Very-Low-Dose Radiation and Clinical Molecular Nuclear Medicine

Emerging molecular and precision medicine makes nuclear medicine a de facto choice of imaging, especially in the era of target-oriented medical care. Nuclear medicine is minimally invasive, four-dimensional (space and time or dynamic space), and functional imaging using radioactive biochemical tracers in evaluating human diseases on an anatomically configured image. Many radiopharmaceuticals are also used in therapies. However, there have been concerns over the emission of radiation from the radionuclides, resulting in wrongly neglecting the potential benefits against little or any risks at all of imaging to the patients. The sound concepts of radiation and radiation protection are critical for promoting the optimal use of radiopharmaceuticals to patients, and alleviating concerns from caregivers, nuclear medicine staff, medical colleagues, and the public alike.

Internally Randomized Control Trial of Radiation Exposure Using Ultra-low Radiation Imaging Versus Traditional C-arm Fluoroscopy for Patients Undergoing Single-level Minimally Invasive Transforaminal Lumbar Interbody Fusion

STUDY DESIGN

Randomized controlled trial.

OBJECTIVE

To compare radiation exposure between ultra-low radiation imaging (ULRI) with image enhancement and standard-dose fluoroscopy for patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).

SUMMARY OF BACKGROUND DATA

Although the benefits of MIS are lauded by many, there is a significant amount of radiation exposure to surgeon and operating room personnel. Our goal with this work was to see if by using ultra-low dose radiation settings coupled with image enhancement, this exposure could be minimized.

METHODS

An institutional review board approved, prospective, internally randomized controlled trial was performed comparing ultra-low dose settings coupled with image enhancement software to conventional fluoroscopic imaging. In this study, each patient served as their own control, randomly assigning one side of MIS-TLIF for cannulation and K-wire placement using each imaging modality. Further, the case was also randomly divided into screw placement and cage placement/final images to allow further comparisons amongst patients. Radiation production from the C-arm fluoroscope and radiation exposure to all operating room personnel were recorded.

RESULTS

Twenty-four patients were randomly assigned to undergo a single level MIS-TLIF. In no case was low radiation imaging abandoned, and no patient had a neurologic decline or required hardware repositioning. Everyone in the operating room-the physician, scrub nurse, circulator, and anesthesiologist-all benefited with 61.6% to 83.5% reduction in radiation exposure during cannulation and K-wire placement to screw insertion aided by ULRI. In every case but the anesthesiologist dose, this was statistically significant (P < 0.05). This benefit required no additional time (P = 0.78 for K-wire placement).

CONCLUSION

ULRI, when aided by image enhancement software, affords the ability for all parties in the operating room to substantially decrease their radiation exposure compared with standard-dose C-arm fluoroscopy without adding additional time or an increased complication rate.

LEVEL OF EVIDENCE

2.

A Review of Radiotherapy-Induced Late Effects Research after Advanced Technology Treatments

The number of incident cancers and long-term cancer survivors is expected to increase substantially for at least a decade. Advanced technology radiotherapies, e.g., using beams of protons and photons, offer dosimetric advantages that theoretically yield better outcomes. In general, evidence from controlled clinical trials and epidemiology studies are lacking. To conduct these studies, new research methods and infrastructure will be needed. In the paper, we review several key research methods of relevance to late effects after advanced technology proton-beam and photon-beam radiotherapies. In particular, we focus on the determination of exposures to therapeutic and stray radiation and related uncertainties, with discussion of recent advances in exposure calculation methods, uncertainties, in silico studies, computing infrastructure, electronic medical records, and risk visualization. We identify six key areas of methodology and infrastructure that will be needed to conduct future outcome studies of radiation late effects.

Dose-dependent expression of CLIP2 in post-Chernobyl papillary thyroid carcinomas

This study showed a clear dose-response relationship for the CLIP2 radiation marker in post-Chernobyl papillary thyroid carcinoma cohorts for young patients and hints to different molecular mechanisms in tumors induced at low doses compared to moderate/high doses.

A previous study on papillary thyroid carcinomas (PTC) in young patients who were exposed to ¹³¹iodine from the Chernobyl fallout revealed an exclusive gain of chromosomal band 7q11.23 in exposed cases compared to an age-matched control cohort. CLIP2, a gene located within band 7q11.23 was shown to be differentially expressed between exposed and non-exposed cases at messenger RNA and protein level. Therefore, a standardized procedure for CLIP2 typing of PTCs has been developed in a follow-up study. Here we used CLIP2 typing data on 117 post-Chernobyl PTCs from two cohorts of exposed patients with individual dose estimates and 24 non-exposed controls to investigate a possible quantitative dose-response relationship of the CLIP2 marker. The ‘Genrisk-T’ cohort consisted of 45 PTCs and the ‘UkrAm’ cohort of 72 PTCs. Both cohorts differed in mean dose (0.59 Gy Genrisk-T, 1.2 Gy UkrAm) and mean age at exposure (AaE) (2 years Genrisk-T, 8 years UkrAm), whilst the median latency (16 years Genrisk-T, 18 years UkrAm) was comparable. We analyzed the association between the binary CLIP2 typing and continuous thyroid dose with logistic regression. A clear positive dose-response relationship was found for young PTC cases [age at operation (AaO) < 20 years, AaE < 5 years]. In the elder age group a higher proportion of sporadic tumors is assumed due to a negligible dose response, suggesting different molecular mechanisms in sporadic and radiation-induced cases. This is further supported by the association of elder patients (AaO > 20 years) with positivity for BRAF V600E mutation.

Low-dose radiation exposure and carcinogenesis

Absorption of energy from ionizing radiation by the genetic material in the cell leads to damage to DNA, which in turn leads to cell death, chromosome aberrations and gene mutations. While early or deterministic effects result from organ and tissue damage caused by cell killing, latter two are considered to be involved in the initial events that lead to the development of cancer. Epidemiological studies have demonstrated the dose-response relationships for cancer induction and quantitative evaluations of cancer risk following exposure to moderate to high doses of low-linear energy transfer radiation. A linear, no-threshold model has been applied to assessment of the risks resulting from exposure to moderate and high doses of ionizing radiation; however, a statistically significant increase has hardly been described for radiation doses below 100 mSv. This review summarizes our current knowledge of the physical and biological features of low-dose radiation and discusses the possibilities of induction of cancer by low-dose radiation.