Paradoxically decreased signal intensity on postcontrast short-TR MR images

Seven lesions are presented in which short TR/short TE images obtained immediately after IV administration of gadopentetate dimeglumine demonstrated an apparent decrease in signal intensity compared with precontrast short TR/short TE images. All seven lesions were hyperintense on precontrast short TR/short TE images. In four cases in which long TR/long TE scans were also obtained, the lesions were hypointense. This phenomenon may be due to a dominant T2 shortening effect by the contrast material that "overwhelms" T1 shortening even on short TR/short TE scans. Other compounding factors may include variations in scanning variables, receive and transmit attenuations, or a photographic phenomenon due to window widths and center levels.     

Intraoperative sonography in spinal trauma

Intraoperative spinal sonography (IOSS) was performed in 39 spinal trauma patients. IOSS was used to detect and assess the significance of bone fragments and spinal malalignment, cord or thecal sac compression, foreign bodies, and the late complications of spinal trauma, namely post-traumatic intramedullary and subarachnoid cysts. IOSS was also used to evaluate the efficacy of reduction of vertebral fractures, guide the shunting of cysts, and differentiate myelomalacia from intramedullary cysts, thus avoiding unnecessary exploration of the spinal cord. IOSS is a safe and simple procedure that can alter surgical management. The use of IOSS during surgery performed for spinal trauma and its complications is recommended.     

Proton MR spectroscopy of the brain in 14 patients with Parkinson disease.

PURPOSETo determine whether the proton spectra from patients with clinically diagnosed Parkinson disease differ from the spectra of age-matched healthy subjects with respect to the major cerebral metabolite resonances as well as lactate.METHODSFourteen patients with Parkinson disease (38 to 81 years of age) and 13 healthy control subjects (37 to 81 years of age) were studied using image-guided, single-voxel (27-cm3 volume) proton MR spectroscopy of the occipital lobe.RESULTSThe peak area ratios of N-acetyl aspartate to creatine and N-acetyl aspartate to choline for Parkinson patients did not show a statistically significant difference from the corresponding ratios for control subjects. There was a very significant increase in the ratio of lactate to N-acetyl aspartate for patients with Parkinson disease, with the greatest increase (threefold) manifested by the subgroup (n = 4) with dementia. The difference in N-acetyl aspartate to choline between women (n = 7) with Parkinson disease and healthy women (n = 9) approached significance. No dependence of the peak ratios on age, duration of Parkinson disease, or medication (L-dopa) regimen was found.CONCLUSIONPreliminary results indicating an increase in cerebral lactate in patients with Parkinson disease support the hypothesis that Parkinson disease is a systemic disorder characterized by an impairment of oxidative energy metabolism. The larger increases for Parkinson patients with dementia may be diagnostically useful in assessing clinical course and in differentiating Parkinson disease from other causes of dementia. Additional studies are needed, though, to quantitate lactate changes and identify potential contributions from lipid resonances better.     

MR characterization of brain and brain tumor response to radiotherapy

This paper describes our experience in using the T1 and T2 relaxation times for quantitative evaluation of brain and brain tumor response to radiation therapy. Twenty-two computed T1 and 22 computed T2 images were obtained from 66 routine inversion-recovery and spin-echo magnetic resonance (MR) brain scans. The relaxation times of the brain tissues, determined from the computed images, were examined as a function of the absorbed dose. Statistical evaluation of the results showed no significant difference between the relaxation times of irradiated and not irradiated tissues, including tumor and normal white matter. Influence of the magnetic field strength and imaging techniques on the computed T1 and T2 values was confirmed. We conclude that the relaxation time values, as obtained today using conventional MR scanner and standard software, are not specific enough to warrant a correct assessment of the acute radiation effect on the brain tissues.     

Sonography and neurodiagnosis (neurosonography)

Sonography is a necessary part of neuroradiology. Its relative importance will increase as the sonographic images improve and the funds provided for diagnostic imaging decrease. We urge the incorporation of neurosonographic training into our neuroradiology fellowship programs and more widespread use of sonography in neurodiagnosis.     

Intraoperative spinal sonography of soft-tissue masses of the spinal cord and spinal canal

Intraoperative spinal sonography (IOSS) was used to evaluate and monitor the progress of surgery in 18 patients with soft-tissue masses of the spinal canal and spinal cord. With intramedullary masses, IOSS showed not only the site of maximum cord enlargement so that a precise biopsy could be performed but also was able to demonstrate the zone of transition between the mass and normal cord tissue. With extradural masses and intradural extramedullary masses, IOSS showed the exact size and location of the masses and confirmed their removal and/or adequate spinal cord decompression. IOSS indicated the extent of bone removal necessary to give adequate exposure to accomplish total removal of these masses or to localize the proper level for tissue biopsy. IOSS also indicated the need to open the dura when there had been unsuspected transdural tumor spread or when bony decompression had not been sufficient to relieve the pressure on the spinal cord in tonsillar ectopia. Intraoperative spinal sonography is recommended in all cases of spinal surgery performed to resect or biopsy soft-tissue masses of the spinal canal or spinal cord.