Nuclear Probes and Intraoperative Gamma Cameras

https://doi.org/10.1053/j.semnuclmed.2010.12.004Get rights and content

Gamma probes are now an important, well-established technology in the management of cancer, particularly in the detection of sentinel lymph nodes. Intraoperative sentinel lymph node as well as tumor detection may be improved under some circumstances by the use of beta (negatron or positron), rather than gamma detection, because the very short range (∼1 mm or less) of such particulate radiations eliminates the contribution of confounding counts from activity other than in the immediate vicinity of the detector. This has led to the development of intraoperative beta probes. Gamma camera imaging also benefits from short source-to-detector distances and minimal overlying tissue, and intraoperative small field-of-view gamma cameras have therefore been developed as well. Radiation detectors for intraoperative probes can generally be characterized as either scintillation or ionization detectors. Scintillators used in scintillation-detector probes include thallium-doped sodium iodide, thallium- and sodium-doped cesium iodide, and cerium-doped lutecium orthooxysilicate. Alternatives to inorganic scintillators are plastic scintillators, solutions of organic scintillation compounds dissolved in an organic solvent that is subsequently polymerized to form a solid. Their combined high counting efficiency for beta particles and low counting efficiency for 511-keV annihilation γ-rays make plastic scintillators well-suited as intraoperative beta probes in general and positron probes in particular Semiconductors used in ionization-detector probes include cadmium telluride, cadmium zinc telluride, and mercuric iodide. Clinical studies directly comparing scintillation and semiconductor intraoperative probes have not provided a clear choice between scintillation and ionization detector-based probes. The earliest small field-of-view intraoperative gamma camera systems were hand-held devices having fields of view of only 1.5-2.5 cm in diameter that used conventional thallium-doped sodium iodide or sodium-doped cesium iodide scintillation detectors. Later units used 2-dimensional arrays (mosaics) of scintillation crystals connected to a position-sensitive photomultiplier tube and, more recently, semiconductors such as cadmium telluride or cadmium zinc telluride. The main problems with the early units were their very small fields of view and the resulting large number of images required to interrogate the surgical field and the difficulty in holding the device sufficiently still for the duration (up to 1 min) of the image acquisition. More recently, larger field-of-view (up to 5 × 5 cm) devices have developed which are attached to an articulating arm for easy and stable positioning. These systems are nonetheless fully portable and small enough overall to be accommodated in typical surgical suites.

Section snippets

Statistics

Radioactive decay is a random process and therefore statistical fluctuations will occur in the measured counts or count rates arising from decay of radioactivity. Thus, if an intraoperative probe were used to repeatedly measure the counts or count rates from activity in a lymph node or tumor, slightly different values would be obtained for the repeat measurements. If such a measurement yields N counts, the standard deviation, σ, of the number of counts isσ=Nand the percentage standard

General Types of Detectors

Radiation detectors can generally be characterized in their operation as either scintillation or ionization detectors.16, 21 In scintillation detectors, visible light produced as radiation excites atoms of a stopping medium (crystal) is converted to an electrical pulse (Fig. 5A). In ionization detectors, free electrons produced as radiation ionizes a stopping medium are collected as an electrical pulse (Fig. 5B). Scintillators used in scintillation-detector probes include thallium-doped sodium

Application-Specific Intraoperative Probes

In practice, the most important performance characteristics of an intraoperative probe are overall sensitivity (efficiency), energy resolution, and spatial resolution. Obviously, a probe having the highest sensitivity, lowest energy resolution and therefore best scatter rejection, and finest spatial resolution for all radionuclides used clinically would be the probe of choice. Unfortunately, no single probe has, or can have, the optimum values of each of these performance parameters. An

Potential Utility of Intraoperative Gamma Cameras

The sensitivity and specificity of detection of sentinel lymph nodes with the use of current approaches, such as preoperative gamma camera imaging, gamma probes, and the “blue dye” technique, are quite high. Newman,40 for example, performed a meta-analysis of nearly 70 published studies and found an overall sensitivity of more than 90% and a false-negative rate of only 8.4% for detection of such nodes in breast cancer. For preoperative gamma camera imaging, detection rates of 72-85% have been

References (61)

  • S.A. Gulec et al.

    The expanding clinical role for intraoperative gamma probes

  • J.M. Woolfenden et al.

    Intraoperative probes

  • H.B. Barber et al.

    Comparison of in vivo scintillation probes and gamma cameras for detection of small, deep tumours

    Phys Med Biol

    (1989)
  • F. Daghighian et al.

    Intraoperative beta probe: A device for detecting tissue labeled with positron or electron emitting isotopes during surgery

    Med Phys

    (1994)
  • R.R. Raylman et al.

    Fluorine-18-fluorodeoxyglucose-guided breast cancer surgery with a positron-sensitive probe: Validation in preclinical studies

    J Nucl Med

    (1995)
  • R.R. Raylman et al.

    A fiber-optically coupled positron-sensitive surgical probe

    J Nucl Med

    (1994)
  • H.B. Barber et al.

    Comparison of NaI(Tl), CdTe, and HgI2 surgical probes: Physical characterization

    Med Phys

    (1991)
  • A.J. Britten

    A method to evaluate intra-operative gamma probes for sentinel lymph node localisation

    Eur J Nucl Med

    (1999)
  • D.P. Kow et al.

    Comparison of NaI(T1), CdTe, and HgI2 surgical probes: Effect of scatter compensation on probe performance

    Med Phys

    (1991)
  • T. Tiourina et al.

    Evaluation of surgical gamma probes for radioguided sentinel node localisation

    Eur J Nucl Med

    (1998)
  • National Electrical Manufacturers' Association: NEMA Standards Publication NU 3-2004: Performance Measurements and...
  • M. Zamburlini et al.

    Comparison of sentinel gamma probes for 99mTc breast cancer surgery based on NEMA NU3-2004 standard

    Nucl Med Commun

    (2009)
  • C. Chiesa et al.

    Intraoperative gamma probes: Systematic inter-comparison of 14 commercial devices under identical experimental conditions—introduction of a simple physical figure of merit

    Eur J Nucl Med

    (2001)
  • C. Chiesa et al.

    Physical performance parameters of intraoperative probes

  • P. Zanzonico

    The intraoperative gamma probe: Design, safety, and operation

  • J.M. Woolfenden et al.

    Design and use of radiation detector probes for intraoperative tumor detection using tumor-seeking radiotracers

  • F.H. Attix

    Introduction to Radiological Physics and Radiation Dosimetry

    (1986)
  • A.F. Kip

    Fundamentals of Electricity and Magnetism

  • D.W. Anderson

    Absorption of Ionizing Radiation

    (1984)
  • Cited by (95)

    • Radioactivity counters and mono-channel probes

      2022, Nuclear Medicine and Molecular Imaging: Volume 1-4
    View all citing articles on Scopus
    View full text