpm) and without tube current modulation using a 2.5 mm collimation was 1.8 mSv and 2.9 mSv for females, and 1.5 mSv and 2.4 mSv for males, respectively. For protocols using a 1 mm collimation with a pitch-factor of 1.5 (1.8), radiation exposure with and without tube current modulation was 5.6 (6.3) mSv and 9.5 (11.2) mSv for females, and 4.6 (5.2) mSv and 7.7 (9.2) mSv for males, respectively. At higher heart rates (80 bpm) radiation exposure is increased from 1.5 - 1.8 mSv to 1.8 - 2.1 mSv, using the 2.5 mm collimation, and from 4.6 - 5.6 mSv to 5.9 - 7.2 mSv, for protocols using 1 mm collimation. CONCLUSIONS: The ECG-controlled tube current modulation allows a dose reduction of 37 % to 44 % when retrospectively ECG-gated MSCT of the heart is performed. The tube current - as a function over time - and therefore the radiation exposure is dependent on the heart rate.

Coronary Angiography↗
PubMed2002

Early postoperative tissue harmonic sonography of the thyroid gland.

PURPOSE: Fundamental gray-scale imaging (FGI) is known to be unuseful for thyroid imaging in the early postoperative setting. Thus, we evaluated the feasability of tissue harmonic imaging (THI) early after thyroid resection. MATERIAL AND METHODS: FGI and THI of the neck were performed in 48 consecutive patients 4 days after surgery. The examiner was blinded to patient diagnoses and types of surgery. FGI and THI examinations were stored on videotape and reviewed offline by two different readers who rated the quality of delineation of the organ borders and presence or absence of focal lesions. The results were compared to neck US performed 12 weeks after surgery. RESULTS: Delineation of the thyroid remnants in THI/FGI was rated to be excellent in 22/2, good in 11/9, poor in 3/16 and not visible at all in 4/13 patients. The correlation between THI-volumetry and control-volumetry was very high (r=0.81; p<0.0001). THI but not FGI depicted presence or absence of solid thyroid nodules with 100% accuracy. CONCLUSION: THI is a feasible method for thyroid US in the early postoperative setting. It permits volumetry of the residual thyroid tissue and accurately depicts nodules within the thyroid remnant.

Female↗
PubMed2002

Contrast-enhanced MR urography in the evaluation of renal transplants with urological complications.

AIM: The diagnostic work-up of renal transplants with impaired function due to urological problems can be difficult. This study was performed to assess sensitivity and specificity of non-invasive contrast-enhanced MR urography (MRU). METHODS AND MATERIALS: Thirty-five patients with renal transplants (25 - 71 years, mean: 53.4 years) with sonographically diagnosed hydronephrosis or perirenal fluid collections were assessed by MR urography. MR examinations were carried out at a 1.5 T clinical scanner (Vision, Siemens, Erlangen, Germany) with a 512 matrix contrast-enhanced fat-suppressed T1-weighted FLASH 3D sequence in breath-hold technique. MIP reconstructions were used to produce MR urography. MRU diagnoses were compared to operative results. RESULTS: In all patients, images with sufficient contrast in the renal collecting system were obtained. Hydronephrosis was confirmed in 20 patients, 8 patients showed a different pathology while 7 had normal findings. Compared to operative results, sensitivity of MRU was 100% with a specificity of 78%, respectively. One ureteral stone was misdiagnosed as a stricture, and 2 suspected ureteral stenoses could not be found upon operation. CONCLUSIONS: Contrast-enhanced MR urography is a highly sensitive and specific non-invasive method to evaluate patients suspected of having typical post-transplant urological complications. It may replace invasive procedures such as antegrade pyelography in the pre-operative work-up.

Adult↗
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↗
PubMed2001

Radiation exposure in multi-slice CT of the heart.

PURPOSE: To assess radiation exposure of patients undergoing Multi-Row Detector CT (Multi-Slice CT, MSCT) of the heart. MATERIAL AND METHODS: Four different cardiac MSCT protocols with changing slice collimation (4 x 1, and 4 x 2.5 mm), and pitch-factor (1.5, 1.8, and 4) were examined. An anthropomorphic Alderson-Rando phantom was equipped with LiF-thermoluminescent dosimeters at several organ sites, and effective doses were calculated using ICRP-weighting factors. These data were compared to data from standard MSCT of chest and abdomen. RESULTS: Effective dose in different protocols for cardiac MSCT varies from 2.8 to 10.3 mSv (male), and from 3.6 to 12.7 mSv (female). In protocols with thin collimation and low pitch or a combination of several heart examinations, radiation exposure may be comparable to the effective dose of standard MSCT of the chest (male: 11.9 mSv, female: 12.9 mSv) or the abdomen (male: 16.1 mSv, female: 15.7 mSv). Highest organ doses were found for the female breast (up to 46.6 mGy), and the lungs (up to 36.4 mGy) with surface doses as high as 54.3 mGy. CONCLUSIONS: Cardiac MSCT adds significantly to the radiation exposure of patients and can reach the effective dose applied by standard MSCT of chest or abdomen.

Bone Marrow↗
PubMed2001

[Gaucher disease: MR evaluation of bone marrow features during treatment with enzyme replacement].

PURPOSE: Enzyme replacement therapy (ERT) arrests and reverses the hematological and visceral symptoms of adult Gaucher disease, the most frequent lysosomal storage disorder. There are only a few studies available evaluating bone disease during ERT. The aim of this study was to investigate the features of bone marrow (bm) by magnetic resonance imaging (MRI) in these patients during ERT. MATERIALS AND METHODS: MRI was performed prospectively in thirty adult type I Gaucher patients before and during ERT with a mean follow-up of 3 years. Spin-echo sequences (T(1)/T(2)) of the lower extremities were obtained and the reconversion (response) or lack of reconversion (non-response) to fatty marrow during treatment was analyzed. The morphological features of bm involvement, a homogeneous or non-homogeneous distribution of bm changes and focal bone lesions surrounded by a rim of reduced signal intensity (SI), were analyzed. RESULTS: Infiltration of bm by Gaucher cells is characterized by a reduction of SI on both T(1)- and T(2)-weighted sequences. Bone marrow responses were seen in 19 patients (63 %) during treatment. Focal bone lesions, surrounded by a rim of reduced SI, did not respond to ERT and correlated with a non-homogenous distribution of bone involvement and splenectomy. CONCLUSION: In adult patients with type I Gaucher disease receiving ERT, treatment effects on bone disease can be demonstrated by MRI using Spin-echo sequences due to the partial reconversion of fat marrow. A non-homogeneous type of signal appearance and a status post splenectomy correlate with the presence of bone infarcts.

Adult↗
PubMed2000

Effect of acute intravenous ace-inhibition on the intrarenal doppler flow characteristics in hypertensive patients with and without unilateral renal artery stenosis.

Assessment of intrarenal doppler signals is of particular importance in screening for renal artery stenosis. We studied the effect of acute ACE-inhibition (1,25 mg enalaprilate i.v.) on intrarenal resistive indices in 10 hypertensive patients with unilateral renal artery stenosis versus 10 patients with essential hypertension. Any changes limited to poststenotic vessels could possibly improve the diagnostic value of duplex sonography. After ACE-inhibition a significant fall of the intrarenal Resistive Index occurred in both patient groups. In cases of unilateral renal artery stenosis we saw a tendency to an increased side difference of the Resistive Index due to a greater fall on the poststenotic side. Therefore a clear advantage of duplex scanning after acute ACE-inhibition due to a limited effect of enalaprilate on poststenotic vessels was not found. The results suggest that the vascular resistance and not only the degree of renal artery stenosis is of significance for the characteristics of the doppler signal.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2000

CT of the head by use of reduced current and kilovoltage: relationship between image quality and dose reduction.

BACKGROUND AND PURPOSE: CT is a frequent examination that is performed using ionizing radiation. We sought to assess image-quality changes on CT scans of the head when the radiation dose is reduced by changing tube current and kilovoltage. METHODS: A formalin-fixed cadaver was examined in conventional and helical mode by use of two CT-scanners. Surface dose was measured with standard scanning parameters, and after reduction of tube current and kilovoltage. Five experienced examiners independently evaluated subjective image quality. RESULTS: In the conventional mode, the highest surface dose was 83.2 mGy (scanner 1: helical mode, 55.6 mGy), and 66.0 mGy (scanner 2: helical mode, 55.9 mGy). By changing kVp and mAs, a dose reduction of up to 75% (scanner 1), and 60% (scanner 2) was achieved. No observable differences in image quality between scans obtained with doses from 100% to 60% of standard settings were noted. Ten of 20 images obtained with the highest dose and 13 of 20 images obtained with lowest dose (19-29.4 mGy) were reliably identified by subjective quality assessment. Scans produced with a surface dose of less than 30 mGy were judged uninterpretable. CONCLUSION: Standard parameters used in cranial CT are oriented toward best image quality. A dose reduction up to 40% may be possible without loss of diagnostic image quality.

Cadaver↗
PubMed1999

Neonatal jaundice and diet.

OBJECTIVE: To determine whether an earlier observation, that infants fed a casein-hydrolysate formula (Nutramigen) have lower neonatal jaundice levels than those fed standard formulas, would be repeated in a larger independent group of infants with more frequent measurements and more rigorous statistical analysis. DESIGN: Newborn infants were fed human milk, a standard whey-predominant formula (Enfamil), or Nutramigen (n = 20 for each group) during the first 3 weeks of life. Transcutaneous jaundice index was measured daily for the first week of life and every 2 to 3 days thereafter, using a noninvasive jaundice meter. Linear regression models of the data were constructed, validated, and compared statistically. SETTING: General community hospital with subsequent home visitation. PARTICIPANTS: Healthy, term newborn infants selected by convenience, based on time of birth. INTERVENTION: Infants were exclusively fed human milk, Enfamil, or Nutramigen. Formulas were randomly assigned. MAIN OUTCOME MEASURE: Jaundice index, a transcutaneous measurement of jaundice. RESULTS: The jaundice index differed significantly among the 3 groups. Paired comparisons showed that the jaundice index of the Nutramigen group was significantly lower than that of the Enfamil group (on days 6-16) and the human milk group (on days 3-20). The jaundice index of the Enfamil-fed group was significantly lower than that of the human milk group on days 13 to 19. CONCLUSIONS: Jaundice levels are lower in neonates fed Nutramigen rather than Enfamil and both these groups have lower jaundice levels than breast-fed infants.

Bilirubin↗
PubMed1999

Venous incompetence in erectile dysfunction: evaluation with color-coded duplex sonography and cavernosometry/-graphy.

The purpose of this study was to assess the accuracy of multi-parameter measurements with color-coded duplex sonography (CCDS) for the diagnosis of venous leakage in patients with erectile dysfunction. Sixty patients with repeated unsatisfactory reactions after intracavernous injection of vasoactive substances underwent CCDS. Following intracavernous injection of prostaglandin E1, peak systolic velocity (PSV), enddiastolic velocity (EDV), time averaged velocity (TAV), resistance index (RI), and pulsatility index (PI) were measured in the cavernous arteries over 30 min (one measurement per minute). The results were compared with independent measurements based on dynamic pharmaco-cavernosometry/cavernosography (DPCC). Dynamic pharmaco-cavernosometry/cavernosography revealed venous leakage in 33 patients. Of 48 patients with normal PSV ( > 25 cm/s), 25 had veno-occlusive dysfunction and the remainder presented normal venous function. No statistically significant differences between these groups were found in EDV, RI, and PI measurements. In contrast, differences in TAV were significant between patients with (mean 9.4 +/- 4.6 cm/s) and without venous leakage (mean 5.5 +/- 2.2 cm/s; p = 0.001). Analysis of relative frequencies revealed a broad overlap of EDV, TAV, RI, and PI measurements between both groups. Sensitivities and specificities determined from receiver-operating-characteristic curves were > 80 % and > 50% for a TAV threshold of 5 cm/s, and an RI threshold of 1.0. Measurements of EDV, TAV, RI, and PI in patients with repeated unsatisfactory reactions on intracavernous prostaglandin injection are poor predictors of venous leakage and should not replace DPCC in the investigation of vasculogenic impotence.

Adult↗