Excretion of radionuclides in human breast milk after nuclear medicine examinations. Biokinetic and dosimetric data and recommendations on breastfeeding interruption.

PURPOSE: To review early recommendations and propose guidelines for breastfeeding interruption after administration of radiopharmaceuticals, based on additional biokinetic and dosimetric data. METHODS: Activity concentrations in breast milk from 53 breastfeeding patients were determined. The milk was collected at various times after administration of 16 different radiopharmaceuticals. The fraction of the activity administered to the mother excreted in the breast milk, the absorbed doses to various organs and tissues and the effective dose to the infant were estimated. RESULTS: The fraction of the administered activity excreted per millilitre of milk varied widely from 10(-10) to 10(-3) MBq/MBq administered. For (99m)Tc-labelled radiopharmaceuticals, the total fraction of the administered activity excreted in the milk varied from 0.0057 % for (99m)Tc-labelled red blood cells (RBC) to 19 % for (99m)Tc-pertechnetate. The effective dose to an infant per unit activity administered to the mother ranged from 6.7 × 10(-6) mSv/MBq for (99m)Tc-labelled RBC to 3.6 × 10(-2) mSv/MBq for (99m)Tc-pertechnetate. For the other radiopharmaceuticals, the total fraction of administered activity excreted in the milk varied from 0.018 % ((51)Cr-EDTA) to 48 % ((131)I-NaI). The effective dose ranged from 5.6 × 10(-5) mSvinfant/MBqmother ((51)Cr-EDTA) to 106 mSvinfant/MBqmother ((131)I-NaI). CONCLUSIONS: Based on an effective dose limit of 1 mSv to the infant and a typical administered activity, we recommend cessation of breastfeeding for (131)I-NaI and interruption of feeding for 12 h for (125)I-iodohippurate, (131)I-iodohippurate, (99m)Tc-pertechnetate and (99m)Tc-MAA. During this 12-h period all breast milk should be expressed at least three times and discarded. For the other radiopharmaceuticals included in this study, no interruption of breastfeeding is necessary.

Invited review--Off-site PET imaging programs: challenges and opportunities.

Veterinarians are gaining interest in and access to Position Emission Tomography (PET and PET/CT) imaging for both clinical and research applications. This manuscript provides an overview of how veterinarians may approach the use of off-site PET and PET/CT scanners already in use for human medical imaging in order to gain access to this technology without direct investment in costly equipment and infrastructure. An overview of general procedures, animal transport, and radiation safety considerations is offered along with references to key regulatory statutes that may apply to the operation of PET imaging facilities in individual states.

Cardiac imaging: does radiation matter?

The use of ionizing radiation in cardiovascular imaging has generated considerable discussion. Radiation should not be considered in isolation, but rather in the context of a careful examination of the benefits, risks, and costs of cardiovascular imaging. Such consideration requires an understanding of some fundamental aspects of the biology, physics, epidemiology, and terminology germane to radiation, as well as principles of radiological protection. This paper offers a concise, contemporary perspective on these areas by addressing pertinent questions relating to radiation and its application to cardiac imaging.

Medical imaging: the radiation issue.

The collective doses of ionizing radiation to Western populations have risen dramatically in the past three decades. Preliminary data on changes in radiation dose to the US population indicate that this increase has been driven largely by medical imaging, to which cardiovascular imaging modalities-such as nuclear stress testing, invasive coronary angiography, and cardiovascular CT-contribute greatly. Given the putative association between low-dose radiation exposure and cancer risk, which most experts agree is supported by the available evidence, the 'radiation issue' in medical imaging has garnered increasing interest. This opinion piece focuses on changes in the use of and doses from medical imaging, the relationship between radiation dose and cancer risk and the controversy surrounding this subject, and clinical implications of radiation exposure from imaging tests.

Significance of radiation dose in medical imaging.

Publicized cases of errant high radiation exposure delivered to patients undergoing diagnostic imaging have led to heightened awareness and scrutiny of the costs and benefits of imaging by physicians, the public, and policymakers.The statistical risks associated with the ever-increasing utilization of modalities employing damaging ionizing radiation across the population are compounded by the development of the latest generation of devices, which are capable of delivering greater radiation doses than their predecessors for comparable diagnostic applications.This article reviews the fundamental concepts and risks of medical radiation exposure, trends in imaging utilization, and the role of radiologists and their physician colleagues in managing and appropriately utilizing imaging for patient diagnosis.

PET/CT and SPECT/CT dosimetry in children: the challenge to the pediatric imager.

Both positron emission tomography (PET) and computed tomography (CT) contribute significantly to the effective dose from PET/CT imaging. For PET imaging, the effective dose is related to the administered activity and age of patient. For CT, there are many factors that determine effective dose. Effective dose is dependent on tube current (mA), tube potential (kVp), rotation speed, pitch, slice thickness, patient mass, and the exact volume of the patient that is being imaged. The CT scan may be acquired at exposure parameters similar to those used for diagnostic CT, but more commonly, the tube current is reduced and a localization CT scan of somewhat less than optimal diagnostic quality is obtained. A very low dose CT scan for attenuation correction may also be considered.

Safety of sentinel node biopsy in pregnant patients with breast cancer.

BACKGROUND: Lymphoscintigraphy (LS) and sentinel lymph node biopsy (SLNB) have typically been contraindicated for pregnant patients diagnosed with breast cancer because they are considered unsafe. PATIENTS AND METHODS: Twenty-six premenopausal non-pregnant patients who were candidates for LS underwent peritumoral injection of approximately 12 MBq of 99mTc-HSA nanocolloids. Static [15 min and 16 h post-injection (p.i.)] and whole-body (16 h p.i.) scintigraphic images were acquired. Activity concentration in the urine (0-2, 2-4, 4-8, 8-16 h p.i.) was evaluated by a gamma-counter. Activity in the bloodstream was measured at 4 and 16 h p.i. Thermoluminescent dosimeters (TLD) were placed, before tracer injection, on the injection site, between injection site and epigastrium (two points), and on the epigastrium, umbilicus and hypogastrium, and were removed before surgery. RESULTS: Scintigraphic images showed no radiotracer concentration except in the injection site and in the sentinel node. In all patients, the total activity excreted within the first 16 h was <2% of the injected activity. Activity in the blood pool was, at each time point, <1% of the injected activity. In 23 of 26 patients, all absorbed dose measurements were lower than the sensitivity of the TLD (<10 microGy); in the remaining three patients, the absorbed doses at the level of epigastrium, umbilicus and hypogastrium were in the following ranges: 40-320, 120-250 and 30-140 microGy, respectively. CONCLUSIONS: According to our standard technique (12 MBq of 99mTc-HAS), LS and SLNB can be performed safely during pregnancy, since the very low prenatal doses from this diagnostic procedure, when properly performed, do not significantly increase the risk of prenatal death, malformation or mental impairment.

Positron emission tomography: a study of PET test-related anxiety.

The objective of this study was to determine whether sending an information pamphlet to patients scheduled for a PET test two weeks prior to the appointment date significantly reduced patient anxiety and increased patient knowledge about the test. This study was conducted as a randomized controlled trial in which patients were randomly allocated to receive a mailed information pamphlet (intervention) or no mailed pamphlet two weeks prior to the appointment (usual care). The results of this study suggested that sending information pamphlets to patients scheduled for PET scans did not decrease pre-test levels of patient anxiety or result in increased patient knowledge about test preparation and procedures.

FDG PET and high-dose therapy for aggressive lymphomas: toward a risk-adapted strategy.

PURPOSE OF REVIEW: Functional metabolic imaging through fluorine-18 fluorodeoxyglucose positron emission tomography has recently come to the forefront in the management of various solid and hematologic malignancies. This review summarizes the developments in risk assessment through positron emission tomography in patients with lymphoma and the implications for management. RECENT FINDINGS: In addition to improving staging and response assessment, positron emission tomography has emerged as a strong prognostic tool in patients with aggressive lymphomas. A positron emission tomographic scan performed after only a few cycles of chemotherapy can accurately predict relapse risk, and most studied patients with abnormal positron emission tomographic scans have had distinctly poorer clinical outcomes than patients with negative scans. SUMMARY: With confirmation of these findings, a more individualized, risk-adapted approach to the treatment of aggressive lymphomas will be feasible. Early identification of high-risk patients through the combination of positron emission tomography and existing prognostic indices could lead to earlier implementation of intensive therapies and improved clinical outcomes.

Iatrogenic FDG foci in the lungs: a pitfall of PET image interpretation.

2-[F-18]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) has become an important staging modality for many tumors, including bronchial carcinoma; however it is important to know that there are several pitfalls in PET image interpretation. In this report we demonstrate three cases in which focal intrapulmonary FDG uptake could possibly represent iatrogenic microembolism. These FDG accumulations would have been interpreted as malignant tumor mass in the lung if no anatomic correlation would have been performed. For this reason, we further present an integrated PET/CT scanner, which recently has been introduced. This correlation of molecular and morphological information enables the specification of the FDG-PET findings.

Metabolic changes after H(2) 15O-positron emission tomography with acetazolamide in a patient with moyamoya disease: case report and review of previous cases.

Perioperative ischemic complications not directly related to surgery require special attention in patients with moyamoya disease; positron emission tomography (H(2) 15O-PET) and single-photon emission computed tomography have been considered indispensable for evaluating pre- and postsurgical cerebral hemodynamics. The clinical records of 14 patients with moyamoya disease who underwent 26 extracranial-intracranial bypass operations were reviewed with special reference to perisurgical complications. One patient developed multiple postoperative ischemic infarctions and died of ischemic brain edema. The history of this patient with prolonged acidosis is analyzed, and the role of metabolic changes induced by H(2) 15O-PET with acetazolamide challenge is reviewed. Seven (77.8%) of nine patients operated on within 48 hours after H(2) 15O-PET with acetazolamide (group 1) developed metabolic acidosis, whereas only three (17.6%) of 17 patients operated on >48 hours (group 2) after the examination had intraoperative pH of <7.35. In group 1, the mean intraoperative pH was 7.328, which was significantly lower than the mean pH of 7.393 (P <.0001) in group 2. After H(2) 15O-PET with acetazolamide challenge, patients must be carefully observed concerning acidosis and volume state. We recommend at least 48 hours between examination and surgery for patients with moyamoya disease so that their conditions can stabilize. Furthermore, special care should be taken to avoid additional perioperative risk factors such as hypotension, hypocapnia, hypercapnia, and hypovolemia.

Cost-minimization analysis of alternative diagnostic approaches in a modeled patient with non-small cell lung cancer and subcarinal lymphadenopathy.

OBJECTIVE: To evaluate the costs of alternative diagnostic evaluations of enlarged subcarinal lymph nodes (SLNs) in modeled patients with non-small cell lung cancer (NSCLC). METHODS: A cost-minimization model was used to compare 5 diagnostic approaches in the evaluation of enlarged SLNs in modeled patients with NSCLC. Values for the test performance characteristics and prevalence of malignancy in patients with SLN were obtained from the medical literature. The target population was adult patients known or suspected to have NSCLC with SLNs with a short axis length of at least 10 mm on thoracic computed tomography (CT). RESULTS: The lowest-cost diagnostic work-up was by initial evaluation with endoscopic ultrasonography-guided fine-needle aspiration (EUS FNA) biopsy ($11,490 per patient) compared with mediastinoscopy (with biopsy) ($13,658), transbronchial FNA biopsy ($11,963), CT-guided FNA biopsy ($13,027), and positron emission tomography ($12,887). The results were sensitive to rate of SLN metastases and EUS FNA sensitivity. The EUS FNA biopsy remained least costly if the probability of SLN metastases exceeded 24% or EUS FNA sensitivity was higher than 76%. Primary mediastinoscopy was the most economical if not. CONCLUSIONS: Which testing strategy is least costly for SLN evaluation in a modeled patient with NSCLC may be determined by the pretest probability of nodal metastases. Use of EUS FNA biopsy minimizes the cost of diagnostic evaluation in most cases.

Positron emission tomography.

Positron emission tomography is a sophisticated, physiology-based imaging technique that provides information about the function of tissues and organs. Combining PET data with computed tomography or magnetic resonance images provides clinicians with physiological information linked to an anatomical site. This overview discusses the biological principles underlying the technology, PET radiopharmaceuticals, PET imaging facilities, specific imaging applications and reimbursement issues.

PET in neuro-oncology.

This article reviews possible clinical applications of positron emission tomography (PET) in brain tumor patients. PET allows quantitative assessment of brain tumor pathophysiology and biochemistry. It therefore provides different information about tumors when compared to histological or neuroradiological methods. Common clinical indications for PET comprise tumor delineation and identification of the metabolically most active tumor regions (target for biopsy, differentiation of viable tumor from necrosis). Further, the spatial relation between brain activated e.g., by speech, and the tumor bulk can be explored by activation studies. PET could also aid in the prediction of treatment response by measurement of tumor perfusion or hypoxia. Moreover, PET tracers could identify treatment targets e.g., gene products. The latter topic has not been systematically evaluated in human patients.