The current role of precision surgery in oligometastatic prostate cancer.

Oligometastatic prostate cancer (omPCa) is a novel intermediate disease state characterized by a limited volume of metastatic cells and specific locations. Accurate staging is paramount to unmask oligometastatic disease, as provided by prostate-specific membrane antigen-positron emission tomography. Driven by the results of prospective trials employing conventional and/or modern staging modalities, the treatment landscape of omPCa has rapidly evolved over the last years. Several treatment-related questions comprising the concept of precision strikes are under development. For example, beyond systemic therapy, cohort studies have found that cytoreductive radical prostatectomy (CRP) can confer a survival benefit in select patients with omPCa. More importantly, CRP has been consistently shown to improve long-term local symptoms when the tumor progresses across disease states due to resistance to systemic therapies. Metastasis-directed treatments have also emerged as a promising treatment option due to the visibility of oligometastatic disease and new technologies as well as treatment strategies to target the novel PCa colonies. Whether metastases are present at primary cancer diagnosis or detected upon biochemical recurrence after treatment with curative intent, targeted yet decisive elimination of disseminated tumor cell hotspots is thought to improve survival outcomes. One such strategy is salvage lymph node dissection in oligorecurrent PCa which can alter the natural history of progressive PCa. In this review, we will highlight how refinements in modern staging modalities change the classification and treatment of (oligo-)metastatic PCa. Further, we will also discuss the current role and future directions of precision surgery in omPCa.

Diffusion measurements in the ischemic human brain with a steady-state sequence.

RATIONALE AND OBJECTIVES: The authors evaluate the clinical usefulness of a diffusion-weighted steady-state free-precession (SSFP) sequence to detect acute and subacute ischemic changes. METHODS: Twenty-four patients were examined on a 1.5-tesla scanner, using a SSFP-sequence (repetition time [TR]/ echo time [TE] = 22/3-8 mseconds). The slice thickness was 5 mm, 10 averages, 57 seconds per slice. The diffusion gradient strength was 23 millitesla/m, with b-values from 165 to 598 seconds/mm2. Diffusion-weighted images (DWI) were compared with T2-weighted images. RESULTS: The diffusion-weighted SSFP sequence produced diagnostic quality images in 23 of 24 patients. Diffusion depicted (group 1: 0-12 hours) more acute lesions (3 of 6) than T2-weighted images (2 of 6); the mean lesion diameter depicted by diffusion was 10.9 mm (standard deviation [SD], 12.3) and in T2-weighted images was 4.7 mm (SD 6.8). A significant correlation (P < 0.017) in subacute lesions was found when diffusion was compared with turbo spin echo (mean size difference/T2 = 18.5/17.5 mm, SD 13.2/12.2). CONCLUSIONS: The diffusion-weighted SSFP-sequence is more sensitive in acute ischemia and delineates likewise in subacute ischemia, when compared with T2-weighted imaging.

Magnetic resonance imaging-controlled laser-induced interstitial thermotherapy.

RATIONALE AND OBJECTIVES: Laser-induced interstitial thermotherapy (LITT) may become an attractive modality for minimally invasive tumor therapy. Magnetic resonance imaging (MRI) could be used to assist this procedure. METHODS: A T1-weighted turbo fast low-angle shot (FLASH) sequence for on-line monitoring of the laser-influenced region (liver, muscle) was investigated. Sequence parameters were optimized for maximal image contrast. Magnetic resonance imaging-controlled LITT was performed in vitro, in vivo (rabbits), and in 8 human investigations (6 patients). Special laser applicators were used to establish a uniform laser light distribution. RESULTS: With the MRI sequence used, the LITT region is visualized as a bright area outlined by a dark border. This dark border corresponds to an isotherm of 45 +/- 2 degrees C depending on the sequence parameters used. CONCLUSION: With the T1-weighted turbo-FLASH sequence, MRI can be used for on-line monitoring of interstitial laser-induced thermotherapy in moving organs.

Constructive interference in steady state-3DFT MR imaging of the inner ear and cerebellopontine angle.

PURPOSE: To assess the value of a three-dimensional Fourier transformation MR technique "CISS" (constructive interference in steady state) in imaging the inner ear. SUBJECTS: We studied 50 normal inner ears (40 axial, 10 coronal) and 10 pathologic inner ears in 60 patients. RESULTS: The cochlea, semicircular canals, and vestibulum were visualized in detail. Cranial nerve VII and the cochlear, superior vestibular, and inferior vestibular branch of cranial nerve VIII were identified in 90%, 94%, 80%, and 88% of the cases, respectively. A vascular loop was recognized inside the internal auditory canal in 6%, and in the porus in 30%, of the cases. The high signal of the cerebrospinal fluid and labyrinthine fluids (perilymph and endolymph) on the CISS images made excellent delineation of tumors in the cerebellopontine angle and internal canal possible and allowed detection of tumoral labyrinth involvement. The thin sections, high resolution of the images, and capability of producing multiplanar and three-dimensional reconstructions often offered additional information. CONCLUSIONS: The CISS sequence allows detailed study of the normal and pathologic inner ear and promises to be highly valuable in the demonstration of the vascular loop.

Diagnostic value of increased diffusion weighting of a steady-state free precession sequence for differentiating acute benign osteoporotic fractures from pathologic vertebral compression fractures.

BACKGROUND AND PURPOSE: Differentiating acute benign from neoplastic vertebral compression fractures can pose a problem in differential diagnosis on routine MR sequences, as signal changes can be quite similar. Our purpose was to assess the value of increasing the diffusion weighting of a diffusion-weighted steady-state free precession (SSFP) sequence for differentiating these two types of vertebral compression fractures. METHODS: Twenty-nine patients with 32 acute vertebral compression fractures caused by osteoporosis (n = 15) or malignancy (n = 17) were examined with a diffusion-weighted SSFP sequence, a T1-weighted spin-echo sequence, and a short-inversion-time inversion recovery sequence. The SSFP sequence was performed with increased diffusion weighting (delta = 0.6, 3.0, 6.0, and 9.0 ms). The signal intensities of the fractured vertebral bodies were rated on a five-point scale from markedly hypointense to markedly hyperintense relative to normal adjacent vertebral bodies. Quantitative analysis was performed by region-of-interest measurements and by calculating the bone marrow contrast ratio. Statistical analysis was performed with the Mann Whitney U test and Student's t test. RESULTS: At delta = 3 ms, the osteoporotic fractures yielded hypointense signal in seven cases, isointense signal in six, and hyperintense signal in two. The fractures showed a progressive signal loss with increased diffusion weighting, so that hypointensity was reached in all but one case. All metastatic fractures had hyperintense signal with delta = 3 and 6.0 ms. With delta = 9.0 ms, four fractures became isointense. CONCLUSION: Increasing diffusion weighting can reduce false-positive hyperintense osteoporotic fractures or make hypointensity more obvious in cases of osteoporotic fractures.

Effect of acute and repeated selenium treatment on hepatic monooxygenase enzyme activity in male rats.

The effect of sodium selenite administered acutely or repeatedly on the biochemical components of the hepatic microsomal monooxygenase enzyme system was examined in male rats. 72 h following acute administration of selenium (2.4 mg Se/kg, i.p.), there was a significant decrease in ethylmorphine-N-demethylase activity and cytochrome P-450 levels but no change in aniline hydroxylase or NADPH cytochrome c reductase activity. Following repeated administration of selenite in the drinking water (1, 2, or 4 ppm Se) for 30 days, there was no alteration in any of the parameters measured. Following the in vitro additions of selenite to microsomes obtained from untreated rats, ethylmorphine-N-demethylase and aniline hydroxylase activities were inhibited at selenium concentrations of 10(-4) M or greater, but the inhibition achieved was less than 50%. No alterations in cytochrome P-450 levels were observed. These results indicate that selenium is a rather weak, indirect, and substrate-specific inhibitor of the hepatic monooxygenase enzyme system.

Fast and precise T1 imaging using a TOMROP sequence.

Proton spin-lattice (T1) relaxation time images were computed from a data set of 32 gradient-echo images acquired with a fast TOMROP (T One by Multiple Read Out Pulses) sequence using a standard whole-body MR imager operating at 64 MHz. The data acquisition and analysis method which permits accurate pixel-by-pixel estimation of T1 relaxation times is described. As an example, the T1 parameter image of a human brain is shown demonstrating an excellent image quality. For white and gray brain matter, the measured longitudinal relaxation processes are adequately described by a single-component least-squares fit, while more than one proton component has to be considered for fatty tissue. A quantitative analysis yielded T1 values of 547 +/- 36 msec and 944 +/- 73 msec for white and gray matter, respectively.

ECG-triggered arterial FLASH-MR flow measurement using an external standard.

In ECG-triggered FLASH-MR images, the inflow of unsaturated spins into the imaging plane results in the reproducible delineation of time variant flow in the arterial system. With the additional acquisition of an external reference image upstream the arterial vessel under investigation, the quantification of flow is possible with the FLASH-MR sequence in one measurement. The method allows the rapid measurement of arterial flow at least in great vessels.

Breath-hold T2-weighted sequences of the liver: a comparison of four techniques at 1.0 and 1.5 T.

T2-weighted images are considered the most sensitive for lesion detection at high field; however, long imaging time is problematic. Accordingly, the authors compared four breath-hold T2 or T2* weighted sequences comprising T2*-weighted FLASH, T2*-weighted PSIF, T2-weighted rapid spin echo (RASE), and T2-weighted Turbo-FLASH (Turbo) in 20 different healthy volunteers, 10 at 1.0 T and 10 at 1.5 T with reference to regular T2-weighted spin echo. Images were evaluated quantitatively by liver signal to noise (S/N) and spleen-liver signal difference to noise (SD/N) ratios and qualitatively for presence of artifacts and image quality. Data were evaluated for 1.0 T and 1.5 T separately and combined. In the combined evaluation, T2*-FLASH had good S/N (23.1 + 5.1) but low SD/N (2.9 + 1.7) and suffered from susceptibility artifacts. T2* PSIF had good S/N (28.1 + 10.0) and moderate SD/N (6.0 + 2.4), but occasionally had heterogeneous signal intensity. Flow signal void was an attractive feature. T2 RASE had very low S/N (4.4 + 1.9) and low SD/N (2.3 + 1.1) and suffered from flow artifacts. T2-Turbo had good S/N (24.6 + 8.6) and SD/N (8.9 + 2.5). Flow signal void was present, but small matrix size decreased image quality. The results of our study suggest that T2*-PSIF and T2-Turbo have good S/N and SD/N and fair image quality which may be clinically useful for breath-hold T2-weighted sequences of the liver.

Low field thoracic MRI--a fast and radiation free routine imaging modality in children.

Radiography of the chest is the most frequently performed radiological examination in pediatric imaging. However, it is associated with the application of ionizing radiation. In order to avoid ionizing radiation in children a new and very fast MRI technique has been developed at our center as an alternative to the pediatric chest X-ray. 100 patients who had received a chest X-ray were additionally investigated in a 0.2 T low-field MR-scanner by a modified true FISP sequence with an acquisition time of 3.6-4.6 s for a coronal triple-slice scan. X-ray and MR images were independently evaluated and later compared by two pediatric radiologists. Total investigation times (door-to-door time) for X-ray and MRI were comparable. The signal-to-noise ratio for lung parenchyma was 4.6-7.3. Of 189 pathologic findings 165 were depicted on MR images as well as radiographs, 18 were noted on MRIs only, 6 on X-rays only. Overall kappa was 0.87. True FISP MRI may be a good alternative to conventional chest X-ray. The main advantages are: fast imaging free of ionizing radiation, easy performance, no need for special equipment, optional imaging in all 3 planes, good image quality, and a high diagnostic value.

Preliminary evaluation: magnetic resonance of urography using a saturation inversion projection spin-echo sequence.

A saturation inversion projection (SIP) spin-echo technique is reported which allows a reliable direct visualization of the urogenital system as well as its functional performance in magnetic resonance imaging. We used an imaging sequence with a 90 degree saturation pulse and two 180 degree inversion pulses followed by a short spin-echo (SE) pulse sequence. The three time intervals in the 90 degree-180 degree-180 degree-SE pulse train were adjusted to suppress the signals of soft tissues and fat. After intravenous injection of the contrast agent Gd-DTPA, a shortening of the kidney T1 and the T1 of the urogenital system is obtained below the T1 values of fat and soft tissues, and these remaining ultra-short T1 tissues were imaged with the SIP sequence. Using a sequential measuring technique a quantitative evaluation of the glomerular filtration rate seems to be possible with a time resolution of 18 sec per image. In addition, magnetic resonance urography using the SIP sequence provided a good visualization of the urogenital system and may show several clinical utilities in further clinical studies.

The effects of fluid-mechanical factors on MR imaging in the arterial model.

Blood flow is a significant factor in MR imaging. The purpose of this investigation was to study fluid-mechanical effects on MR imaging. MR images generated by the pulsatile flow of bovine blood in an elastic model of the aorta with both renal arteries were studied. The high-frequency pulse sequence was synchronized to an ECG trigger signal. It was demonstrated that different flow velocities, laminar and turbulent flow, and backward flow can be visualized with MR imaging.

[Importance of rapid gradient echo sequences for nuclear magnetic tomographic diagnosis of joint diseases]. / Bedeutung schneller Gradientenechosequenzen für die kernspintomographische Gelenkdiagnostik.

The possibilities and limitations of rapid echo acquisition methods in various posttraumatic, degenerative and inflammatory diseases of the joints are demonstrated and discussed on the basis of a pilot study. It is evident that specific information important for clarifying effusions and meniscopathies is supplied especially by "water"-like images. Limitations of spatial resolution are at present still a limiting factor.

[A new multislice measurement sequence for the complete dynamic MR examination of the larger organs: application to the breast]. / Eine neue Multischicht-Messsequenz für die komplette dynamische MR-Untersuchung an grösseren Organen: Anwendung an der Brust.

Our experience indicates that the most accurate information concerning abnormalities in the breast is obtained by a dynamic technique, in which the signal intensity before and after contrast medium injection is compared. Up to the present, only a small number of sections (1 to 5) could be obtained by dynamic MR, so that only 30-50% of the breast, depending on its size, could be examined. The availability of gradient systems, with rapid switching and high gradient amplitude and duty cycle, makes it possible to obtain a larger number of sections. A new multi-section gradient echo sequence is described, which enables one to examine the entire breast using a dynamic technique (136 images of both breasts in 14.4 minutes). Subsequent automatic post-processing, using a graphic programme, results in quantitative evaluation of the contrast images. This new sequence can be applied to dynamic MR investigations of all large organs.

[MR tomographic demonstration of liquor pulsation]. / MR-tomographische Darstellung von Liquorpulsationen.

With ECG-gated FLASH-sequences motion of cerebrospinal fluid (CSF) is demonstrated in axial slices of the zervikal vertebral column. The course of the movement is dissolved by signal enhancement of flowing structures in magnitude images and by velocity-dependent phases. It is shown with both methods, that the oscillation of the CSF within the cardiac cycle is superimposed by a directed movement, with is cranial directed in the lateral cervical subarachnoidal spaces and caudal in the ventral subarachnoidal spaces.

[Nuclear spin tomography of the male pelvis. Methods, anatomy and initial clinical results]. / Kernspintomographie des männlichen Beckens. Methode, Anatomie und erste klinische Ergebnisse.

A pilot study of MRI was carried out on three normal male volunteers and 15 patients with tumours in the prostate or bladder. One advantage of the method is the ability to obtain images in three planes, without moving the patient. It is therefore possible for the first time to demonstrate lesions in the base of the bladder in their cranio-caudal extent. Tissue contrast of MRI, using long sequences with suitable proton or T2-weighted images is better than with CT and provides more accurate diagnosis. Even non-expansive tumours within the gland can be differentiated from normal glandular tissue. It has been noted that carcinoma of the prostate in the T2-mode provides an increased signal, whereas tumours of the bladder look dark. Up to a point, tissue characterisation may be possible.

[MR diagnosis of cerebrospinal fluid fistulas using a 3D-CISS sequence]. / MR-Diagnostik bei Liquorfisteln mit einer 3D-CISS-Sequenz.

PURPOSE: We compared a new MR method for diagnosis of CSF fistulas with CT cisternography. MATERIAL AND METHODS: In a prospective case study we examined 35 patients with posttraumatic CSF fistulas and compared the results with the intraoperative findings. The MR investigation was performed using a 1.0T whole body MR-system. We used a strongly T2*-weighted 3D-CISS sequence. The examinations were performed in prone position, in patients with severe CSF rhinorrhoea additionally in supine position. RESULTS: The sensitivity and specificity of the MR method (88.9% and 95.1%) is higher compared with CT cisternography (77.8% and 87.8%). The reason for the lower sensitivity of CT compared with MRI are complex fracture systems, involving several paranasal cavities in patients with false positive results in CT cisternography. Reasons for the lower specificity of CT cisternography are false negative results in patients with small dural lesions below 2 mm2. CONCLUSION: Using a new method MRI can detect CSF-fistulas. The MR method is superior to CT cisternography, is noninvasive, the administration of contrast and agent is no longer necessary.

[More rapid MRT with T2-weighted spin-echo sequences through variation of the flip angle]. / Schnellere MRT mit T2-gewichteten Spinecho-Sequenzen durch Variation des Anregungswinkels.

In the present study the influence of the flip angle on image contrast in spin echo imaging was investigated. It was evaluated, whether variation of the flip angle allows for shorter repetition and imaging times in T2-weighted spin echo sequences. 10 patients with cerebral white matter lesions were investigated with an 1.5 Tesla whole body tomograph using a conventional double-spin echo sequence (TR = 2500 ms, TE = 15 and 70 ms) and time-optimized double-spin echo sequences (TR = 1900 ms, TE 15 and 70 ms) at flip angles of 90, 80, 70, 60 and 50 degrees. A reduction of the flip angles resulted in a decrease of T1-weighting and a relative increase of T2-weighting of the images. Despite the reduced repetition time at a flip angle of 70 degrees visually and quantitatively assessed contrast between lesions and brain as well as image artifacts of the time-optimized sequence were comparable to the conventional spin echo sequence; however, imaging time was shortened about 25%.

[Clinical use of gradient echo sequences of longer repetition times]. / Klinische Anwendung von Gradientenecho-Sequenzen mit längeren Repetitionszeiten.

Studies designed to optimise image contrasts of gradient echo sequences showed, that especially repetition times between 250 and 500 ms in combination with adequate echo times and flip angles provide new image contrasts. The clinical purpose of gradient echo sequences with longer TR was systematically evaluated in 450 patients. A major advantage of GE sequences was the low signal intensity of fat and bone tissue. On the other hand different pathologic changes showed a high signal intensity in comparison to T2 weighted spin echo sequences as well. With the possibility of multiple slices GE sequences were of outstanding diagnostic value especially in MR of soft tissue and of the musculoskeletal system. T2 weighted SE sequences provided no additional informations and could therefore be omitted in a great number of examinations.

[Rapid nuclear magnetic resonance tomography. Initial results of studies using the new gradient echo sequence]. / Schnelle Kernspintomographie. Erste Untersuchungresultate mit der neuen Gradientenechosequenz.

In 60 patients with intracerebral lesions, examined by MRI, a new gradient-echo sequence was employed. This imaging technique uses excitation pulse angles smaller than 90 degrees and echoes are produced by an inversion of the read gradient. Since no 180 degrees pulse between successive excitations is necessary, very short repetition times can be used. Depending on matrix-size and signal averaging, MR imaging time can be reduced to approximately 5 to 40 seconds for single slice scan. For comparison, conventional T1- and T2-weighted spin-echo images were performed. Diagnostic results of the T1-weighted fast gradient-echo images corresponded with T1-weighted spin-echo images in 30% of cases. Diagnostic information was lower in 40% of cases. In the remainder of cases (30%) lesions were not detected with the gradient-echo technique. This especially applied to multiple sclerosis, infarctions and low-grade gliomas. Due to image artefacts and low contrast, visualization of small pathologic lesions was limited. Significant improvement of tumor visualization on gradient-echo scans was observed after injection of Gd-DTPA (0.1 mmol/kg).