Xiangyu Liu, RT*; Jiaxu Wei, RT*; Xi Zhao, MD**; Ji Wang, RT*

* Department of Radiology, Shanghai Jiao Tong University School of Medicine Affiliated Renji Hospital, Shanghai, P. R. China** Siemens Healthineers, China

2025-07-02

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History

A 15-year-old male patient, complaining of a growing lump on the right of his forehead over the past 20 days, came to the hospital for a check-up. He was otherwise asymptomatic. His medical history was unremarkable. Physical examination revealed no abnormalities. A contrast-enhanced CT scan was performed with a dual source photon-counting CT (PCCT), NAEOTOM Alpha, using an ultra-high resolution (UHR) scan mode, for assessment.

Diagnosis

CT images showed an expansive frontotemporal mass, measuring 66 mm x 65 mm in size, protruding into the right orbit, the right frontal sinus and subcutaneously. It was also compressing the right lateral ventricle, shifting the cerebral midline and both the anterior cerebral arteries (ACA) leftwards, and the right middle cerebral artery (MCA) backwards, and causing bone erosion of the squamous part of the right temporal bone and posterolateral orbital wall. The mass, homogeneous and slightly hyperdense in the virtual non-contrast (VNC) images, showed uniformed contrast enhancement in the virtual monoenergetic images (VMI) displayed at 55 keV, as well as in the iodine maps, with multiple hyperdense foci inside. Hypodense areas around the mass were seen, suggesting edema. The intraorbital segment of the optic nerve was compressed, however, not invaded. CT findings suspected a meningioma. A MRI was suggested for further assessment, also suspecting a meningioma. A lymphoma was considered in the differential diagnosis, however, there were no typical signs in either CT or MRI.

Subsequently, the patient underwent surgical removal of the mass. Histologic and immunophenotypic findings revealed an anaplastic large cell lymphoma (ALCL), anaplasticlymphoma-kinase (ALK) positive. The patient recovered well and was discharged two weeks later with scheduled outpatient follow-ups.

Fig. 1: Coronal view of a 0.2 mm UHR image (Fig. 1a) shows bone erosion (arrows) of the squamous part of the right temporal bone and the posterolateral orbital wall. 1 mm slices with spectral information are reconstructed from the UHR data to reformat coronal views of a VMI displayed at 55 keV (Fig. 1b), a VNC (Fig. 1c), and an iodine map (Fig. 1d). These images show an expansive frontotemporal mass, homogeneous and slightly hyperdense in VNC, uniformly contrast enhanced in VMI and iodine images, with multiple hyperdense foci inside, protruding into the right orbit and shifting the cerebral midline to the left.

Fig. 2: Oblique MPR images show the tumor protruding into the right frontal sinus and the right orbit, compressing the intraorbital segment of the optic nerve. The fine separation (arrows) between the tumor edge and optic nerve is better seen in 0.2 mm UHR image (Fig. 2a) and in VMI displayed at 55 keV (Fig. 2b), in comparison to a VMI displayed at 70 keV (Fig. 2c) corresponding to an image acquired at 120 kV in standard scan.

Fig. 3: cVRT images, reconstructed using 0.2 mm UHR slices, show bone erosion of the squamous part of the right temporal bone and the posterolateral orbital wall (Fig. 3a, arrows), the extracranial (Fig. 3b) and intracranial (Fig. 3c) feeding arteries (arrowheads) to the tumor in detail. Both ACA are shifted leftwards and the right MCA is shifted backwards.

Comments

Primary ALCLs, occurring in the central nervous system (CNS), are extremely rare. They tend to occur in children and young adults, predominantly male patients, with a prognosis correlated with ALK positivity. A favorable course has been exhibited in younger patients with ALK-positive ALCL. As the imaging characteristics are atypical, diagnosis and differential diagnosis are difficult with traditional imaging alone, especially when the tumor is massive and invasive, such as in this case.

A unique combination of high spatial resolution and spectral information, provided by PCCT, is helpful in visualizing the detailed cerebral, vascular and bony structures using the image data acquired from one UHR scan. The VMI of the cerebrum are routinely set to be displayed at a low keV level (55 keV) allowing for enhanced contrast. VNC images can be displayed with one mouse click, without having to perform a native scan. In daily practice, these different image types – VMI, VNC and iodine – can be interactively toggled, using Interactive Spectral Imaging (ISI) technique available in image reading. In UHR mode, small sub-pixels are defined by electric fields, instead of physical separations, and are read out separately to increase the spatial resolution. This approach improves the geometrical dose efficiency of the detector to enable UHR imaging without radiation dose penalty. In addition, PCCT optimizes the contrast-to-noise ratio (CNR) with a combination of missing down-weighting of the lower energy X-ray photons, the absence of the electronic noise and the inherent spectral information. A practical example is that the UHR images, acquired and reconstructed at 0.2 mm slice width, can be used to create lifelike three-dimensional images with cinematic volume rendering technique (cVRT). In this very rare case, although diagnosis based on imaging differs from histologic and immunophenotypic results, the detailed visualization and demonstration help the neurosurgeons understand the complexity of the case prior to surgical planning.

Examination Protocol

Városmajor Heart and Vascular Centre, Cardiac CT Working Group, Budapest, Hungary

September 29, 2026

History

Why did the patient come for a CT exam?

A 63-year-old female patient, presenting with typical chest pain, was referred for coronary imaging to clarify her coronary status and exclude acute coronary syndrome.

Laboratory tests showed marked myocardial injury and neurohormonal activation, with highly elevated high-sensitivity troponin I of 2032 ng/L, CK of 565 U/L, CK-MB of 43 U/L, and NT-proBNP of 1589.7 pg/mL.

Mild inflammatory activity was also present, with leukocytosis of 12.86 G/L, neutrophilia, and mildly elevated CRP of 6.2 mg/L. Renal function was preserved, with an eGFR of 107 mL/min.

An initial transthoracic echocardiography showed mildly to moderately reduced global left ventricular systolic function, with a left ventricular ejection fraction of 42% by Simpson’s method. Regional wall motion abnormalities were present, with hypokinesis of the midventricular segments and near akinesia of the apical third of the left ventricle. Mild mitral regurgitation and moderate tricuspid regurgitation were present.

Right ventricular size was normal, and right ventricular longitudinal systolic function was preserved. The estimated pulmonary artery systolic pressure was mildly elevated.

Coronary CT angiography (CCTA) was recommended to exclude obstructive coronary artery disease.

Diagnosis

What were the CT findings, and what happened to the patient after CT?

Coronary CT angiography was performed using a dual-source photoncounting detector CT scanner (Siemens NAEOTOM Alpha Peak).

The estimated CCTA radiation dose was 397 mGy·cm. Iomeron 400 was administered with a contrast volume of 90 mL and a flow of 5.5 ml/s. The patient received 0.8 mg sublingual nitroglycerin prior to the examination. Heart rate during the scan was 93–97/min with sinus rhythm.

The coronary calcium score was 4.

The patient had a left-dominant coronary artery system and normal origin and course of the coronary arteries. No relevant coronary atherosclerosis or luminal stenosis were detected. Only minimal vessel wall irregularities were observed, with small specks of calcified plaque in the distal left anterior descending (LAD) artery (Figure 1. and 2.)

Figure 1. CT coronary angiography demonstrating
normal coronary artery anatomy with no
evidence of a significant stenosis.

Figure 2. Electrocardiogram (ECG) during Prospective
Sequential Cardiac CT Acquisition.

Coronary CT angiography was performed using a prospectively ECG-triggered sequential axial acquisition. Given the patient’s heart rate, exceeding 90 beats/min, multiphase image reconstruction was performed to ensure optimal image quality and to allow simultaneous assessment of coronary anatomy and left ventricular function.

In addition to coronary artery evaluation, the multiphase datasets were analyzed for regional wall-motion abnormalities and cardiac chamber volumetry.

Coronary analysis demonstrated non-obstructive coronary artery disease, with only minimal calcified plaque in the distal left anterior descending artery. Functional assessment revealed severe apical hypokinesis/akinesis with associated midventricular dyskinesis and preserved basal contractility, resulting in the characteristic apical ballooning pattern of a classical Takotsubo syndrome (Figure 3).

Figure 3. Left Ventricular Apical Dysfunction Consistent with Takotsubo Pattern on Multiphase Cardiac CT Functional
Analysis. Multiphase cardiac CT-derived left ventricular wall-motion bull’s-eye map demonstrating a regional
gradient of myocardial contractility with preserved basal function (red–yellow), reduced mid-ventricular motion,
and markedly impaired apical wall motion (blue–purple). The pattern shows an apical-dominant distribution of
dysfunction, consistent with a classical Takotsubo-type contraction abnormality in the appropriate clinical context
(left). Mildly increased left ventricular end-diastolic and end-systolic volume indices (indexed to body surface area)
were detected, with mildly reduced systolic function (LVEF 45%) based on the available cardiac phases.

Mildly increased left ventricular end-diastolic and end-systolic volume indices were detected, with mildly reduced systolic function (LVEF 45%).

As an incidental extracardiac finding, scattered bilateral ground-glass opacities with patchy consolidations were detected, most consistent with bronchopneumonia given the elevated inflammatory laboratory markers.

Comments

Is there any clinically interesting aspect of the case to discuss?
What difference did photon-counting CT make for the patient?

This case highlights the clinical value of the photon-counting coronary CT angiography in the diagnostic work-up of patients presenting with acute chest pain, elevated cardiac biomarkers, and electrocardiographic changes suggestive of acute coronary syndrome.

Beyond excluding obstructive coronary artery disease, CT angiography enables comprehensive myocardial functional assessment, allowing identification of the characteristic apical ballooning pattern consistent with Takotsubo syndrome, thereby supporting a working diagnosis of MINOCA – now defined as myocardial injury with non-obstructive coronary arteries (Fifth Universal Definition of Myocardial Infarction, 2026) – with Takotsubo syndrome as the most likely final diagnosis.

The ability of photon-counting CT to simultaneously evaluate coronary anatomy, plaque burden, and left ventricular function in a single examination may facilitate rapid differentiation between obstructive coronary disease and alternative causes of acute myocardial injury, potentially reducing the need for additional imaging or invasive angiography in selected patients.

This case also demonstrates the technical advantages of photoncounting coronary CT angiography for combined coronary and functional cardiac assessment in an acute setting.

The system provides excellent spatial and temporal resolution, enabling high-quality coronary plaque evaluation, even at elevated heart rates (>90 beats/min), with minimal motion artefact. This allows for a reliable assessment of the coronary lumen and detection of only minimal calcified plaque in the distal LAD.

In addition, multiphase ECG-gated reconstructions offer excellent temporal resolution for detailed motion analysis of all cardiac chambers, permitting accurate depiction of regional wall-motion abnormalities.

Overall, the combination of high spatial fidelity for plaque characterization and high temporal resolution for functional assessment underscores the robustness of photon-counting CT for integrated “one-stop” coronary and myocardial evaluation, even under challenging heart rate conditions.

Note that the role of CT in this case should be interpreted within its limits. CCTA was requested to rule out obstructive coronary artery disease in a haemodynamically stable patient; because of the elevated heart rate, a multiphase acquisition was used, which additionally depicted the wall-motion pattern. CCTA can therefore exclude obstructive coronary artery disease and further reinforce echocardiographic findings suggestive of Takotsubo syndrome, but it does not establish the diagnosis on its own. Current recommendations advise cardiac magnetic resonance imaging when the final diagnosis remains uncertain—particularly in the presence of inflammatory red flags—and follow-up echocardiography to document recovery of left ventricular function. In our patient, who was referred to our centre for CT only, further diagnostic work-up and follow-up were performed at the referring institution.

Examination Protocol

DISCLAIMER

The statements by customers of Siemens Healthineers described herein are based on results that were achieved in the customer’s unique setting. Because there is no “typical” hospital and many variables exist (e.g., hospital size, case mix, level of IT and/or automation adoption) there can be no guarantee that other customers will achieve the same results.

The products/features (mentioned herein) are not commercially available in all countries. Their future availability cannot be guaranteed.

Ferenc Imre Suhai, Barbara Sipos, Milán Vecsey-Nagy, Bálint Szilveszter

Városmajor Heart and Vascular Centre, Cardiac CT Working Group, Budapest, Hungary

September 29, 2026

History

Why did the patient come for a CT exam?

A 29-year-old male patient, with a history of hypertension and bronchial asthma, was referred to the Városmajor Heart and Vascular Centre from the emergency department due to acute retrosternal chest pain and markedly elevated cardiac biomarkers.

His symptoms occurred in the setting of a recent upper respiratory tract infection with fever and follicular tonsillitis. He had been treated with azithromycin before admission.

At the emergency department, laboratory tests showed significant inflammatory activity and myocardial injury, with elevated C-reactive protein, leukocytosis with neutrophilia, and markedly elevated high-sensitivity troponin T, which increased from 1302 ng/L to 1689 ng/L. CK-MB was also elevated.

Electrocardiography showed ST-segment elevation in the inferior leads with reciprocal ST depression in aVL.

Transthoracic echocardiography revealed preserved left ventricular systolic function without regional wall motion abnormalities. Given the combination of acute chest pain, elevated troponin, inflammatory syndrome, and ECG changes, acute myocarditis was suspected; however, acute coronary syndrome had to be excluded.

Therefore, a coronary CT angiography was performed as the initial imaging modality to assess the coronary status. Cardiac magnetic resonance imaging was subsequently performed for detailed myocardial tissue characterization and confirmation of the diagnosis.

Diagnosis

What were the CT findings, and what happened to the patient after CT?

Coronary CT angiography was performed using a photon-counting detector CT on a Siemens NAEOTOM Alpha Peak scanner. Native calcium scoring, contrast-enhanced ECG-gated coronary CTA, and a 6-minute delayed-phase acquisition for myocardial tissue characterization and visual assessment of late iodine enhancement were performed.

The estimated radiation dose was 350 mGy·cm for the CCTA and 245 mGy·cm for the delayed scan.

Iomeron 400 was administered with a contrast volume of 80 mL. The patient received 75 mg oral metoprolol and 0.8 mg sublingual nitroglycerin prior to the examination. Heart rate during the scan was 85/min with sinus rhythm.

The coronary calcium score was 0.

The patient had a left-dominant coronary artery system and normal origin and course of the coronary arteries. No relevant coronary atherosclerosis or luminal stenosis were detected (Figure 1).

Figure 1. CT coronary angiography demonstrating normal coronary artery anatomy with no evidence of significant stenosis.

Cardiac magnetic resonance imaging was performed on a 1.5-T Siemens Aera scanner. Short-axis images demonstrate myocardial edema on T2-weighted fat-suppressed imaging and corresponding non-ischemic late gadolinium enhancement on LGE imaging in the mid-ventricular anterior-anterolateral and inferior-inferolateral left ventricular segments, predominantly in a subepicardial to midmyocardial distribution.

The concordant presence of edema and LGE supports acute myocarditis rather than ischemic infarction.

On the 6-minute delayed-phase PCCT images, visually detectable late iodine enhancement was observed, in a non-ischemic distribution. The enhancement involved the basal and midventricular anterolateral and inferolateral regions, the inferior segment in a subepicardial to midmyocardial pattern, and the apical inferior and lateral segments (Figure 2).

Figure 2. Electrocardiogram (ECG) During Prospective Sequential Cardiac CT Acquisition. Multimodality comparison of an acute myocardial injury from basal to apical short-axis images. The first column shows 6-minute delayed-phase PCCT images, the second column shows corresponding color-coded LUT maps, the third column shows iodine maps, and the fourth column shows matched cardiac MRI late gadolinium enhancement images. Blue arrows indicate areas of abnormal myocardial iodine enhancement on PCCT and corresponding non-ischemic myocardial injury on CMR. The abnormalities are predominantly located in the anterolateral, inferolateral, and inferior left ventricular segments, with a subepicardial to midmyocardial distribution, consistent with acute myocarditis.

The visual delayed iodine enhancement pattern indicated abnormal myocardial tissue characteristics and supported the diagnosis of an acute myocarditis.

Cardiac magnetic resonance (CMR) imaging was performed on a 1.5-T Siemens Aera scanner using Gadovist contrast agent. The CMR protocol included cine b-SSFP imaging, T2-weighted imaging, native T1 and T2 mapping, first-pass perfusion, late gadolinium enhancement imaging, and post-contrast T1 mapping for extracellular volume assessment.

CMR demonstrated mildly reduced left ventricular systolic function, with an LVEF of 45.4%. Left ventricular volumes were within the normal range, stroke volume was preserved, and left ventricular myocardial mass was normal. Right ventricular size and systolic function were preserved, with an RVEF of 52.2%.

T2-weighted images demonstrated myocardial edema in the basal and midventricular anterolateral and inferolateral segments, the midventricular inferior and partly anterior segments, and the apical inferior segment, predominantly in a subepicardial to midmyocardial distribution (Figure 3).

Figure 3. Cardiac MRI confirmation of acute myocarditis: myocardial edema and non-ischemic injury

After gadolinium administration, pathological late gadolinium enhancement was observed in the same edematous myocardial segments.

Parametric mapping further supported the diagnosis. Native T1, T2, and ECV values were elevated in the affected lateral myocardial regions. ECV was increased in the basal lateral wall and midventricular lateral wall, while septal values remained within the normal range.

Overall, the CMR findings confirmed acute myocarditis with mildly reduced left ventricular ejection fraction and mild diffuse hypokinesis.

Comments

Is there any clinically interesting aspect of the case to discuss?
What difference did photon-counting CT make for the patient?

This case highlights the potential diagnostic value of photon-counting CT in patients presenting with acute chest pain, elevated cardiac biomarkers, and electrocardiographic changes suggestive of acute coronary syndrome.

The 6-minute delayed-phase acquisition allowed visual assessment of myocardial iodine retention. Delayed-phase spectral reconstruction using monoenergetic plus images and color-coded iodine maps improved visualization of myocardial iodine distribution and enabled myocardial tissue characterization.

Focal subepicardial to mid-myocardial iodine accumulation indicated abnormal myocardial tissue characteristics. The distribution of delayed iodine enhancement corresponded closely to the edema, late gadolinium enhancement, and elevated CMR-derived ECV values in the affected myocardial segments.

An important limitation is the additional radiation exposure associated with the delayed-phase of CT imaging. This is particularly relevant in young patients, in whom radiation dose should be carefully justified and minimized.

Therefore, delayed-phase PCCT acquisitions should not be considered for routine in all patients with suspected myocarditis, but rather reserved for selected cases in which the expected diagnostic benefit outweighs the additional dose, such as when CMR is contraindicated, unavailable, or unlikely to be feasible.

PCCT could serve as a comprehensive first-line imaging tool in selected patients with suspected myocarditis and possible acute coronary syndrome. Its inherent spectral capabilities, together with its high spatial resolution, allow rapid exclusion of obstructive coronary artery disease while also enabling visual myocardial tissue characterization through delayed-phase spectral imaging, monoenergetic reconstructions, and iodine mapping.

These capabilities support comprehensive coronary artery evaluation while simultaneously providing additional insights into myocardial tissue characteristics within a single examination.

Examination Protocol

Disclaimer

The statements by customers of Siemens Healthineers described herein are based on results that were achieved in the customer’s unique setting. Because there is no “typical” hospital and many variables exist (e.g., hospital size, case mix, level of IT and/or automation adoption) there can be no guarantee that other customers will achieve the same results.

The products/features (mentioned herein) are not commercially available in all countries. Their future availability cannot be guaranteed.

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Video interview:

Source: Shim D, Chong L, Cannata M, et al. J Am Coll Cardiol. 2026;88(7).

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This 2026 EACVI/ESC clinical consensus statement provides a broad practical framework for cardiac CT (CCT), but importantly identifies photon-counting detector CT (PCD-CT/PCCT) as the latest major technological advance in cardiac CT. The central advantage of PCCT is the substantial improvement in spatial resolution: whereas conventional 64-slice, dual-source, and wide-coverage systems generally remain around 0.5–0.6 mm, PCCT can achieve spatial resolution down to approximately 0.2 mm. At the same time, contemporary photon-counting systems can retain the high temporal-resolution advantages associated with dual-source technology.

Why PCCT matters clinically

The increased spatial resolution is particularly relevant where conventional CCTA is limited by very small structures or high-attenuation material. The consensus specifically highlights heavily calcified coronary lesions, assessment of in-stent restenosis (ISR), and detection of myocardial injury as promising applications. This is clinically important because coronary stent assessment remains substantially more difficult than evaluation of native coronary arteries, while heavily calcified native vessels—particularly in previously revascularized patients—can also be challenging with conventional CCTA.

Thus, PCCT is positioned less as a completely different cardiac CT examination than as a technological refinement of CCTA that may extend diagnostic performance into situations traditionally limited by spatial resolution. The potential value is especially intuitive for coronary lumen evaluation adjacent to calcium or metallic stent struts, where conventional CT has difficulty resolving small residual luminal dimensions.

PCCT examination / acquisition considerations

The general cardiac CT principles remain applicable: acquisition is ECG-synchronized to minimize cardiac-motion artefacts and requires a short 5–10 s breath-hold. CCTA requires intravenous iodinated contrast, whereas coronary calcium scoring is performed without contrast.

For coronary imaging, careful heart-rate control remains important even with advanced CT technology. High heart rate, heart-rate variability, obesity, and respiratory motion impair interpretability. Unless contraindicated, the document recommends pharmacological heart-rate reduction toward ≤60 bpm, using agents such as beta-blockers or ivabradine; sublingual nitroglycerin approximately 5 min before CCTA improves coronary vasodilatation and visualization of peripheral coronary segments.

A key PCCT-specific trade-off is that its ultra-high-resolution mode still requires acquisition over multiple heartbeats. Consequently, the maximum spatial-resolution capability of PCCT does not eliminate the importance of rhythm stability and motion control. In other words, the ≈0.2-mm resolution represents a major improvement in spatial resolution, but ultra-high-resolution coronary PCCT does not necessarily provide single-heartbeat acquisition.

Radiation and reconstruction

The consensus emphasizes maintaining the ALARA principle. Contemporary CT dose-reduction approaches include prospective ECG triggering, high-pitch acquisition, tube-current/voltage modulation, low-kV protocols, iterative or deep-learning reconstruction, faster rotation, and motion-correction techniques. Across modern CCT generally, typical effective doses are around 3 mSv and can fall below 1 mSv with the latest technologies, although the document does not provide a separate PCCT-specific dose figure for ultra-high-resolution coronary acquisitions.

PCCT datasets can be evaluated with the usual cardiac CT post-processing tools—including axial images, MPR/cMPR, MIP, and volume rendering—with the increased intrinsic spatial resolution providing the principal technical advantage.

Clinical perspective

The consensus therefore presents PCCT as a particularly promising next step for high-resolution coronary imaging, potentially addressing some of the hardest problems for conventional CCTA: dense coronary calcium, small coronary structures and stented segments. However, it stops short of establishing PCCT as a new evidence-based standard for these indications. The authors explicitly note that intra-patient randomized controlled trials are still lacking, so the technological advantages and encouraging early clinical applications currently exceed the level of definitive comparative outcome evidence.

Take-home: PCCT pushes cardiac CT spatial resolution from roughly 0.5–0.6 mm toward 0.2 mm, with the greatest expected benefit in calcified coronary disease and stent imaging. The price of maximal ultra-high resolution is currently multi-beat acquisition, making excellent ECG synchronization, low/stable heart rate and breath-holding particularly important. The 2026 EACVI/ESC consensus views the technology as highly promising, but not yet supported by definitive randomized comparative evidence.

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Figure 2. Cardiac PCCT imaging of the three false positive cases (a–c). Left atrial appendage thrombi were found in PCCT imaging (arrows) but not in transesophageal echocardiography.

Protocol

Key Results

Source: Kirschfink A, Elhalal M, Seidel S, Kammer S, Hasan D, Frick M, Marx N, Schulz JB, Wiesmann M, Altiok E, Ridwan H, Reich A, Pinho J. Cardiac photon-counting detector computed tomography in acute ischemic stroke: diagnostic accuracy for detection of left atrial appendage thrombus. Therapeutic Advances in Neurological Disorders. 2026;19:17562864261466073. doi:10.1177/17562864261466073.

Nguyen KV, Nguyen VT, Nguyen NT, et al. Photon-Counting Computed Tomography for In-Stent Occlusion: Lumen Visualization and Myocardial Viability. JACC Case Rep. 2026;108566. doi:10.1016/j.jaccas.2026.108566.

History of Presentation

A 58-year-old man presented with a 2-day history of progressive crescendo chest pain. He remained symptomatic despite strict adherence to dual antiplatelet therapy and high-intensity statins.
Take-Home Message Photon-counting detector computed tomography may improve diagnostic workflows and enhance precision for the management of complex coronary artery disease.

Past Medical History

His medical history was notable for percutaneous coronary intervention 12 months prior with the deployment of 2 drug-eluting stents (3.8 mm and 2.8 mm) in the right coronary artery (RCA). Differential Diagnosis Differential diagnoses for the patient’s recurrent chest pain included in-stent restenosis, acute in-stent thrombosis, and progression of native coronary artery disease.

Investigations

To evaluate stent patency, the patient underwent ultra-high-resolution photon-counting detector computed tomography (UHR PCCT) in UHR cardiac mode (120 kVp, 0.2 mm slice thickness; temporal resolution 66 milliseconds) after injection of 60 mL contrast (370 mgI/mL at 5.5 mL/s). Images were reconstructed with a 1,024 x 1,024 matrix using the Quantum pure lumen algorithm to reduce blooming artifacts and optimize in-stent lumen assessment, with simultaneous acquisition of iodine maps from intrinsic spectral data without additional scan phases, which definitively identified a chronic total in-stent occlusion of the RCA (Figure 1A). Crucially, the scan also clearly delineated a robust network of intercoronary collaterals originating from the left anterior descending artery, which retrogradely filled the distal RCA territory (Figure 1D).

Figure 1. Photon-Counting Computed Tomography of Coronary Stent Occlusion and Collateral Perfusion (A) UHR PCCT acquisition of the RCA. The arrow below indicates a total in-stent occlusion. Axial images (arrow above) demonstrate high-fidelity delineation between the metallic struts and the intraluminal thrombus. (B) The LAD is widely patent without significant stenosis. (C and D) Whole-heart reconstruction highlighting the recruitment of rich collateral circulation from the LAD to the distal RCA territory (arrow). LAD = left anterior descending artery; PCCT = photon-counting detector computed tomography; RCA = right coronary artery; UHR = ultra-high-resolution.

A comprehensive, noninvasive study was performed using UHR PCCT spectral datasets. Arterial-phase iodine perfusion maps revealed a distinct transmural perfusion defect in the posteroinferior wall, matching the anatomical distribution of the occluded RCA (Figure 2). This functional assessment was complemented by late iodine enhancement acquired 5 minutes postcontrast, which demonstrated dense transmural hyperenhancement in the same territory, identifying a chronic myocardial scar and confirming the lack of viability (Figure 3A).

Figure 2. Photon-Counting Detector Computed Tomography Spectral Perfusion (A and B) Spectral-derived iodine map: a transmural perfusion defect (red/blue) (arrow) is clearly visible in the posteroinferior wall, matching the right coronary artery territory. (C and D) LV transmurality index and binary enhanced volume maps showing predominantly transmural abnormal enhancement and advanced myocardial injury in the inferoposterior wall (arrows). CTA = computed tomography angiography; LV = left ventricle; UHR = ultra-high-resolution.

Figure 3. Myocardial Scar on Photon-Counting Computed Tomography and Magnetic Resonance Imaging (A) Photon-counting detector computed tomography late iodine enhancement map and (B) magnetic resonance imaging late gadolinium enhancement show matching transmural scar (arrow) in the posteroinferior wall, consistent with nonviable right coronary artery territory myocardium.

To confirm the PCCT findings, the patient underwent digital subtraction angiography (DSA) and cardiac magnetic resonance. DSA corroborated the chronic total in-stent occlusion of the dominant RCA, demonstrating a complete interruption of antegrade flow at the proximal edge of the stent. Crucially, DSA and PCCT together provided a complementary evaluation of the complex collateral network: DSA visualized the dynamic recruitment of robust intercoronary collaterals (Werner class CC2) originating from the left anterior descending artery, which retrogradely filled the distal RCA territory (Figure 4). Subsequent cardiac magnetic resonance sequences (perfusion and late gadolinium enhancement) showed high concordance with the PCCT-derived findings; magnetic resonance perfusion imaging verified a rest perfusion defect that precisely matched the iodine maps in location and transmurality. Furthermore, quantitative PCCT-derived extracellular volume estimates showed high agreement with cardiac magnetic resonance reference standards; the late gadolinium enhancement mirrored the PCCT-derived late iodine enhancement with high spatial fidelity (Figure 3B). This multimodality alignment confirmed a nonviable transmural scar, providing the definitive evidence required for the heart team to opt for a management strategy.

Figure 4. Invasive Angiography (Digital Subtraction Angiography) (A) Right coronary artery (RCA) angiogram showing total in-stent occlusion of the RCA (right arrow), while the left arrow points to collateral branches arising from the proximal RCA. (B) Left anterior descending artery (LAD) angiogram showing patent LAD with septal and epicardial collaterals supplying retrograde flow to the distal RCA (arrow).

Within this multimodality framework, each imaging modality contributed complementary and incremental value: PCCT provided a comprehensive anatomical and functional assessment, DSA enabled real-time characterization of collateral flow dynamics, and cardiac magnetic resonance served as the reference standard for myocardial viability. Together, these integrated findings confirmed a nonviable transmural scar and provided the decisive evidence for confident clinical decision-making.

Management

The heart team’s decision-making was guided by an integrated anatomical-functional assessment. PCCT played a pivotal role by providing high-confidence confirmation of true in-stent occlusion and co-registered perfusion assessment, thereby reducing diagnostic uncertainty beyond angiography alone. In conjunction with magnetic resonance imaging–confirmed nonviable myocardium and robust collateral supply on DSA, these findings supported a conservative management strategy, avoiding potentially unnecessary high-risk intervention.

Outcome and Follow-Up

The patient was discharged following conservative medical management in stable condition. At short-term follow-up, he remained asymptomatic with no recurrence of chest pain.

Discussion

Accurate assessment of in-stent restenosis and total occlusions remains challenging with conventional CT techniques, particularly in small-caliber stents. PCCT marks a paradigm shift in cardiovascular imaging, effectively overcoming the “3-mm imaging barrier” that has long hampered conventional energy-integrating detector CT (EID-CT). In conventional coronary computed tomography angiography, metallic stent struts frequently produce pronounced stent blooming artifacts and electronic noise, which lead to a significant overestimation of stenosis severity and a high rate of nondiagnostic evaluations in small-caliber vessels. In our case, in-stent patency assessment on UHR PCCT was based on direct visualization of intraluminal contrast opacification and distal runoff, allowing reliable differentiation between severe stenosis and complete occlusion. This overcomes the key limitation of EID-CT, where blooming artifacts hinder accurate lumen evaluation and reduce diagnostic confidence.The diagnostic accuracy of PCCT in stent assessment has been robustly validated in recent literature. A landmark study by Sakai et al involving over 7,800 patients reported that PCCT increases per-patient specificity to 98% (compared with 93% for EID-CT) and significantly reduces unnecessary invasive coronary angiography referrals. Furthermore, Hagar et al demonstrated that UHR PCCT achieves a sensitivity of 100% and a specificity of 87% for coronary stent patency, even in high-risk populations with heavy calcification. By accurately delineating the 2.8-mm distal stent lumen in our patient, PCCT demonstrated high-resolution visualization beyond the limitations of conventional imaging, matching the diagnostic precision of DSA.A key transformative feature of PCCT is its capacity for a “one-stop-shop” assessment, combining high-resolution anatomical detail with functional myocardial characterization. The integration of spectral-derived iodine mapping in our case identified a transmural perfusion defect with perfect concordance with cardiac magnetic resonance findings. This synergy mirrors the outcomes of the ADVANTAGE study, which established that the addition of CT perfusion to computed tomography angiography significantly boosts diagnostic accuracy for in-stent restenosis to 96.1%. Recent data from Klambauer et al further confirm this reliability, reporting a Kappa coefficient of up to 0.956 for the agreement between PCCT late enhancement and cardiac magnetic resonance. Despite its promising capabilities, PCCT has several important limitations that may restrict its broader clinical application. Its availability remains limited to select advanced centers, and the associated high acquisition and maintenance costs further constrain widespread use. Radiation dose and contrast use are comparable to contemporary coronary computed tomography angiography protocols, although optimization is ongoing. In addition, broader clinical adoption is currently limited by the lack of large multicenter outcome studies, as well as the absence of standardized interpretation criteria and practical challenges in integrating PCCT into routine clinical workflows.Finally, the ability of PCCT to provide a comprehensive, noninvasive evaluation of both stent patency and myocardial viability directly influenced high-stakes clinical decision-making. The visualization of total in-stent occlusion alongside robust collateralization and a confirmed transmural scar allowed the heart team to confidently prioritize a conservative management strategy. This approach avoided high-risk invasive revascularization in a stable patient by definitively identifying nonsalvageable myocardium, highlighting the potential utility of PCCT as a noninvasive imaging tool in complex coronary artery disease.

Conclusions

UHR PCCT provides a comprehensive, noninvasive “one-stop-shop” for managing complex coronary artery disease. By integrating UHR anatomical detail with definitive tissue characterization, PCCT facilitates clinical decision-making while simplifying diagnostic workflows. This technology represents a shift toward high-fidelity, less invasive diagnostic imaging and suggests a potential role for PCCT in cardiovascular care. However, this is a single case report and is not sufficient to draw definitive conclusions, and should be further validated in larger-scale studies.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Comment: This is not a complete case report

Examination Protocol

Images: Royal Healthcare Heart Stroke & Cancer Center, Singapore

Mohammed Bin Khalifa Bin Salman Al Khalifa Specialist Cardiac Centre (MKCC), Bahrain

June 3, 2026

lntroduction
Cardiovascular care and imaging requirements have undergone a significant transformation in recent years. Advanced diagnostic imaging must rise to meet the increasing complexity of patient needs, ensuring precise, tailored diagnostics and improved clinical outcomes. The introduction of dual-source photon­counting CT systems has marked a revolutionary step in cardiac imaging. These systems utilize native temporal resolution and sub-second scanning, enabled by their unparalleled rotational speed and high-pitch capabilities.

This state-of-the-art technology delivers exceptional image clarity, even in the most challenging clinical scenarios, and has opened new avenues for cardiac imaging.

In this article, we aim to highlight the impact of this technology by presenting 10 cases performed du ring the early days of the photon-counting detector (PCD) system implementation in our department. These cases underscore the potential of PCD systems to enhance diagnostic accuracy and optimize patient care.

Ultra-High-Resolution Cardiac CT lmaging with Photon­-Counting CT Technology
The advent of Ultra-High-Resolution (UHR) photon-counting CT (PCD-CT) technology is revolutionizing cardiac imaging, providing unmatched clarity and enhanced diagnostic capabilities. With the ability to deliver images at 0.2 mm and 0.4 mm slice thickness, UHR PCD-CT enables visualization of minute anatomical details of the heart and vessels that were previously undetectable. This groundbreaking advancement is setting a new benchmark in cardiovascular diagnostics, paving the way for more precise and tailored patient care. In this article, we discuss the early experiences and findings from the initial days of PCD-CT implementation in our department.

Advantages in Highly Calcified Vessels
One of the key challenges in cardiac imaging has been the accurate evaluation of heavily calcified vessels. Calcifications often obscure the visualization of vascular structures and impede precise disease quantification, leading to diagnostic uncertainty. UHR PCD-CT overcomes this limitation by delivering exceptional spatial resolution and significantly reducing blooming artifacts. This advanced technology enables accurate assessment of coronary stenosis, even in cases with severe calcification, allowing clinicians to distinguish between calcified plaque and true vessel lumen. By improving diagnostic confidence and facilitating more precise treatment planning, UHR PCD-CT represents a major advancement in the management of patients with complex coronary artery disease.

Enhanced Stent Evaluation
Stent assessment is another area where UHR PCD-CT demonstrates significant advantages. lts advanced resolution capabilities overcome the limitations of conventional CT in visualizing stent struts and accurately detecting in-stent restenosis. This enhanced imaging quality ensures more reliable follow-up evaluations, enabling clinicians to make better-informed decisions for patients with prior stent placement, ultimately improving patient outcomes.

Pre- and Post-Cardiac Prosthesis Evaluation
Ultra-High-Resolution UHR PCD-CT has proven invaluable for both pre- and post-procedural evaluation of cardiac prostheses. lts ability to capture intricate anatomical details facilitates meticulous planning of interventions, ensures the accurate placement of prosthetic devices, and enables thorough monitoring of their performance post-implantation. This advanced imaging technology significantly enhances procedural outcomes and long-term patient care.

lmproved Coronary Stenosis Quantification Accuracy
Compared to conventional energy-integrating detector (EID) CT systems, Ultra-UHR PCD-CT offers a significant improvement in the quantification of coronary stenosis, particularly in plaques with calcified components. This enhanced capability leads to more accurate disease assessment and allows clinicians to develop more targeted and effective treatment plans.

High Diagnostic Accuracy in CAD Detection
UHR PCD-CT Angiography has demonstrated exceptional diagnostic accuracy in detecting coronary artery disease (CAD), even in high-risk populations. lts ability to assess patients with severe coronary calcification or prior stent placement makes it an indispensable tool in modern cardiology, enhancing both diagnostic precision and treatment planning.

Methods: Scan Technique
Patients were scanned using the NAEOTOM Alpha® CT scanner. This advanced imaging platform features a state-of-the-art Al-powered cardiac imaging package. The illustrated cases were performed with UHR PCD-CT protocols that facilitate slice thicknesses of 0.2 mm and 0.4 mm with the possibility of high-sharp kernel reconstructions. Protocols were adapted according to the patient's heart rate and included:

• Adaptive Perspective Acquisition (CorAdSeq)
• Adaptive Retrospective Acquisition
• Prospective ECG-Triggered Sequences (0.2 mm and 0.4 mm)

These protocols, combined with Al-driven algorithms and dual­source CT (DSCT) technology, ensure optimal image quality with the lowest achievable radiation dose. The automatic exposure control for kV and mAs further minimizes patient-specific dose requirements, enhancing both safety and efficiency.

Ultra-High-Resolution imaging using PCD technology
UHR reconstruction is a key advantage of the PCD detector. Due to the small pixel size mentioned earlier, current PCD-CT scanners achieve superior in-plane and longitudinal spatial resolution compared to conventional clinical energy-integrating detector (EID) CT systems, with resolutions as fine as 150 µm. This enhanced resolution facilitates the evaluation of in-stents and the imaging of heavily calcified vessel lumen structures.

Clinical Case Studies
Multi-ln-Stent Evaluation - Proximal and Distal

Figure 1. Coronary CT Imaging of the Left Anterior Descending (LAD) Artery and Branches for In-Stent Patency Evaluation Using an Ultra-High-Resolution Photon-Counting CT Protocol: Coronary CT imaging of the left anterior descending (LAD) artery and its branches for in-stent patency evaluation was performed using a photon-counting CT (Ultra-High-Resolution protocol. Reconstructions included consecutive slice thicknesses with tailored kernel applications: 0.2 mm with an ultra-sharp kernel, 0.4 mm with a sharp kernel, and 0.6 mm with a soft kernel. Optimized windowing further enhanced the visualization of the stent lumen and adjacent structures, highlighting the protocol’s advanced diagnostic capabilities.

Figure 2. Coronary CT Imaging for In-Stent Patency Evaluation: Coronary CT imaging using an Ultra-High-Resolution (UHR) photon-counting CT protocol with adaptive sequence acquisition offers significant dose reduction while ensuring excellent image clarity. Images were reconstructed at 0.2 mm, 0.4 mm, and 0.6 mm slice thicknesses. Key technical details include protocol CTDIvol of 5.43 mGy, 192 mAs exposure, and 90 kVp tube voltage. A contrast protocol of 60 mL was administered at a flow rate of 6 mL/s. Multi-kernel reconstructions enhanced the evaluation of in-stent patency, with Spider views and ciné VRT images of stents in the left anterior descending artery (LAD), LAD to obtuse marginal branch 1 (OM1), and right coronary artery (RCA). These high-resolution images allowed confident assessment without artifacts or diagnostic ambiguity.

Figure 3. Coronary CT Imaging of the Left Anterior Descending (LAD) Artery and Branches for In-Stent Patency Evaluation Using an Ultra-High-Resolution Photon-Counting CT Protocol: Coronary CT imaging of the left anterior descending (LAD) artery and its branches for in-stent patency evaluation was performed using a photon-counting CT (Ultra-High-Resolution protocol. Reconstructions included consecutive slice thicknesses with tailored kernel applications: 0.2 mm with an ultra-sharp kernel, 0.4 mm with a sharp kernel, and 0.6 mm with a soft kernel. Optimized windowing further enhanced the visualization of the stent lumen and adjacent structures, highlighting the protocol’s advanced diagnostic capabilities.

LAD - UHR 0.2mm	LAD - UHR 0.2 mm	RCA - UHR 0.2mm
CINI VRT Spider view with sharp kernel	RCA - UHR 0.2 mm	RCA - UHR 0.2 mm
RCA - VRT	LAD - second stent VRT

Images: Courtesy of Mohammed Bin Khalifa Bin Salman Al Khalifa Specialist Cardiac Centre (MKCC), Bahrain

Figure 2. ACTA protocol workflow illustrating the combined acquisition strategy: non-contrast CAC scoring, UHR coronary CTA, rapid thoraco-cervical high-pitch sweep, and delayed ECG-triggered late iodine enhancement imaging.

Source: De Gori et al., European Heart Journal – Imaging Methods and Practice, 2026.

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Examination protocol

BP, blood pressure; CAC, coronary artery calcium; CCTA, coronary CT angiography; COPD, chronic obstructive pulmonary disease; ECG, electrocardiogram; ECV, extracellular volume; HR, heart rate; LIE, late iodine enhancement; DLP, dose-length product; UHR, ultra-high resolution; VMI, virtual monoenergetic images.

De Gori C, Aimo A, Latorre L, et al. Single-session photon-counting CT protocol for simultaneous screening of coronary and carotid artery disease and lung pathology. Eur Heart J Imaging Methods Pract. 2026;4(1):qyag074.