Effect of oxygen tension on NMR spin-lattice relaxation rate of blood in vivo.

Spin-lattice relaxation rate (1/T1) was measured in the left (LV) and right (RV) ventricular cavities in four conscious normal humans and four anesthetized greyhound dogs breathing spontaneously. Inspired oxygen concentration (FIO2) was varied in five steps from 21 to 100%. In dogs, blood was sampled from indwelling catheters in the pulmonary artery and aorta for measurement of PO2. Saturation-recovery and inversion-recovery tomographic images of the ventricular cavities were obtained supine during quiet breathing using a whole-body NMR scanner operating at a static magnetic field strength of 0.15 Tesla. From FIO2 21 to 100%, 1/T1 of LV increased by 11.6% in humans and 9.6% in dogs. In dogs, 1/T1 increased by 2.8% per 100 mm Hg increase in aortic PO2 (r greater than 0.87). There was no correlation in dogs between 1/T1 in RV and pulmonary artery PO2. The LV/RV 1/T1 ratio in dogs increased by 4% per 100 mm Hg increase in the LV-RV PO2 difference, and by 8% in humans as FIO2 increased from 21 to 100%. A rise in dissolved oxygen concentration increases NMR spin-lattice relaxation rates of blood in vivo to a small but significant extent.

Magnetic resonance imaging in infections of the central nervous system.

The magnetic resonance (MR) images in 24 patients with infections of the central nervous system (CNS) were reviewed, and the use of a paramagnetic contrast agent (Gd-DTPA) in two cases is reported. The clinical diagnoses in the patients, aged neonate to 71 years old, comprised meningitis, meningitis and subdural empyema, meningoencephalitis, encephalitis, and single or multiple cerebral abscesses. A new sign of CNS infection, the pial-ependymal line, is described. Other consequences of infection, such as atrophy, delayed myelination, periventricular cerebrospinal fluid extravasation, changes in T1 and T2, and mass effect, are reported and discussed. MR imaging may have a significant application in the study of CNS infections because of the importance of early diagnosis in instituting effective treatment.

MR imaging in progressive multifocal leukoencephalopathy.

The MR imaging appearance of progressive multifocal leukoencephalopathy is described in four cases that were confirmed by brain biopsy. Characteristic aspects are long T1 and long T2 lesions limited to white matter. At first the lesions are round or oval, then confluent and large. There is no mass effect. The involvement is most often asymmetric and distant from the periventricular region. The differential diagnosis includes other diseases affecting white matter: demyelination, infarction, infection, and tumors.

Magnetic resonance imaging of intracranial tumors in children and adolescents.

Magnetic resonance (MR) scans were reviewed of 25 children and adolescents from the age of 9 months to 18 years referred with a suspected or proven diagnosis of intracranial tumor. Twenty-one of these children had MR scans positive for tumor. Histology was available in 14. The other seven patients were managed clinically as cases of cerebral tumor, although histologic confirmation was lacking. Seventeen tumors displayed an increase in both T1 and T2. One dermoid tumor and part of another displayed a very short T1 (less than that of white matter). Two hamartomas had T1s similar to that of gray matter and a small increase in T2. Four of the children did not show MR or computed tomographic (CT) evidence of intracranial tumors. Follow-up of these cases for 1-23 months after the MR and CT studies revealed no subsequent clinical evidence of tumor. MR scans showed more extensive abnormality than did third-generation CT scans in eight of 10 cases and more extensive abnormality than EMI CT 1010 scans in 10 of 11 cases. Mass effects were better demonstrated in 14 of the 16 patients in whom they were seen. CT demonstrated calcification better than did MR in all four cases in which it was identified. The tumor-edema interface was shown better on CT in each of the three cases with contrast enhancement on CT. MR is a sensitive method of evaluating intracranial tumors in children and adolescents.

Contrast-enhanced MR imaging of malignant brain tumors.

Magnetic resonance (MR) imaging was performed before and serially after intravenous injection of 1 mmol/kg gadolinium-DTPA (Schering) in 17 patients with clinical and histologic diagnosis of malignant cerebral tumors. There was a decrease of 1% in T1 and 10% in T2 in normal white matter and a decrease of 8% in T1 and 14% in T2 in normal gray matter. Contrast enhancement was observed in 16 of the 17 tumors. In the region of maximal enhancement a mean decrease of 16% in T1 was observed in low-grade gliomas, a mean decrease in T1 of 29% was seen in high-malignancy gliomas, and a mean decrease in T1 of 33% was observed in metastases. The decreases in T1 persisted for at least 50 min. In one case the central cystic region of the tumor displayed a decrease in T1 and T2. Measurements of signal intensity displayed maximal contrast enhancement with an IR 1500/500/44 sequence, much less with SE 1500/44, and least with SE 1500/80. Edema was observed on precontrast images in 14 cases, but satisfactory definition of the tumor-edema margin was only possible in four cases. After contrast enhancement this margin was defined in 10 cases. In four of the 17 cases areas of apparent "edema" seen before administration of Gd-DTPA displayed significant contrast enhancement and probably represented tumor infiltration. Comparison with CT showed a greater degree of contrast enhancement on MR images in eight cases, an equal degree in eight cases, and greater enhancement on CT in one case.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of NMR imaging in the diagnosis and management of acoustic neuroma.

Nuclear magnetic resonance (NMR) scans of 15 patients with acoustic neuroma are compared with the results of computed tomography (CT). The absence of signal from bone has meant that the images are unaffected by artifacts and that small intracanalicular tumors can be visualized. The multiplanar facility of NMR is emphasized as this allows precise assessment of both tumor volume and its relationship to the ventricular system, brainstem, and tentorial hiatus. The different appearances produced by alternative scan sequences are illustrated and the possibility of predicting the physical constitution from scan appearances is discussed.

Extracerebral collections: recognition by NMR imaging.

After head injury, nuclear magnetic resonance (NMR) scanning is, like computed tomography (CT), an effective method of distinguishing between intracerebral and extracerebral lesions. The location and shape of extracerebral collections are excellently displayed using the multiplanar facility of NMR. There are good grounds for believing that the problem of the isodense subdural hematoma encountered in CT scanning can almost certainly be overcome by the use of NMR imaging.

NMR imaging in the diagnosis and management of intracranial angiomas.

Fourteen intracranial angiomas were clearly visualized and diagnosed with certainty on fast saturation-recovery images, which highlight blood vessels without the use of contrast media, and on steady-state free-precession images, in which the moving blood leads to removal of signal. Performed as the initial investigation, nuclear magnetic resonance obviates angiography when the site and extent of the angioma would preclude operation, and in other cases provides useful anatomic information complementing the angiogram. When clinical presentation follows hemorrhage the size and position of the associated hematoma can be reliably assessed.

Total stabilization of the cervical spine in patients with cervical spondylotic myelopathy.

Certain patients with cervical spondylotic myelopathy demonstrate instability in the upper cervical vertebral column associated with marked narrowing of the vertebral canal in the neighboring lower cervical segments. This combination of causative mechanisms creates difficulty in using routine surgical procedures, especially in elderly and severely debilitated patients. We present three cases that typify this situation and illustrate marked resolution of debilitating myelopathy through total posterior fusion of the cervical spine usually incorporating the occiput.

Distraction rod stabilization in the treatment of metastatic carcinoma.

Stabilization of the spinal column with Harrington distraction rods and acrylic fusion was the primary form of treatment in a select group of patients with metastatic carcinoma of the spinal column. Clinical criteria included patients in poor general medical condition with intractable pain originating from metastatic tumor involvement in the ventral components of the thoracic or upper lumbar spinal column and minimal evidence or absence of spinal cord compression. After stabilization, pain relief was almost total and sustained, and neurological status generally remained unchanged from preoperative findings without any evidence of improvement of preexisting abnormalities or occasions of rapid neurological deterioration. This form of spinal stabilization may offer significant relief of debilitating pain, lessen the risk of pathological fracture-dislocation of the thoracic or upper lumbar vertebral column, and reduction in the local compressive effects on the spinal cord caused by ventrally situated metastatic tumor.

The short TI inversion recovery sequence--an approach to MR imaging of the abdomen.

Initial clinical experience with magnetic resonance imaging (MRI) of the abdomen using short TI inversion-recovery (STIR) pulse sequences is described and compared with X-ray CT in a variety of abdominal disease. The extent of abnormality shown with MRI was greater than that with CT in 21 of 30 cases and equal in 9 cases. Lesion contrast was greater with MRI in 15 cases, equal in 14 and less in 1. The level of artefact was equal in 27 cases and greater with MRI in 3 cases. The STIR pulse sequence has significant advantages in producing high soft-tissue contrast, controlling respiratory artefact, avoiding confusion with intra-abdominal fat and identifying bowel loops.

Contrast-enhanced magnetic resonance imaging of tumours of the central nervous system: a clinical review.

The clinical application of the intravascular paramagnetic contrast agent gadolinium-DTPA for magnetic resonance imaging (MRI) imaging of tumours of the central nervous system (CNS) has been assessed over the past 3 years. Various patterns of contrast enhancement were observed, and situations in MRI where the administration of contrast medium may be useful have been defined. These include lesions which are isointense with normal brain matter, the separation of tumour from surrounding oedema, evaluation of the degree of blood-brain barrier breakdown, delineation of tumours obscured by overlying calcification on computed tomography (CT) and in the investigation of lesions in anatomical areas where CT has known limitations (brain stem, cervical spine). Changes in relaxation times in normal and abnormal tissues following contrast medium, toxicity and dosage of gadolinium-DTPA, and MRI pulse sequence techniques are reviewed.

Measurement of regional pulmonary oedema in man using radioactive water (H215O).

Regional extravascular lung water (rELW) has been measured in normal subjects and in patients with left heart diseases using a double-indicator dilution technique and external counting over the chest. Gamma-emitting radioisotopes were injected intravenously, 113Inm as a vascular non-duffusible indicator, and H215O as a freely diffusible indicator. Time activity curves were then recorded over the upper and lower zones of the lung in the supine position with external probes. rELW per unit of blood volume and rELW per unit of blood flow were increased in patients with raised left atrial pressure even in the presence of radiologically clear lung fields. There was a uniform distribution of these ratios between upper and lower zones in normals, whereas in patients rELW was preferentially distributed in the lower zones.

NMR imaging of central nervous system diseases before and after radiotherapy.

Two brain tumors, a foramen magnum tumor and an arterio-venous malformation (AVM) were treated with radiation but without chemotherapy or surgical removal. These cases were monitored by NMR imaging for a period of 16 months after radiotherapy to detect the response of the tumors and brain tissue to radiation. The T1 and T2 of the tumors behaved independently. T1 decreased after radiation related to clinical improvement. T2 did not change to the same degree as T1. An increased T2 area around the tumors and along the lateral ventricle developed about six months in one case and 16 months in the other case after radiotherapy, without associated clinical change in either case.