19 Quo Vadis? Christiaan Schiepers

Quo Vadis? 343

19 Quo Vadis?

Christiaan Schiepers

C. Schiepers, MD, PhD

Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, AR-144 CHS, Los Angeles, CA 90095-6942, USA

This book presents the status of nuclear medicine in the new millennium from the clinical, technical and gene imaging point of view. An update was provided of the progress in the last decade. Promising devel- opments in receptor and metabolic imaging turned out to be important clinically, and attest that these radiopharmaceutical and technical developments are here to stay. The introduction of dual modality imaging with PET/CT caught on in record time, and over 90% of new equipment sold in 2004 was PET/

CT. Applications in oncology were the main driv- ing force behind this development. A few dedicated PET scanners of high resolution were installed for neuro-imaging.

Image quality improved due to complete digiti- zation of cameras, multi-head detectors, and faster computers with advanced processing and recon- struction techniques. Adaptation of existing tests and imaging protocols by adding pharmacological interventions, common in nuclear cardiology, that were proposed for renal and hepatobiliary imaging, are now routine in the nuclear medicine clinic. A small number of new

Tc-based radiopharmaceu- ticals was approved.

Metabolic imaging with FDG, introduced as the

“new kid on the block” in the 1990s, is now com- monplace and has propelled diagnostic imaging in oncology. FDG is still the most frequently used PET pharmaceutical. Networks have been set up both in the US and EU for the distribution of FDG over densely populated areas. The once heralded develop- ment of hybrid gamma camera systems (with coinci- dence detection) has stalled and no new applications were approved. Hybrid imaging now refers to dual- modality imaging with a multi-slice CT system and a whole-body PET system.

The future of nuclear medicine imaging is con- tinuously being discussed and opinions encompass the whole spectrum from negative to positive. The demise of the field has been predicted on many an occasion, but every time nuclear medicine appears extremely adaptive. New radiopharmaceuticals and imaging systems lead to new tests, and the term

“molecular imaging” is used more and more for our field. From the clinical section in this book, the progress in certain fields is obvious, and dual modality imaging with both PET/CT and SPECT/CT, has a bright future (Chaps. 11–13 and 16). Oncology is currently the main engine for this image integra- tion, and will be followed by cardiac applications once the resolution of the multi-slice CT component of PET/CT is sufficiently high, both in the spatial and temporal domain. One of the great advantages of multimodality imaging is the ease of localization of lesions and abnormalities. The lack of landmarks or reference points in routine nuclear medicine images is thus circumvented. This allows for the develop- ment of very specific tracers, which disclose only those tissues that take up the radiopharmaceutical, whereas the anatomic modality provides the refer- ence framework for localization of the lesions. Soon, multi-slice CT will provide sub-millimeter spatial resolution. Functional imaging is not up there, yet.

Currently, the high-resolution neuro-PET scanners have a spatial resolution of 2.5 mm in the center of the field of view. The situation for SPECT is different and these devices still trail PET by a factor of three.

Standard systems currently available (i.e. parallel hole collimators of ultra high resolution) yield a spa- tial resolution approaching 1 cm. To detect smaller lesions, specialized and dedicated equipment is necessary. Innovative designs are needed to bring SPECT within the same range of resolution as PET.

This will be especially relevant for receptor imag- ing, which is highly specific but still suffers from low uptakes. The anatomic modality CT will again provide the reference frame for localization.

Presentation of multimodality images has great

influence, not only on imaging specialists, but also

344 C. Schiepers

at hospital tumor boards, where surgical, medical, and radiation oncologists can directly appreciate anatomic and functional assessment of tumors and tissues. In joint discussion, they decide which ther- apy is best for the individual cancer patient. This approach appears effective and provides the patient with the optimal treatment plan available in a par- ticular institution.

Merger and fusion are frequently encountered entities in our society. Mergers have happened between hospitals, health care organizations, tele- communication industries, media networks and other businesses. Academic disciplines are now doing the same. Nuclear medicine as a relatively small specialty will have to follow. At our own institution, UCLA, the integration of nuclear medi- cine with medical and molecular pharmacology is another example of bringing together basic science with clinical applications. The intention is to develop new diagnostic imaging products and manufacture new radiopharmaceuticals as well as equipment.

Instruments such as micro-PET and micro-CT, com- bined CT-PET and MR-PET scanners, and optical imaging systems, are continuously being improved.

These innovations will keep NM in the forefront of the imaging field and will result in new diagnostic strategies for work-up of patients.

Cost-effectiveness of diagnostic tests and combi- nation of imaging modalities to arrive at the diagno- sis in the shortest amount of time with an adequate balance between tests performed and costs incurred, was mentioned only sporadically. In the present envi- ronment of managed care and budget shortfalls, there is a need for objective assessment and evaluation of imaging strategies for specific clinical problems. At UCLA, a method based on decision tree analysis was used to evaluate such strategies. Models have been designed for staging of lung cancer (G

1996, S

1998), and management of solitary pulmo- nary nodules (G

1998). A combined model for

detection and staging of lung lesions has also been proposed (S

1999). A decision model for the workup and staging of recurrent colorectal cancer was reported by P

(2001).

NM as a biological imaging modality will keep expanding and continuously evolving. NM as a molecular imaging modality is an active field, despite reservations in the eye of some beholders that it is an appendix of radiology. It has shown to be an adaptive imaging field, with enthusiastic clini- cians, scientists, and scholars. The continuous input from scientists and interested clinicians from other fields is mandatory for progress. In addition, new ways of inter-disciplinary collaboration need to be explored to assemble the best team of experts that will arrive at the diagnosis in the shortest amount of time and provide the best treatment plan, with- out prohibitive costs of health care to society. In this way, the patient will benefit by being provided with optimum care.

References

Gambhir SS, Hoh CK, Phelps ME, Madar I, Maddahi J (1993) Decision tree sensitivity analysis for cost-effectiveness of FDG-PET in the staging and management of non-small- cell lung carcinoma. J Nucl Med 37:1428–1436

Gambhir SS, Shepherd JE, Shah BD, Hart E, Hoh CK, Valk PE, Emi T, Phelps ME (1998) Analytical decision model for the cost-effective management of solitary pulmonary nodules.

J Clin Oncol 16:2113–2123

Park KC, Schwimmer J, Shepherd JE, Phelps ME, Czernin JR, Schiepers C, et al. (2001) Decision analysis for the cost- effective management of recurrent colorectal cancer. Ann Surg 233:310-9

Scott WJ, Shepherd J, Gambhir SS (1998) Cost effectiveness of FDG-PET for staging non-small cell lung cancer: a decision analysis. Ann Thorac Surg 66:1876–1885

Shepherd JE, Phelps ME, Czernin J, Gambhir SS (1990) Cost

effectiveness analysis for the role of FDG-PET in lung car-

cinoma. J Nucl Med 40:56P