Marcel Opitz

¹⁸F-PSMA-1007 PET is used in the management of patients with prostate cancer. However, recent reports indicate a high rate of unspecific bone uptake (UBU) with ¹⁸F-PSMA-1007, which may lead to a false-positive diagnosis. UBU has not been evaluated thoroughly. Here, we evaluate the frequency of UBU and bone metastases separately for ¹⁸F-PSMA-1007 and ⁶⁸Ga-PSMA-11 in biochemical recurrence (interindividual comparison). Additionally, we investigate UBU seen in ¹⁸F-PSMA-1007 through follow-up examinations (intraindividual comparison) using ⁶⁸Ga-PSMA-11 PET, bone scintigraphy, and MRI. <b>Methods:</b> First, all patients (<i>n</i> = 383) who underwent ⁶⁸Ga-PSMA-11 PET between January 2020 and December 2020 and all patients (<i>n</i> = 409) who underwent ¹⁸F-PSMA-1007 PET between January 2020 and November 2021 due to biochemical recurrence were included for an interindividual comparison of bone metastases and UBU rate. In a second approach, we regarded all patients with UBU in ¹⁸F-PSMA-1007, characterized by focal bone uptake with an SUV_max &gt; 4 and prostate-specific antigen (PSA) ≤ 5 ng/mL, who underwent additional ⁶⁸Ga-PSMA-11 PET (<i>n</i> = 17) (interindividual comparison). Of these, 12 patients also had bone scintigraphy and whole-body MRI within a 1- to 5-wk interval. Bone uptake seen on ¹⁸F-PSMA-1007 but not on any of the other 4 modalities (CT, MRI [<i>n</i> = 1], bone scanning, and ⁶⁸Ga-PSMA-11 PET) was recorded as false-positive. <b>Results:</b> Patients scanned with ¹⁸F-PSMA-1007 PET had a significantly higher rate of UBU than those scanned with ⁶⁸Ga-PSMA-11 (140 vs. 64; <i>P</i> &lt; 0.001); however, the rate of bone metastases was not significantly different (72 vs. 64; <i>P</i><b>=</b> 0.7). In the intraindividual comparison group, workup by CT, MRI, bone scanning, and ⁶⁸Ga-PSMA-11 PET resulted in a positive predictive value for ¹⁸F-PSMA-1007 focal bone uptake (mean SUV_max, 6.1 ± 2.9) per patient and per lesion of 8.3% and 3.6%, respectively. <b>Conclusion:</b> In patients with PSA ≤ 5 ng/mL and SUV &gt; 4 at biochemical recurrence, most ¹⁸F-PSMA-1007 focal bone uptake is likely to be false-positive and therefore due to UBU. In the case of low clinical likelihood of metastatic disease, ¹⁸F-PSMA-1007 bone uptake without morphologic surrogate should be assessed carefully with regard to localization and clinical context. However, the rate of bone metastases was not higher with ¹⁸F-PSMA-1007 in the clinical routine, indicating that experienced reporting physicians adjust for UBU findings.

The aim of this study was to evaluate the roles of 67Ga-citrate and 99Tcm-methylene diphosphonate (99Tcm-MDP) planar and single photon emission tomographic (SPET) imaging in patients with vertebral osteomyelitis. Thirty patients (22 females, 8 males) aged 62.7 +/- 16.4 years (mean +/- s) were enrolled prospectively between May 1995 and May 1998. The patients had been on antibiotics for 7 +/- 4 weeks prior to the study. Histology was available for all but nine patients with mild infections, who were evaluated by a combination of magnetic resonance imaging (MRI), clinical and laboratory tests. 67Ga-citrate (185 MBq) and three-phase bone (555 MBq 99Tcm-MDP) planar and SPET imaging were performed in all patients, together with MRI as a comparison. In total, 67 infectious foci were detected. Based on histology, there were four cases of severe, 13 cases of moderate and four cases of mild osteomyelitis; nine mild infections were also classified by the combination of MRI, clinical and laboratory results. Combined MRI and 67Ga-citrate SPET correctly classified all patients; MRI detected all 67 infectious foci, whereas 67Ga-citrate SPET identified 54 only. False-negative results were seen with all other modalities, especially in cases of mild and moderate infection. 67Ga-citrate SPET identified unsuspected cases of endocarditis (n = 2), paravertebral abscess (n = 1), subaxillary soft tissue abscess (n = 1) and rib osteomyelitis (n = 1). For 67Ga-citrate SPET, the target-to-background ratio was 2.24 +/- 0.31, 1.76 +/- 0.07 and 1.30 +/- 0.18 for severe, moderate and mild osteomyelitis, respectively. Significant differences were noted between severe and moderate infection (P = 0.0051) and between severe and mild infection (P < 0.0001); that between moderate and mild infection was non-significant. For 99Tcm-MDP planar and SPET imaging, and for planar 67Ga-citrate imaging, there was no correlation with severity. We conclude that 67Ga-citrate SPET is able to identify vertebral osteomyelitis and detect additional sites of infection. It can also aid in determining the severity of infection and, potentially, the response to therapy.

BACKGROUND: Computed tomography (CT) studies are requested by specialists from most medical disciplines and play a vital role in the diagnosis and treatment of patients. It follows that physicians of all specialties should possess basic knowledge of computed tomography, its proper use, and the radiation exposure associated with it. METHODS: This review is based on publications retrieved by a selective search of the literature. RESULTS: Approximately 12 million CT studies are carried out in Germany each year, and the trend is rising. Approximately 9% of all diagnostic studies involving ionizing radiation are CT studies. On average, more than 60% of the collective effective dose due to medical radiation exposure is attributable to CT. There are two types of radiation effects caused by ionizing radiation: sto - chastic and deterministic. The additional, individual relative lifetime cancer mortality risk due to ionizing radiation with wholebody exposure at a low single dose is estimated at 5% per sievert. Radiation exposure from CT studies of the head and trunk, e.g. of a patient with polytrauma, corresponds to an additional lifetime cancer mortality risk of approximately 0.1% at an effective dose of approximately 20 millisievert. CONCLUSION: The radiation exposure due to CT, and the risks to which patients are subjected by it, have become more important with greater use of CT. Technical advances, targeted dose monitoring, and analyses of dose data can help identify areas where improvement is necessary, in furtherance of the overriding goal of lowering patients' radiation exposure while preserving adequate image quality.

Abstract Purpose To assess suspected acute stroke, the computed tomography (CT) protocol contains a non-contrast CT (NCCT), a CT angiography (CTA), and a CT perfusion (CTP). Due to assumably high radiation doses of the complete protocol, the aim of this study is to examine radiation exposure and to establish diagnostic reference levels (DRLs). Methods In this retrospective study, dose data of 921 patients with initial CT imaging for suspected acute stroke and dose monitoring with a DICOM header–based tracking and monitoring software were analyzed. Between June 2017 and January 2020, 1655 CT scans were included, which were performed on three different modern multi-slice CT scanners, including 921 NCCT, 465 CTA, and 269 CTP scans. Radiation exposure was reported for CT dose index (CTDI vol ) and dose-length product (DLP). DRLs were set at the 75th percentile of dose distribution. Results DRLs were assessed for each step (CTDI vol /DLP): NCCT 33.9 mGy/527.8 mGy cm and CTA 13.7 mGy/478.3 mGy cm. Radiation exposure of CTP was invariable and depended on CT device and its protocol settings with CTDI vol 124.9–258.2 mGy and DLP 1852.6–3044.3 mGy cm. Conclusion Performing complementary CT techniques such as CTA and CTP for the assessment of acute stroke increases total radiation exposure. Hence, the revised DRLs for the complete protocol are required, where our local DRLs may help as benchmarks.