MR imaging of intracranial hemorrhage in neonates and infants at 2.35 Tesla

Summary The variations of the relative signal intensity and the time dependent changing contrast of intracranial hemorrhages on high-field spin-echo magnetic resonance images (MRI) were studied in 28 pediatric patients. For T1-weighted images, a repetition time (TR) of 500 ms and an echo time (TE) of 30 or 23 ms was used. The corresponding times for T2-weighted images were TR 3000 ms and TE 120 ms. Intracranial hematomas, less than 3 days old, were iso- to mildly hypointense on short TR/TE scans and markedly hypointense on long TR/TE scans (acute stage). In the following four days the signal of the hematomas became hyperintense on short TR/TE scans, beginning in the periphery and proceeding towards the center. On long TR/TE scans the signal remained markedly hypointense (early subacute stage). 7–14 days old hematomas were of high signal intensity on short TR/TE scans. On long TR/TE scans they appeared hypointense in the center and hyperintense in the periphery (late subacute stage). By the end of the second week the hematomas were of high signal intensity on all pulse sequences (chronic stage). Chronic hematomas were surrounded by a parenchymal rim of hypointensity on long TR/TE scans. 28 neonates and infants (with 11 follow-up examinations) of 31.5–70.6 weeks postconceptional age (PCA), with an intracranial hemorrhage were examined. The etiologies of the hemorrhages were: asphyxia (17 cases), brain infarct (2), thrombocytopenia (1), clotting disorder (1) and unknown origin (7). The aim of this study was to describe the appearance of intracranial hemorrhages inneonates and infants with MRI at2.35 Tesla using spine-cho sequences.     

Spin-echo MR imaging of intracranial hemorrhage

Summary This retrospective study was performed to describe the appearance of intracranial hemorrhagic lesions on magnetic resonance (MR) imaging at 0.35 tesla using the spin-echo technique, and define the present clinical role of MRI in this particular pathology. Forty-eight examinations of forty-three patients with forty-seven intracranial hemorrhagic lesions (39 true hematomas and 8 hemorrhagic lesions mixed with other tissues) were reviewed for this study. Comparative CT studies were available for all the patients. In our limited experience with acute hematomas (less than 3 days old), low or isointense signal was seen with a short TR (0.5 s), but a relative increase in signal intensity was observed with a long TR (2.0 s). This appearance of acute hematoma was not specific. Chronic hematomas (more than 3 days old) were imaged as foci of bright signal intensity on both short and long TR. This pattern was characteristic of chronic hematoma. With a short TR (0.5 s), two hemorrhagic lesions (5 and 7 days old) were displayed as an isointense signal surrounded by a rim of high intensity signal. This peripheral zone most likely represented liquefaction at the clot's periphery and the initial formation of methemoglobin. T1 and T2 relaxation times were found to be very long for acute hematomas (first two days). T1 values of chronic hematomas (more than 3 days old) were compaaatively short and in the same range as T1 of white matter. T2 values of chronic hematomas decreased also but remained very long.     

MR imaging of experimentally induced intracranial hemorrhage in rabbits during the first 6 hours.

PURPOSE: To evaluate the MR appearance of intracranial, especially intraparenchymal, hemorrhage during the first 6 hours after bleeding with various pulse sequences in an animal model. MATERIAL AND METHODS: Intracerebral hematomas and subarachnoid hemorrhage were created by injecting autologous blood in 9 rabbits. MR studies were performed using a 1.5 T scanner with pixel size and slice thickness comparable to those used in clinical practice before blood injection, immediately after injection, and at regular intervals during 6 hours. The images were compared with the hematoma sizes on formalin-fixed brain slices. RESULTS: In every animal, susceptibility-weighted gradient-echo (GRE) pulse sequences depicted the intraparenchymal hematomas and blood escape in the ventricles or subarachnoid space best as areas of sharply defined, strong hypointensity. The findings remained essentially unchanged during follow-up. The sizes corresponded well to the post-mortem findings. Gradient- and spin-echo (GRASE) imaging revealed some hypointensities, but these were smaller and less well defined. Spin-echo (SE) sequences (proton density-, T1- and T2-weighted) as well as a fluid-attenuated inversion recovery turbo spin-echo sequence (fast FLAIR) depicted the hemorrhage sites as mostly isointense to brain. CONCLUSION: Susceptibility-weighted GRE imaging at 1.5 T is highly sensitive to both hyperacute hemorrhage in the brain parenchyma and to subarachnoid and intraventricular hemorrhage.     

Acute intracranial hemorrhage: intensity changes on sequential MR scans at 0.5 T

Thirty-seven patients underwent MR imaging at 0.5 T within 7 days of a CT-documented intracranial hemorrhage. A total of 57 hematomas were evaluated. Twelve patients underwent serial scanning and 12 patients had multiple hemorrhages into different intracranial compartments. The appearances of the hematomas on spin-echo (SE) images with a short repetition time (TR) of 500 msec and short echo time (TE) of 32 msec (SE 500/32), long TR/intermediate TE (SE 2000/60), and long TR/long TE (SE 2000/120) were carefully evaluated with specific attention to the precise time after ictus. Hematomas showed heterogeneous, complex, rapidly changing intensities. There was a significant amount of variation among patients, especially between the third and seventh days. Hematomas studied between 12 and 24 hr after hemorrhage were mildly hyperintense on short TR scans and markedly hyperintense on long TR (intermediate and long TE) scans (stage I). These findings in acute hemorrhage have received little prior attention. Over the next 1-2 days, hematomas became iso- to mildly hypointense on short TR scans and markedly hypointense on long TR scans (stage II). Hypointensity on long TR scans has previously been described at high field strengths; our communication demonstrates that this phenomenon is seen routinely at intermediate field strengths as well. Hematomas became markedly hyperintense on short TR scans beginning on approximately the fourth day postictus and redeveloped hyperintensity on long TR scans approximately 5-6 days after ictus (stage III). By the end of the first week they were hyperintense on all pulse sequences (stage IV). MR findings on the first day after intracranial hemorrhage (in particular, subtle hyperintensity on short TR scans) probably allow for a specific diagnosis, while the variable, hetergeneous, and rapidly changing intensities noted between days 2 and 7 are often less specific.     

MR imaging of intracranial metastatic melanoma

Ten patients with intracerebral metastases from malignant melanoma were evaluated with magnetic resonance (MR) imaging performed at 1.5 T using spin-echo techniques. On the basis of histopathologic findings in three of 10 cases and CT appearances in all 10 cases, three patterns were identified on analysis of MR signal intensities in both short repetition time/echo time (TR/TE) and long TR/TE spin-echo scans. In comparison to normal cortex, nonhemorrhagic melanotic melanoma appeared markedly hyperintense on short TR/TE images and isointense, mildly hypointense on long TR/TE images. Nonhemorrhagic, amelanotic melanoma appeared isointense or mildly hypointense on short TR/TE and isointense or mildly hyperintense on long TR/TE images. Hemorrhagic melanoma varied in appearance, depending on the stage of hemorrhage. Melanotic, nonhemorrhagic melanoma can be distinguished from early and late subacute hemorrhage by its signal intensity on long TR/TE images. Spin-echo MR appears to be the method of choice for diagnosing melanotic metastases.     

High-field MR imaging of extracranial hematomas

The MR features of 20 extracranial hematomas studied on a 1.5-T system and imaged with both short repetition-time/echo-time (TR/TE) and long TR/TE pulse sequences were reviewed. In four of five acute hematomas (those less than 7 days of age), signal intensity was markedly decreased on long TR/TE images and was either intermediate or slightly decreased on short TR/TR images. Fourteen subacute hematomas (7 days to 7 weeks of age) and one chronic hematoma (9 months) were studied. The appearance of the subacute lesions varied from intermediate to high intensity on short TR/TE sequences, but all demonstrated increased signal on long TR/TE sequences. A low-signal rim was noted at the margin of nine subacute lesions. In one patient with this finding, pathologic examination showed that the low-signal margin corresponded to a region containing hemosiderin-laden macrophages at the periphery of the hematoma. These results correlate well with those reported for intracranial hematomas examined at this field strength. We conclude that analysis of signal-intensity patterns at 1.5 T is useful in staging the evolution of hematomas.     

MR imaging of brain abscesses

The MR images and CT scans of 14 patients with surgically verified pyogenic cerebral abscesses were reviewed. The MR findings correlated well with those seen on CT and were believed to be sufficiently characteristic to allow early and accurate diagnosis with MR alone. These features include (1) peripheral edema producing mild hypointensity on short TR/short TE and marked hyperintensity on long TR/intermediate to long TE scans; (2) central necrosis with abscess fluid hypointense relative to white matter and hyperintense relative to CSF on short TR/short TE scans and hyperintense relative to gray matter on long TR/intermediate to long TE scans (the fluid had concentric zones of varying intensity in seven cases, a finding not previously identified in other lesions); (3) extraparenchymal spread (intraventricular or subarachnoid), which was detected more easily on MR than on CT and was manifested by increased intensity relative to normal CSF on both short TR/short TE and long TR/intermediate TE scans; and (4) visualization of the abscess capsule, which was iso- to mildly hyperintense relative to brain on short TR/short TE scans and iso- to hypointense relative to white matter on long TR/intermediate to long TE scans. On the long TR scans, the relative hypointensity of the rim allowed for visualization of the typical morphologic features of the capsule, which in turn aided in differentiation of abscesses from other lesions (as it does on CT). To investigate the cause of the capsular intensity, pathologic studies of the capsules were reviewed when available (10 cases). Fibrosis was identified in all mature abscess capsules, but the combination of the intensities seen on short TR/short TE and long TR/intermediate to long TE scans as well as the temporal changes in intensity were believed to be incompatible with fibrosis as a cause of the capsular changes. Intensity patterns were suggestive of hemorrhage, but neither acute nor chronic hemorrhage was identified on routine H and E stains, while iron stain revealed scant hemorrhage in only two of the eight patients in whom these stains were used. We believe the capsular intensity (in particular the hypointense rims on long TR scans) may reflect paramagnetic T1, and to a greater extent T2, shortening, possibly due to the presence of heterogeneously distributed free radicals that are products of the respiratory burst produced by actively phagocytosing macrophages in the capsule wall. Distinctive MR features of pyogenic abscesses should afford early and accurate diagnosis.     

Acute hypertensive intracranial hemorrhage: MR imaging at 1.5T

Twelve patients with acute hypertensive intracranial hemorrhage underwent magnetic resonance (MR) imaging within 7 days after the ictus. T1-weighted (TR = 400 msec; TE = 20 msec) and T2-weighted (TR = 2000 msec; TE = 80 msec) images were obtained on a 1.5 Tesla MR system. Signal intensities of hematomas were carefully evaluated and were compared with white matter intensity. A 9-hour-old hematoma was mildly hypointense on T1-weighted images, and was mildly hyperintense on T2-weighted images, suggesting a reflection of the high water content. On T2-weighted images, thin peripheral hypointense rim, probably due to deoxyhemoglobin, was also observed. Both of 15-hour-old hematoma and 21-hour-old hematoma had peripheral hypointensity on T2-weighted images. Both of 39-hour-old hematoma and 43-hour-old hematoma had central hyper-intensity on T1-weighted images and iso-to-mild central hypointensity on T2-weighted images, suggesting a reflection of decreased water content. A 3-day-old hematoma had thin peripheral iso-to-mild hyperintense rim on T1-weighted images, presumably due to intracellular methomoglobin. A 5-day-old hematoma had thin peripheral hyperintense rim on T2-weighted images, probably due to free methemoglobin. A 7-day-old hematoma was hyperintense on T1-weighted images and was mildly hypointense to hyperintense on T2-weighted images, presumably due to mixed intracellular methemoglobin and free methemoglobin.     

MR imaging of intracerebral blood: diversity in the temporal pattern at 0.5 and 1.0 T

MR scans were obtained at 0.5 and 1.0 T in 40 patients with 46 intracerebral hematomas categorized as hyperacute (0-2 days), acute (3-7 days), subacute (8-14 days), and chronic (15 days to 6 years). In a retrospective review, the signal intensity of the lesions was compared with that of normal white matter of the brain on spin-density, T1-, and T2-weighted spin-echo and T1-weighted gradient-echo sequences. The classic appearance and evolution of hematomas described in the literature at 1.5 T were not found in a significant number of the cases reviewed. In the hyperacute group, only five of eight hematomas had signal intensities that were hypointense relative to brain on T2-weighted images. Two of eight hyperacute hematomas were hyperintense relative to brain on the T1-weighted spin-echo images. However, T1-weighted gradient-echo images reliably demonstrated a hypointense signal in some portion of the hematoma in 45 of 46 cases. We conclude that while there is no constant temporal pattern on spin-echo or gradient-echo sequences, there are signal-intensity changes suggestive of hemorrhage in nearly all hematomas imaged at 0.5 and 1.0 T. Although the inconsistency may be frustrating from a diagnostic standpoint, this variability may reveal important individual differences in hematomas and the brain that surrounds them, and thus be clinically significant. Before these data can be mechanistically analyzed, the reason for contrast on MR scans of hematoma must be better understood.     

Experimental acute intracerebral hemorrhage. Value of MR sequences for a safe diagnosis at 1.5 and 0.5 T

Purpose: To determine the detectability of intracerebral hematomas with MR imaging at 1.5 T and 0.5 T with fluid attenuated inversion recovery turbo spin-echo (FLAIR) and gradient-echo sequences.Material and Methods: Twenty-seven intracerebral hematomas were created in 25 piglets by injection of venous blood into the brain through a burr hole. All were imaged with T2*-weighted gradient echo sequences (fast field echo, FFE), T2-weighted fluid attenuated inversion recovery turbo spin-echo sequences (FLAIR), T2-weighted turbo spin-echo (TSE) and T1-weighted spin-echo sequences. Follow-up was performed on the 2nd, 4th and 10th postoperative days. Ten animals were additionally investigated with similar sequences at 0.5 T. Histologic correlation was obtained in all cases.Results: T2* FFE sequences detected all acute intracerebral hematomas and demonstrated the size correctly at 1.5 T and 0.5 T. The conspicuity was better at 1.5 T. FLAIR sequences were unreliable in the hyperacute phase at 1.5 T. However, subarachnoid and intraventricular extension was best appreciated with FLAIR images. T2 TSE images were incapable of detecting paraventricular and subarachnoid hemorrhages, but clearly demonstrated intracerebral blood in other locations. T1-weighted images were insensitive to hemorrhage in the acute state but very useful in subacute and chronic hematomas.Conclusion: The safe and reliable diagnosis of intracerebral hemorrhage is probably possible with MR imaging at 1.5 T and 0.5 T even of hematomas less than 90 min old, but requires the application of at least FLAIR, T2* FFE and T1 sequences and is therefore time consuming.     

Intracranial hemorrhage studied with a high-field (1.5T) NMR apparatus

Fifty-two patients were studied with high-field magnetic resonance imaging (1.5T), with T1- and T2-weighted spin-echo pulse sequences. The study was aimed at assessing the efficacy of MR imaging in the evaluation of intracranial hematomas. Characteristic intensity patterns were observed in the evolution of the hematomas, due to the physicochemical changes in hemoglobin. No acute hematomas were observed. In 35 sub-acute hematomas, peripheral hyperintensity could be observed on T1- and T2-weighted pulse sequences. This hyperintensity eventually fills in the hematoma in the chronic stage. In 17 chronic hematomas, a peripheral hypointense ring due to hemosiderin deposits was seen on T1- and T2-weighted scans. The authors conclude that high-field MR imaging is a very sensible diagnostic method in the evaluation of sub-acute and chronic hematomas.     

MR imaging of hyperacute intracranial hemorrhage in the cat

Hyperacute intracerebral hematomas were successfully created in five cats by injecting a prepared blood sample in which the oxygen (O2) saturation ranged from 0-80%. T1- and T2-weighted spin-echo sequences and T2-weighted gradient refocused scans were obtained 2.5-10 hr after injection on a 1.5-T imaging system. Detailed histology or electron microscopy was performed on each brain to confirm the presence of intact red blood cells in a retracted clot matrix. Areas of the hematoma were hypointense relative to brain in all five cats on the gradient refocused scans. The hematoma was isointense relative to brain on the T1- and T2-weighted spin-echo scans in all cats except one, which suffered a seizure/respiratory arrest and died during the scanning procedure. Portions of the hematoma in this animal had a hypointense T2-weighted signal and a hyperintense T1-weighted signal, which corresponded to the predicted MR properties of intracellular methemoglobin. We hypothesize that acute (less than 10 hr old) hematomas that contain virtually 100% intracellular deoxyhemoglobin may not appear hypointense relative to brain on T2-weighted scan sequences at 1.5 T unless surrounding tissue hypoxia and/or anoxia promote additional changes, one of which may be the formation of intracellular methemoglobin.     

Magnetic resonance appearance of slow flow vascular malformations of the brainstem

Summary Twelve patients with slow flow brain stem vascular malformations had magnetic resonance scans performed on a 1.5 Tesla scanner using T1 (TR=400–800 ms, TE=25 ms) and T2 (TR=2000 ms, TE=20, 25, 80 ms) weighted scans. Eight patients (70%) had solitary brainstem vascular malformations while 4 (30%) had multiple lesions both supra and infratentorially. Five patients had venous angiomas demonstrated by angiography and MR. There were 26 lesions seen on MR of which only 14 were identified by CT. These lesions demonstrated a specific MR image pattern indicative of subacute or chronic parenchymal hematoma. It was characterized by an iso to hyperintense central signal surrounded by a well defined thin band of low signal intensity. The central zone could appear to be single or multilocular. In multilocular lesions the hemorrhages within different cells could be of different ages. One patient did not have findings of a chronic hematoma but exhibited only low signal secondary to calcification and a venous angioma. None of these lesions had surrounding edema. Despite the variable etiologies of slow flow vascular malformations of the brainstem, their MRI manifestations seem to indicate a final common pathway of chronic hematoma. These lesions are quite distinct from MS or tumor, the usual clinical considerations in the differential diagnosis.     

MR imaging of the brain in patients with migraine headaches

Forty-one patients with migraine headaches were referred for MR imaging of the brain. Intermediate and T2-weighted images were obtained to determine the frequency of areas of high intensity within the white matter. The average age of these patients was 29.8 years; only five were over 40 years old. Each patient was evaluated in the axial plane with long TR/short and long TE images. Twenty-three patients also had T1-weighted short TR/short TE MR scans; enhancement with gadopentetate dimeglumine was used in three patients. Intracranial abnormalities were seen in only six patients: foci or white matter high intensity on intermediate and T2-weighted images in five and a venous angioma in one. Prior studies have indicated that parenchymal brain abnormalities may be found in up to 46% of patients with migraines. The current study demonstrated parenchymal brain lesions in only 12%. This study suggests that the frequency of foci of high intensity seen on long TR sequences in the migraine patient is much lower than previously reported, especially in patients under 40 years old (5.5% in our series).     

MR characteristics of subdural hematomas and hygromas at 1.5 T

MR images of 24 patients with 33 subdural collections were retrospectively reviewed to determine the spectrum of MR findings associated with such lesions. The lesions were dated by history, when available. Hematomas were grouped as follows: acute, four; early subacute, four; late subacute, four; chronic, 13. Six collections were classified as rehemorrhage; and two patients had CSF hygromas. Subdural hematomas evolved in a pattern similar to intracerebral hemorrhage with the exception of chronic subdural hematomas, in which isointensity of hypointensity relative to gray matter was observed on short TR/TE images compared with the persistent very high signal intensity noted in chronic parenchymal hematomas. Hemosiderin was rarely seen in chronic hematomas. These findings are most likely the result of the absence of a blood-brain barrier, which allowed clearance and dilution of blood products. Subdural hematomas with repeat hemorrhage demonstrated multiple phases of bleeding with layering phenomenon and more frequent hemosiderin deposition. It is possible that the clearance of blood products, as observed in chronic subdural hematomas, is impaired or poorly functional when rehemorrhage occurs. The persistence of high signal from methemoglobin in a hematoma that is expected to be in the chronic phase also suggests repeated hemorrhage. Acute CSF subdural hygromas had signal intensities identical to CSF without MR evidence of blood products. At surgery, clear fluid under pressure was found. MR imaging, with its unique ability to delineate the various phases of hemorrhage, is well suited to the evaluation of subdural hemorrhage.     

MR detectability and appearance of small experimental intracranial hematomas at 1.5 T and 0.5 T. A 6-7-month follow-up study

PURPOSE: To investigate the detectability and appearance of small experimental intracranial hemorrhages on MR at 0.5 T and 1.5 T in a long-term follow-up. MATERIAL AND METHODS: Autologous blood (1 ml) was injected into the brain of 7 rabbits to create intraparenchymal hematomas. The injected blood leaked partially into the cerebrospinal fluid (CSF) spaces. MR imaging at 0.5 T and 1.5 T were performed immediately before and after hematoma creation, at 2 weeks and monthly up to 6 or 7 months using T1-, proton density- and T2-weighted (w) spin-echo (SE), FLAIR and T2*-w gradient echo (GE) pulse sequences. RESULTS: Blood was detected both in the brain and in the CSF spaces of all animals during the first hours after hematoma creation at 1.5 T. In the last examination after 6-7 months, the T2*-w GE sequences still showed residues of the intraparenchymal hematomas in all the rabbits at 1.5 T, but the signal pattern was not specific for the age of the hematomas. SE and FLAIR sequences were insensitive. The histopathology revealed iron deposits in all brains. CONCLUSION: Residues of small intraparenchymal hematomas can be seen for months with T2*-w GE sequences on brain MR imaging at 1.5 T. The age of the microhematomas cannot be estimated with MR imaging.     

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.     

MR imaging of extracranial hematomas: comparison with CT

Thirty MR examinations of twenty-five patients with extracranial hemorrhagic lesions were reviewed. Comparative CT studies were available in 11 patients. The acute hematomas (less than 3 days old) showed intermediate intensity on the short TR (0.5 sec.) and increased in signal intensity on the long TR (2.0 sec.). The MR appearance of acute hematoma was not specific. Clot (more than 3 days old) demonstrated an intermediate intensity on the short TR and increased markedly in signal intensity on the long TR equaling the signal intensity of fat. Serum (more than 3 days old) was imaged as a high intensity lesion on both short and long TR. It is concluded that MR can be very useful for the differential diagnosis of subacute and chronic hemorrhagic lesions from other lesions.     

Hepatic cavernous hemangioma: magnetic resonance imaging. Work in progress

Using a 0.35-T superconducting magnet and spin echo imaging, we prospectively evaluated 11 patients who had proved hepatic cavernous hemangioma. Magnetic resonance (MR) identified more lesions than either contrast-enhanced CT, or ultrasonography. The MR appearance was consistent; hemangiomas were homogeneous and generally isointense at short TR and TE intervals but were hyperintense at long TR intervals and greatly hyperintense at long TR and long TE intervals. However, the MR appearance of hemangioma was not specific; 2/14 other focal hepatic masses had similar features. The calculated relaxation times (T1, T2) were not useful in lesion characterization, although the intensity ratio of hemangioma to normal liver at the TR = 2.0 sec TE = 56 msec pulse sequence was useful in diagnosis since hemangiomas always had a ratio greater than 1.4.     

Acute and subacute intracerebral hemorrhages: comparison of MR imaging at 1.5 and 3.0 T--initial experience

PURPOSE: To assess and describe the appearance of intracerebral hemorrhage (ICH) at 3.0-T magnetic resonance (MR) imaging as compared with the appearance of this lesion type at 1.5-T MR imaging. MATERIALS AND METHODS: Sixteen patients with 21 parenchymal ICHs were examined. ICHs were classified as hyperacute, acute, early subacute, late subacute, or chronic. Patients underwent 1.5- and 3.0-T MR imaging with T2-weighted fast spin-echo, fluid-attenuated inversion-recovery (FLAIR), and T1-weighted spin-echo (1.5-T) and gradient-echo (3.0-T) sequences within 4 hours of each other. The central (ie, core) and peripheral (ie, body) parts of the ICHs were analyzed quantitatively by using contrast-to-noise ratio (CNR) calculations derived from signal intensity (SI) measurements; these values were statistically evaluated by using the Mann-Whitney U test. Two readers qualitatively determined SIs of the cores and bodies of the ICHs, degrees of apparent susceptibility artifacts, and lesion ages. The chi(2) test was used to determine statistically significant differences. RESULTS: With the exception of the bodies of late subacute ICHs at 3.0-T T2-weighted imaging, which had increased positive CNRs and SI scores (P .05). With the exception of minor susceptibility artifacts seen in acute and early subacute ICHs at 3.0-T T1-weighted gradient-echo imaging, no susceptibility artifacts were noticed. The ages of most lesions were identified correctly without significant differences between the two field strengths (P >.05), with the exception of the ages of acute ICHs, which were occasionally misinterpreted as early subacute lesions at 3.0 T. CONCLUSION: At 3.0 T, all parts of acute and early subacute ICHs had significantly increased hypointensity on FLAIR and T2-weighted MR images as compared with the SIs of these lesions at 1.5 T. However, 1.5- and 3.0-T MR images were equivalent in the determination of acute to late subacute ICHs.