Jorma T. Sipponen

A method for chemical shift imaging: demonstration of bone marrow involvement with proton chemical shift imaging

A new method for chemical shift imaging is described. In this method the spin-echo signals are collected with the field gradient switched on, which reduces the imaging time considerably. A human bone marrow pathology is demonstrated by proton chemical shift imaging.

A Method for Tlp Imaging

The spin lattice relaxation time (Tl) is dependent on the strength of the polarizing magnetic field. The relaxation at low field strengths provides information from the processes at macromolecular level. However, the decrease of the polarizing magnetic field decreases the signal-to-noise ratio that determines the resolution of magnetic resonance images. In this report we describe a method for Tip imaging. The method possesses the relaxation time contrast of low field strengths with signal-to-noise ratio provided by the higher polarizing field. The relaxation time Tip is obtained under spin lock conditions. The spin system relaxes toward thermal equilibrium along the locking field. This process is analogous to the spin lattice relaxation at low field strength and characterized by the time constant Tip. Tip and Tip-dispersion may provide new imaging parameters for noninvasive tissue characterization.

Usefulness of extracorporeal membrane oxygenation as a bridge to lung transplantation: A descriptive study

BACKGROUND This retrospective study investigated early outcome in patients with end-stage pulmonary disease bridged with extracorporeal membrane oxygenation (ECMO) with the intention of lung transplantation (LTx) in 2 Scandinavian transplant centers. METHODS ECMO was used as a bridge to LTx in 16 patients between 2005 and 2009 at Sahlgrenska and Helsinki University Hospitals. Most patients were late referrals for LTx, and all failed to stabilize on mechanical ventilation. Thirteen patients (7 men) who were a mean age of 41 ± 8 years (range, 25-51 years) underwent LTx after a mean ECMO support of 17 days (range, 1-59 days). Mean follow-up at 25 ± 19 months was 100% complete. RESULTS Three patients died on ECMO while waiting for a donor, and 1 patient died 82 days after LTx; thus, by intention-to-treat, the success for bridging is 81% and 1-year survival is 75%. All other patients survived, and 1-year survival for transplant recipients was 92% ± 7%. Mean intensive care unit stay after LTx was 28 ± 18 days (range, 3-53 days). All patients were doing well at follow-up; however, 2 patients underwent retransplantation due to bronchiolitis obliterans syndrome at 13 and 21 months after the initial ECMO bridge to LTx procedure. Lung function was evaluated at follow-up, and mean forced expiratory volume in 1 second was 2.0 ± 0.7 l (62% ± 23% of predicted) and forced vital capacity was 3.1 ± 0.6 l (74% ± 21% of predicted). CONCLUSION ECMO used as a bridge to LTx results in excellent short-term survival in selected patients with end-stage pulmonary disease.

Cerebral NMR and CT imaging in dementia.

Thirteen patients with different types of dementia were studied with nuclear magnetic resonance (NMR) and CT imaging of the brain. The overall correlation between CT and NMR findings was good. Areas of hypodensity in cerebral white matter on CT were especially well visualized in the T2-weighted NMR images. Hypodense areas were seen in the white matter of patients with vascular dementias but not in those with primary degenerative dementias. Thus, the presence or absence of white matter changes may be an important factor in the differential diagnosis of vascular dementia and primary degenerative dementia. On the basis of NMR and CT findings, it was difficult to distinguish between the lacunar state type and Binswanger type of vascular dementia. It is suggested, therefore, that these two subgroups of vascular dementia be commonly named angiopathic dementia.

Nuclear magnetic resonance (NMR) imaging of intracerebral hemorrhage in the acute and resolving phases.

Nuclear magnetic resonance imaging of intracerebral hemorrhage revealed a considerable difference in the appearance of the bleedings in the acute and resolving phases. Attention is drawn to the shortening of the relaxation time T1 within the first 2 weeks after the acute onset of symptoms with the location of the change at the periphery of the lesion. The change was most evident with T1 dependent inversion recovery sequence (IR1,500/400). With this pulse scheme the acute hemorrhage was visualized as a dark area during its early days. A bright zone, reflecting the shorter T1, was not seen until the resolving phase at the end of the 1st week. Although its pathophysiological aspects are so far unknown, this finding may offer an opportunity for dating intracerebral hemorrhages.

Natural course and risk factors for impaired renal function during the first year after heart transplantation

BACKGROUND Post-operative renal failure is a common and potentially hazardous complication after heart transplantation (HTx). In this study we characterized pre- and post-operative risk factors for acute renal failure requiring renal replacement therapy (RRT). METHODS Ninety-three patients underwent orthotopic HTx between 2000 and 2007. The risk factors for RRT during the early post-operative period and predictors contributing to impaired renal function within the first post-transplant year were analyzed by regression analysis. The impact of pre-operative renal failure and early post-operative RRT on renal function within 1 year were studied. RESULTS Before HTx, 55% of patients (51 of 93) had normal renal function or mild renal failure (glomerular filtration rate [GFR] >60 ml/min/1.73 m(2)). Before discharge from the hospital, 25% (23 of 93) developed acute renal failure and required RRT. Of these, 16% (8 of 51) had pre-operatively normal renal function or mild renal failure, and 36% (15 of 42) had moderate or severe renal failure (GFR <60 ml/min/1.73 m(2); p = 0.02). The prognosticators for early RRT were prolonged graft dysfunction, re-admission to the operating room due to post-operative bleeding, poor diuresis during surgery (<1,000 ml), pre-operative pacemaker implantation, intubation time >24 hours, pre-operative GFR <60 ml/min/1.73 m(2), post-operative troponin T >6 microg/liter and pre-operative use of angiotensin receptor blocker. CONCLUSIONS Pre-operative renal failure is a significant risk factor for RRT during the immediate post-operative period and requires aggressive treatment. Patients with pre-operative renal failure secondary to severe heart failure and acute post-operative renal failure requiring RRT tend to recover within the first year post-HTx.

Visualization of brain infarction with nuclear magnetic resonance imaging

SummaryNine patients with cerebral or cerebellar hemispheric infarction and two patients with brain stem lesions were studied with NMR imaging in order to examine the lesion with different weightings on the various NMR parameters. The time interval between examination and the acute onset of the stroke varied from one day to six months. The lesions were clearly detected by the T1 weighted inversion recovery sequence but the tissue contrast was better using the spin echo sequence with a long repetition rate and a long echo delay (SE2000/100). In two patients the brain stem lesions were invisible with CT, but were easily depicted with NMR. In one of them the further progress of the lesion was also confirmed and visualized with the follow-up NMR study.

Low field (0.02 T) nuclear magnetic resonance imaging of the brain.

Many technical and instrumental alternatives are available to obtain good spatial and contrast resolution in magnetic resonance (MR) imaging. Optimum field strength remains a controversial question. In spite of its inherent low signal-to-noise ratio, low field imaging exhibits some advantages. It is well established that the relaxation times are dependent on the magnetic field strength. In low fields the relaxation times, especially T1, are shorter and the relative differences of T1 between different tissues are larger. Other benefits are the ease of installation of the device, its cost effectiveness, and the obvious avoidance of hazards caused by the magnetic field. In this report we describe six cases of cerebral lesions studied with an MR imager operating at a field strength of 0.02 T (200 G). This is the lowest field strength reported in clinical MR imaging. The information obtained was equal to that of the CT studies performed on the same patients.

Bronchoscopy in the diagnosis and surveillance of respiratory infections in lung and heart–lung transplant recipients

Fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) and transbronchial biopsies (TBB) is a widely used method to detect respiratory infections and to differentiate them from other postoperative complications in lung transplant (LTX) recipients, but the usefulness of surveillance FOBs is not yet established. The aim of this study was to evaluate the usefulness of FOB in the diagnosis and surveillance of infections in LTX recipients. We reviewed all the consecutive 609 FOBs performed on 40 lung or heart–LTX recipients between February 1994 and November 2002. The overall diagnostic yield was 115/190 (61%) and 43/282 (15%) for clinically indicated and surveillance FOBs respectively (P < 0.001). Infection was established by bronchoscopic samples in 96/190 (50.5.%) of the clinically indicated FOBs and 34/282 (12.1%) of the surveillance FOBs (P < 0.001). The diagnostic yield of the clinically indicated FOBs was highest (72%) from 1 to 6 months post‐transplant (P = 0.04). Pneumocystis carinii was detected in 23 (4.9%) of the bronchoscopic specimens and 15 (65%) of the P. carinii infections were detected during adequate chemoprophylaxis. To conclude, in LTX recipients clinically indicated FOB has a good diagnostic yield in detecting infections and other postoperative complications, whereas the information received from surveillance FOB has remained less significant. With current prophylaxis and screening strategies FOB is still required to detect P. carinii infections.

Intracranial hematomas studied by MR imaging at 0.17 and 0.02 T

The contrast in magnetic resonance (MR) images relies mainly on the relaxation time differences between the tissues. The relative differences in relaxation times T1 are bigger at lower field strengths, although the absolute values of T1 are smaller. A shorter T1 is also advantageous for the contrast of the T2 and proton density weighted images because of the more complete recovery of the spin system during the repetition time TR. Scrutiny of the clinical results of MR shows some unsolved problems in the specificity of diagnosing fresh intracranial hematomas. Low field MR imaging at 0.02 T seems to offer new vistas in this sense. Fresh subdural hematoma was more easily detected and differentiated at 0.02 T than at 0.17 T. The T2 of fresh intracranial hematomas was rather short compared with cerebrospinal fluid and edema and, unlike T1, was not highly dependent on magnetic field strength. The different visualization of acute versus late intracerebral hematoma and the changes during the resorption were demonstrated in follow-up studies of two patients at 0.17 T and of one at 0.02 T. In one patient the same lesion was imaged successively at both field strengths, showing the divergent contrast in the inversion recovery images at 0.02 and 0.17 T.