Dynamic contrast-enhanced MR imaging evaluation of osteosarcoma response to neoadjuvant chemotherapy

Technical Note: Quantitative dynamic contrast-enhanced MRI of a 3-dimensional artificial capillary network

PURPOSE

Variability across devices, patients, and time still hinders widespread recognition of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as quantitative biomarker. The purpose of this work was to introduce and characterize a dedicated microchannel phantom as a model for quantitative DCE-MRI measurements.

METHODS

A perfusable, MR-compatible microchannel network was constructed on the basis of sacrificial melt-spun sugar fibers embedded in a block of epoxy resin. Structural analysis was performed on the basis of light microscopy images before DCE-MRI experiments. During dynamic acquisition the capillary network was perfused with a standard contrast agent injection system. Flow-dependency, as well as inter- and intrascanner reproducibility of the computed DCE parameters were evaluated using a 3.0 T whole-body MRI.

RESULTS

Semi-quantitative and quantitative flow-related parameters exhibited the expected proportionality to the set flow rate (mean Pearson correlation coefficient: 0.991, P < 2.5e-5). The volume fraction was approximately independent from changes of the applied flow rate through the phantom. Repeatability and reproducibility experiments yielded maximum intrascanner coefficients of variation (CV) of 4.6% for quantitative parameters. All evaluated parameters were well in the range of known in vivo results for the applied flow rates.

CONCLUSION

The constructed phantom enables reproducible, flow-dependent, contrast-enhanced MR measurements with the potential to facilitate standardization and comparability of DCE-MRI examinations.

Percent slope analysis of dynamic magnetic resonance imaging for assessment of chemotherapy response of osteosarcoma or Ewing sarcoma: systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review is to provide an up-to-date and unprecedented summary of percent slope analysis of dynamic magnetic resonance imaging (MRI) for the preoperative evaluation of the chemotherapy response of osteosarcoma or Ewing sarcoma.

MATERIALS AND METHOD

Studies evaluating dynamic MRI for the preoperative evaluation of the chemotherapy response of osteosarcoma or Ewing sarcoma were systematically searched for in MEDLINE, EMBASE, and Web of Science. More than 60 % reduction of the slope of the time intensity curve derived from dynamic MRI was defined as a positive response. Pooled sensitivity and specificity for each study were calculated into 2 × 2 contingency tables. The DerSimonian-Laird random-effects method was used for determining the pooled diagnostic odds ratio and the area under curve (AUC) of the summary receiver operating characteristic (SROC) curve.

RESULTS

A total of six studies with 66 patients who fulfilled all of the inclusion criteria were considered for the meta-analysis. The pooled sensitivity and specificity were 0.73 (95 % CI, 0.54-0.88) and 0.83 (95 % CI, 0.67-0.94), respectively. A significant difference was found between the good and poor responders in the diagnostic odds ratio. The SROC curve showed that the AUC was 0.839, indicating diagnostic accuracy in estimating good therapy response.

CONCLUSION

The slope of the time intensity curve derived from dynamic MRI was useful for evaluating the histological response of patients to neoadjuvant chemotherapy in osteosarcoma or Ewing sarcoma.

Coregistration of Dynamic Contrast Enhanced MRI and Broadband Diffuse Optical Spectroscopy for Characterizing Breast Cancer

A handheld scanning probe based on broadband Diffuse Optical Spectroscopy (DOS) was used in combination with dynamic contrast enhanced MRI (DCE-MRI) to quantitatively characterize locally-advanced breast cancers in six patients. Measurements were performed sequentially using external fiducial markers for co-registration. Tumor patterns were categorized according to MRI morphological data, and 3D DCE-MRI slices were converted into a volumetric matrix with isotropic voxels to generate views that coincided with the DOS scanning plane. Tumor volume and depth at each DOS measurement site were determined, and a tissue optical index (TOI) that reflects both angiogenic and stromal characteristics was derived from broadband DOS data.

In all six cases, optical scans showed significant TOI contrast corresponding to MRI morphological information. Sharp TOI peaks were recovered for well-circumscribed masses. A reduction in TOI was found inside a tumor with a necrotic center. A broadened peak was observed for a diffuse tumor pattern, and an inflammatory septal case provided two TOI peaks that correlated qualitatively with MRI enhancement. These results provide qualitative confirmation of the common signal origin and complementary information content that can be achieved by combining optical and MR imaging for breast cancer detection and clinical management.

Diffusion-weighted imaging in musculoskeletal radiology-clinical applications and future directions

Diffusion-weighted imaging (DWI) is an established diagnostic tool with regards to the central nervous system (CNS) and research into its application in the musculoskeletal system has been growing. It has been shown that DWI has utility in differentiating vertebral compression fractures from malignant ones, assessing partial and complete tears of the anterior cruciate ligament (ACL), monitoring tumor response to therapy, and characterization of soft-tissue and bone tumors. DWI is however less useful in differentiating malignant vs. infectious processes. As of yet, no definitive qualitative or quantitative properties have been established due to reasons ranging from variability in acquisition protocols to overlapping imaging characteristics. Even with these limitations, DWI can still provide clinically useful information, increasing diagnostic accuracy and improving patient management when magnetic resonance imaging (MRI) findings are inconclusive. The purpose of this article is to summarize recent research into DWI applications in the musculoskeletal system.

Dynamic contrast-enhanced magnetic resonance imaging: fundamentals and application to the evaluation of the peripheral perfusion

INTRODUCTION

The ability to ascertain information pertaining to peripheral perfusion through the analysis of tissues' temporal reaction to the inflow of contrast agent (CA) was first recognized in the early 1990's. Similar to other functional magnetic resonance imaging (MRI) techniques such as arterial spin labeling (ASL) and blood oxygen level-dependent (BOLD) MRI, dynamic contrast-enhanced MRI (DCE-MRI) was at first restricted to studies of the brain. Over the last two decades the spectrum of ailments, which have been studied with DCE-MRI, has been extensively broadened and has come to include pathologies of the heart notably infarction, stroke and further cerebral afflictions, a wide range of neoplasms with an emphasis on antiangiogenic treatment and early detection, as well as investigations of the peripheral vascular and musculoskeletal systems.

APPLICATIONS TO PERIPHERAL PERFUSION

DCE-MRI possesses an unparalleled capacity to quantitatively measure not only perfusion but also other diverse microvascular parameters such as vessel permeability and fluid volume fractions. More over the method is capable of not only assessing blood flowing through an organ, but in contrast to other noninvasive methods, the actual tissue perfusion. These unique features have recently found growing application in the study of the peripheral vascular system and most notably in the diagnosis and treatment of peripheral arterial occlusive disease (PAOD).

REVIEW OUTLINE

The first part of this review will elucidate the fundamentals of data acquisition and interpretation of DCE-MRI, two areas that often remain baffling to the clinical and investigating physician because of their complexity. The second part will discuss developments and exciting perspectives of DCE-MRI regarding the assessment of perfusion in the extremities. Emerging clinical applications of DCE-MRI will be reviewed with a special focus on investigation of physiology and pathophysiology of the microvascular and vascular systems of the extremities.

Recent advances in the management of osteosarcoma and forthcoming therapeutic strategies

Osteosarcoma is the most frequent primary bone tumor and occurs mainly in young patients (average age: 18 years). No evolution of the survival rates has been recorded for two decades in response to current treatment, associating often toxic and badly tolerated cures of chemotherapy (given a significant rate of bad responders) with preserving surgery. Among the proposed innovative strategies, immune-based therapy, antiangiogenesis agents, tumor-suppressor or suicide gene therapy, or anticancer drugs not commonly used in osteosarcoma are presented. A further strategy is to target the tumor microenvironment rather than the tumor itself.

A physiological perspective on the use of imaging to assess the in vivo delivery of therapeutics

Our goal is to provide a physiological perspective on the use of imaging to optimize and monitor the accumulation of nanotherapeutics within target tissues, with an emphasis on evaluating the pharmacokinetics of organic particles. Positron emission tomography (PET), magnetic resonance imaging (MRI) and ultrasound technologies, as well as methods to label nanotherapeutic constructs, have created tremendous opportunities for preclinical optimization of therapeutics and for personalized treatments in challenging disease states. Within the methodology summarized here, the accumulation of the construct is estimated directly from the image intensity. Particle extravasation is then estimated based on classical physiological measures. Specifically, the transport of nanotherapeutics is described using the concept of apparent permeability, which is defined as the net flux of solute across a blood vessel wall per unit surface area of the blood vessel and per unit solute concentration difference across the blood vessel wall. The apparent permeability to small molecule MRI constructs is accurately shown to be far larger than that estimated for proteins such as albumin or nanoconstructs such as liposomes. Further, the quantitative measurements of vascular permeability are shown to facilitate detection of the transition from a pre-malignant to a malignant cancer and to quantify the delivery enhancement resulting from interventions such as ultrasound. While PET-based estimates facilitate quantitative comparisons of many constructs, high field MRI proves useful in the visualization of model drugs within small lesions and in the evaluation of the release and intracellular trafficking of nanoparticles and cargo.

Effects of neoadjuvant chemotherapy on image-directed planning of surgical resection for distal femoral osteosarcoma

BACKGROUND

Standard therapy for localized osteosarcoma includes neoadjuvant chemotherapy preceding local control surgery, followed by adjuvant chemotherapy. When limb-salvage procedures were being developed, preoperative chemotherapy allowed a delay in definitive surgery to permit fabrication of custom endoprosthetic reconstruction implants. One rationale for its continuation as the care standard has been the perception that it renders surgery easier and safer. Our objective was to compare surgical procedures planned on the basis of magnetic resonance images (MRIs) of distal femoral osteosarcomas acquired before neoadjuvant chemotherapy with surgical procedures planned on the basis of MRIs acquired after neoadjuvant chemotherapy as a measure of the surgically critical anatomic effects of the chemotherapy.

METHODS

Twenty-four consecutive patients with distal femoral osteosarcoma had available digital MRIs preceding and following neoadjuvant chemotherapy. Thorough questionnaires were used to catalogue surgically critical anatomic details of MRI-directed surgical planning. Four faculty musculoskeletal oncologic surgeons and two musculoskeletal radiologists evaluated the blinded and randomly ordered MRIs. Interrater and intrarater reliabilities were calculated with intraclass correlation coefficients. The Student t test and chi-square test were used to compare pre-chemotherapy and post-chemotherapy continuous and categorical variables on the questionnaire. Mixed-effect regression models were employed to compare surgical procedures planned on the basis of pre-chemotherapy MRIs and with those planned on the basis of post-chemotherapy MRIs.

RESULTS

The blinded reviews generated strong intraclass correlation coefficients for both interrater (0.772) and mean intrarater (0.778) reliability. The MRI-planned resections for the majority of tumors changed meaningfully after chemotherapy, but in inconsistent directions. On the basis of mixed-effect regression modeling, it appeared that more amputations were planned on the basis of post-chemotherapy MRIs. No other parameters differed in a significant and clinically meaningful fashion. Surgeons demonstrated their expectation that neoadjuvant chemotherapy would improve resectability by planning more radical surgical procedures on the basis of scans that they predicted had been obtained pre-chemotherapy.

CONCLUSIONS

Surgeons can reliably record the anatomic details of a planned resection of an osteosarcoma. Such methods may be useful in future multi-institutional clinical trials or registries. The common belief that neoadjuvant chemotherapy increases the resectability of extremity osteosarcomas remains anecdotally based. Rigorous assessment of this phenomenon in larger cohorts and at other anatomic sites as well as re-evaluation of other arguments for neoadjuvant chemotherapy should be considered.

Imaging pediatric bone sarcomas

Primary malignant bone tumors are rare and account for about 6% of all new pediatric cancer cases per year in the United States. Identification of the lesion not uncommonly occurs as a result of imaging performed for trauma. Clinical and standard imaging characteristics of the various tumor types are evolving in concert with treatment advancements and clinical trial regimens. This article reviews the 3 most common pediatric bone sarcomas-osteosarcoma, Ewing sarcoma, and chondrosarcoma-and their imaging as applicable to contemporary disease staging and monitoring, and explores the roles of evolving imaging techniques.

Frontline treatment of localized osteosarcoma without methotrexate: results of the St. Jude Children's Research Hospital OS99 trial

BACKGROUND

The standard treatment of osteosarcoma includes cisplatin and high-dose methotrexate (HDMTX); both agents exert significant toxicity, and HDMTX requires complex pharmacokinetic monitoring and leucovorin rescue. In the previous OS91 trial, the treatment of localized disease with carboplatin, ifosfamide, doxorubicin, and HDMTX yielded outcomes comparable to those of cisplatin-based regimens and caused less toxicity. To build on this experience, the authors conducted a multi-institutional trial (OS99) that evaluated the efficacy of carboplatin, ifosfamide, and doxorubicin without HDMTX in patients with newly diagnosed, localized, resectable osteosarcoma.

METHODS

Treatment was comprised of 12 cycles of chemotherapy administered over 35 weeks: 3 cycles of carboplatin (dose targeted to area under the concentration-time curve of 8 mg/mL × min on Day 1) and ifosfamide (at a dose of 2.65 g/m(2) daily ×3 days) and 1 cycle of doxorubicin (at a dose of 25 mg/m(2) daily ×3 days) before surgical resection, followed by 2 additional cycles of the combination of carboplatin and ifosfamide and 3 cycles each of doxorubicin (25 mg/m(2) daily ×2 days) combined with ifosfamide or carboplatin.

RESULTS

A total of 72 eligible patients (median age, 13.4 years) were enrolled between May 1999 and May 2006. Forty of the 66 (60.6%) evaluable patients had good histologic responses (>90% tumor necrosis) to preoperative chemotherapy. The estimated 5-year event-free survival rate was 66.7% ± 7.0% for the OS99 trial compared with 66.0% ± 6.8% for the OS91 trial (P = .98). The estimated 5-year survival rate was 78.9% ± 6.3% for the OS99 trial and 74.5% ± 6.3% for the OS91 trial (P = .40).

CONCLUSIONS

The regimen used in the OS99 trial was found to produce outcomes comparable to those of cisplatin-containing or HDMTX-containing regimens. This therapy offers a good alternative for patients, particularly those who demonstrate an intolerance of HDMTX, and for institutions that cannot provide pharmacokinetic monitoring for MTX.

DCE-MRI pixel-by-pixel quantitative curve pattern analysis and its application to osteosarcoma

PURPOSE

To present a novel curve pattern analysis (CPA) method to characterize and quantify signal curves from the dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) data without any prerequisites such as arterial input function (AIF) or T(1) measurement.

MATERIALS AND METHODS

CPA parameters represent characteristics of the scaled DCE signal curve. Simulations were performed to investigate the dependence of CPA parameters on T(1), TR, and flip angle. In vivo studies were performed on five pediatric patients with osteosarcoma. Parametric maps were generated using the CPA method and a pharmacokinetic model-based method for comparison.

RESULTS

Simulations show that CPA parameters varied less than 2% when T(1) changed from 300 msec to 1500 msec, and less than 10% when the flip angle changed from 30 degrees to 40 degrees. Various curve patterns can be qualitatively identified and recognized from CPA parameter maps. Simulation and in vivo studies showed that the CPA parameter had a strong correlation with k(ep), with correlation coefficients of 0.9983 in the simulation and 0.95 in the in vivo studies.

CONCLUSION

A novel CPA method is presented. Simulations and in vivo studies showed that the CPA method provides a feasible alternative to quantifying DCE-MRI studies with possibly higher repeatability by minimizing variations potentially induced by AIF and T(1) estimations and model dependence.

Diffusion-weighted imaging of the appendicular skeleton with a non-Carr-Purcell-Meiboom-Gill single-shot fast spin-echo sequence

OBJECTIVE

The objective of our study was to prospectively evaluate the signal-to-noise ratio (SNR) improvement in diffusion-weighted imaging (DWI) of the appendicular skeleton with the use of a newly developed non-Carr-Purcell-Meiboom-Gill (non-CPMG) single-shot fast spin-echo (SSFSE) sequence and to evaluate its effect on apparent diffusion coefficient (ADC) measurements.

SUBJECTS AND METHODS

DWI of the bone was performed in 32 patients with an echo-planar imaging (EPI)-based sequence followed by a non-CPMG SSFSE technique. SNR and ADC values were measured over a lesion-free right femoral head. A score was assigned for each set of images to assess image quality. When a bone lesion was present, contrast-to-noise ratio (CNR) and ADC were also measured. Paired Student's t tests were used for statistical analysis.

RESULTS

The mean (+/- SD) SNR values were 9.89 +/- 2.20 and 81.68 +/- 4.87 for EPI and non-CPMG SSFSE DWI, respectively. SNR values associated with the non-CPMG SSFSE technique were found to be significantly higher than those measured with the EPI-based DWI technique (p < 0.01). Mean ADCs of the bone were 0.57 +/- 0.20 and 0.29 +/- 0.15 x 10(-3) mm2/s, respectively, for EPI and non-CPMG SSFSE DWI. Image quality scores were higher for the non-CPMG SSFSE DWI technique (p < 0.05) than for the EPI-based DWI technique. Overall lesion CNR was found to be higher in DWI performed with the non-CPMG SSFSE technique.

CONCLUSION

The non-CPMG SSFSE technique provides a significant improvement over the currently used EPI-based DWI technique and has the potential to be a powerful tool in imaging the appendicular skeleton.

Surgical management of pelvic sarcoma in children

Survival rates of children with pelvic sarcoma have demonstrated unprecedented improvement during the past few decades, with a corresponding increase in the number of limb-sparing surgical procedures being performed. This increase may be attributed to earlier detection with advanced imaging techniques, the availability of a wider armamentarium of surgical techniques of reconstruction and limb salvage, and advances achieved in neoadjuvant chemotherapy and radiation therapy. Undertaking reconstruction after resection of pelvic sarcoma while preserving function of the hip and limb can be extremely challenging; this is especially true in children, who invite concern regarding growth potential and limb-length discrepancy. Decisions for surgery and reconstruction are individualized based on tumor type, size, and location as well as the probability of achieving a wide resection with negative margins and acceptable morbidity.

The Cause and Clinical Significance of Central Tumor Photopenia on Thallium Scintigraphy of Pediatric Osteosarcoma of the Extremity

OBJECTIVE

The objectives of our study were to determine whether central tumor photopenia on thallium-201 (201Tl) scintigraphy of primary osteosarcoma results from central tumor necrosis or dense central tumor ossification and to determine the relation of this finding to tumor response to chemotherapy and to patient survival.

MATERIALS AND METHODS

After the institutional review board approved our study and waived the need for patient or parental consent, two radiologists independently reviewed 201Tl scans, conventional radiographs, and MR images of 57 patients obtained at diagnosis of extremity primary nonmetastatic osteosarcoma to detect the presence of central tumor photopenia on 201Tl scintigraphy and estimate outer tumor ossification versus inner tumor ossification and enhancement. The dynamic enhanced MRI parameters dynamic vector magnitude (DVM) and k(ep) (measure of the exchange rate between plasma and extracellular fluid space) were compared for outer tumor versus inner tumor, and the relation among 201Tl scintigraphy, conventional radiography, MRI, and the dynamic enhanced MRI parameters was analyzed. We examined whether central tumor photopenia on 201Tl imaging was related to histologic response or to patient survival.

RESULTS

Thirty-three patients (58%) had central tumor photopenia on 201Tl imaging that was not associated with central tumor ossification (p = 0.8) or with the difference between outer tumor and inner tumor contrast enhancement (p = 0.4). Central tumor photopenia on 201Tl scintigraphy was significantly associated with an increasing difference between outer tumor DVM and inner tumor DVM (i.e., outer tumor DVM minus inner tumor DVM) (p = 0.05), an increasing difference between outer tumor k(ep) and inner tumor k(ep) (i.e., outer k(ep) minus inner k(ep)) (p = 0.01), and an increasing outer k(ep)-inner k(ep) ratio (p = 0.02). We found no relation between central tumor photopenia and histologic response (p > or = 0.2). Older patients (age, > or = 13 years) with central tumor photopenia were least likely to survive, whereas younger patients (age, < 13 years) without central tumor photopenia were most likely to survive (p = 0.07).

CONCLUSION

Central tumor photopenia on 201Tl scintigraphy of primary osteosarcoma is unlikely to reflect central ossification but may be due to central necrosis reflected by higher outer tumor DVM and k(ep) than inner tumor DVM and k(ep) and may be negatively associated with survival in older patients. Prospective studies are needed to determine the value of this information in planning treatment.

Dynamic enhanced MRI predicts chemosensitivity in breast cancer patients

BACKGROUND

Primary chemotherapy for breast cancer is effective as postoperative adjuvant therapy. However, one of the critical disadvantages was a treatment delay for patients with progressive disease. The present study attempts to clarify quantitative parameters on MRI which can be used to predict the sensitivity to treatment in breast cancer patients.

METHODS

The subjects consisted of 26 patients with invasive ductal breast cancer who received primary chemotherapy before surgery. The mean maximum tumor dimension was 3.3cm, and 21 cases had nodal involvements. Three cases demonstrated histological grade 3. Dynamic enhanced MRI was evaluated at three different time periods; prior to, in the midst of preoperative chemotherapy, and just before the initial operation. The signal intensity ratio (SIR) and early contrast uptake (ECU) were calculated, as well as the correlation between these dynamic data and the tumor reduction rates were analyzed retrospectively. P-values of less than 0.05 were considered to indicate statistically significant.

RESULTS

Responders to chemotherapy had the significantly higher SIR and ECU values than non-responders (p=0.0454 and 0.0334, respectively). ECU value significantly decreased as tumor reduction by chemotherapy (p=0.0028). Pathological tumor dimension was significantly correlated with the tumor size estimated on presurgical MRI (p<0.0001).

CONCLUSIONS

Our current series demonstrated the significant correlation between pretreatment MRI data and tumor reduction by chemotherapy in breast cancer patients. With these results, it seems possible to define good and non-responders prior to treatment.

Ewing's sarcoma family of tumors: current management

Ewing's sarcoma is the second most frequent primary bone cancer, with approximately 225 new cases diagnosed each year in patients less than 20 years of age in North America. It is one of the pediatric small round blue cell tumors, characterized by strong membrane expression of CD99 in a chain-mail pattern and negativity for lymphoid (CD45), rhabdomyosarcoma (myogenin, desmin, actin) and neuroblastoma (neurofilament protein) markers. Pathognomonic translocations involving the ews gene on chromosome 22 and an ets-type gene, most commonly the fli1 gene on chromosome 11, are implicated in the great majority of cases. Clinical presentation is usually dominated by local bone pain and a mass. Imaging reveals a technetium pyrophosphate avid lesion that, on plain radiograph, is destructive, diaphyseal and classically causes layered periosteal calcification. Magnetic resonance best defines the extent of the lesion. Biopsy should be undertaken by an experienced orthopedic oncologist. Approximately three quarters of patients have initially localized disease. About two thirds survive disease-free. Management, preferably at a specialist center with a multi-disciplinary team, includes both local control-either surgery, radiation or a combination-and systemic chemotherapy. Chemotherapy includes cyclic combinations, incorporating vincristine, doxorubicin, cyclophosphamide, etoposide, ifosfamide and occasionally actinomycin D. Topotecan in combination with cyclophosphamide has shown preliminary activity. Patients with initially metastatic disease fare less well, with about one quarter surviving. Studies incorporating intensive therapy followed by stem cell infusion show no clear benefit. New approaches include anti-angiogenic therapy, particularly since vascular endothelial growth factor is an apparent downstream target of the ews-fli1 oncogene.

Imaging vascular physiology to monitor cancer treatment

The primary physiological function of the vasculature is to support perfusion, the nutritive flow of blood through the tissues. Vascular physiology can be studied non-invasively in human subjects using imaging methods such as positron emission tomography (PET), magnetic resonance imaging (MRI), X-ray computed tomography (CT), and Doppler ultrasound (DU). We describe the physiological rationale for imaging vascular physiology with these methods. We review the published data on repeatability. We review the literature on 'before-and-after' studies using these methods to monitor response to treatment in human subjects, in five broad clinical settings: (1) antiangiogenic agents, (2) vascular disruptive agents, (3) conventional cytotoxic drugs, (4) radiation treatment, and (5) agents affecting drug delivery. We argue that imaging of vascular physiology offers an attractive 'functional endpoint' for clinical trials of anticancer treatment. More conventional measures of tumour response, such as size criteria and the uptake of fluorodeoxyglucose, may be insensitive to therapeutically important changes in vascular function.

MR angiography of tumor-related vasculature: from the clinic to the micro-environment

Angiogenesis is a very important process for tumor growth and proliferation. Given its high temporal and spatial resolution, magnetic resonance (MR) imaging is well suited for use in the assessment of angiogenesis. MR angiography can be used clinically and experimentally for identification of tumor feeding and draining vessels, for tumor characterization, and for treatment planning. The morphologic structure of tumor vessels can be investigated in relation to tumor vessel permeability with use of specific contrast agents. To gain insight into tumor angiogenesis in vivo, the authors compared images obtained with digital photography, high-resolution MR angiography, and intravital microscopy through a dorsal skin-fold window in a rodent model. The close correlation between images obtained with these various modalities, with regard to the depiction of the developing tumor vasculature, indicates that noninvasive quantification of angiogenesis may be possible with MR imaging. Future directions in tumor imaging may include so-called four-dimensional MR angiography, in which high-resolution three-dimensional MR angiography is combined with dynamic contrast-enhanced MR imaging.

Metastatic osteosarcoma

BACKGROUND

The outcome of patients with metastatic osteosarcoma treated in two consecutive trials from 1986 to 1997 was analyzed to evaluate the efficacy of carboplatin-based multiagent chemotherapy and to identify prognostic factors. The initial study (OS-86) used ifosfamide, cisplatin, doxorubicin, and high-dose methotrexate, and the subsequent study (OS-91) used the same agents at similar doses, but carboplatin was substituted for cisplatin.

METHODS

Twelve patients (median age, 15.1 yrs) were treated in OS-86 for osteosarcoma metastatic to the lung only (11 patients) or bone only (1 patient), and 17 patients (median age, 15.1 yrs) were treated in OS-91 for osteosarcoma metastatic to the lung only (12 patients), bone only (2 patients), lung and bone (2 patients), or other site (1 patient).

RESULTS

Patients with metastatic disease enrolled in OS-86 and those with metastatic disease enrolled in OS-91 did not differ in terms of demographic features, histologic subtype, site of primary tumor, or site of metastases. There was a difference in survival according to treatment protocol (P = 0.054). All survivors (four of whom were enrolled in OS-86 and one of whom was enrolled in OS-91) had lung metastases only. Five-year survival estimates for patients with lung metastases only were 45.5 +/- 13.7% (OS-86) and 8.3 +/- 5.6% (OS-91) (P = 0.084). Unilateral lung metastases (P = 0.006), no more than three lung nodules (P = 0.014), and surgical remission (P = 0.001) were associated with improved survival probability.

CONCLUSIONS

The poor outcome of patients with metastatic osteosarcoma treated in OS-91 justifies the use of cisplatin with its associated toxicity in patients with high-risk disease.

Imaging of malignant tumours of the long bones in children: monitoring response to neoadjuvant chemotherapy and preoperative assessment

This review focuses on imaging of osteosarcoma and Ewing's sarcoma of the long bones in children during preoperative neoadjuvant chemotherapy. Morphological criteria on plain films and conventional static MRI are insufficiently correlated with histological response. We review the contribution of dynamic MRI, diffusion-weighted MR and nuclear medicine (18FDG-PET) to monitor tumoural necrosis. MRI is currently the best method to evaluate local extension prior to tumour resection, especially to assess the feasibility of conservative surgery. Quantitative models in dynamic MRI and 18FDG-PET are currently being developed in order to find new early prognostic criteria, but for the time being, treatment protocols are still based on the gold standard of histological response.

Monitoring response to primary chemotherapy in breast cancer using dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) allows analysis of both tumor volume and contrast enhancement pattern using a single tool. We sought to investigate whether DCE-MRI could be used to predict histological response in patients undergoing primary chemotherapy (PCT) for breast cancer.

PATIENTS AND METHODS

Thirty patients with breast cancer, clinical diameter > 3 cm or stage III A/B, received anthracycline and taxane based PCT. DCE-MRI was performed at the baseline, after two cycles and after four cycles of PCT, before surgery. Histological response was assessed using a five-point scheme. Grade 4 (small cluster of dispersed residual cancer cells) and grade 5 (no residual viable cancer cell) were defined as a major histopathological response (MHR).

RESULTS

Univariate analysis showed that a > 65% reduction in the tumor volume and a reduction in the early enhancement ratio (ECU) after two cycles of PCT were associated with a MHR. Multivariate analysis revealed that tumor volume reduction after two cycles of PCT was independently associated with a MHR (odds ratio [OR] 39.968, 95% confidence interval [CI] 3.438-464.962, p < 0.01). ECU reduction was still associated with a MHR (OR 2.50, 95% CI 0.263-23.775), but it did not retain statistical significance (p = 0.42). Combining tumor volume and ECU reduction after two cycles of PCT yielded a 93% diagnostic accuracy in identifying tumors achieving a pathological complete response (pCR) (histopathological grade 5).

CONCLUSIONS

DCE-MRI allows prediction of the effect of neoadjuvant chemotherapy in breast cancer. Although in our study tumor volume reduction after two cycles had the strongest predictive value, DCE-MRI has the potential to provide functional parameters that could be integrated to optimize neoadjuvant chemotherapy strategies.

Dynamic contrast-enhanced MR imaging

Dynamic contrast-enhanced magnetic resonance imaging is a useful clinical tool in evaluation of soft tissue neoplasm and lymph nodes in head and neck. It is thought to be a useful predictor of response to radiotherapy for head and neck carcinoma and used to monitor the treatment and distinguish post-therapeutic changes from recurrent mass with greater confidence. It can be used to distinguish between normal and malignant tissue and to differentiate a malignant lymphoma from other lymph nodal enlargements. The technique utilizes relative differences in microvasculature and microcirculation between malignant and non-malignant tissue to achieve greater contrast in signal imaging following bolus contrast administration. This article explains the underlying principles and imaging techniques for this new diagnostic tool. The clinical applications and technical challenges are discussed. The future challenges and some contradictions in results are also outlined.

Dynamic contrast-enhanced MR imaging in monitoring response to isolated limb perfusion in high-grade soft tissue sarcoma: initial results

The objective of this study was to evaluate whether dynamic contrast-enhanced MR imaging can determine tumor response and localize residual viable tumor after isolated limb perfusion (ILP) chemotherapy in soft tissue tumors. Twelve consecutive patients, with histologically proven high-grade soft tissue sarcoma, prospectively underwent non-enhanced MR and dynamic contrast-enhanced MR imaging before and after ILP. Tumor volume was measured on non-enhanced MR images. The temporal change of signal intensity in a region of interest on dynamic contrast-enhanced MR images was plotted against time. Start, pattern, and progression of enhancement were recorded. Histopathologic response was defined as complete response if no residual viable tumor was present, partial remission if <50% viable tumor was present, and no change if > or =50% viable tumor was present in the resection specimen. Resected specimens for correlation with histopathology were available for 10 patients; 5 patients had partial remission and 5 had no change. Volume measurements correctly predicted tumor response in 6 of 10 patients. Dynamic contrast-enhanced MR correctly predicted tumor response in 8 of 10 patients. Early rapidly progressive enhancement correlated histologically with residual viable tumor. Late and gradual, or absence of enhancement, was associated with necrosis, predominantly centrally located, or granulation tissue. These preliminary results show that dynamic contrast-enhanced MR imaging offers potential for non-invasive monitoring of response to isolated limb perfusion in soft tissue sarcomas due to identification of residual areas of viable tumor and subsequently may provide clinically useful information with regards to timing and planning of additional surgery. Further prospective studies in a larger patient population is warranted.

Combretastatin A4 phosphate has tumor antivascular activity in rat and man as demonstrated by dynamic magnetic resonance imaging

PURPOSE

Combretastatin A4 phosphate (CA4P) is a novel vascular targeting agent. Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) studies were performed to examine changes in parameters related to blood flow and vascular permeability in tumor and normal tissue after CA4P treatment.

MATERIALS AND METHODS

Changes in kinetic DCE-MRI parameters (transfer constant [Ktrans] and area under contrast medium-time curve [AUC]) over 24 hours after treatment with CA4P were measured in 18 patients in a phase I trial and compared with those obtained in the rat P22 carcinosarcoma model, using the same imaging technique. Rats were treated with 30 mg/kg of CA4P; patients received escalating doses from 5 to 114 mg/m2.

RESULTS

A similar pattern and time course of change in tumor and normal tissue parameters was seen in rats and humans. Rat tumor Ktrans was reduced by 64% 6 hours after treatment with CA4P (30 mg/kg). No significant reductions in kidney or muscle parameters were seen. Significant reductions were seen in tumor Ktrans in six of 16 patients treated at >or= 52 mg/m2, with a significant group mean reduction of 37% and 29% at 4 and 24 hours, respectively, after treatment. The mean reduction in tumor initial area under the gadolinium-diethylenetriamine pentaacetic acid concentration-time curve (AUC) was 33% and 18%, respectively, at these times. No reduction was seen in muscle Ktrans or in kidney AUC in group analysis of the clinical data.

CONCLUSION

CA4P acutely reduces Ktrans in human as well as rat tumors at well-tolerated doses, with no significant changes in kidney or muscle, providing proof of principle that this drug has tumor antivascular activity in rats and humans.

Challenges in dynamic contrast-enhanced MRI imaging of cervical lymph nodes to detect metastatic disease

PURPOSE

To identify and overcome challenges in using dynamic contrast-enhanced magnetic resonance imaging (MRI) to distinguish tumor from nontumor in the cervical lymph nodes of patients with squamous cell carcinoma of the head and neck.

MATERIALS AND METHODS

Signal-to-noise ratio (S/N), motion, node heterogeneity, and tissue normalizations were examined. Twenty-one patients with squamous cell carcinoma of the head and neck were scanned before a neck dissection (two-dimensional fast spoiled gradient-echo: 10 locations/13 seconds). Peak time, peak enhancement, maximum upslope, and washout slope were measured in pathologically confirmed tumor and nontumor nodes and in the submandibular gland and the sternocleidomastoid muscle.

RESULTS

Surface coil arrays provided high coverage and high S/N. Motion averaged 1.1 pixels and was corrected. Large tumor nodes were heterogeneous in their contrast enhancement, while the nontumor nodes were homogeneous. The contrast enhancement parameters were significantly different for all regions except for the submandibular gland compared to the nontumor nodes.

CONCLUSION

Challenges of dynamic imaging of cervical lymph nodes were overcome and significant differences were found between the tumor and nontumor nodes, indicating that dynamic imaging is feasible and may aid this patient population.

Detection of malignant bone marrow involvement with dynamic contrast-enhanced magnetic resonance imaging

BACKGROUND

The purpose of this study was to evaluate the role of dynamic contrast-enhanced magnetic resonance imaging (dMRI) in detecting bone marrow involvement in cancer patients.

PATIENTS AND METHODS

We studied 50 consecutive patients with histologically confirmed malignant dissemination to the bone marrow, using dMRI of the lumbosacral spine. Time-signal intensity curves were generated from regions of interest (ROIs) obtained from areas of obvious bone marrow disease (group B). In 16 patients from group B with focal disease, ROIs were also placed on areas with apparently normal bone marrow on static magnetic resonance images (group C). Twenty-two patients with no history of malignancy were used as a control group (group A). Wash-in (WIN) and wash-out (WOUT) rates, time to peak (TTPK), time to maximum slope (TMSP) values and WIN/TMSP ratios were calculated for each patient. Mean values for the three groups were compared statistically. Six patients from group B had follow-up dMRI after chemotherapy: four patients achieved a clinical partial response and two had resistant disease.

RESULTS

A significant difference was found between groups A and B for all values. Between groups A and C, in spite of the similar static MRI appearance, all values were significantly different. Between groups B and C, a significant difference was found for WIN, WOUT rates and WIN/TMSP ratio. Follow-up dMRI data analysis correlated well with clinical staging.

CONCLUSIONS

dMRI can distinguish normal from malignant bone marrow. It may identify malignant bone marrow infiltration in patients with negative static MRI and serve as both a diagnostic and prognostic tool for patients with bone marrow malignancies.

Primary skeletal neoplasms: osteosarcoma and ewing sarcoma

The care for children and adolescents with malignant bone tumors such as osteosarcoma and Ewing sarcoma will be improved by the magnetic resonance imager that can recognize the tumor early in its course and can stage it correctly for proper chemotherapy and local control. This can be accomplished by attention to the proper magnetic resonance imaging technique, recognition of the magnetic resonance appearance, and knowledge of the prognostic factors at diagnosis. Determination of response on follow-up static and dynamic contrast-enhanced magnetic resonance imaging and knowledge of optimal methods to determine recurrent tumor will improve the outcome for these children.

Reproducibility of dynamic contrast-enhanced MRI in human muscle and tumours: comparison of quantitative and semi-quantitative analysis

The purpose of this study was to determine the reproducibility of dynamic contrast-enhanced (DCE)-MRI and compare quantitative kinetic parameters with semi-quantitative methods, and whole region-of-interest (ROI) with pixel analysis. Twenty-one patients with a range of tumour types underwent paired MRI examinations within a week, of which 16 pairs were evaluable. A proton density-weighted image was obtained prior to a dynamic series of 30 T(1)-weighted spoiled gradient echo images every 11.9 s with an intravenous bolus of gadopentetate dimeglumine given after the third baseline data point. Identical ROIs around the whole tumour and in skeletal muscle were drawn by the same observer on each pair of examinations and used for the reproducibility analysis. Semi-quantitative parameters, gradient, enhancement and AUC (area under the curve) were derived from tissue enhancement curves. Quantitative parameters (K(trans), k(ep), v(e)) were obtained by the application of the Tofts' model. Analysis was performed on data averaged across the whole ROI and on the median value from individual pixels within the ROI. No parameter showed a significant change between examinations. For all parameters except K(trans), the variability was not dependent on the parameter value, so the absolute values for the size of changes needed for significance should be used for future reference rather than percentages. The size of change needed for significance in a group of 16 in tumours for K(trans), k(ep) and v(e) was -14 to +16%, -0.20 ml/ml/min (15%) and -1.9[?]ml/ml (6%), respectively (pixel analysis), and -16 to +19%, -0.23 ml/ml/min (16%) and +/- 1.9[?]ml/ml (6%) (whole ROI analysis). For a single tumour, changes greater than -45 to +83%, +/- 0.78 ml/ml/min (60%) and +/- 7.6 ml/ml (24%), respectively, would be significant (pixel analysis). For gradient, enhancement and AUC the size of change needed for significance in tumours was -0.24 (17%), -0.05 (6%) and -0.06 (8%), respectively for a group of 16 (pixel analysis), and +/- 0.96 (68%), +/- 0.20 (25%) and +/- 0.22 (32%) for individuals. In muscle, the size of change needed for significance in a group of 16 for K(trans), k(ep) and v(e) was -30 to +44%, +/- 0.81 ml/ml/min (61%) and +/- 1.7 ml/ml (13%). For gradient, enhancement and AUC it was +/- 0.09 (20%), +/- 0.02 (8%) and +/- 0.03 (12%). v(e), enhancement and AUC are highly reproducible DCE-MRI parameters. K(trans), k(ep) and gradient have greater variability, with larger changes in individuals required to be statistically significant, but are nevertheless sufficiently reproducible to detect changes greater than 14-17% in a cohort of 16 patients. Pixel analyses slightly improve reproducibility estimates and retain information about spatial heterogeneity. Reproducibility studies are recommended when treatment effects are being monitored.

Treatment-induced pathologic necrosis: a predictor of local recurrence and survival in patients receiving neoadjuvant therapy for high-grade extremity soft tissue sarcomas

PURPOSE

To determine whether treatment-induced pathologic necrosis correlates with local recurrence and overall survival in patients who receive neoadjuvant therapy for high-grade extremity soft tissue sarcomas.

PATIENTS AND METHODS

Four hundred ninety-six patients with intermediate- to high-grade extremity soft tissue sarcomas received protocol neoadjuvant therapy. All patients underwent surgical resection after neoadjuvant therapy and had pathologic assessment of tumor necrosis in the resected specimens.

RESULTS

The 5- and 10-year local recurrence rates for patients with > or = 95% pathologic necrosis were significantly lower (6% and 11%, respectively) than the local recurrence rates for patients with less than 95% pathologic necrosis (17% and 23%, respectively). The 5- and 10-year survival rates for the patients with > or = 95% pathologic necrosis were significantly higher (80% and 71%, respectively) than the survival rates for the patients with less than 95% pathologic necrosis (62% and 55%, respectively). Patients with less than 95% pathologic necrosis were 2.51 times more likely to develop a local recurrence and 1.86 times more likely to die of their disease as compared with patients with > or = 95% pathologic necrosis. The percentage of patients who achieved > or /= 95% pathologic necrosis increased to 48% with the addition of ifosfamide as compared with 13% of the patients in all the other protocols combined.

CONCLUSION

Treatment-induced pathologic necrosis is an independent predictor of both local recurrence and overall survival in patients who receive neoadjuvant therapy for high-grade extremity soft tissue sarcomas. A complete pathologic response (> or = 95% pathologic necrosis) correlated with a significantly lower rate of local recurrence and improved overall survival.

Current treatment of osteosarcoma

A comprehensive multidisciplinary approach has transformed osteosarcoma from a disease with a modest long-term survival to one in which at least two-thirds of patients will be cured. Surgery remains the vital modality for treating the primary tumor, whereas adjuvant chemotherapy plays an essential role in the control of subclinical metastatic disease. Complete surgical excision of the primary tumor remains an essential element of treatment. For many patients, a combination of advances in surgical technique, improved imaging modalities to accurately document tumor extent, and the effect of neoadjuvant chemotherapy has made limb salvage procedures a safe alternative to amputation. In some patients for whom complete surgical excision is impossible, the addition of radiation therapy may allow local tumor control. The most effective chemotherapy agents currently in use include high-dose methotrexate, doxorubicin, cisplatin, and ifosfamide/etoposide. The optimal schedule of therapy is still being investigated, as is the role of dose intensification. Unfortunately, some groups of patients remain at high risk of eventual relapse. Those whose tumors show relatively low degrees of necrosis after administration of chemotherapy have poorer survival than patients with more chemotherapy-responsive tumors. Similarly, patients who present with overt metastatic disease (particularly bone metastases), as well as patients with tumors that recur after treatment, continue to have an unsatisfactory outcome. These groups, in particular, may benefit from future investigations into novel agents, such as biological response modifiers, antiangiogenesis factors, and growth receptor modulation.

Carboplatin/ifosfamide window therapy for osteosarcoma: results of the St Jude Children's Research Hospital OS-91 trial

PURPOSE

To determine the activity of carboplatin/ifosfamide in patients with previously untreated osteosarcoma and to estimate patient outcomes after a multiagent chemotherapy protocol that eliminated cisplatin.

PATIENTS AND METHODS

Sixty-nine patients with newly diagnosed, previously untreated osteosarcoma received three cycles of carboplatin (560 mg/m(2) x 1) and ifosfamide (2.65 g/m(2)/d x 3). Assessment of response was evaluated after two (week 6) and three (week 9) chemotherapy cycles. At week 9, histologic response was assessed. Adjuvant therapy comprised two additional carboplatin/ifosfamide cycles, doxorubicin, and high-dose methotrexate. Patients were stratified at enrollment: stratum A, resectable primary tumor without metastases; stratum B, unresectable primary tumor; and stratum C, metastatic disease at diagnosis. Week 6 response was compared with that of a historic group that received only ifosfamide during the initial window evaluation.

RESULTS

The clinical and radiographic response rate to three cycles of carboplatin/ifosfamide was 67.7% (95% confidence interval, 55.0% to 78.8%). Compared with the historic population who received only ifosfamide, the combination of carboplatin and ifosfamide reduced the progressive disease rate at week 6 (31.9% v 9%, P: = .003). For patients in stratum A, the 3-year event-free survival and survival were 72.3% +/- 6.7% and 76.4% +/- 6.4%, respectively. Patients who received carboplatin-based therapy had less long-term renal toxicity and ototoxicity.

CONCLUSION

This pilot trial suggests that carboplatin/ifosfamide combination chemotherapy has substantial antitumor activity. In the context of a multiagent chemotherapy protocol comprising high-dose methotrexate and doxorubicin, we found that the addition of carboplatin/ifosfamide resulted in patient outcomes comparable to trials using cisplatin-based therapy with less long-term toxicity.

Bone and soft tissue tumors: the role of contrast agents for MR imaging

Magnetic resonance imaging is an important modality for the imaging evaluation of musculoskeletal tumors. Although there is general agreement on the value of unenhanced MR in detection, diagnosis and staging, intravenous use of gadolinium-contrast media (gd-CM) is indicated in selected cases. The purpose of this article is to review the basic pharmacokinetic principles and imaging techniques for static and dynamic contrast-enhanced MR imaging and to highlight the most important indications for administration of gd-CM in patients with musculsokeletal tumors and tumor-like lesions: adding specificity in tissue characterization, staging of local extent and biopsy planning, monitoring preoperative chemotherapy and detection of recurrence.

Prediction of gene therapy-induced tumor size changes by the vascularity changes measured using dynamic contrast-enhanced MRI

We studied the changes of tumor size after gene therapy treatment and its relationship with the changes of vascular volume as measured by dynamic contrast-enhanced magnetic resonance imaging (MRI), to investigate whether the vascular changes is predictive of tumor regression. The study was carried out using a spontaneously regressing rat tumor model (C6 Glioma grown subcutaneously in rats). Three rats were treated with recombinant adenoviruses expressing three genes, mouse interleukin 1-alpha (IL1-alpha), mouse interferon gamma (IFN-gamma), and human transforming growth factor beta (TGF-beta), one from each kind. Two rats were treated with saline as controls. Longitudinal studies were performed to monitor the changes of tumor volume (based on T(2)-weighted images) and the vascular volume (based on dynamic contrast enhanced images). In untreated animals, tumor regression was preceded by several days with a decrease in vascular volume. When the tumor growth was perturbed by expression of mouse IL-1alpha, the increase in vascular volume was correlated with the continuing growth in size, and the decrease in vascular volume was predictive of the onset of tumor regression. As new advances in immunotherapy in cancer treatment emerge, the ability to determine the efficacy of therapy as early as possible will enable optimization of treatment regiments. The vascularity changes measured by dynamic MRI may provide a means to serve for this purpose.

Evolution from empirical dynamic contrast-enhanced magnetic resonance imaging to pharmacokinetic MRI

For chemotherapy to be effective against cancers which grow as solid tumors, agents must reach all tumor cells in effective quantities. Although many clinical trials include studies of the pharmacokinetics of the agents in body fluids such as blood or cerebrospinal fluid (CSF), there is presently no widely applicable way to determine access of chemotherapeutic agents to all regions of a solid tumor in an individual patient. This review discusses a relatively new methodology in MR imaging - dynamic contrast-enhanced imaging for exploring tumor microcirculation and drug access by imaging the uptake, or leakage, of contrast agent into tumor interstitial (extracellular and extravascular) space. The aims and methods of dynamic contrast-enhanced MRI evaluations to measure contrast uptake are distinguished from dynamic contrast-enhanced MRI to measure blood volume or flow, by MR imaging of the first-pass effects of a contrast bolus. Measures of contrast uptake by dynamic MRI have demonstrated a convincing ability to aid in diagnosing the presence of viable tumor and to measure response for a range of human tumors. This body of clinical results will be summarized. While questions remain to be answered about how to extract non-invasive pharmacokinetic measures of drug access from these novel dynamic imaging methods, we are optimistic that these methods can provide important new clinical measures that reflect the range of biological variation within and between naturally-occurring solid tumors.

Dynamic MR imaging (DEMRI) of microcirculation in bone sarcoma

If chemotherapy is to be effective against bone sarcoma, the cytotoxic agents must reach all tumor cells in effective quantities. Although many clinical trials include studies of the pharmacokinetics of these agents in blood or cerebrospinal fluid, there have been no accurate or widely applicable methods of determining whether chemotherapeutic agents reach all regions of a solid tumor. This review discusses the use of dynamic contrast-enhanced magnetic resonance imaging (DEMRI) to assess the microcirculation and interstitium of bone sarcoma. DEMRI studies provide a means of exploring leakage of contrast agent into tumor interstitium (extracellular extravascular spaces [EES]). In clinical observations of numerous series of patients with bone sarcoma, measures of contrast uptake (access) have convincingly demonstrated a relationship with measures and predictions of the tumor's response to preoperative chemotherapy. The results of these studies have indicated that greater access at the time of presentation, greater decrease in access during therapy, and low access at the completion of preoperative therapy correspond to better response and longer disease-free survival. Although questions remain about how these novel dynamic imaging methods can best be used to measure drug access noninvasively, we are optimistic that such measures can be developed to reflect the range of biological variation within and between naturally occurring solid tumors.

Evaluation of angiogenesis and perfusion of bone marrow lesions: role of semiquantitative and quantitative dynamic MRI

Magnetic resonance imaging (MRI) is a noninvasive technique that complements computed tomography (CT), conventional X-ray, and bone marrow biopsies by sampling a large volume of musculoskeletal bone and providing information that aids the diagnosis, staging, and follow-up of various lesions. Although less sensitive to the mineral components of bones, the MRI appearance of physiologic bone marrow is mainly a reflection of the relative amounts of red marrow, yellow marrow, and trabecular bone. Therefore, use of T1-and T2-weighted MR sequences with or without fat suppression currently remains the most common approach to musculoskeletal bone lesion imaging. An additional imaging strategy to characterize various bone lesions is the application of contrast-enhanced dynamic MRI. This article examines semiquantitative and quantitative dynamic imaging, evaluation, and postprocessing techniques in various benign and malignant musculoskeletal lesions. Practical guidelines for performing a dynamic contrast-enhanced MR examination are proposed.

Causes and effects of heterogeneous perfusion in tumors

A characteristic of solid tumors is their heterogeneous distribution of blood flow, with significant hypoxia and acidity in low-flow regions. We review effects of heterogeneous tumor perfusion are reviewed and propose a conceptual model for its cause. Hypoxic-acidic regions are resistant to chemo- and radiotherapy and may stimulate progression to a more metastatic phenotype. In normal tissues, hypoxia and acidity induce angiogenesis, which is expected to improve perfusion. However, aggressive tumors can have high local microvessel density simultaneously with significant regions of hypoxia and acidosis. A possible explanation for this apparent contradiction is that the mechanisms regulating growth and adaptation of vascular networks are impaired. According to a recent theory for structural adaptation of vascular networks, four interrelated adaptive responses can work as a self-regulating system to produce a mature and efficient blood distribution system in normal tissues. It is proposed that heterogeneous perfusion in tumors may result from perturbation of this system. Angiogenesis may increase perfusion heterogeneity in tumors by increasing the disparity between parallel low- and high-resistance flow pathways. This conceptual model provides a basis for future rational therapies. For example, it indicates that selective destruction of tumor vasculature may increase perfusion efficiency and improve therapeutic efficacy.

Investigation of longitudinal vascular changes in control and chemotherapy-treated tumors to serve as therapeutic efficacy predictors

The impact of chemotherapy on longitudinal vascular changes taking place during the growth of an animal tumor, R3230 AC adenocarcinoma, was investigated. Two contrast agents of different molecular weights, gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA; < 1 kD) and gadomer-17 (35 kD), were used in the dynamic imaging studies. Enhancement kinetics were analyzed by a pharmacokinetic model to derive parameters related to vascular volume and permeability on a pixel-by-pixel basis. Responders and non-responders were separated according to tumor size 10 days after the therapy. Changes in the vascular volume measured by gadomer-17 at 4 days after therapy revealed a clear distinction between the controls and the responders/non-responders. Mean vascular volume decreased by 42% in responders but was not significantly changed in the controls. The one non-responder had increased vascular volume after chemotherapy. Enhancement kinetics of gadomer-17 detected the changes earlier and with greater sensitivity than Gd-DTPA. In the control group, vascular permeability determined by gadomer-17 correlated with the longitudinal growth rates of tumors, suggesting that vascular permeability assessed by gadomer-17 could potentially serve as an indicator of aggressive tumor growth.

Limb salvage and outcome of osteosarcoma. The University of Muenster experience

One hundred thirty-six patients with non-metastatic high grade osteosarcoma treated from 1978 to 1994 in one institution with a multidisciplinary approach that included intravenous neoadjuvant chemotherapy were studied to evaluate which factors influence the outcome of modern orthopaedic therapy. Anatomic location, tumor volume, surgical margins, complications, and functional outcome were analyzed. Seventy-nine patients had a limb salvage procedure, 21 had a rotationplasty, and 33 had an amputation. Limb salvage consisted of 32 endoprostheses, 39 allograft replacements, six autograft replacements, and two shortening procedures. Three patients died during preoperative chemotherapy treatment. At a mean followup of 43 months, 81 patients continue to be disease free, three are alive after local recurrence, 17 are alive after having metastatic lesions, five are alive with metastatic lesions present, and 30 patients died of their disease. Forty-seven patients had pulmonary metastatic lesions, 14 had osseous metastatic lesions, three had abdominal metastatic lesions, two had lymphatic metastatic lesions, and eight patients had skip metastatic lesions. Prognosis correlated with chemotherapy response, surgical margins, and tumor volume. The minor complication rate for limb salvage was 4% and the major complication rate was 52%. Amputations had a 6% minor complication rate and 34% major complication rate. Rotationplasties had 10% minor and 48% major complication rates. The Musculoskeletal Tumor Society functional evaluation after limb salvage showed that 23 (38%) patients had more than 75% of the maximum functional score, 34 (56%) were from 50% to 75%, and three (5%) less than 50%. Of the rotationplasties, six (67%) were functionally better than 75% and three (33%) were functionally better than from 50% to 75%. In the group of amputations, 13 (56%) were from 50% to 75%, and 10 (44%) less than 50%. The extent of preoperative necrosis, surgical margins, and tumor volume are the most important prognostic factors. The increase in limb salvage procedures and the better long term survival of patients results in a higher rate of immediate and delayed complications. Functional outcome after rotationplasty is superior to limb salvage reconstruction and amputation.

Hybrid artificial neural network segmentation and classification of dynamic contrast-enhanced MR imaging (DEMRI) of osteosarcoma

The evaluation of pediatric osteosarcoma has suffered from the lack of an accurate imaging measure of response. One major problem is that osteosarcoma do not shrink in response to chemotherapy; instead, viable tumor is replaced by necrotic tissue. Currently available techniques that use dynamic contrast-enhanced magnetic resonance imaging to quantitatively evaluate tumor response fail to assess the percentage of necrosis. At present, histopathologic evaluation of resected tissue is the only means of measuring the percentage of necrosis in treated osteosarcoma. The current study presents a non-invasive method to visualize necrotic and viable tumor and quantitatively assess the response of osteosarcoma. Our technique uses a hybrid neural network consisting of a Kohonen self-organizing map to segment dynamic contrast-enhanced magnetic resonance images and a multi-layer backpropagation neural network to classify the segmented images. Because the hybrid neural network is completely automated, our technique removes both inter- and intra-operator error. An analysis comparing the percentage of necrosis from our technique to the histopathologic analysis revealed a highly significant Spearman correlation coefficient of 0.617 with p < 0.001.