Diffusion-weighted MR imaging in assessing cervical tumour response to nonsurgical therapy

Purpose

This study was undertaken to assess whether there is a correlation between the response of cervical tumours to nonsurgical therapy (chemo- and/or radiotherapy) and apparent diffusion coefficient (ADC) values.

Patients and methods

Seventeen consecutive patients prospectively underwent pelvic magnetic resonance (MR) imaging including diffusion-weighted imaging (DWI) sequences before and after nonsurgical therapy for cervical cancer. A control group of 17 patients without cervical pathology was matched to the study group. Differences in baseline ADC maps between the two groups and within the study group before and after therapy were assessed by nonparametric tests.

Results

The diameter and volume of cervical cancers decreased after therapy in 14/17 lesions (responders) and increased in 3/17 lesions (nonresponders). The ADC values of responders increased significantly (p=0.0009). Percent changes in ADC values before and after therapy were higher in responders than nonresponders (p=0.04). There was no significant difference in ADC values between responders and nonresponders at the staging MR examination (p=0.09) and no significant correlation between pretreatment ADC values and percentage of tumour reduction. Tumours with higher percent ADC value increase showed higher tumour reduction volume, but this was not significant (p=0.12).

Conclusions

ADC values of cervical cancer after therapy showed significant differences compared with pretherapy values, particularly for responders.     

Diffusion-weighted and perfusion MR imaging for brain tumor characterization and assessment of treatment response

Diffusion-weighted magnetic resonance (MR) imaging and perfusion MR imaging are advanced techniques that provide information not available from conventional MR imaging. In particular, these techniques have a number of applications with regard to characterization of tumors and assessment of tumor response to therapy. In this review, the authors describe the fundamental principles of diffusion-weighted and perfusion MR imaging and provide an overview of the ways in which these techniques are being used to characterize tumors by helping distinguish tumor types, assess tumor grade, and attempt to determine tumor margins. In addition, the role of these techniques for evaluating response to tumor therapy is outlined.     

MR imaging of the cervical spine: assessment of image quality with parallel imaging compared to non-accelerated MR measurements

To compare the quality of cervical spine MR images obtained by parallel imaging [generalized autocalibrating partially parallel acquisition (GRAPPA)] with those of non-accelerated imaging, we conducted both phantom studies and examinations of ten volunteers at 1.5Tesla with a dedicated 12-element coil system and a head-spine-neck coil combination. Acquisitions included axial T2-weighted (T2w) images with both methods, and sagittal T2w and T1w images in vivo with the latter coil combination. Non-accelerated MRI with two averages and GRAPPA (acceleration factor 2) with two averages (GRAPPA/2AV, time reduction of approximately 50%) and four averages (GRAPPA/4AV) were compared. In the phantom, the signal-to-noise ratio of the GRAPPA/2AV was lower than that of the other two settings. In vivo, the image inhomogeneity (non-uniformity, NU) was significantly higher in T2w GRAPPA/2AV than in both other settings, and in T1w GRAPPA/2AV compared to GRAPPA/4AV. Subjectively, the delineation of anatomical structures was sufficient in all sequences. Only the spinal cord was considered to be better delineable on the non-accelerated T1w sequence compared to GRAPPA/2AV. In part, GRAPPA/4AV performed better than the other settings. The subjective image noise was lowest with GRAPPA/4AV. In cervical spine MRI, the examination time can be reduced by nearly 42% with GRAPPA, while preserving sufficient image quality.     

Thoracic spine disc-related abnormalities: longitudinal MR imaging assessment

Objective To describe and characterize the temporal changes in disc-related disorders of the thoracic spine using MR imaging.Design and patients A retrospective longitudinal cohort study was carried out of 40 patients with two sequential thoracic spine MR images at variable intervals. The images were assessed for baseline presence of, new incidence of and changes in disc herniation, degenerative disc disease, endplate marrow signal alteration and Schmorl nodes.Results The range of follow-up was 4–149 weeks. Baseline presence was: disc herniation, 10% (49/480); degenerative disc disease, 14% (66/480); endplate marrow signal alteration, 2.3% (11/480); Schmorl nodes 9.6% (46/480). Most pre-existing lesions tended to remain unchanged. Herniations showed the most change, tending to improve in 27%. New incidence was: disc herniation, 1.5% (7/480), degenerative disc disease, 2% (10/480); endplate marrow signal alteration, 1.6% (8/480); Schmorl nodes, 2.1% (10/480). Disc degeneration was first visible at an 11-week interval and once established almost never changed over many weeks to months. Endplate signal alterations (Modic changes) were uncommon. Schmorl nodes show no change from baseline for up to 2 1/2 years. All findings predominated in the lower intervertebral levels from T6 to T10.Conclusion The most prevalent thoracic spine disc-related findings are degeneration and herniation. Disc herniations predominate in the lower segments and are a dynamic phenomenon. Disc degeneration can be rapidly evolving but tends to remain unchanged after occurrence. Endplate marrow signal changes were an uncommon manifestation of thoracic disc disease. Schmorl nodes showed the least change over time.     

Diffusion-weighted MR imaging of the brain

Diffusion-weighted magnetic resonance (MR) imaging provides image contrast that is different from that provided by conventional MR techniques. It is particularly sensitive for detection of acute ischemic stroke and differentiation of acute stroke from other processes that manifest with sudden neurologic deficits. Diffusion-weighted MR imaging also provides adjunctive information for other cerebral diseases including neoplasms, intracranial infections, traumatic brain injury, and demyelinating processes. Because stroke is common and in the differential diagnosis of most acute neurologic events, diffusion-weighted MR imaging should be considered an essential sequence, and its use in most brain MR studies is recommended.     

Lumbar spine: postoperative assessment with surface-coil MR imaging

A prospective study of 15 patients who were scheduled to undergo various types of lumbar spine surgery was undertaken to assess the postoperative changes observable with magnetic resonance (MR) imaging. Patients underwent imaging preoperatively, immediately postoperatively (1-10 days), and late postoperatively (2-6 months). A retrospective review of MR images obtained in 62 patients who had undergone lumbar surgery but still had low back pain was also conducted. Epidural soft-tissue change and mass effect mimicking preoperative findings were present in nine of 13 patients who underwent laminectomy and diskectomy. Mass effect improved in appearance by the late postoperative period in eight of nine patients. T2-weighted sagittal images were best in demonstrating the site of anulus disruption immediately after diskectomy, which was seen in 11 of 13 patients, and the rent resolved on the late images in eight of ten cases. Sites of foraminotomy were seen as a loss of the normal foraminal fat signal. Extensive soft-tissue changes present in the immediate postoperative period severely limit the usefulness of MR imaging in that period for evaluating persistent symptoms. The exception may be hemorrhage, as its distinctive signal on T1-weighted images makes its identification possible.     

Diffusion-weighted single-shot echoplanar MR imaging for liver disease.

OBJECTIVE: The aims of this study were to determine apparent diffusion coefficients (ADCs) of the abdominal organs and liver lesions, to determine the effect of the magnitude of b values on the ADCs, and to determine whether measured ADCs of liver tumors help differentiate benign from malignant lesions. SUBJECTS AND METHODS: Six healthy volunteers and 126 patients were examined with diffusion-weighted single-shot echo-planar imaging using multiple b values (maximum, 846 sec/mm2). The ADCs of the liver, spleen, kidney, 49 malignant liver lesions (33 hepatocellular carcinomas, 15 metastatic liver tumors, and one cholangiocellular carcinoma), and 30 benign lesions (17 cysts, 12 hemangiomas, and one angiomyolipoma) were calculated. RESULTS: The ADCs of the abdominal organs and liver lesions showed smaller values when calculated with the greater maximum b values. The ADCs of the benign lesions calculated with all the b values of less than 850 sec/mm2 (2.49+/-1.39 x 10(-3) mm2/sec) were significantly (p = .0024) greater than those of the malignant lesions (1.01+/-0.38 x 10(-3) mm2/sec). When the maximum b value is 846 sec/mm2, use of a threshold ADC of 1.6 x 10(-3) mm2/sec would result in a sensitivity of 98% and a specificity of 80% for differentiation of malignant liver lesions from benign lesions. CONCLUSION. Measurement of ADC has good potential for characterizing liver lesions, but the calculated ADCs could be affected by the magnitude of the maximum b value.     

MR imaging of the spine: trauma and degenerative disease

The purpose of this paper is to discuss the capabilities and drawbacks of MR imaging in patients with trauma to the spine and degenerative spinal conditions. In spinal trauma MR imaging is secondary to plain X-ray films and CT because of the greater availability and ease of performance of these techniques and their superior capability for detecting vertebral fractures. Magnetic resonance imaging is useful for detecting ligamentous ruptures and intraspinal mass lesions such as hematoma, and for assessing the state of the spinal cord and prognosis of a cord injury. In degenerative spinal disease the necessity is emphasized of critically evaluating the clinical relevance of any abnormal feature detected, as findings of degenerative pathology are common in individuals without symptoms. Magnetic resonance myelography permits rapid and accurate assessment of the state of the lumbar nerve roots (compressed or not). In the cervical region the quality of the myelographic picture is often degraded in patients with a narrow spinal canal.     

Diffusion-weighted MR imaging for determination of hepatocellular carcinoma response to yttrium-90 radioembolization

Early detection of the response of hepatocellular carcinoma (HCC) to yttrium-90 radioembolization therapy may be important to permit repeat radioembolization or alternative treatment options. Water-mobility measurements with use of diffusion-weighted (DW) magnetic resonance (MR) imaging are useful for noninvasive interrogation of microstructural tissue properties. Findings of DW MR imaging may serve as an early biomarker of HCC response. This study tested the hypothesis that DW MR imaging can detect changes in tumor tissue water diffusion in response to (90)Y therapy. In each of six patients with HCC included in the study, tumor water diffusion increased significantly after therapy. DW MR imaging is a promising technique for noninvasive assessment of tumor response to (90)Y radioembolization.     

Diffusion-weighted MR imaging in leukodystrophies

Leukodystrophies are genetically determined metabolic diseases, in which the underlying biochemical abnormality interferes with the normal build-up and/or maintenance of myelin, which leads to hypo- (or arrested) myelination, or dysmyelination with resultant demyelination. Although conventional magnetic resonance imaging has significantly contributed to recent progress in the diagnostic work-up of these diseases, diffusion-weighted imaging has the potential to further improve our understanding of underlying pathological processes and their dynamics through the assessment of normal and abnormal diffusion properties of cerebral white matter. Evaluation of conventional diffusion-weighted and ADC map images allows the detection of major diffusion abnormalities and the identification of various edema types, of which the so-called myelin edema is particularly relevant to leukodystrophies. Depending on the nature of histopathological changes, stage and progression gradient of diseases, various diffusion-weighted imaging patterns may be seen in leukodystrophies. Absent or low-grade myelin edema is found in mucopolysaccharidoses, GM gangliosidoses, Zellweger disease, adrenomyeloneuropathy, L-2-hydroxyglutaric aciduria, non-ketotic hyperglycinemia, classical phenylketonuria, Van der Knaap disease and the vanishing white matter, medium grade myelin edema in metachromatic leukodystrophy, X-linked adrenoleukodystrophy and HMG coenzyme lyase deficiency and high grade edema in Krabbe disease, Canavan disease, hyperhomocystinemias, maple syrup urine disease and leukodystrophy with brainstem and spinal cord involvement and high lactate.     

MR imaging of the postoperative lumbar spine: assessment with gadopentetate dimeglumine

This study defines the accuracy of gadopentetate-dimeglumine-enhanced MR imaging in patients with failed back surgery syndrome by comparing the imaging studies with surgical findings in a large patient population. From June 1988 to March 1989, 193 postoperative patients had MR imaging of the lumbar spine both with and without contrast administration. Of this group, 27 had repeat surgery at 31 levels: these patients comprise the study group. Postcontrast MR diagnoses were as follows: scar only (n = 4), disk only (n = 13), scar and disk (n = 9), and no aberrant epidural tissue (n = 5). Surgical diagnoses differed from the MR diagnoses in two patients at two levels. In one patient, disk was diagnosed on MR while osteophyte was present at surgery. In the other patient, scar only was diagnosed by MR but disk and scar were present at surgery. These data, when combined with the authors' previous experience, give pre- and postcontrast MR a 96% accuracy in differentiating scar from disk in 44 patients at 50 reoperated levels. For patients 6 or more weeks past surgery, sagittal and axial T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is an effective method of evaluating the postoperative lumbar spine.     

Gaucher disease: assessment with MR imaging

The skeletal system, spleen, and liver of five patients with proved Gaucher disease were studied with magnetic resonance (MR) imaging. Homogeneous, low intensity signals resulting from relaxation times different than normal (longer T1 and shorter T2 values) were found in the marrow of long bones, vertebrae, and hips in all patients. In three patients, normal signals were noted in the patella, epiphysis of the knee, and capital femoral epiphysis. In two patients with acute bone pain in the tibial region, a higher signal was received from the tibial marrow. This signal was related to increased accumulation of fluid following an avascular episode. Soft tissues in the same area were also involved. Liver and spleen enlargement was readily visible, especially on coronal images. T1 values of spleen were significantly shorter than normal. MR imaging provides an excellent assessment of the extent of involvement of the liver, spleen, and bone marrow in Gaucher disease.     

Diffusion-weighted MR imaging of pyogenic ventriculitis

OBJECTIVE: The purpose of this study was to describe the features of pyogenic ventriculitis (ventricular empyema, pyocephalus) on diffusion-weighted MR imaging. CONCLUSION: Markedly increased signal intensity of dependent intraventricular fluid on diffusion-weighted MR imaging and an apparent diffusion coefficient that is less than that of normal cerebral white matter indicate restricted water diffusion in purulent fluid and suggest the diagnosis of pyogenic ventriculitis.     

MR imaging of the postoperative lumbar spine: assessment with gadopentetate dimeglumine

This study defines the accuracy of gadopentetate-dimeglumine-enhanced MR imaging in patients with failed back surgery syndrome by comparing the imaging studies with surgical findings in a large patient population. From June 1988 to March 1989, 193 postoperative patients had MR imaging of the lumbar spine both with and without contrast administration. Of this group, 27 had repeat surgery at 31 levels: these patients comprise the study group. Postcontrast MR diagnoses were as follows: scar only (n = 4), disk only (n = 13), scar and disk (n = 9), and no aberrant epidural tissue (n = 5). Surgical diagnoses differed from the MR diagnoses in two patients at two levels. In one patient, disk was diagnosed on MR while osteophyte was present at surgery. In the other patient, scar only was diagnosed by MR but disk and scar were present at surgery. These data, when combined with the authors' previous experience, give pre- and postcontrast MR a 96% accuracy in differentiating scar from disk in 44 patients at 50 reoperated levels. For patients 6 or more weeks past surgery, sagittal and axial T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is an effective method of evaluating the postoperative lumbar spine.     

Diffusion-weighted MR imaging of the spinal cord

Diffusion-weighted MR imaging may increase the sensitivity and specificity of MR imaging for certain pathologic conditions of the spinal cord but is rarely performed because of several technical issues. We therefore tested a novel phase-navigated spin-echo diffusion-weighted interleaved echo-planar imaging sequence in seven healthy volunteers and six patients with intramedullary lesions. We performed diffusion-weighted MR imaging of the spinal cord with high spatial resolution. Different patterns of diffusion abnormalities observed in patient studies support the possible diagnostic impact of diffusion-weighted MR imaging for diseases of the spinal cord.     

Diffusion-weighted MR imaging of thyroid nodules

Introduction  The purpose of our study was to determine the diagnostic role of diffusion-weighted imaging (DWI) in the differentiating of malignant and benign thyroid nodules by using fine needle aspiration biopsy cytology criteria as a reference standard. The apparent diffusion coefficient (ADC) values of the normal-looking thyroid parenchyma were also evaluated both in normal patients and in patients with nodules. Methods  Between March 2007 and February 2008, 76 consecutive patients with ultrasound-diagnosed thyroid nodules and 20 healthy subjects underwent diffusion-weighted MR imaging by using single-shot spin echo, echo planar imaging. A total of 93 nodules were included in the study using the following b factors 100, 200, and 300 mm²/s. ADC values of thyroid nodules and normal area in all subjects were calculated and compared using suitable statistical analysis. Results  Mean ADC values for malignant and benign nodules were and for b-100 factor, and for b-200, and and , for b-300, respectively. Mean ADC values of malignant nodules were lower than benign nodules. There were significant differences in ADC values between benign and malignant nodules. ADC values among normal-appearing thyroid parenchyma of patients and normal-appearing thyroid parenchyma of healthy subjects were insignificant at all b factors. Conclusion  Benign nodules have higher ADC values than malignant ones. DWI may be helpful in differentiating malign and benign thyroid nodules.     

Diffusion-weighted MR imaging of Carmofur-induced leukoencephalopathy

Carmofur (1-hexylcarbamyl-5-fluorouracil), a derivative of 5-fluorouracil (5-FU), has been widely used in Japan as a postoperative adjuvant chemotherapy agent for colorectal and breast cancer. Periventricular hyperintensity on T2-weighted MR images in carmofur-induced leukoencephalopathy confront the physician with a broad range of differential diagnoses. We describe two cases of carmofur-induced leukoencephalopathy in which diffusion-weighted MR imaging revealed periventricular hyperintensity. We compared their findings with those of age-related periventricular hyperintensity in five patients and found discrepancies in signal intensity of periventricular areas. Our results suggest that diffusion-weighted MR imaging may be useful to differentiate carmofur-induced leukoencephalopathy from age-related periventricular hyperintensity.