Dynamic MRI scan plane control for passive tracking of instruments and devices.

This paper describes a novel image-based method for tracking robotic mechanisms and interventional devices during Magnetic Resonance Image (MRI)-guided procedures. It takes advantage of the multi-planar imaging capabilities of MRI to optimally image a set of localizing fiducials for passive motion tracking in the image coordinate frame. The imaging system is servoed to adaptively position the scan plane based on automatic detection and localization of fiducial artifacts directly from the acquired image stream. This closed-loop control system has been implemented using an open-source software framework and currently operates with GE MRI scanners. Accuracy and performance were evaluated in experiments, the results of which are presented here.

Patient specific simulation and navigation of ventriculoscopic interventions.

In this paper a comprehensive framework for pre-operative planning, procedural skill training, and intraoperative navigation is presented. The goal of this system is to integrate surgical simulation with surgical planning in order to improve the individual treatment of patients. Various surgical approaches and new, more complex procedures can be assessed using a safe and objective platform that will allow the physicians to explore and discuss possible risks and benefits prior to the intervention. A simulation environment extends the pre-operative planning in a natural way, as it allows for direct evaluation of the surgical approach envisioned for each case. In addition, by providing intraoperative navigation based on this simulation, surgeons can carry out the previously optimized plan with higher precision and greater confidence.

Robot-assisted needle placement in open MRI: system architecture, integration and validation.

In prostate cancer treatment, there is a move toward targeted interventions for biopsy and therapy, which has precipitated the need for precise image-guided methods for needle placement. This paper describes an integrated system for planning and performing percutaneous procedures with robotic assistance under MRI guidance. A graphical planning interface allows the physician to specify the set of desired needle trajectories, based on anatomical structures and lesions observed in the patient's registered pre-operative and pre-procedural MR images, immediately prior to the intervention in an open-bore MRI scanner. All image-space coordinates are automatically computed, and are used to position a needle guide by means of an MRI-compatible robotic manipulator, thus avoiding the limitations of the traditional fixed needle template. Automatic alignment of real-time intra-operative images aids visualization of the needle as it is manually inserted through the guide. Results from in-scanner phantom experiments are provided.

Needle artifact localization in 3T MR images.

This work explores an image-based approach for localizing needles during MRI-guided interventions, for the purpose of tracking and navigation. Susceptibility artifacts for several needles of varying thickness were imaged, in phantoms, using a 3 tesla MRI system, under a variety of conditions. The relationship between the true needle positions and the locations of artifacts within the images, determined both by manual and automatic segmentation methods, have been quantified and are presented here.

Robot-assisted needle placement in open-MRI: system architecture, integration and validation.

This work describes an integrated system for planning and performing percutaneous procedures-such as prostate biopsy-with robotic assistance under MRI-guidance. The physician interacts with a planning interface in order to specify the set of desired needle trajectories, based on anatomical structures and lesions observed in the patient's MR images. All image-space coordinates are automatically computed, and used to position a needle guide by means of an MRI-compatible robotic manipulator, thus avoiding the limitations of the traditional fixed needle template. Direct control of real-time imaging aids visualization of the needle as it is manually inserted through the guide. Results from in-scanner phantom experiments are provided.

Double primary malignancies: osteosarcoma and medulloblastoma.

We report the case of an 8 1/2-year-old boy who, after successful treatment for osteosarcoma, had a fatal medulloblastoma. We discuss the possible causes for such an association.

A fatal case of lead poisoning due to a retained bullet.

Lead poisoning from a retained bullet or missile is rare and is usually dependent on the location of the missile in a bone or immediately adjacent to a joint. A review of the literature revealed only 14 cases in which there was adequate laboratory documentation of plumbism caused by a retained bullet or missile. Only one of these previously reported cases resulted in death. We report a second death due to lead poisoning from a retained bullet with elevated blood lead levels documented by toxicologic analysis.

Association between neuroendocrine (Merkel cell) carcinoma and squamous carcinoma of the skin.

Among 32 neuroendocrine carcinomas of the skin, 11 were from patients with previous or concomitant squamous carcinoma. The medical records and pathologic material for these 11 cases were reviewed, and the diagnosis of neuroendocrine carcinoma was confirmed in each instance by electron microscopy. In two cases, the squamous and neuroendocrine carcinomas were admixed, but each preserved its identity and transition between the two was not identified. Despite the lack of evidence for origin from a single cell, the observations nevertheless indicate a common carcinogenetic influence for squamous and neuroendocrine carcinomas of the skin.

Neurosarcomatous transformation in malignant melanoma: an ultrastructural study.

Six cases of desmoplastic melanoma were studied by light and electron microscopy. The tumors fulfilled one or more of the following criteria: (1) having the presence of atypical intraepidermal melanocytic proliferation bordering the primary lesions; (2) an antecedent history of melanoma at the site of recurrence; (3) a metastatic lesion in the direct lymphatic drainage route of a previously excised melanoma. Premelanosomes were not identified in the neoplastic cells. Ultrastructural features common to the six tumors were interpreted as evidence of Schwann cell differentiation, i.e., neurosarcomatous transformation occurring in malignant melanoma. The ultrastructural findings provide further support for the concept that melanocytic lesions may simulate tumors of Schwann cell origin, presumably reflecting the common embryologic origin of the two cell types from the neural crest.

Oncocytic carcinoma of the nasal cavity.

We have described a case of oncocytic carcinoma arising in the nasal mucosa which had invaded the maxillary and ethmoidal sinuses. Seven years after local resection with postoperative low-dose irradiation, the tumor recurred as a poorly differentiated adenocarcinoma. It is our opinion that oncocytic neoplasms arising in the nasal mucosa and demonstrating aggressive infiltrative growth should be regarded as malignant neoplasms, albeit sluggishly metastasizing ones, despite their deceptively benign histologic appearance.

Fatal water intoxication in a case of psychogenic polydipsia.

The term "water intoxication" is used to describe a condition of agitation, delirium, convulsion, and coma brought on by excessive intake of water, resulting in severe hyponatremia. Psychogenic polydipsia (compulsive water drinking) has until recently been considered a relatively benign process. Since 1974, however, three fatal cases of water intoxication, resulting from psychogenic polydipsia, have been reported. All three individuals died while hospitalized, thereby permitting performance of blood electrolyte determinations and documentation of the associated electrolyte imbalance. In the authors' case, there was a well-documented prior episode of water intoxication in which serum electrolytes showed a pattern typical of this entity. Death, however, occurred at home, thus preventing valid serum electrolyte determinations to be performed. Analysis of the vitreous humor revealed a severe hyponatremia, thus substantiating the diagnosis of fatal water intoxication. This case, once again, points out the usefulness of electrolyte analyses on the vitreous humor as an aid to establishing a cause of death.

Sudden, unexpected deaths due to primary intracranial neoplasms.

In 10,995 consecutive medicolegal autopsies, there were 19 deaths due to an unsuspected primary intracranial neoplasm. Nine (47.4%) of the tumors were in the astrocytoma-glioblastoma category. The remainder included four cases of oligodendroglioma and one case each of medulloblastoma, microglioma, meningioma, teratoma, colloid cyst and pituitary chromophobe adenoma. In six cases, death occurred following abrupt loss of consciousness, or else the patient was found dead. In five of these six cases, there were no known preceding symptoms. The remaining 13 patients exhibited the characteristic symptoms produced by intracranial neoplasms, including symptoms of increased intracranial pressure, epilepsy, and psychiatric manifestations. Only one patient presented with a focal neurologic deficit which resolved in 24 hours. A comparison of the duration and type of symptomatology exhibited by these patients with a hospital patient population in which death was caused by a previously diagnosed primary intracranial neoplasm and an autopsy was performed underscored 1) the shorter duration of acute symptomatology, 2) the nonlocalizing nature of the symptoms manifested, 3) the lack of progression or change in symptoms in those patients in whom epilepsy was the primary manifestation of their underlying disease, and 4) the lower incidence of focal neurologic deficits as the presenting symptoms in our series.