Noninvasive detection of clinically occult lymph-node metastases in prostate cancer

Imaging magnetically labeled cells with magnetomotive optical coherence tomography

We introduce a novel contrast mechanism for optical coherence tomography (OCT) whereby the optical scattering of magnetically labeled cells is modified by means of an externally applied magnetic field. This modification is made through the addition of a small electromagnet to the imaging arm of a conventional OCT interferometer. We measure the magnetomotive OCT signal by differencing pairs of axial scans (A-scans) acquired with the magnetic field on and off. Magnetomotive contrast is demonstrated in bulk three-dimensional cell scaffolds containing macrophages labeled with microparticles of iron oxide, demonstrating magnetic-specific contrast over a dynamic range of 30 dB.

Patients with penile carcinoma benefit from immediate resection of clinically occult lymph node metastases

PURPOSE

In this retrospective study we compared the clinical outcome of early vs delayed excision of lymph node metastases in patients with penile squamous cell carcinoma.

MATERIALS AND METHODS

A total of 40 patients with a T2-3 penile carcinoma with lymph node metastases were included in this study. All patients initially presented with bilateral impalpable lymph nodes. In 20 patients (50%) metastases were removed when they became clinically apparent during meticulous followup (median interval 6 months, range 1 to 24). There were 20 patients (50%) who underwent resection of inguinal metastases detected on dynamic sentinel node biopsy before they became palpable. The histopathological characteristics of the tumors and lymph nodes were reevaluated.

RESULTS

The 2 populations were similar in terms of patient age, T-stage, pathological tumor grade, vascular invasion and infiltration depth. Disease specific 3-year survival of patients with positive lymph nodes detected during surveillance was 35% and in those who underwent early resection, 84% (log rank p = 0.0017). In multivariate analysis early resection of occult inguinal metastases detected on dynamic sentinel node biopsy was an independent prognostic factor for disease specific survival (p = 0.006).

CONCLUSIONS

Early resection of lymph node metastases in patients with penile carcinoma improves survival.

Ultrasonography-guided fine-needle aspiration cytology before sentinel node biopsy in patients with penile carcinoma

OBJECTIVE

To assess the accuracy of ultrasonography (US)-guided fine-needle aspiration cytology (FNAC) for detecting occult lymph node metastases in patients with squamous cell carcinoma of the penis.

PATIENTS AND METHODS

Forty-three patients with 83 clinically node-negative inguinal regions were assessed with US and FNAC. The results were compared with histology from subsequent dynamic sentinel-node biopsy (DSNB) or inguinal lymph node dissection.

RESULTS

Thirty-four groins in 27 patients were considered to be suspicious by US and the lymph nodes were aspirated. Nine nodes contained tumour cells and this was confirmed by subsequent lymph node dissection. The sensitivity and specificity of US-guided FNAC were 39% (nine of 23) and 100% (60 of 60), respectively. The number of groins requiring DSNB was reduced by 11% (nine of 83).

CONCLUSION

US-guided FNAC can be used as the initial investigation in clinically node-negative groins. If tumour is confirmed then therapeutic inguinal lymph node dissection can be earlier and fewer DSNBs are required.

MR and optical approaches to molecular imaging

With an increasing understanding of the molecular basis of disease, various new imaging targets have recently been defined that potentially allow for an early, sensitive, and specific diagnosis of disease or monitoring of treatment response. Different approaches to depict these molecular structures in vivo are currently being explored by the molecular imaging community. We briefly review methodologies for molecular imaging by magnetic resonance imaging and optical methods. Special emphasis is put on different contrast agent designs (e.g., targeted and smart probes). New technical developments in optical imaging are briefly discussed. In addition, current research results are put into a clinical perspective to elucidate the potential merits one might expect from this new research field.

In vivo uptake of [11C]choline does not correlate with cell proliferation in human prostate cancer

PURPOSE

Prostate cancer is the second leading cause of death from cancer among US men. Positron emission tomography (PET) with [(11)C]choline has been shown to be useful in the staging and detection of prostate cancer. The background of the increased uptake of choline in human prostate cancer is not completely understood. The aim of this study was to prospectively investigate the relationship between the [(11)C]choline uptake and the cell proliferation in human prostate cancer.

METHODS

Prostate cancer tissue from 18 patients who had undergone a radical prostatectomy for histologically proven disease was studied. An [(11)C]choline PET scan was performed prior to surgery. Post-prostatectomy specimens were prepared and stained with the antibody MIB-1 for Ki-67, which depicts proliferation. Two independent observers counted the amount of stained nuclei per specimen.

RESULTS

Prostate cancer showed Ki-67 staining and high uptake of [(11)C]choline. Statistical analysis showed no significant correlation between [(11)C]choline uptake and Ki-67 staining (R=0.23; P=0.34). No significant relationships were found between the uptake of [(11)C]choline (SUV) and either preoperative PSA (R=0.14; P=0.55) or Gleason sum score (R=0.28; P=0.25).

CONCLUSION

In vivo uptake of [(11)C]choline does not correlate with cell proliferation in human prostate cancer as depicted by Ki-67. Our results suggest that a process other than proliferation is responsible for the uptake of [(11)C]choline in prostate cancer.

Positron emission tomography for prostate, bladder, and renal cancer

Prostate cancer, renal cancer, bladder, and other urothelial malignancies make up the common tumors of the male genitourinary tract. For prostate cancer, common clinical scenarios include managing the patient presenting with 1) low-risk primary cancer; 2) high-risk primary cancer; 3) prostate-specific antigen (PSA) recurrence after apparently successful primary therapy; 4) progressive metastatic disease in the noncastrate state; and 5) progressive metastatic disease in the castrate state. These clinical states dictate the appropriate choice of diagnostic imaging modalities. The role of positron emission tomography (PET) is still evolving but is likely to be most important in determining early spread of disease in patients with aggressive tumors and for monitoring response to therapy in more advanced patients. Available PET tracers for assessment of prostate cancer include FDG, 11C or 18F choline and acetate, 11C methionine, 18F fluoride, and fluorodihydrotestosterone. Proper staging of prostate cancer is particularly important in high-risk primary disease before embarking on radical prostatectomy or radiation therapy. PET with 11C choline or acetate, but not with FDG, appears promising for the assessment of nodal metastases. PSA relapse frequently is the first sign of recurrent or metastatic disease after radical prostatectomy or radiation therapy. PET with FDG can identify local recurrence and distant metastases, and the probability for a positive test increases with PSA. However, essentially all studies have shown that the sensitivity for recurrent disease detection is higher with either acetate or choline as compared with FDG. Although more data need to be gathered, it is likely that these two agents will become the PET tracers of choice for staging prostate cancer once metastatic disease is strongly suspected or documented. 18F fluoride may provide a more sensitive bone scan and will probably be most valuable when PSA is greater than 20 ng/mL in patients with high suspicion or documented osseous metastases. Several studies suggest that FDG uptake in metastatic prostate cancer lesions reflects the biologic activity of the disease. Accordingly, FDG can be used to monitor the response to chemotherapy and hormonal therapy. Androgen receptor imaging agents like fluorodihydrotestosterone are being explored to predict the biology of treatment response for progressive tumor in late stage disease in castrated patients. The assessment of renal masses and primary staging of renal cell carcinoma are the domain of helical CT. PET with FDG may be helpful in the evaluation of "equivocal findings" on conventional studies, including bone scan, and also in the differentiation between recurrence and posttreatment changes. The value of other PET tracers in renal cell carcinoma is under investigation. Few studies have addressed the role of PET in bladder cancer. Because of its renal excretion, FDG is not a useful tracer for the detection of primary bladder tumors. The few studies that investigated its role in the detection of lymph node metastases at the time of primary staging were largely disappointing. Bladder cancer imaging with 11C choline, 11C methionine, or 11C- acetate deserves further study.

Limited pelvic lymphadenectomy using the sentinel lymph node procedure in patients with localised prostate carcinoma: a pilot study

PURPOSE

The purpose of this study was to determine the potential role of the sentinel lymph node (SLN) procedure in limited lymph node dissection in patients with apparently localised prostate carcinoma.

METHODS

In 27 patients with organ-confined prostate cancer, a single injection of 0.3 ml/30 MBq( 99m)Tc-rhenium sulphur colloid was injected transrectally into the peripheral zone of each lobe of the prostate (total 0.6 ml/60 MBq) under ultrasound guidance. Two hours after injection, scintigraphy was performed. The first step in surgery was the detection and dissection of lymph nodes identified as SLNs. Then, standard lymphadenectomy was performed, consisting in a limited dissection that included all lymph nodes from the obturator fossa and along the external iliac vein. Lymphatic tissue along the hypogastric artery was not systematically removed, except in the presence of SLNs.

RESULTS

Mean patient age was 66 years (48-77); the mean serum prostate-specific antigen value was 10.6 ng/ml. In a high proportion of patients (21/27, 77.8%) an SLN was located along the initial centimetres of the hypogastric artery. The second most frequent site of SLNs was in the obturator fossa (11/27 patients, 40.7%), followed by the external iliac area (5/27 patients, 18.5%). Four patients had lymph node metastases, all in SLNs: two in the hypogastric area and two in the obturator fossa.

CONCLUSION

The SLN procedure revealed the individual variability in the lymphatic drainage of the prostate. The main site of SLNs was the hypogastric area, and two of the four metastatic nodes were located at this site. A limited standard pelvic lymphadenectomy, excluding the hypogastric lymph nodes, would have missed half of the lymph node metastases in this study. A radionuclide SLN procedure could assist in the correct staging of patients with early prostate cancer, especially when performing limited lymphadenectomy.

Management of recurrent disease after radical prostatectomy

Prostate cancer has undergone a stage migration since the advent of widespread PSA testing, yet still a significant number of men develop PSA recurrence following radical prostatectomy. This causes anxiety to the patient and the urologist. This review examines the clinical significance of biochemical relapse and the role of imaging modalities and anastomotic biopsies. The importance of the radical prostatectomy pathological features and the PSA kinetics in determining the site of recurrence and the best treatment modality is emphasised. The optimal timing and dose of salvage radiotherapy and the role of hormonal therapy is discussed.

The role of heparanase in lymph node metastatic dissemination: dynamic contrast-enhanced MRI of Eb lymphoma in mice

Heparanase expression has been linked to increased tumor invasion, metastasis, and angiogenesis and with poor prognosis. The aim of the study was to monitor the effect of heparanase expression on lymph node metastasis, in heparanase-overexpressing subcutaneous Eb mouse T-lymphoma tumors, and their draining lymph node. Dynamic contrast-enhanced magnetic resonance imaging (MRI) using biotin-BSA-GdDTPA-FAM/ROX was applied for analysis of blood volume, vascular permeability, and interstitial convection, and for detection of very early stages of such metastatic dissemination. Eb tumors increased extravasation, interstitial convection, and lymphatic drain of the contrast material. Interstitial flow directions were mapped by showing radial outflow interrupted in some tumors by directional flow toward the popliteal lymph node. Heparanase expression significantly increased contrast enhancement of the popliteal lymph node but not of the primary tumor. Changes in MR contrast enhancement preceded the formation of pathologically detectable metastases, and were detectable when only a few enhanced green fluorescent protein (EGFP)-expressing Eb cells were found near and within the nodes. These results demonstrate very early, heparanase-dependent vascular changes in lymph nodes that were visible by MRI following administration of biotin-BSA-GdDTPA-FAM/ROX, and can be used for studying the initial stages of lymph node infiltration.

Cancer nanotechnology: opportunities and challenges

Nanotechnology is a multidisciplinary field, which covers a vast and diverse array of devices derived from engineering, biology, physics and chemistry. These devices include nanovectors for the targeted delivery of anticancer drugs and imaging contrast agents. Nanowires and nanocantilever arrays are among the leading approaches under development for the early detection of precancerous and malignant lesions from biological fluids. These and other nanodevices can provide essential breakthroughs in the fight against cancer.

Imaging angiogenesis: applications and potential for drug development

Recognition of the importance of angiogenesis to tumor growth and metastasis has led to efforts to develop new drugs that are targeted to angiogenic vasculature. Clinical trials of these agents are challenging, both because there is no agreed upon method of establishing the correct dosage for drugs whose mechanism of action is not primarily cytotoxic and because of the long time it takes to determine whether such drugs have a clinical effect. Therefore, there is a need for rapid and effective biomarkers to establish drug dosage and monitor clinical response. This review addresses the potential of imaging as a way to accurately and reliably assess changes in angiogenic vasculature in response to therapy. We describe the advantages and disadvantages of several imaging modalities, including positron emission tomography, x-ray computed tomography, magnetic resonance imaging, ultrasound, and optical imaging, for imaging angiogenic vasculature. We also discuss the analytic methods used to derive blood flow, blood volume, empirical semiquantitative hemodynamic parameters, and quantitative hemodynamic parameters from pharmacokinetic modeling. We examine the validity of these methods, citing studies that test correlations between data derived from imaging and data derived from other established methods, their reproducibility, and correlations between imaging-derived hemodynamic parameters and other pathologic indicators, such as microvessel density, pathology score, and disease outcome. Finally, we discuss which imaging methods are most likely to have the sensitivity and reliability required for monitoring responses to cancer therapy and describe ways in which imaging has been used in clinical trials to date.

Future directions in body magnetic resonance imaging

Technologic innovations in instrumentation and contrast agents naturally lead to new clinical and research applications in body MRI. Although long-range predictions of innovation are an uncertain process, short-term trends in development are more readily discernable. This review will provide examples of recent developments in magnetic resonance spectroscopic imaging, contrast agent development and molecular imaging, instrumentation, post-processing, and screening in an attempt to describe areas of active research.

Fast Whole-Body Assessment of Metastatic Disease Using a Novel Magnetic Resonance Imaging System

OBJECTIVE

The objective of this study was to investigate the clinical use of a novel whole-body magnetic resonance imaging (MRI) system for comprehensive assessment of tumor spread in clinical routine.

MATERIAL AND METHODS

Sixty-five patients with different tumors with known metastatic disease and 6 healthy volunteers were included. High-resolution MRI from head to toe was performed using multiple phased-array surface coil elements, 24 independent receiver channels, and an integrated parallel acquisition technique (iPAT). A total room time of less than 60 minutes was required. Whole-body MRI and conventional spiral computed tomography (CT) were independently evaluated and compared in terms of feasibility, location/number of detected metastases, and therapeutic relevance.

RESULTS

Whole-body MRI was successfully performed in 68 of 71 subjects. Compared with CT, more metastases were detected by MRI in 11 of 63 patients (17%), particularly in brain, liver, spleen, lymph nodes, bone marrow, muscle, and subcutaneous fat tissue. According to these findings, therapy had to be modified in 6 of 63 patients (10%).

CONCLUSIONS

High-resolution whole-body MRI is feasible in clinical routine within 1 single examination and offers great potential for fast assessment of individual tumor spread and total tumor burden.

Improved biochemical relapse-free survival with increased external radiation doses in patients with localized prostate cancer: The combined experience of nine institutions in patients treated in 1994 and 1995

PURPOSE

To study the radiation dose-response as determined by Kaplan-Meier prostate-specific antigen (PSA) disease-free survival (PSA-DFS) estimates in patients with stage T1-T2 prostate cancer treated within a 2-year period (1994-1995).

METHODS

Nine institutions combined data on 4839 patients with stage T1 and T2 adenocarcinoma of the prostate who received > or =60 Gy external beam radiation therapy (RT) as sole treatment. No patient received neoadjuvant androgen deprivation or planned adjuvant androgen deprivation. Of the 4839 patients, 1325 were treated in 1994 and 1995; 1061 were treated with <72 Gy and 264 with > or =72 Gy. The median RT doses for the <72 Gy and the > or =72 Gy groups were 68.4 Gy and 75.6 Gy, respectively. The median follow-up for the <72 Gy and the > or =72 Gy groups were 5.8 and 5.7 years, respectively. Risk groups, defined on the basis of T stage, pretherapy PSA level, and biopsy Gleason score (GS), were as follows: low risk--T1b, T1c, T2a, GS < or =6 and PSA < or =10 ng/mL; intermediate risk--T1b, T1c, T2a, GS < or =6 and PSA >10 ng/mL but < or =20 ng/mL or T2b, GS < or =6 and PSA < or =20 ng/mL or GS 7 and PSA < or =20 ng/mL; high risk--GS 8-10 or PSA >20 ng/mL. The endpoint for outcome analysis was PSA-DFS at 5 years after therapy using the American Society for Therapeutic Radiology and Oncology failure definition.

RESULTS

Patients receiving > or =72 Gy had significantly more advanced cancers. The proportion of stage T2b/T2c cancers in the > or =72 Gy group was 42% compared with 32% in the <72 Gy group (p = 0.027). The mean pretherapy PSA was 11.4 ng/mL in the > or =72 Gy group compared with 10.7 ng/mL in the <72 Gy group (p = 0.001). The proportion of GS > or =8 cancers in the > or =72 Gy group was 9% compared with 7% in the <72 Gy group (p = 0.309). Overall, 15% of patients receiving <72 Gy had high-risk disease, compared with 22% of patients receiving > or =72 Gy (p = 0.034). The > or =72 Gy group had a greater number of follow-up PSA levels (mean 10.6/patient) compared with the <72 Gy group (mean 9.6/patient) (p = 0.007). For all 1325 patients, the 5- and 8-year PSA-DFS estimates were 64% and 62%, respectively. The 5-year PSA-DFS estimates for <72 Gy vs. > or =72 Gy were 63% vs. 69%, respectively (p = 0.046). Multivariate analysis for factors affecting PSA-DFS was performed for all cases using the following variables: pretherapy PSA (continuous), biopsy GS (continuous), stage (T1 vs. T2), radiation dose (continuous), and radiation technique (three-dimensional conformal vs. conventional). Pretreatment PSA (p < 0.001, chi-square 112.2), GS (p < 0.001, chi-square 12.8), radiation dose (p < 0.001, chi-square 13.5), and stage (p = 0.007, chi-square 7.2) were independent predictors of outcome. Radiotherapy technique was not (p = 0.50).

CONCLUSION

Differences in PSA-DFS estimates observed in multiple retrospective series have been attributed to differences in follow-up duration between patients treated to conventional doses (longer follow-up intervals) and those treated to higher doses (shorter follow-up intervals). In this report, the median follow-up duration in the > or =72 Gy group was essentially identical to the <72 Gy group, because the study included a large number of patients treated consecutively during a narrow time range (1994-1995). With similar follow-up duration, higher than conventional radiotherapy doses were associated with improved PSA-DFS when controlled for the influence of pretreatment PSA levels, biopsy GS, and clinical T stage.

Detection of vascular adhesion molecule-1 expression using a novel multimodal nanoparticle

Endothelial vascular adhesion molecule-1 (VCAM-1) is a critical component of the leukocyte-endothelial adhesion cascade, and its strict temporal and spatial regulation make it an ideal target for imaging and therapy. The goal of this study was to develop novel VCAM-1-targeted imaging agents detectable by MRI and fluorescence imaging using phage display-derived peptide sequences and multimodal nanoparticles (NPs). We hypothesized that VCAM-1-mediated cell internalization of phage display-selected peptides could be harnessed as an amplification strategy to chaperone and trap imaging agents inside VCAM-1-expressing cells, thus improving target-to-background ratios. To accomplish our goal, iterative phage display was performed on murine endothelium under physiological flow conditions to identify a family of VCAM-1-mediated cell-internalizing peptides. One specific sequence, containing the VHSPNKK motif that has homology to the alpha-chain of very late antigen (a known ligand for VCAM-1), was shown to bind VCAM-1 and block leukocyte-endothelial interactions. Compared with VCAM-1 monoclonal antibody, the peptide showed 12-fold higher target-to-background ratios. A VHSPNKK-modified magnetofluorescent NP (VNP) showed high affinity for endothelial cells expressing VCAM-1 but surprisingly low affinity for macrophages. In contrast, a control NP without VCAM-1-targeting sequences showed no affinity for endothelial cells. In vivo, VNP successfully identified VCAM-1-expressing endothelial cells in a murine tumor necrosis factor-alpha-induced inflammatory model and colocalized with VCAM-1-expressing cells in atherosclerotic lesions present in cholesterol-fed apolipoprotein E apoE-/- mice. These results indicate that: (1) small peptide sequences can significantly alter targeting of NPs, (2) the used amplification strategy of internalization results in high target-to-background ratios, and (3) this technology is useful for in vivo imaging of endothelial markers.

Lymph node involvement in patients with bladder cancer treated with radical cystectomy: a patho-anatomical study--a single center experience

PURPOSE

To our knowledge the extent of lymphadenectomy with cystectomy, the number of lymph nodes to be retrieved and the anatomical groups to be dissected are still undetermined. This study was done to clarify these issues.

MATERIALS AND METHODS

A total of 200 patients underwent radical cystectomy and extended lymphadenectomy up to the level of origin of the inferior mesenteric artery. Removed tissues were labeled according to anatomical location and sent separately for pathological evaluation. In each group the number and status of lymph nodes were determined. The number of positive nodes was correlated with the number of retrieved nodes. Cases with a single positive node were identified and the anatomical location was defined.

RESULTS

The mean number of retrieved nodes per patient +/- SE was 50.6 +/- 14.4 and 48 (24%) patients had nodal disease. The mean number of positive nodes per involved case was 8.08 +/- 13.2. There was a weak correlation between the number of positive nodes and the number of harvested nodes. Bilateral disease was noted in 39.6% of cases. Single node involvement was observed in 22 cases, of which all except 1 were in the endopelvic region.

CONCLUSIONS

There is a sentinel region, which is the endopelvic region (that is the internal iliac and obturator groups of lymph nodes). There are no skipped lesions. Negative nodes in the endopelvic region indicate that more proximal dissection is not necessary. Bilateral endopelvic dissection is mandatory.

Interpretation of magnetic resonance imaging for locally advanced rectal carcinoma after preoperative chemoradiation therapy

PURPOSE

Neoadjuvant concomitant chemoradiotherapy has been used in cases of locally advanced rectal cancer to preserve sphincter function, decrease local recurrence, and improve survival. Preoperative staging is essential for planning and providing optimal therapy. The purpose of this study is to determine the accuracy of staging with magnetic resonance imaging and to define any factors that interfere in interpretation of images obtained after preoperative chemoradiation therapy.

METHODS

Thirty-six patients with biopsy-proven, locally advanced rectal cancer were treated with preoperative concomitant 5-fluorouracil-based chemotherapy and radiation, followed six to eight weeks later by radical surgery. Preoperative magnetic resonance images were reinterpreted by one radiologist and the results compared with histopathologic staging.

RESULTS

T-level downstaging occurred in 10 of 36 patients (28 percent), and N-level downstaging occurred in 29 of 36 patients (80 percent) after completion of chemoradiation therapy. Pathologic complete remission after chemoradiotherapy occurred in five patients (12 percent). Of the 36 patients, 17 (47 percent) were overstaged and 2 (6 percent) were understaged in T-level, whereas 10 patients (28 percent) were overstaged and 3 patients (8 percent) were understaged in N-level. The accuracy of magnetic resonance imaging for determining depth of wall invasion was 47 percent, with 64 percent accuracy for nodal staging.

CONCLUSIONS

Magnetic resonance imaging is commonly used in staging of pelvic malignancies because of its fine resolution, but chemoradiotherapy may decrease its accuracy. Thickening of the rectal wall after radiation by marked fibrosis, and peritumoral infiltration of inflammatory cells and vascular proliferation may contribute to overestimation of stage. By contrast, pathologic residual cancer beneath normal mural structure after chemoradiation therapy may result in understaging of rectal cancer.

1H/19F magnetic resonance molecular imaging with perfluorocarbon nanoparticles

Developments in genomics, proteomics, and cell biology are leading a trend toward individualized segmentation and treatment of patients based on early, noninvasive recognition of unique biosignatures. Although developments in molecular imaging have been dominated by nuclear medicine agents in the past, the advent of nanotechnology in the 1990s has led to magnetic resonance (MR) molecular agents that allow detection of sparse biomarkers with a high-resolution imaging modality that can provide both physiological and functional agents. A wide variety of nanoparticulate MR contrast agents have emerged, most of which are superparamagnetic iron oxide-based constructs. However, this chapter focuses on a diagnostic and therapeutic perfluorocarbon (PFC) nanoparticulate platform that is not only effective as a T1-weighted agent, but also supports (19)F MR spectroscopy and imaging. The unique capability of (19)F permits confirmation and segmentation of MR contrast images as well as direct quantification of nanoparticle concentrations within a voxel. PFC nanoparticles have the capability to effectively deliver therapeutic agents to target sites by a novel mechanism termed "contact-facilitated drug delivery." Combined with MR spectroscopy, the concentration of drug delivered to the target site can be determined and the expected response predicted. Moreover, mixtures of nanoparticles with different perfluorocarbon cores can provide a quantitative, multispectral signal, which can be used to simultaneously distinguish the relative concentrations of several important epitopes within a region of interest. In conjunction with rapid improvements in MR imaging, the prospects for personalized medicine and early recognition and treatment of disease have never been better.

MR techniques for in vivo molecular and cellular imaging

MR-based molecular imaging is a science in infancy. Current clinical contrast agents are often geared toward the assessment of gross physiologic function, rather than targeting specific biochemical pathways. The development of specific targeted smart contrast agents for Food and Drug Administration approval or clinical trials has only begun. The fact that MR imaging can obtain images of extremely high resolution, coupled with its ability to simultaneously assess structure and function through the use of targeted contrast agents indicates that MR will play a pivotal role in clinical molecular imaging of the future. Many of the challenges that face MR imaging and spectroscopy are inherent to all modalities in the rapidly growing field of molecular imaging. The development of smart contrast agents to report on receptor function, and to monitor gene expression or the results of gene therapy in humans is paramount. These compounds need to undergo rigorous testing to be approved for clinical use: the assessment of acute toxicity, pharmacokinetics, long-term accumulation, and subsequent chronic effects. For receptor-targeted contrast agents, the degree of receptor occupancy and the intrinsic agonist or antagonist properties of the probe that may affect normal cellular function need to be determined to avoid undesired side effects. The particular problems that face MR imaging, those of sensitivity and target specificity, need to be overcome. Signal amplification achieved through high relaxivity contrast agents containing multiple paramagnetic centers, or of larger superparamagnetic particles, is the first step in this direction. The modulation of relaxivity through oligomerization, or other modifications that cause restriction of rotational motions, shows great promise for improving the discriminative powers of MR imaging, and may permit multiple targets to be assessed simultaneously. Moreover, the introduction of smart indicators that lead to changes in spectroscopic properties will allow further discrimination to be achieved through the implementation of chemical shift or spectroscopic imaging. The growing number of MR imaging applications in this rapidly expanding field point to a bright future for MR imaging in molecular imaging.

Medical Nanotechnology

Nanotechnology, the science of creating structures, devices, and systems with a length scale of approximately 1-100 nanometers, is poised to have a revolutionary effect on biomedical research and clinical science. By operating at the same scale as most biomacromolecules, nanoscale devices can afford a detailed view of the molecules and events that drive cellular systems and that lie at the heart of disease, and thus, nanotechnology can impact the drug discovery, development, and clinical testing of novel pharmaceuticals. Already, nanoscale drug delivery vehicles are in clinical use, but those successes represent just one way in which nanotechnology will prove useful. One promising nanoscale technology under development may provide real-time, in vivo measurements of apoptosis, and thus may afford an early signal of therapeutic efficacy, both in human clinical trials and in preclinical screening. Microfluidic systems, built of nanoscale components, can enable a host of rapid, massively parallel, high-throughput screening systems, while nanoscale sensors in a wide variety of formats are ready to provide multiplexed biochemical and genetic measurements in living systems. These advances could be utilized to shave time and expense from multiple stages of the drug discovery and development effort.

Magnetic Resonance Imaging: Utility as a Molecular Imaging Modality

Significant scientific effort has gone into the deconvolution and understanding of complex biological systems. These efforts have yielded much information about the molecular changes that are causative or arise as a result of disease. Molecular imaging is a relatively newer field that is attempting to use these molecular data to generate images that report on changes in gene expression. It has been demonstrated that generating images based on molecular differences rather than anatomical differences between tissues has resulted in more sensitive detection of diseased tissues and has allowed imaging of drug efficacy against particular drug targets. This chapter discusses the application of magnetic resonance imaging (MRI) to molecular imaging. It begins with a review of the basis for magnetic resonance image generation and how manipulation of different parameters of the system can be applied to molecular imaging. It then specifically reviews some of the problematic areas for magnetic resonance application to molecular imaging and how these can be resolved by manipulating the magnetic resonance system, altering magnetic resonance probe characteristics, or exploiting the biology to be imaged. It concludes with several examples demonstrating the utility of MRI to generate high-resolution, noninvasive images of molecular events occurring in vivo.

Comparison of Gd [DTPA-bis (2-aminoethoxy) ethane] polymeric contrast agent with gadodiamide injection for interstitial MR lymphography: Experimental study with rabbits

PURPOSE

To compare the differences between macromolecular and small molecular contrast agents in interstitial magnetic resonance (MR) lymphography.

MATERIALS AND METHODS

In two groups of rabbits (N = 12 each), 0.5-mL volumes of 0.5 M and 0.1 M gadodiamide, respectively, were injected subcutaneously into the dorsal feet of both hind legs. After a 24-hour interval, 0.5 mL of Gd [DTPA-bis (2-aminoethoxy) ethane] polymeric contrast agent (Gd-poly-DTPA-EOEA) injection (0.1 M) was injected into the same sites in each rabbit. T1-weighted three-dimensional gradient-echo and maximum intensity projection (MIP) images were obtained before and after the administration of each agent. The nodal maximum short-axis diameter (MSAD) and signal-to-noise ratio (SNR) at each time point were measured. Postmortem measurements of nodal MSADs were also performed. The nodal MSAD measurements obtained by MR lymphography were compared with the postmortem measurements. As an additional control experiment, six rabbits received a subcutaneous injection of 0.5 mL of 0.1 M gadodiamide at the same sites as those described above. This procedure was repeated after a 24-hour interval to determine whether the first injected gadodiamide had any effect on the performance of the subsequently injected agent, by comparing the differences in nodal MSADs obtained by MR lymphography after each injection.

RESULTS

Gd-poly-DTPA-EOEA showed a significantly longer enhancement plateau compared to gadodiamide. In comparison with postmortem measurements, nodal measurements by MR lymphography with Gd-poly-DTPA-EOEA at the peak-enhancement phase revealed no significantly different MSADs (P > 0.05), whereas nodal measurements by MR lymphography with gadodiamide showed significantly smaller MSADs (P < 0.05). A comparison of the nodal MSADs measured in two gadodiamide-enhanced MR examinations after the 24-hour interval showed no significant difference (P > 0.05).

CONCLUSION

Interstitial MR lymphography with polymeric Gd-poly-DTPA-EOEA enhancer enables more sufficient and reliable visualization of lymph nodes compared to small molecular gadodiamide.

Sensitive, noninvasive detection of lymph node metastases

BACKGROUND

Many primary malignancies spread via lymphatic dissemination, and accurate staging therefore still relies on surgical exploration. The purpose of this study was to explore the possibility of semiautomated noninvasive nodal cancer staging using a nanoparticle-enhanced lymphotropic magnetic resonance imaging (LMRI) technique.

METHODS AND FINDINGS

We measured magnetic tissue parameters of cancer metastases and normal unmatched lymph nodes by noninvasive LMRI using a learning dataset consisting of 97 histologically proven nodes. We then prospectively tested the accuracy of these parameters against 216 histologically validated lymph nodes from 34 patients with primary cancers, in semiautomated fashion. We found unique magnetic tissue parameters that accurately distinguished metastatic from normal nodes with an overall sensitivity of 98% and specificity of 92%. The parameters could be applied to datasets in a semiautomated fashion and be used for three-dimensional reconstruction of complete nodal anatomy for different primary cancers.

CONCLUSION

These results suggest for the first time the feasibility of semiautomated nodal cancer staging by noninvasive imaging.

Iron oxide MR contrast agents for molecular and cellular imaging

Molecular and cellular MR imaging is a rapidly growing field that aims to visualize targeted macromolecules or cells in living organisms. In order to provide a different signal intensity of the target, gadolinium-based MR contrast agents can be employed although they suffer from an inherent high threshold of detectability. Superparamagnetic iron oxide (SPIO) particles can be detected at micromolar concentrations of iron, and offer sufficient sensitivity for T2(*)-weighted imaging. Over the past two decades, biocompatible particles have been linked to specific ligands for molecular imaging. However, due to their relatively large size and clearance by the reticuloendothelial system (RES), widespread biomedical molecular applications have yet to be implemented and few studies have been reproduced between different laboratories. SPIO-based cellular imaging, on the other hand, has now become an established technique to label and detect the cells of interest. Imaging of macrophage activity was the initial and still is the most significant application, in particular for tumor staging of the liver and lymph nodes, with several products either approved or in clinical trials. The ability to now also label non-phagocytic cells in culture using derivatized particles, followed by transplantation or transfusion in living organisms, has led to an active research interest to monitor the cellular biodistribution in vivo including cell migration and trafficking. While most of these studies to date have been mere of the 'proof-of-principle' type, further exploitation of this technique will be aimed at obtaining a deeper insight into the dynamics of in vivo cell biology, including lymphocyte trafficking, and at monitoring therapies that are based on the use of stem cells and progenitors.

Magnetic resonance molecular imaging with nanoparticles

Molecular imaging agents are extending the potential of noninvasive medical diagnosis from basic gross anatomic descriptions to complicated phenotypic characterizations based on the recognition of unique cell surface biochemical signatures. Although originally the purview of nuclear medicine, molecular imaging is now a prominent feature of most clinically relevant imaging modalities, in particular magnetic resonance (MR) imaging. MR nanoparticulate agents afford the opportunity not only for targeted diagnostic studies but also for image-monitored site-specific therapeutic delivery, much like the "magic bullet" envisioned by Paul Erhlich 100 years ago. Combining high-resolution MR molecular imaging with drug delivery will facilitate verification and quantification of treatment (ie, rational targeted therapy) and will offer new clinical approaches to many diseases.

Urinary Bladder Cancer: Preoperative Nodal Staging with Ferumoxtran-10–enhanced MR Imaging

PURPOSE

To prospectively evaluate ferumoxtran-10-enhanced magnetic resonance (MR) imaging for nodal staging in patients with urinary bladder cancer.

MATERIALS AND METHODS

Fifty-eight patients with proved bladder cancer were enrolled. Results of MR imaging performed before and after injection of ferumoxtran-10 were compared with histopathologic results in surgically removed lymph nodes. High-spatial-resolution three-dimensional T1-weighted magnetization-prepared rapid acquisition gradient-echo (voxel size, 1.4 x 1.4 x 1.4 mm) and T2*-weighted gradient-echo (voxel size, 0.8 x 0.8 x 3.0 mm) sequences were performed before and 24 hours after injection of ferumoxtran-10 (2.6 mg iron per kilogram of body weight). On precontrast images, lymph nodes were defined as malignant by using size and shape criteria (round node, >8 mm; oval, >10 mm axial diameter). On postcontrast images, nodes were considered benign if there was homogeneous decrease in signal intensity and malignant if decrease was absent or heterogeneous. Qualitative evaluation was performed on a node-to-node basis. Sensitivity, specificity, predictive values, and accuracy were evaluated with logistic regression analysis.

RESULTS

In 58 patients, 172 nodes imaged with use of ferumoxtran-10 were matched and correlated with results of node dissection. Of these, 122 were benign and 50 were malignant. With nodal size and shape criteria, accuracy, sensitivity, specificity, and positive and negative predictive values on precontrast images were 92%, 76%, 99%, 97%, and 91%, respectively; corresponding values on postcontrast images were 95%, 96%, 95%, 89%, and 98%. In the depiction of pelvic metastases, sensitivity and negative predictive value improved significantly at postcontrast compared with those at precontrast imaging, from 76% to 96% (P < .001) and from 91% to 98% (P < .01), respectively. At postcontrast imaging, metastases (4-9 mm) were prospectively found in 10 of 12 normal-sized nodes (<10 mm); these metastases were not detected on precontrast images. Postcontrast images also showed lymph nodes that were missed at pelvic node dissection in two patients.

CONCLUSION

Ferumoxtran-10-enhanced MR imaging significantly improves nodal staging in patients with bladder cancer by depicting metastases even in normal-sized lymph nodes.

ANATOMICAL EXTENT OF LYMPH NODE DISSECTION: IMPACT ON MEN WITH CLINICALLY LOCALIZED PROSTATE CANCER

PURPOSE

This study evaluates the influence of the anatomical extent of pelvic lymph node dissection performed at radical prostatectomy on lymph node yield, staging accuracy and time to prostate specific antigen progression.

MATERIALS AND METHODS

Between February 1992 and April 2003, 2 surgeons at 1 hospital performed 2,135 and 1,865 radical prostatectomies with pelvic lymph node dissection, respectively. One surgeon routinely performed an extended lymph node dissection while the second surgeon performed a limited pelvic lymphadenectomy. The number of lymph nodes extracted and the number of patients with positive lymph nodes detected were analyzed and compared. Kaplan-Meier analysis was used to compare the biochemical recurrence-free survival between the 2 groups of patients with occult nodal disease.

RESULTS

Extended lymph node dissection removed more lymph nodes (mean 11.6 vs 8.9, p<0.0001) and detected more lymph node positive disease (3.2% vs 1.1%, p<0.0001) than the more anatomically limited technique. This finding held true for patients across all pathology groups. Among men with lymph node positive disease involving less than 15% of extracted nodes, the 5-year prostate specific antigen progression-free rate for extended lymph node dissection was 43% versus 10% for the more limited lymph node dissection (p = 0.01).

CONCLUSIONS

Compared to limited lymph node dissection, extended pelvic lymphadenectomy appears to identify men with positive lymph nodes more frequently. A significant benefit in biochemical recurrence-free survival may exist for certain subgroups undergoing the extended dissection. However, because the results may be influenced by stage migration, longer followup is necessary to determine whether the apparent therapeutic effect persists.

Decrease of Signal Intensity of Myometrium and Cervical Stroma After Ultrasmall Superparamagnetic Iron Oxide (USPIO) Particles Administration

OBJECTIVES

Following the empiric observation of a significant decrease of signal intensity of both myometrium and cervical stroma on ultrasmall superparamagnetic iron oxide (USPIO)-enhanced images, the aim of our study was to evaluate whether USPIO-enhanced T2*-weighted gradient echo (GRE) images might provide any potential advantage on T-staging of uterine malignancies having surgery and histology as standard of reference

MATERIALS AND METHODS

Seventeen female patients with known uterine malignancies underwent magnetic resonance (MR) imaging before and 24 hours after the intravenous administration of the USPIO agent. Imaging protocol included proton density-weighted turbo spin echo and T2*-weighted GRE sequences. Each patient underwent surgery within 14 days from the first MR examination, and histologic confirmation of tumor T-stage was obtained. Quantitative (calculation of signal-to-noise and contrast-to-noise ratios) and qualitative (visual assessment of T staging) analyses were performed on unenhanced and USPIO-enhanced images.

RESULTS

Quantitative analysis showed a significantly lower (P < 0.05) signal-to-noise ratio of myometrium and cervical stroma on USPIO-enhanced compared with unenhanced images. In 15 of 17 patients (88.2%), the contrast-to-noise ratio between tumor and myometrium and between tumor and cervical stroma was higher on USPIO-enhanced compared with unenhanced images (P < 0.001). Qualitative analysis demonstrated that the GRE T2* USPIO-enhanced MR offers a better definition of the depth of tumor infiltration rather than the unenhanced GRE T2* images.

CONCLUSION

The decrease of signal intensity of myometrium and cervical stroma on T2*-weighted GRE images after the intravenous administration of USPIO should be considered a constant and physiologic finding that improves tumor conspicuity in the majority of the cases, allowing more accurate T-staging of neoplastic lesions.

Applications of ultrasmall superparamagnetic iron oxide contrast agents in the MR study of animal models

Ultrasmall superparamagnetic iron oxide nanoparticles have been widely used during the past decade as MR intravascular contrast agents in the study of animal models. Such agents enhance both T1 and T2/T2* relaxation, although for animal studies it is the later type of enhancement that is most commonly exploited. Their strong microscopic intravascular susceptibility effect enables the local blood volume distribution to be mapped in various organs. High spatial resolution and sensitivity can be achieved, because the long half-life of these agents in blood, combined with anesthetization, permits steady-state measurements over extended periods. This capability has been utilized to study the cerebrovascular blood volume distributions and their changes in normal, activated, pathologic and pharmacologically or genetically modified states, particularly in rodent animal models. It has also been applied to study blood volume changes in other tissues, such as the myocardium. The relaxation rate shifts Delta R2 and Delta R2* induced by iron oxide agents may differ depending on certain morphological characteristics of the microvascular network, and sensitive Delta R2 and Delta R2* mapping can potentially provide, in addition to blood volume, measurement of other important microvascular parameters such as blood vessel density and size. This work aims to review the applications of ultrasmall superparamagnetic iron oxide contrast agents in MR animal studies, with an emphasis on the investigation of microvascular parameters.

USING MOLECULAR MARKERS TO PREDICT OUTCOME

PURPOSE

Developing molecular tests to predict prostate cancer progression requires first defining meaningful clinical end points and defining strategies to take advantage of emerging technology.

MATERIALS AND METHODS

The select relevant literature was reviewed concerning clinical trials, clinical prostate cancer nomograms, molecular biomarker development and molecular prostate cancer imaging.

RESULTS

There is controversy regarding the use of prostate specific antigen or biochemical failure following prostatectomy or radiation therapy for clinically localized prostate cancer as a marker of progression. As a consequence, advances in prostate cancer biomarker development may require using population based cohorts or cases from clinical trials to identify meaningful associations. Whereas the discovery of novel candidate biomarkers was slow 5 to 10 years ago and often resulted from serendipity, advances in high throughput technologies have led to the identification of a large number of candidate genes. Strategies to identify candidate genes include the use of expression array analysis, single nucleotide polymorphism arrays (single nucleotide polymorphism chips), proteomics and bioinformatics. Monitoring the progression of prostate cancer has been limited to standard approaches such as computerized tomography or magnetic resonance imaging, which in general do not delineate the extent of disease. By carefully selecting novel prostate cancer biomarkers future work should allow in vivo monitoring of prostate cancer. This will represent a revolutionary advance in our ability to monitor prostate cancer progression and ultimately it may be one of the most important applications of cancer biomarkers.

CONCLUSIONS

Emerging technology should allow us to analyze clinical prostate cancer trials with sufficient followup to help develop meaningful markers of prostate cancer progression.

Surface-functionalized nanoparticle library yields probes for apoptotic cells

We have developed techniques for the efficient synthesis and screening of small libraries of surface-functionalized nanoparticles for the recognition of specific types of cells. To illustrate this concept we describe the development of a nanoparticle that preferentially recognizes apoptotic Jurkat cells in a manner similar to the apoptosis-recognizing protein annexin V. The nanoparticle, which is detectable by fluorescence or NMR relaxometry, was analyzed for the ability to recognize normal and apoptotic cells by fluorescence-activated cell sorting (FACS) analysis and fluorescence microscopy. The capability to develop nanoparticles which interact with specific target cells could be applied to the design of materials for diverse applications including quantum dots, which serve as fluorescence tracers, colloidal gold, which serves as a tracer for electron micrographs, or the crystalline forms of drugs.

Use of magnetic nanoparticles as nanosensors to probe for molecular interactions

Biocompatible magnetic nanosensors have been designed to detect molecular interactions in biological media. Upon target binding, these nanosensors cause changes in the spin-spin relaxation times of neighboring water molecules, which can be detected by magnetic resonance (NMR/MRI) techniques. These magnetic nanosensors have been designed to detect specific mRNA, proteins, enzymatic activity, and pathogens (e.g., virus) with sensitivity in the low femtomole range (0.5-30 fmol).

Pretreatment Evaluation of Prostate Cancer: Role of MR Imaging and1H MR Spectroscopy

Magnetic resonance (MR) imaging and hydrogen 1 MR spectroscopy of the prostate gland are performed during the same examination with a conventional clinical MR unit. Prostate zonal anatomy and prostate cancer are best depicted on multiplanar T2-weighted MR images. MR imaging and 1H MR spectroscopy are not used as an initial diagnostic tool. Their use in tumor detection is reserved for patients with elevated prostate-specific antigen levels in whom previous biopsy results were negative. The use of MR imaging and 1H MR spectroscopy for the evaluation of tumor location, local extent (extracapsular extension and/or seminal vesicle invasion), volume, and aggressiveness is generating strong clinical interest. In staging and treatment planning, MR imaging has been shown to have an incremental value additive to the value of clinical nomograms. Furthermore, anatomic and metabolic mapping of the prostate gland with 1H MR spectroscopy offers the possibility of optimizing treatment planning (watchful waiting, surgery, or radiation therapy [intensity-modulated radiation therapy or brachytherapy]), thus further expanding the role of MR imaging in the achievement of patient-specific, individualized treatment.

Nanotechnology and Tumor Imaging: Seizing an Opportunity

Nanoparticles, labeled with a signaling moiety for in vivo imaging, and one or more ligands for molecularly targeted specificity, hold considerable promise in oncology. Nanoparticles can serve as modular platforms, from which a wide variety of highly sensitive and specific imaging agents can be created. For example, many hundreds or thousands of atoms that provide imaging signals, such as radioisotopes, lanthanides, or fluorophores, can be attached to each nanoparticle, to form imaging agents that would provide higher sensitivity that can be obtained from agents based on small molecules. Similarly, many copies of targeted ligands can be attached to nanoparticles to markedly increase specific binding. Drugs or therapeutic isotopes can be added to create multifunctional nanoparticles. Appropriately labeled and targeted nanoparticles could lead to a paradigm change in which cancer detection, diagnosis, and therapy are combined in a single molecular complex.

Role of ProstaScint for brachytherapy in localized prostate adenocarcinoma

ProstaScint (CYT-356 or capromab pendetide, Cytogen) is an 111In-labeled monoclonal mouse antibody specific for prostate-specific membrane antigen, a prostate transmembrane glycoprotein that is upregulated in prostate adenocarcinoma. ProstaScint scans are US Food and Drug Administration approved for pretreatment evaluation of metastatic disease in high-risk patients. They are also approved for post-prostatectomy assessment of recurrent disease in patients with a rising prostate-specific antigen level. This review explores the literature on ProstaScint and its use in guiding the treatment of prostate cancer. A novel technique for identifying areas of cancer within the prostate using ProstaScint images fused with pelvic computed tomography scans is also described. The identification of areas of high antibody signal provides targets for radiotherapeutic dose escalation, with the overall goals of improving treatment outcome while preserving adjacent tissue structures and decreasing treatment morbidity.

Imaging inflammation of the pancreatic islets in type 1 diabetes

Type 1 diabetes is the clinical manifestation of aberrant leukocytic infiltration of the pancreatic islets; it is usually diagnosed only very late in disease progression, after the critical autoimmune phenomena have mostly played out. A noninvasive means of directly monitoring the evolution of islet infiltrates would have important research and clinical applications. We have exploited fluorescence and MRI of long-circulating magnetofluorescent nanoparticles to visualize micro-vascular leakage, as an indicator of inflammation, in pancreata of mouse models of type 1 diabetes ex vivo or in vivo. We could detect the onset and evolution of insulitis in vivo and in real time, permitting us to study the natural history of diabetes in individual animals.

Impact of Fusion of Indium-111 Capromab Pendetide Volume Data Sets with Those from MRI or CT in Patients with Recurrent Prostate Cancer

OBJECTIVE

Our goal was to evaluate the impact of image fusion on the interpretation of indium-111 Prosta-Scint SPECT scans.

MATERIALS AND METHODS

Sixty-seven consecutive patients referred for rising prostate-specific antigen (PSA) levels after initial therapy for primary prostate cancer underwent SPECT 96 hr after infusion of (111)In Prosta-Scint, with simultaneous technetium-99m blood pool imaging. Volume data sets from the SPECT scans were then fused with those from CT and MR images of the pelvis using a 3D landmark-based warping program. The SPECT scans were initially interpreted without benefit of MRI or CT fusion. The fused Prosta-Scint MRI-CT volumes were reevaluated by a nuclear radiologist and an MRI radiologist. Independent reviews before and after fusion were available in these patients. Validation of results after fusion was performed through correlation with PSA changes after radiation therapy.

RESULTS

Six patients with sites that could not be evaluated and three without their original Prosta-Scint scanning reports were excluded; thus, 58 patients were studied clinically. Seventy-four of 161 prefusion-positive sites were found to be negative after fusion. These 74 sites subsequently were identified primarily as showing bowel, vessel, or marrow uptake after fusion. In two patients, nodal disease was identified although the review before perfusion indicated none. Twenty-five patients previously thought to have nodal disease appeared to have only local disease after fusion. After local radiation therapy, PSA levels decreased in 12 of 25 patients, increased in five, and were unavailable in eight.

CONCLUSION

Although Prosta-Scint SPECT alone can help in the proper management of recurrent prostate cancer, fusion with MRI-CT of the pelvis can improve the specificity of the examination.

MR imaging of the bladder

MR imaging is a useful modality for evaluating diseases of the bladder. MR imaging can detect and stage bladder cancer by determining the presence and depth of muscle invasion. Direct multiplanar imaging and superb soft-tissue contrast make MR imaging an ideal modality for evaluating less common neoplastic diseases of the bladder, such as urachal carcinoma, and tumors that develop within bladder diverticula. Dynamic breath-held fast T2-weighted imaging can evaluate for cystocele and other components of pelvic floor relaxation.

Contrast-enhanced MR imaging of the heart: overview of the literature

The use of magnetic resonance (MR) imaging for cardiac diagnosis is expanding, aided by the administration of paramagnetic contrast agents for a growing number of clinical applications. This overview of the literature considers the principles and applications of cardiac MR imaging with an emphasis on the use of contrast media. Clinical applications of contrast material-enhanced MR imaging include the detection and characterization of intracardiac masses, thrombi, myocarditis, and sarcoidosis. Suspected myocardial ischemia and infarction, respectively, are diagnosed by using dynamic first-pass and delayed contrast enhancement. Promising new developments include blood pool contrast media, labeling of myocardial precursor cells, and contrast-enhanced imaging at very high fields.

Lymphatic drainage imaging of breast cancer in mice by micro-magnetic resonance lymphangiography using a nano-size paramagnetic contrast agent

BACKGROUND

The presence of lymph node metastases is an important factor in breast cancer patient prognosis. Therefore, the precise identification of sentinel lymph nodes in these patients is critical. Improving current magnetic resonance (MR) imaging methods using a newly synthesized nano-size paramagnetic molecule, G6, as a contrast agent, provides an attractive means toward attaining this goal.

METHODS

A four-dimensional method of micro-MR lymphangiography using G6 (9 nm/240 kd) was developed to visualize the lymphatic ducts and lymph nodes draining mouse mammary tumors over time. The ability of micro-MR lymphangiography with the G6 contrast agent to visualize lymphatic drainage of normal mouse mammary tissue was compared with that of the conventional MR contrast agent, Gd-[DTPA]-dimeglumine (<1 kd). Lymphatic drainage in spontaneous and xenografted breast tumor models was visualized using the G6 contrast agent.

RESULTS

Draining lymphatic ducts and lymph nodes were clearly visualized in the mammary tissue of normal mice and in spontaneous and xenografted breast tumor models after a direct mammary gland or peritumoral injection of G6. Gd-[DTPA]-dime-glumine, by contrast, failed to depict lymphatic flow from the mammary tissue in normal mice using the same method. Micro-MR lymphangiography using the G6 contrast agent revealed the absence of filling in the metastatic foci of affected lymph nodes.

CONCLUSIONS

The superior temporal and spatial resolution of micro-MR lymphangiography using the contrast agent G6 may facilitate the study of tumor lymphatic drainage and lymphatic metastasis in both experimental animals and clinical medicine. In addition, this may be a powerful new method for sentinel lymph node localization in human breast cancer.

Management of patients with an increasing prostate-specific antigen after radical prostatectomy

Since the late 1980s, early detection and monitoring of men for prostate cancer by serum prostate-specific antigen (PSA) measurement has resulted in an increase in the number of men presenting with a potentially curable disease. During the same time, in an attempt to provide a definitive cure, radical prostatectomy has been performed increasingly and now is regarded as the management option of choice for many patients with clinically localized prostate cancer. Radical prostatectomy involves the removal of all of the prostate tissue resulting in the serum PSA level to steadily decline to an undetectable level within 4 to 6 weeks after surgery. Despite improvements in surgical technique and a marked downward stage shift brought about by serum PSA testing, approximately 25% of men ultimately will experience a subsequent increase in serum PSA to a detectable level indicating disease recurrence after radical prostatectomy within 15 years. In this brief review, the factors associated with a high risk for disease recurrence after radical prostatectomy are discussed. Factors indicating whether the increasing serum PSA is caused by local recurrence or metastatic disease and the management options available to address serum PSA recurrence also are discussed.

MR Lymphangiography: Imaging Strategies to Optimize the Imaging of Lymph Nodes with Ferumoxtran-10

Detection of local or regional metastases to lymph nodes is clinically important in virtually any type of primary tumor. Current imaging techniques rely heavily on the size criterion for characterization of nodal disease. However, size can be an ineffective parameter for diagnosis of tumor spread to lymph nodes. Magnetic resonance (MR) imaging performed before and after administration of ferumoxtran-10 is a promising technique for characterization of lymph nodes in patients with various primary tumors. Normal homogeneous uptake of ferumoxtran-10 in nonmetastatic nodes shortens the T2 and T2*, turning these nodes dark, whereas malignant nodes lack uptake and remain hyperintense. To optimize acquisition strategies, the following factors should be considered: the timing of contrast material-enhanced imaging, the section thickness, the imaging plane, and the imaging parameters for T2*-weighted sequences. In addition, MR imaging with ferumoxtran-10 allows presurgical mapping of lymph nodes and quantitative estimation of T2*.

Critique of laparoscopic lymphadenectomy in genitourinary oncology

Regional lymphadenectomy is prognostic and selectively therapeutic in urologic oncology. The role of lymphadenectomy continues to be defined with the evolving multimodal management of genitourinary malignancies. Laparoscopy is playing a greater role in the management of genitourinary malignancies and thus, it is germane to critique the role of laparoscopic lymphadenectomy in the management of these tumors. Review of the literature suggests that laparoscopic pelvic lymphadenectomy is feasible with nodal yields commensurate to those in open published series. Although laparoscopic retroperitoneal lymph node dissection for nonseminomatous germ cell tumor is feasible, the technique and efficacy of this procedure require further investigation.