Biomedical subjects

A F Heuck

Publications and source records attributed to A F Heuck.

17 recordsLinked to original sources

PubMed2001

Perioperative prediction by MRI of prostate volume six to twelve months after laser-induced thermotherapy of benign prostatic hyperplasia.

The purpose of this study was to predict prostate volume outcome 6-12 months after interstitial, laser-induced thermotherapy (LITT) for benign prostatic hyperplasia (BPH) on the basis of prostate magnetic resonance (MR) images obtained within 48 hours before and after LITT. Twenty patients (age, 64.2 +/- 7.4 years) with symptomatic BPH had LITT of the transitional zone of the prostate. MRI was performed within 48 hours before and after LITT, and 6-12 months after LITT (late follow-up). MRI included axial and sagittal T2-weighted fast spin-echo (FSE) images and contrast-enhanced, axial T1-weighted images. Volumes of different prostatic compartments (total prostate, transitional zone, peripheral zone, LITT lesions) were measured by planimetry. Subtraction of LITT lesion volume less than 48 hours after LITT from total and transitional zone volume before LITT, respectively, predicted respective prostatic volumes at late follow-up. Pearson correlations of predicted and measured total prostate and transitional zone volumes were 0.972 and 0.975, respectively. Total prostate volume at late follow-up was accurately predicted (difference, -0.5 +/- 5.7 cc; P = 0.6981, two-tailed paired t-test). Transitional zone volume was underestimated (difference, -3.1 +/- 4.7 cc; P = 0.0075). Peripheral zone volume was overestimated (difference, 2.6 +/- 3.5 cc; P = 0.0034). Perioperative MRI allows accurate prediction of prostate volume 6-12 months after LITT for BPH. Underestimation of transitional zone volume may be due to ongoing growth of BPH. LITT appears to affect peripheral zone tissue outside the target region. J. Magn. Reson. Imaging 2001;13:64-68.

Follow-Up Studies↗

PubMed1999

Coagulative interstitial laser-induced thermotherapy of benign prostatic hyperplasia: online imaging with a T2-weighted fast spin-echo MR sequence--experience in six patients.

PURPOSE: To determine if hypointense lesions clearly outline on T2-weighted fast spin-echo (SE) magnetic resonance (MR) images obtained during coagulative interstitial laser-induced thermotherapy (LITT) of a prostate with benign hyperplasia. MATERIALS AND METHODS: In six patients with benign prostatic hyperplasia (BPH), 12 LITT treatments were followed online with repetitive axial T2-weighted fast SE imaging (repetition time, 3,700 msec; echo time, 138 msec; acquisition time, 19 seconds). Development, time course, correlation with interstitial tissue temperature, and diameters of hypointense lesions around the laser diffusor tip were investigated. Lesion diameters on T2-weighted images acquired during LITT were compared with diameters of final lesions on T2-weighted images and unperfused lesions on enhanced T1-weighted SE images obtained at the end of therapy. RESULTS: Hypointense lesions developed within 20-40 seconds of LITT. Average correlation coefficients between interstitial temperature development and signal intensity development were 0.92 during LITT and 0.90 after LITT. Regression slopes were significantly steeper during LITT (0.67% signal intensity change per degree Celsius) than after LITT (0.47% per degree Celsius; P = .038). Lesions remained visible after LITT for all procedures. Average maximum diameters of lesions were 1-3 mm larger during LITT than after LITT (P = .0006-.019). CONCLUSION: Repetitive T2-weighted fast SE MR imaging during interstitial coagulative LITT of BPH demonstrates the development of permanent hypointense prostate lesions. However, posttherapeutic lesion diameters tend to be overestimated during LITT.

Aged↗

PubMed1998

[Control and monitoring of focal thermotherapy with magnetic resonance tomography. An overview].

Minimally invasive thermotherapies for focal tissue destruction on the basis of laser-, microwave-, focused ultrasound-, or cryogen-induced changes of tissue temperature represent an alternative to surgical tissue ablation, particularly in the treatment of tumors. The thermotherapy modalities listed necessitate indirect guidance and monitoring, since they often do not lend themselves to immediate visual control. In the brain, in head and neck tumors, in the liver, and in the prostate, MRI reliably and accurately delineates both the positions of interstitial thermotherapy applicators and--in contrast-enhanced, T1-weighted images--the perfusion defects in tissue necrosis induced by thermotherapy. The transfer of results of in-vitro and in-vivo model studies to assess interstitial temperature and lesion development during thermotherapy to the actual treatment of patients, however, is still in an initial phase. Further development of both rapid MRI sequences and MRI scanners suited for interventions will show how far treatment systems and guidance systems can be adapted to one another.

Cryotherapy↗

PubMed1998

[Virtual colonoscopy using CT and MRI].

PURPOSE: To evaluate experimentally and in patients the sensitivity and effective dose of virtual electron-beam tomography (EBT) colonoscopy for detecting small colon tumors and to compare the methods and results with virtual colonoscopy using spiral CT and MR imaging in a review of the literature. MATERIALS AND METHODS: Six polyps with diameters between 3 and 12 mm were created and randomly placed in resected pig colon. After distension with air, the pig colon was scanned with continuous volume scanning (CVS, 3 mm collimation) and a pitch of 0.4, 0.8 and 1.5. Twenty patients positive for the fecal blood test were examined after rectal CO2 insufflation and i.v. administration of 1 mg glucagon. A 13 s CVS scan was used to cover the entire colon within one breath-hold. 3D volume-rendered fly-throughs were evaluated by two independent radiologists. Effective dose equivalent was estimated using an Alderson phantom equipped with thermoluminescence dosimeters. RESULTS: In the tumor model, all polyps were detectable at a pitch of 1.5. A further reduction of the pitch ratio did not improve the conspicuity of the polyps. In patient studies, all tumors (n = 4) and polyps (n = 3) were correctly identified on 3D fly-throughs. Two false positive results were obtained. Effective dose equivalent was calculated at 3.2 mSv per scan. CONCLUSIONS: Our preliminary results indicate that virtual EBT colonoscopy holds promise for fast screening for colon polyps. The best technique for virtual colonoscopy (Spiral CT, EBT, MRI) has not yet been determined and the future role of virtual colonoscopy must still be defined.

Colonic Polyps↗

PubMed1998

Parametrial invasion in cervical carcinoma: evaluation of detection at MR imaging with fat suppression.

PURPOSE: To evaluate detection of parametrial invasion at magnetic resonance (MR) imaging with fat suppression. MATERIALS AND METHODS: In 35 patients with cancer of the cervix, MR imaging was performed with the following sequences: T2-weighted turbo spin echo (SE), turbo short inversion time inversion recovery (STIR), and unenhanced or gadolinium-enhanced T1-weighted SE with and without excitation-spoiling fat suppression. Images obtained with each sequence were evaluated for parametrial invasion by two blinded radiologists separately, who scored their level of diagnostic confidence from 0 to 10 (no confidence to high confidence). Then, all images were evaluated together and findings were correlated with histopathologic findings. RESULTS: No statistically significant differences were found between staging with T2-weighted turbo SE, turbo STIR, and T1-weighted fat-suppressed gadolinium-enhanced SE images. Staging with T1-weighted SE, T1-weighted gadolinium-enhanced SE, and T1-weighted fat-suppressed SE images was significantly worse (P < .05). Diagnostic confidence was lower (P < .001) with T1-weighted gadolinium-enhanced SE and T1-weighted fat-suppressed gadolinium-enhanced SE images (5.5 and 6.2 points, respectively) compared to staging with T2-weighted turbo SE and turbo STIR images (8.2 and 7.6 points, respectively). No statistically significant improvement in staging accuracy was found when all images were evaluated together. CONCLUSION: In MR diagnosis of parametrial invasion, the addition of fat-suppressed or gadolinium-enhanced MR images did not improve the accuracy with T2-weighted turbo SE images alone.

Cervix Uteri↗

PubMed1997

[Morphology and contrast enhancement of ductal carcinoma in situ in dynamic 1.0 T MR mammography].

PURPOSE: The detectability with magnetic resonance mammography (MR-M) of non-invasive ductal carcinoma in situ (DCIS), its morphology, and patterns of contrast enhancement were studied. MATERIAL AND METHODS: A total of 849 MR-M examinations were performed in 741 patients using a dynamic, contrast-enhanced FLASH 3D sequence at 1.0 T. Surgical breast biopsies were obtained in 332 cases. Histological work-up confirmed 164 carcinomas, including 20 DCIS. RESULTS: Of 20 DCIS, 14 were correctly diagnosed by MR-M on the basis of focal increase of signal intensity. In two cases (10%), no increase of signal intensity was observed. In another three cases (15%), multifocal enhancement lead to a false-negative diagnosis. In one case (5%), DCIS was a random finding in a patient diagnosed and treated for adjacent phylloides tumour. The sensitivity of MR-M was 70%. 4 (20%) of the DCIS did not show microcalcifications at conventional mammography and were only detected at MR-M. The sensitivity of conventional mammography also amounted to 70%. However, the combination of both imaging methods increased sensitivity to 90%. CONCLUSION: Ductal carcinoma in situ is not reliably detectable by MR-mammography alone due to lack of a uniform pattern of enhancement.

Biopsy↗

PubMed1997

Magnetic resonance imaging of the female pelvis. New circularly polarized body array coil versus standard body coil.

RATIONALE AND OBJECTIVES: The authors compare the value of a new circularly polarized body array coil (BAC) system with a standard body coil (BC) for high-resolution magnetic resonance imaging of the female pelvis. METHODS: Twenty patients with cervical cancer were examined with a BC and BAC. Imaging parameters were kept constant (sagittal T2-weighted turbo spin-echo: repetition time = 4000 mseconds; effective echo time = 99 mseconds; 160 x 160 mm field of view; 256 x 256 matrix; 0.63 x 0.63 mm pixel size; 4-mm slice thickness). Images were scored for lesion-to-organ delineation and overall image quality/ artifacts using a scale from 5 to 1 (excellent to poor). Signal-to-noise (S/N) ratios for different tissues (tumor, uterus, vagina, rectum, muscle, and fat) as well as contrast-to-noise (C/N) ratios between tumor and (1) uterus, (2) vagina, and (3) rectum were calculated. Magnetic resonance tumor staging was performed according to the International Federation of Gynecology and Obstetrics (FIGO) classification. RESULTS: Using the BAC, S/N and C/N ratios increased significantly compared with the BC (S/N: 2.7-3.4-fold increase for all organs evaluated, P < 0.001: C/N: tumor versus uterus 2.4-fold, P < 0.01; tumor versus vagina 6.1-fold, P < 0.001; tumor versus rectum 3.1-fold, P < 0.01). This resulted in an improved overall image quality (average ratings: BAC-4.3 points; BC-2.6 points; P < 0.001). Lesion-to-organ delineation (average ratings: BAC 4.3-4.1 points, BC 3.5-2.7 points for all organs evaluated; P < 0.001) was increased noticeably on BAC images. No significant difference was found for staging accuracy. CONCLUSIONS: Circularly polarized BAC provide superior S/N and C/N ratios and improve lesion conspicuity compared with standard BC.

Adult↗

PubMed1996

[Dynamic MR mammography: is the course of signal intensification suitable for the differentiation of different forms of mastopathy?].

PURPOSE: The capacity of dynamic contrast-enhanced MR mammography to distinguish between different forms and grades of mastopathy according to Prechtel's classification was evaluated in a retrospective study. PATIENTS AND METHODS: MR mammograms of 51 patients with histologically proven mastopathy were retrospectively evaluated in areas subsequently biopsied. RESULTS: Mean values of regressive and hyperplastic types of mastopathy differed significantly no significant differences were found between proliferating and non-proliferating mastopathies or Prechtel grades I-III mastopathy when MRI data obtained with a FLASH 3 D sequence (TR = 8.4 ms, TE = 3 ms, flip angle = 30 degrees at 1.0 T) were compared one minute, three, 5 and 8 minutes after i.v. bolus administration of contrast media (Gd-DTPA, 0.1 mmol/kg body weight). CONCLUSION: Our data indicate that dynamic contrast-enhanced MR mammography does not allow the differentiation of proliferating and non-proliferating mastopathy according to the Prechtel classification. Dynamic MR mammography assessment of breast cancer risk does not seem to be feasible.

Breast↗

PubMed1995

[Static and dynamic MR tomography of the pancreas: contrast media kinetics of the normal pancreatic parenchyma in pancreatic carcinoma and chronic pancreatitis].

PURPOSE: We aimed both at improving image quality and diagnostic value of pancreatic MRI by using fast multislice imaging techniques and at demonstrating normal and pathologic signal enhancement in the pancreas after i.v. gadopentate-dimeglumine. METHODS: MR imaging at was performed in 30 patients with suspicion of pancreatic neoplasm or chronic disease and in 15 patients without pancreatic abnormalities. RESULTS: SNR, CNR, mean signal enhancement, and time/signal-intensity curves were calculated. Signal enhancement after i.v. Gd-DTPA averaged 34.4% in neoplasms (n = 14) vs 58.8% in pancreatic tissue not involved by tumour (p < 0.05) in T1-w SE and was also significant in the T1-w GE sequence (p < 0.005). CNR (pancreas vs lesion) and SNR improved significantly (p < 0.005; pancreas: p < 0.001; lesion: p < 0.05) after i.v. Gd-DTPA administration. In patients without pancreatic disease enhancement curves of pancreas demonstrate a rapid signal increase (79.0% after 34 s). Patients with adenocarcinoma or chronic pancreatitis demonstrated flattened signal intensity curves and higher peak signal intensity values (90.1, 111.3% after 68 s). The slope of signal increase of neoplastic tissue was significantly different (p < 0.01) from unaffected parenchyma (48.3% after 51 s, 90.1% after 68 s). CONCLUSION: MR imaging with fast T2-w SE and T1-w SE sequences provides excellent visualisation of the pancreas and adequate conspicuity of pancreatic adenocarcinoma. Following i.v. Gd-DTPA significant enhancement of tumour/parenchyma contrast is found.

Adenocarcinoma↗

PubMed1990

Spinal bone mineral density measured with quantitative CT: effect of region of interest, vertebral level, and technique.

This study documents the relationship between different vertebral bone compartments with quantitative computed tomography (CT). Four distinct patient groups were investigated: healthy pre- and early postmenopausal women as well as healthy and osteoporotic late postmenopausal women. Three different regions of interest (ROIs) were employed: the elliptical ROI located in the anterior trabecular portion of the vertebral body, the peeled ROI of irregular shape that circumscribes most of the trabecular bone, and the integral ROI including all bone except for the transverse processes. Both single- and dual-energy quantitative CT techniques were employed at T-12 through L-3. Correlation between measurements in the elliptical and peeled ROIs was high (r = .985). The authors concluded that either ROI is acceptable for clinical use. The decrements in bone mineral density (BMD) for the integral ROI were smaller than those for the elliptical ROI. Dual-energy measurements were consistently higher than single-energy measurements. BMD as a function of vertebral level decreased systematically from T-12 to L-3. However, the average density of T-12 through L-3 can be accurately predicted by the average density of L-1 and L-2 (r = .997). Precision did not deteriorate significantly when BMD was expressed as the average of L-1 and L-2 (1.5%) instead of T-12 through L-3 (1.4%). In this study the data suggest a modified quantitative CT protocol for clinical applications in which BMD of only L-1 and L-2 are measured at a fixed gantry tilt.

Adult↗

PubMed1989

Mild versus definite osteoporosis: comparison of bone densitometry techniques using different statistical models.

The purpose of this investigation was to determine the ability of three bone densitometry techniques to discriminate subjects with mild vertebral deformities from those with definite compression fractures. We determined bone mineral density (BMD) in 68 postmenopausal women by quantitative computed tomography (QCT) and dual-photon absorptiometry (DPA) of the spine, as well as single-photon absorptiometry (SPA) of the radius. Forty four individuals were classified as having mild deformities of the spine and 24 were considered to have definite vertebral compressions. Several statistical approaches were used to compare these subgroups and to estimate the relative risk of vertebral fracture. Included among these were percent decrements and zeta-scores, ROC curves, odds ratio estimations, and logistic regression analysis. Individuals with definite vertebral fractures had lower bone mineral density at all sites, but measurement of radial compact bone by SPA failed to reach significance. Using ROC analysis to distinguish mild deformities from true compressions, we found that measurement of spinal trabecular bone by QCT to be the most sensitive discriminator; although measurement of spinal integral bone by DPA also gave satisfactory discrimination, whereas assessment of radial compact bone did not adequately differentiate patients with mild deformities from those with definite compressions. Likewise, we found determination of spinal trabecular bone to be the most robust predictor of relative risk of definite fracture using either odds ratios or logistic regression analysis. Measurement of BMD in the peripheral cortical skeleton offered no predictive power for true vertebral fracture. We concluded that direct assessment of the spine, particularly of the trabecular portion, offered the strongest discrimination and relative risk prediction for definite osteoporotic fractures compared with milder forms of this condition.

Aged↗

PubMed1989

Structure, function, and degeneration of bovine hyaline cartilage: assessment with MR imaging in vitro.

The basic magnetic resonance (MR) imaging pattern of normal and degenerated hyaline articular cartilage was studied in vitro in 40 fresh bovine patellae. With the use of an ample spectrum of strongly T1- to T2-weighted sequences, two zones of cartilage with different signal intensities were observed in all specimens. A superficial cartilaginous layer in the MR image with higher water content and longer T1 and T2 correlated with the tangential and transitional zones of normal articular cartilage, whereas a second MR imaging zone with shorter T1 and T2 was identified in the depth of the articular cartilage. Different functional properties in pressure resistance were observed in the two layers. In early cartilage degeneration without thinning, there was increased hydration of the superficial cartilage layer. This study suggests that strongly T1- and T2-weighted images are indispensable for evaluating details in articular cartilage degeneration.

Animals↗

PubMedDate not supplied

MRI of pelvic masses: efficacy of the rectal superparamagnetic contrast agent Ferumoxsil.

The purpose of this study was to determine the potential value of rectally administered Ferumoxsil for pelvic MRI. Twenty patients with suspected rectosigmoid and ovarian tumors were prospectively examined before and after rectal administration of 300 to 600 ml of the superparamagnetic contrast agent Ferumoxsil. Imaging parameters (1.5-T system, phased-array coil, transverse T1-weighted spin echo (SE) and T2-weighted turbo-SE sequences, 6-mm slice thickness, 350-mm field of view [FOV], 512 x 512 matrix) were kept constant. Images were evaluated for tumor presence, lymphadenopathy, bowel involvement, and peritoneal implants. Precontrast and postcontrast studies were rated for bowel delineation, lesion/organ-to-bowel differentiation, presence of artifacts, and confidence of diagnosis. Delineation of rectum and sigmoid colon (P < .001) as well as separation of bowel and vagina, uterus/adnexa, dome of the urinary bladder, lymph nodes, and vessels improved significantly (P < .01) on both T1-weighted and T2-weighted postcontrast sequences. The rectal contrast agent did not increase the level of artifacts. Changes in diagnosis in 7 of 20 patients were mainly due to identification of colorectal tumors or bowel involvement on postcontrast images. The readers' diagnostic confidence was significantly higher on contrast-enhanced than on unenhanced studies (93 +/- 6.4% vs 68 +/- 25.2%). Rectal application of Ferumoxsil improves lesion/organ-to-bowel delineation and overall diagnostic confidence in pelvic MRI.

Administration, Rectal↗

PubMedDate not supplied

Predictability of the size of laser-induced lesions in T1-Weighted MR images obtained during interstitial laser-induced thermotherapy of benign prostatic hyperplasia.

The purpose of this study was to predict diameters of lesions induced by laser-induced thermotherapy (LITT) of benign prostatic hyperplasia (BPH) from MRI signal/tissue temperature correlations during on-line monitoring with a temperature-sensitive fast low-angle shot (FLASH) sequence. Twenty LITT procedures with Nd:YAG (1,064 nm) and diode (830 nm) lasers were monitored on line with a T1-weighted FLASH sequence at 1.5 Tesla. Interstitial prostate temperature (T) was measured on line in 10 LITT procedures and laser energy deposition in 12. Slopes of linear regression curves for signal intensity (SI) over T were applied to determine SI at 60 degrees C to estimate diameters of intraprostatic LITT lesions. Diameters of unperfused LITT lesion cores in contrast-enhanced T1-weighted images served as gold standards. Linear regression curves with an average slope of -.54% SI/degrees C were obtained in 17 LITT procedures. Correlation coefficients were r = .92-.95 for SI/T and SI/energy deposition. Baseline variation of SI at body temperature was +/-3.9%, corresponding to +/-7 degrees C. Prediction of size (13 lesions) from on-line FLASH imaging was correct in 10 of 13, whereas 3 lesions were overestimated. Prediction of LITT lesion diameters from on-line MRI monitoring is possible with a temperature-sensitive FLASH sequence in the prostate. Accuracy may suffice to assign target regions of interest to tissue locations to be protected from coagulation.

Aged↗

PubMedDate not supplied

Quantification of knee joint fluid volume by MR imaging and CT using three-dimensional data processing.

A noninvasive, quantitative technique to estimate joint fluid volume using three-dimensional (3D) processing of magnetic resonance (MR) imaging and CT data was evaluated. The mean accuracy error of this 3D approach with MR imaging, performed on five fresh cadaver knees, was -2.4 +/- 5.1% SD when volume estimates were based on heavily T2-weighted transverse images. A considerably higher mean accuracy error of -12.5 +/- 16.9% SD was found when the 3D approach with CT was used (four fresh cadaver knees), probably because of the small attenuation differences between articular soft-tissue structures and joint fluid. A mean precision error of 4.9 +/- 2.3% SD was found when two radiologists independently evaluated in vivo MR imaging studies of 12 knees with joint effusion. Because of the low CT accuracy, no in vivo studies were performed using CT. Thus, this preliminary study shows that quantification of joint fluid volume with 3D data processing offers more accuracy with MR imaging than with CT. The 3D approach with MR imaging provides a potential tool for clinical studies.

Humans↗

PubMedDate not supplied

Postoperative MRI in patients undergoing interstitial laser coagulation thermotherapy of benign prostatic hyperplasia.

OBJECTIVE: We conducted MRI of the effects of laser-induced thermal therapy (LITT) in benign prostatic hyperplasia (BPH). MATERIALS AND METHODS: Eighteen patients (average age 64 years) were examined with MRI 24-48 h before and after LITT of BPH. Sagittal and axial T2-weighted FSE MR images were evaluated for signs of coagulation necrosis in the prostate gland and the presence of intra- and extraprostatic edema. RESULTS: Coagulation areas showed as a hypointense central core with a hyperintense rim. Intraprostatic edema led to a volume increase of 18-108% both in the central and in the total gland. Periprostatic edema was severe in preprostatic and prevesical tissue as well as lateral to the prostate, moderate in the presacral space, and mild perirectally and dorsal to the prostate. Follow-up examinations 2 weeks to 6 months after LITT in five patients showed decrease of coagulation necrosis volume, prostate size, and edema. CONCLUSION: MRI appears to be a reliable method to monitor LITT effects in patients with BPH.

Aged↗

PubMedDate not supplied

Whole-body bone marrow MRI in patients with metastatic disease to the skeletal system.

PURPOSE: The purpose of this study was to evaluate the diagnostic potential of a whole-body bone marrow MR protocol in the detection of bone metastases. METHOD: Whole-body bone marrow MRI was performed in 18 patients with known malignant tumors and suspected bone metastases. The imaging protocol consisted of fast T1-weighted and STIR sequences applied in different anatomical positions covering the whole skeleton. MRI findings indicating bone metastases were compared with findings from bone scintigraphy. Metastatic lesions were confirmed by follow-up MR examinations, bone scintigraphy, radiography, or CT. RESULTS: A total number of 216 lesions were detected with MRI in comparison with 159 lesions detected with bone scintigraphy. Follow-up examinations confirmed 105 lesions. MRI detected 96 (91.4%) of the confirmed lesions, whereas bone scintigraphy detected 89 (84.8%). The entire examination, including patient positioning and changing of imaging coils, required 45 min of room time. CONCLUSION: Whole-body bone marrow MRI as used in this study is an effective method for evaluating the entire skeletal system in patients with suspected metastatic disease.

Bone Marrow↗