Detection of bone marrow abnormalities in patients with Hodgkin's disease by T1 mapping of MR images of lumbar vertebral bone marrow

On the selection of sampling points for myocardial T1 mapping

PURPOSE

To provide a method for the optimal selection of sampling points for myocardial T1 mapping, and to evaluate how this selection affects the precision.

THEORY

The Cramér-Rao lower bound on the variance of the unbiased estimator was derived for the sampling of the longitudinal magnetization curve, as a function of T1 , signal-to-noise ratio, and noise mean. The bound was then minimized numerically over a search space of possible sampling points to find the optimal selection of sampling points.

METHODS

Numerical simulations were carried out for a saturation recovery-based T1 mapping sequence, comparing the proposed point selection method to a uniform distribution of sampling points along the recovery curve for various T1 ranges of interest, as well as number of sampling points. Phantom imaging was performed to replicate the scenarios in numerical simulations. In vivo imaging for myocardial T1 mapping was also performed in healthy subjects.

RESULTS

Numerical simulations show that the precision can be improved by 13-25% by selecting the sampling points according to the target T1 values of interest. Results of the phantom imaging were not significantly different than the theoretical predictions for different sampling strategies, signal-to-noise ratio and number of sampling points. In vivo imaging showed precision can be improved in myocardial T1 mapping using the proposed point selection method as predicted by theory.

CONCLUSION

The framework presented can be used to select the sampling points to improve the precision without penalties on accuracy or scan time.

Quantified tumor t1 is a generic early-response imaging biomarker for chemotherapy reflecting cell viability

PURPOSE

Identification of a generic response biomarker by comparison of chemotherapeutics with different action mechanisms on several noninvasive biomarkers in experimental tumor models.

EXPERIMENTAL DESIGN

The spin-lattice relaxation time of water protons (T(1)) was quantified using an inversion recovery-TrueFISP magnetic resonance imaging method in eight different experimental tumor models before and after treatment at several different time points with five different chemotherapeutics. Effects on T(1) were compared with other minimally invasive biomarkers including vascular parameters, apparent diffusion coefficient, and interstitial fluid pressure, and were correlated with efficacy at the endpoint and histologic parameters.

RESULTS

In all cases, successful chemotherapy significantly lowered tumor T(1) compared with vehicle and the fractional change in T(1) (DeltaT(1)) correlated with the eventual change in tumor size (range: r(2) = 0.21, P < 0.05 to r(2) = 0.73, P < 0.0001), except for models specifically resistant to that drug. In RIF-1 tumors, interstitial fluid pressure was decreased, but apparent diffusion coefficient and permeability increased in response to the microtubule stabilizer patupilone and 5-fluorouracil. Although DeltaT(1) was small (maximum of -20%), the variability was very low (5%) compared with other magnetic resonance imaging methods (24-48%). Analyses ex vivo showed unchanged necrosis, increased apoptosis, and decreased %Ki67 and total choline, but only Ki67 and choline correlated with DeltaT(1). Correlation of Ki67 and DeltaT(1) were observed in other models using patupilone, paclitaxel, a VEGF-R inhibitor, and the mammalian target of rapamycin inhibitor everolimus.

CONCLUSIONS

These results suggest that a decrease in tumor T(1) reflects hypocellularity and is a generic marker of response. The speed and robustness of the method should facilitate its use in clinical trials.

Hodgkin Disease: Diagnostic Value of FDG PET/CT after First-Line Therapy—Is Biopsy of FDG-avid Lesions Still Needed?

PURPOSE

To retrospectively determine the sensitivity and specificity of co-registered fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with Hodgkin lymphoma after first-line therapy, with use of clinical follow-up or biopsy results as the reference standard.

MATERIALS AND METHODS

Informed consent was obtained for imaging and included consent to use patient data for research purposes. Institutional review board approval was obtained. Between May 2001 and July 2005, the data for all patients (n=66) at the authors' institution with proved Hodgkin lymphoma after first-line therapy were retrospectively reviewed. PET/CT scans were evaluated for the presence of abnormal FDG uptake and residual masses after the end of treatment and at further follow-up. All patients with pathologic FDG lesions underwent surgical biopsy for histopathologic confirmation. All patients with negative PET/CT scans at follow-up were evaluated for disease-free survival.

RESULTS

An FDG-avid lesion was detected at PET/CT in 27 of the 66 patients (mean age +/- standard deviation, 33.0 years +/- 12.2). Recurrence of Hodgkin lymphoma was confirmed with biopsy in 23 of the 27 patients. The mean maximum standardized uptake value (SUV) of the histopathologically proved lesions was 7.32 (+/-2.01). Four patients had false-positive findings at PET/CT: Biopsy revealed only inflammatory changes, and the mean maximum SUV was 7.30 (+/-2.53). Thirty-nine patients (mean age, 36.7 years +/- 10.8) did not have FDG-avid lesions and remained free of disease after a mean clinical follow-up of 26.2 months (+/-12.5) (specificity, 91% [39 of 43 patients]; sensitivity, 100% [23 of 23 patients]). The presence of bulky disease (>5 cm) after the end of treatment was a significant predictor of recurrent disease (P<.05).

CONCLUSION

The authors conclude that FDG PET/CT can help exclude persistent and/or recurrent Hodgkin lymphoma after first-line therapy. Because of the false-positive results and the toxicity of salvage chemotherapy, including high-dose chemotherapy with autologous stem cell support, biopsy of the FDG-avid lesion is still needed.

Magnetic resonance imaging of bone marrow versus bone marrow biopsy in malignant lymphoma

Bone marrow involvement is a frequent finding in malignant lymphoma. Bone marrow biopsy of the posterior iliac crest is routinely performed for staging. Abnormal magnetic resonance imaging (MRI) signals of bone marrow was also reported to be indicative of bone marrow involvement. This study included 60 patients with malignant lymphoma. Unilateral bone marrow biopsy of the posterior iliac crest was performed. MRI of lumbar spine was studied within 24 hours of bone marrow biopsy. 22 healthy controls were used for the detection of MRI objectivity during visual evaluation. In 83% of patients (50/60), biopsy and MRI results agreed completely. In two patients, histologic sections failed to show any evidence of bone marrow involvement despite abnormal MRI signals suggestive of involvement. In three patients, MRI was completely normal despite biopsy proven bone marrow infiltration. False negativity (3/60) and false positivity (2/60) rates were very low. Negative biopsy findings with positive or equivocal MRI results should not exclude bone marrow involvement and needs further evaluation with bilateral or guided biopsy. Thus, we conclude that MRI of bone marrow is a fairly sensitive, noninvasive modality and might be of potential value in detecting bone marrow infiltration in malignant lymphoid neoplasms which can be utilized as a useful adjunct to standard staging procedures.

Prognostic importance of magnetic resonance imaging in bone marrow involvement of Hodgkin disease

BACKGROUND

Determination of bone marrow involvement is important in staging Hodgkin disease (HD), so we compared the effectiveness of magnetic resonance imaging (MRI) with bone marrow biopsy in diagnosing bone marrow involvement in HD patients.

PROCEDURE

Twenty-six patients with the diagnosis of HD were included in this study. The ages of the patients were between 4 and 24 years, with a median of 12. Eleven of them had stage III or IV disease and 15 had been previously diagnosed as having HD and were in relapse. They were evaluated by bone marrow biopsy and MRI of lumbar vertebrae. The biopsies were taken from the anterosuperior iliac spine with an age-appropriate Jamshidi biopsy needle. Within 14 days following biopsy, MRI of lumbar vertebrae was carried out.

RESULTS

MRI revealed decreased signal intensity in T1-weighted images in 7 of 26 patients. On the other hand, bone marrow biopsies showed HD involvement in three out of seven patients. The remaining 19 patients who had normal bone MRI were negative for HD in their bone marrow biopsies. The patients with positive MRIs and negative biopsy for HD had bone pain. One of them had a femoral periosteal reaction on bone survey; the other two had height loss in their lumbar vertebral bodies. There was a statistically significant difference in the disease-free survival rates between MRI-positive and -negative patients in the following 24 months period (P < 0.0001).

CONCLUSIONS

This study suggests that MRI is a useful method for diagnosing bone marrow involvement in HD, in that our MRI-positive patients had a higher relapse rate in the 24 months follow-up period than the MRI-negative patients.

T2 relaxation times of irradiated vertebral bone marrow in patients with seminoma

Our purpose was to demonstrate the effects of localized radiotherapy on lumbar vertebral bone marrow with the use of quantitative MRI with measurements of T2 relaxation times. Ten patients with early stage testicular seminoma with a history of radiation therapy to a "dog-leg" field including the lumbar vertebrae underwent MR imaging of their lumbar spine using a 0.5 Tesla magnet. Five healthy subjects and two nonirradiated patients were imaged as well. The intervals from the beginning of radiotherapy to MRI examination varied from 1.5 to 52 months, and the radiation dose ranged from 3000-4200 cGy. The T2 relaxation times of the lumbar vertebral bone marrow and subcutaneous fat were calculated for each subject. Postirradiation bone marrow in irradiated seminoma patients exhibited significantly longer T2 relaxation times than nonirradiated bone marrow in controls (71.1 vs. 63.6 ms, p = 0.047, t-test). The differences between the T2 relaxation times of bone marrow and subcutaneous fat for each subject allowed for even better differentiation between irradiated patients and controls (10.4 vs. 0.4 ms, p = 0.0004, t-test). Postirradiation bone marrow had significantly longer T2 relaxation times than subcutaneous fat in irradiated patients (N = 10, 71.1 vs. 60.7 ms, p = 0.00009, t-test), while nonirradiated bone marrow had T2 relaxation times not statistically different from subcutaneous fat in nonirradiated subjects (N = 7, 63.6 vs. 63.2 ms). Measurements of T2 relaxation times of bone marrow enabled us to differentiate between irradiated seminoma patients and controls. Postirradiation bone marrow undergoes late radiation effects resulting in longer T2 relaxation times than nonirradiated bone marrow and subcutaneous fat.

MRI in the evaluation of late bone marrow changes following bone marrow transplantation

Measurements of MR spin-lattice (T1), and spin-spin (T2) relaxation times in lumbar vertebrae have been performed in a pilot study on six adult patients, treated for acute myeloid leukaemia (AML). All patients were treated with initial chemotherapy and then proceeded to bone marrow transplantation (BMT), conditioned with Melphalan and total body irradiation (TBI). MR measurements were made between 21 and 89 months after TBI. The relaxation times in the six patients were compared with those in six healthy age-matched volunteers to establish whether there were differences between the two groups. Average T1 values in the vertebrae of the treated patients are significantly shorter (p < 0.01) than in the healthy volunteers. This is consistent with the observation of a relatively hyperintense vertebral bone marrow in the T1 weighted images and is likely to be a consequence of treatment induced fatty replacement of marrow. Shorter T1 values tend to be distributed within the centre of the lumbar vertebrae compatible with observations, made by others, which suggest that the peripheral zone of the vertebral body has been repopulated with bone marrow cells whereas the central zone, around the basivertebral vein, is predominantly fat. Histogram displays of vertebral body relaxation time distributions (T1, T2) for both patients and healthy age-matched volunteers are similar in that both patients and volunteers give histograms that are only slightly skewed. This similarity is probably a reflection of the fact that the patients have been in remission for over a year and have generally healthy bone marrow.

Radiotherapy effects on vertebral bone marrow: easily recognizable changes in T2 relaxation times

The effect of localized radiotherapy on vertebral bone marrow was demonstrated in two patients using quantitative MRI studies with pixel-by-pixel measurement of T2 relaxation times with generation of T2 images. Conventional T1-weighted spin-echo images were obtained as well. Irradiated vertebral bone marrow was found to have longer T2 relaxation times than the neighboring nonirradiated bone marrow. These changes corresponded to the increased signal intensity on T1-weighted images and to the field of radiotherapy and were noted 2.5 to 32 mo after radiotherapy. Radiologists should be aware of the increased T2 relaxation times in irradiated bone marrow to correctly assess spinal disorders in irradiated patients. The reported T2 changes may reflect the abundance of adipose cells that proliferate in bone marrow after radiotherapy, or may indicate an additional histological change, such as bone marrow necrosis or edema. Conclusive histological proof remains to be obtained.

Magnetic resonance imaging in patients with bone marrow disorders

Magnetic resonance imaging (MRI) provides a non-invasive means to evaluate a large fraction of marrow in less than one hour. Marrow disorders produce non-specific changes in marrow signal intensities which primarily reflect changes in proportions of fat and cellular elements. The pattern of these signal changes narrows the differential diagnosis, and the combination of these features with the clinical context allows interpretations which are clinically useful in many ways. These include: 1) the diagnosis of avascular necrosis (and its distinction from other causes of joint pain), 2) detection of osteomyelitis, 3) differential diagnosis of hypoplastic disorders, 4) staging of lymphomas and myeloma, 5) selection of patients for autologous bone marrow transplant, 6) objective measures of marrow response to therapy, 7) detection of leukemic transformation, and 8) improved detection of marrow disease (primary or secondary) in patients with otherwise unexplained bone pain.