Teaching Nuclear Medicine

Nuclear medicine (NM) has been taught in the medical program at the University of Bergen (UiB) since 2006. Despite many incremental improvements in content delivery including a full set of online lectures since 2006, my teaching failed to captitative my target audience, leading to disappointing student responses over many years. The new curriculum “Medisin 2015” introduced e-learning/blended learning based on UiB’s new learning management system (LMS) https://mitt.uib.no, while at the same reducing the volume of face-to-face (F2F) teaching. This forced me to redesign my teaching in NM from the ground up. Inspired by team-based learning, I introduced each course module by new succinct online-lectures, followed by an online readiness assessment test (RAT) in the LMS. To engage the entire audience during the F2F sessions, I not only taught with live case in interactive format as under the old curriculum but introduced a classroom response system. Finally, I shifted the focus from transferring knowledge to teaching PET/CT reading competency both in the third and the fifth year. In the following I describe my development as a university teacher and outline my teaching philosophy

TeV Cherenkov Events as Bose-Einstein Gamma Condensations

The recent detection of gamma radiation from Mkn 501 at energies as high as 25 TeV suggests stringent upper bounds on the diffuse, far infrared, extragalactic radiation density. The production of electron-positron pairs through photon-photon collisions would prevent gamma photons of substantially higher energies from reaching us across distances of order 100 Mpc. However, coherently arriving TeV or sub-TeV gammas - Bose-Einstein condensations of photons at these energies - could mimic the Cherenkov shower signatures of extremely energetic gammas. To better understand such events, we describe their observational traits and discuss how they might be generated.Comment: 12 pages, 2 figures, accepted for publication in Ap.J.(Lett.

Ultra-High Energy Cosmic Ray Propagation in the Local Supercluster

We present detailed numerical simulations and analytical approximations of the propagation of nucleons above 10**(19) eV in the Local Supercluster, assuming that the ambient magnetic field is turbulent, and its strength 0.01 < B_rms < 1 micro-Gauss. In such strong magnetic fields, protons in the low energy part of the spectrum, 10**(19) eV < E < E_C diffuse, while the higher energy particles, with E > E_C propagate along nearly straight lines. The magnitude of the transition energy E_C depends mainly on the strength of the magnetic field, the coherence length, and the distance to the source; for B_rms=0.1 micro-Gauss, a largest eddy of length 10 Mpc, and a distance to the source of 10 Mpc, E_C=100 EeV. Our numerical treatment substantially improves on previous analytical approximations, as it allows to treat carefully the transition between the two propagation regimes, as well as the effects due to inhomogeneities expected on scales of a few Mpc. We show that a turbulent magnetic field B_rms=0.1 micro-Gauss, close to equipartition, would allow to reproduce exactly the observed spectrum of ultra high energy cosmic rays, up to the highest energy observed, for a distance to the source below 10 Mpc, for the geometry of the Local Supercluster, i.e. a sheet of thickness 10 Mpc. Diffusion, in this case, allows to reproduce the high flux beyond the Greisen Zatsepin Kuzmin cut-off, with a soft injection spectrum proportional to E**(-2.4). Moreover, the large deflection angles at the highest energies observed, typically 10 degrees for the above values, would explain why no close-by astrophysical counterpart could be associated with these events.Comment: 17 latex pages (tightened format), 9 updated postscript figures, uses revtex.sty and epsf.sty, extended discussion of numerical results, to appear in Astroparticle Physic

Flow synchronization for network coding

Abstract—Network Coding (NC) is a means to improve network performance in various ways. Most evaluations so far were done with simplified assumptions about the application scenario, namely equal data rates and packet sizes for traffic to be encoded. Traffic in real networks, however, does not have thisproperty.Hence, as deterministic and random NC require these properties, flows have to be synchronizedpriortoencodingtoguarantee theseproperties and to be able to benefit from NC in real networks. In this paper, we present a set of algorithms that synchronize arbitrary flows in wired and wireless scenarios for joint encoding later on. These algorithms are based on fragmentation and Active Queue Management (AQM) techniques. To demonstrate the benefits of our approach, we developed an encoder and decoder for deterministic XOR NC that uses this synchronization technique. Simulation results show that with our synchronization techniques, NC, even in scenarios with bursty, self-similar traffic where NC could not have been deployed so far, increases throughput and lowers packet loss and variance of end-to-end delay compared to plain forwarding. Index Terms—network coding, deterministic, random, intersession, flow, packet, synchronizatio

High cardiac background activity limits 99mTc-MIBI radioguided surgery in aortopulmonary window parathyroid adenomas

Background: Radioguided surgery using 99m-Technetium-methoxyisobutylisonitrile (99mTc-MIBI) has been recommended for the surgical treatment of mediastinal parathyroid adenomas. However, high myocardial 99mTc-MIBI uptake may limit the feasibility of radioguided surgery in aortopulmonary window parathyroid adenoma. Case presentation: Two female patients aged 72 (#1) and 79 years (#2) with primary hyperparathyroidism caused by parathyroid adenomas in the aortopulmonary window were operated by transsternal radioguided surgery. After intravenous injection of 370 MBq 99mTc-MIBI at start of surgery, the maximum radioactive intensity (as counts per second) was measured over several body regions using a gamma probe before and after removal of the parathyroid adenoma. Relative radioactivity was calculated in relation to the measured ex vivo radioactivity of the adenoma, which was set to 1.0. Both patients were cured by uneventful removal of aortopulmonary window parathyroid adenomas of 4400 (#1) and 985 mg (#2). Biochemical cure was documented by intraoperative measurement of parathyroid hormone as well as follow-up examination. Ex vivo radioactivity over the parathyroid adenomas was 196 (#1) and 855 counts per second (#2). Before parathyroidectomy, relative radioactivity over the aortopulmonary window versus the heart was found at 1.3 versus 2.6 (#1) and 1.8 versus 4.8 (#2). After removal of the adenomas, radioactivity within the aortopulmonary window was only slightly reduced. Conclusion: High myocardial uptake of 99mTc-MIBI limits the feasibility of radioguided surgery in aortopulmonary parathyroid adenoma.publishedVersio

Terahertz quantum-cascade lasers as high-power and wideband, gapless sources for spectroscopy

Terahertz (THz) quantum-cascade lasers (QCLs) are powerful radiation sources for high-resolution and high-sensitivity spectroscopy with a discrete spectrum between 2 and 5 THz as well as a continuous coverage of several GHz. However, for many applications, a radiation source with a continuous coverage of a substantially larger frequency range is required. We employed a multi-mode THz QCL operated with a fast ramped injection current, which leads to a collective tuning of equally-spaced Fabry-Pérot laser modes exceeding their separation. A continuous coverage over 72 GHz at about 4.7 THz was achieved. We demonstrate that the QCL is superior to conventional sources used in Fourier transform infrared spectroscopy in terms of the signal-to-noise ratio as well as the dynamic range by one to two orders of magnitude. Our results pave the way for versatile THz spectroscopic systems with unprecedented resolution and sensitivity across a wide frequency range

Impact of EMG Changes in Continuous Vagal Nerve Monitoring in High-Risk Endocrine Neck Surgery

Background: Continuous vagal intraoperative neuromonitoring (CIONM) of the recurrent laryngeal nerve (RLN) may reduce the risk of RLN lesions during high-risk endocrine neck surgery such as operation for large goiter potentially requiring transsternal surgery, advanced thyroid cancer, and recurrence. Methods: Fifty-five consecutive patients (41 female, median age 61 years, 87 nerves at risk) underwent high-risk endocrine neck surgery. CIONM was performed using the commercially available NIM-Response 3.0 nerve monitoring system with automatic periodic stimulation (APS) and matching endotracheal tube electrodes (Medtronic Inc.). All CIONM events (decreased amplitude/increased latency) were recorded. Results: APS malfunction occurred on three sides (3 %). A total of 138 CIONM events were registered on 61 sides. Of 138, 47 (34 %) events were assessed as imminent (13 events) or potentially imminent (34 events) lesions, whereas 91 (66 %) were classified as artifacts. Loss of signal was observed in seven patients. Actions to restore the CIONM baseline were undertaken in 58/138 (42 %) events with a median 60 s required per action. Four RLN palsies (3 transient, 1 permanent) occurred: one in case of CIONM malfunction, two sudden without any significant previous CIONM event, and one without any CIONM event. The APS vagus electrode led to temporary damage to the vagus nerve in two patients. Conclusions: CIONM may prevent RLN palsies by timely recognition of imminent nerve lesions. In high-risk endocrine neck surgery, CIONM may, however, be limited in its utility by system malfunction, direct harm to the vagus nerve, and particularly, inability to indicate RLN lesions ahead in time.publishedVersio

Wireless motility capsule compared with scintigraphy in the assessment of diabetic gastroparesis

Background: Gastroparesis is a potentially severe late complication of diabetes mellitus. Today, delayed gastric emptying (GE) is mandatory for establishing the diagnosis. In this study, we compared wireless motility capsule (WMC) with gastric emptying scintigraphy (GES). Methods: Seventy‐two patients (49 women) with diabetes mellitus (59 type 1) and symptoms compatible with gastroparesis were prospectively included between 2014 and 2018. Patients were simultaneously examined with GES and WMC. Symptoms were assessed with the Patient Assessment of Upper Gastrointestinal Symptom Severity Index (PAGI‐SYM) questionnaire. All patients were on intravenous glucose‐insulin infusion during testing. Key Results: WMC and GES correlated r = .74, P < .001. Compared to GES, WMC at ordinary cutoff for delayed GE (300 minutes) had a sensitivity of 0.92, specificity 0.73, accuracy 0.80, and Cohen's kappa κ = 0.61 (P < .001). By receiver operating characteristics (ROC), the area under the curve was 0.95 (P < .001). A cutoff value for delayed GE of 385 minutes produced sensitivity 0.92, specificity 0.83, accuracy 0.86, and Cohen's kappa κ = 0.72 (P < .001). Inter‐rater reliability for GE time with WMC was r = .996, κ = 0.97, both P < .001. There was no difference in symptom severity between patients with normal and delayed GE. Conclusions & Inferences: Our findings demonstrate the applicability of WMC as a reliable test to assess gastric emptying in diabetic gastroparesis showing very high inter‐observer correlation. By elevating the cutoff value for delayed emptying from 300 to 385 minutes, we found higher specificity without reducing sensitivity.publishedVersio