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FIGURE 1. a) Relative distribution of the radiologists' assessments regarding image quality, sharpness and noise on a Likert scale from 1 (insufficient) to 5 (very good). b) Bar chart showing the average radiation dose in radiation-sensitive thoracic organs for both computed tomography modalities, along with the corresponding radiation dose reduction factor achieved by the use of photon-counting detector computed tomography (PCCT), with a five-fold reduction benchmark indicated by a red dashed line. c) Representative axial slices of lesions obtained using the virtual navigation bronchoscopy protocol, with energy-integrating detector computed tomography (EID-CT) (top) and PCCT (bottom) shown for different subjects. Lesions are located in the right upper lobe (left column) and the right lower lobe (right column), emphasising improved image quality, enhanced sharpness and reduced noise, as assessed by radiologists.

Source: Opitz M, Funke F, Darwiche K, et al. First assessment of photon-counting CT for virtual bronchoscopic navigation. Eur Respir J. 2025;65(4):2402476. doi:10.1183/13993003.02476-2024.

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Figure 1. Comparison of CXR and ULD-CT in 6 patients of our study cohort demonstrating the clinical significance and the limitations of ULD-CT. a, b Consolidation in the right lower lobe, occult in the CXR hidden behind the right diaphragm. c, d Bilateral opacities, occult in the CXR due to the low density. e, f Bilateral opacities in the CXR; the ULD-CT shows the pattern of an organizing pneumonia as additional information. g, h Bilateral opacities in the CXR; the ULD-CT shows the pattern of sarcoidosis as additional information. i, j Bilateral opacities in the CXR; the ULD-CT shows pleural masses. k, l Basal opacities in CXR and consolidation and pleural effusion in ULD-CT; for the diagnosis of a pleural empyema, the ULD-CT was not sufficient and a standard CT with contrast was needed.

Protocol

Key Results

Source:
Dettmer S, Werncke T, Nikolova Mitkovska V, Brod T, Joean O, Vogel-Claussen J, Wacker F, Welte T, Rademacher J. Photon Counting Computed Tomography with the Radiation Dose of a Chest X-Ray: Feasibility and Diagnostic Yield. Respiration. 2024;103(2):88–94. doi:10.1159/000536065.

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Figure 2. Case examples for photon-counting detector CT–derived images in adrenal adenoma. Left column: Axial true unenhanced (TUE) images. Middle column: Virtual unenhanced (VUE) images. Right column: Corresponding contrast-enhanced portal venous phase images. (A–C) Images in a 79-year-old woman with lipid-rich adenoma of the left adrenal gland. VUE images led to overestimation of adrenal gland attenuation, which hampered correct classification as lipid-rich adenoma using the 10-HU threshold. (D–F) Images in a 65-year-old woman with lipid-rich adenoma in the left adrenal gland. Classification based on VUE images was in concordance with classification based on TUE images, albeit with a slight overestimation of attenuation on VUE images. (G–I) Images in a 79-year-old woman with lipid-poor adenoma in the left adrenal gland show high contrast material enhancement. VUE images led to 12-HU underestimation when compared with TUE attenuation, which would still result in the correct classification.

Protocol

Key Results

Source: Lennartz S, Schoenbeck D, Kröger JR, Borggrefe J, Niehoff JH. Photon-counting CT Material Decomposition: Initial Experience in Assessing Adrenal Adenoma. Radiology. 2023;306(1):202–204. doi:10.1148/radiol.220919.

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Practical PCCT takeaway:

Low-keV reconstructions are attractive for increasing iodine conspicuity, but they should not be used uncritically for HU-based renal lesion characterization. For renal cyst enhancement, 70 keV appears to be a safer reference reconstruction in this study.

The observed misclassification was not significantly dependent on cyst size, location, or patient BMI, suggesting that the VMI energy itself is the dominant issue.

Protocol:

Clinical PCCT, 120 kVp, image-quality level 68; triphasic examination. Venous-phase VMIs were reconstructed from 40–190 keV in 10-keV increments. Only cysts ≥7 mm confirmed as non-enhancing (<10 HU difference between unenhanced and venous 70-keV images) were analyzed.

Source: Schade KA, Mergen V, Sartoretti T, Alkadhi H, Euler A. Pseudoenhancement in Cystic Renal Lesions – Impact of Virtual Monoenergetic Images of Photon-Counting Detector CT on Lesion Classification. Academic Radiology. 2023;30(Suppl 1):S305-S313. doi:10.1016/j.acra.2023.04.005. Published online May 5, 2023.

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Image taken from LinkedIn:

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Source: Huang R, Yang Y, Gao M, et al. Eur J Radiol. 2026;195:112596.

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Figure 2: CT attenuation measurements in a 58-year-old man referred for follow-up examination after an acute type B aortic dissection. Axial CT images acquired with photon-counting detector CT depict exemplary region-of-interest (ROI) measurements on venous virtual noncontrast reconstructions. avg = average attenuation within region of interest; d = diameter of region of interest.

Protocol

Key Results

The liver showed particularly small VNC attenuation errors, with left-lobe mean errors around 1.5 HU. Phantom testing confirmed higher and blotchier VNC noise but similar middle-frequency spatial resolution and a detectability index consistently above 20.

Take-home: PCCT VNC can provide quantitatively accurate abdominal attenuation without a dedicated noncontrast acquisition. The principal trade-off is higher, blotchier image noise and somewhat poorer subjective image quality, although diagnostic quality remained very high.

Source: Mergen V, Racine D, Jungblut L, et al. Virtual Noncontrast Abdominal Imaging with Photon-counting Detector CT. Radiology. 2022;305(1):107–115. doi:10.1148/radiol.213260.

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Figure 1. Axial photon-counting CT images at (A) 0.4-mm, (C) 2-mm, and (D) 4-mm section thickness demonstrate an incidental hypoattenuating pancreatic lesion (arrowhead). The lesion communicates with the main pancreatic duct via a connection (arrow) visible at 0.4-mm section thickness. (B) Iodine overlay image at 0.4-mm section thickness displays iodine content in orange, demonstrating no uptake within the hypoattenuating lesion or main duct communication.

Figure 2. Coronal cinematic rendering of the intraductal papillary mucinous neoplasm (arrowhead) in relation to the pancreatic duct

Figure 3. Axial T2-weighted image at 5-mm section thickness from MR cholangiopancreatography confirms the cystic nature of the lesion (arrow) but does not show the connection to the main pancreatic duct.

Source: Khanungwanitkul K, Schwartz FR. Photon-Counting CT Shows Side-Branch Intraductal Papillary Mucinous Neoplasm–Pancreatic Duct Connection. Radiology. 2024;312(2). doi:10.1148/radiol.240611.

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Source: Graafen D, Müller L, Halfmann MC, et al. Soft Reconstruction Kernels Improve HCC Imaging on a Photon-Counting Detector CT. Academic Radiology. 2023;30(Suppl 1):S143–S154. doi:10.1016/j.acra.2023.03.026.

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Figure 1. Example of semiautomatic segmentation of a left adrenal adenoma using 3D Slicer.

Protocol

Key Results

Source:
Bette S, Risch F, Canalini L, Becker J, Leithner EV, Huber A, Haerting M, Jehs B, Wollny C, Schwarz F, Tehlan K, Scheurig-Muenkler C, Wendler T, Kroencke T, Decker JA. Diagnostic performance of photon-counting detector CT for differentiation between adrenal adenomas and metastases. European Radiology. 2024;34:5944–5953.

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Figure 4. Example of PCD-VMIs (40–190 keV) in a patient with hypovascularized liver metastases of pleura mesothelioma. Hypovascularized metastasis in segment VI (arrow).

Protocol

Key Results

Source:
Bette S, Decker JA, Braun FM, Becker J, Haerting M, Haeckel T, Gebhard M, Risch F, Woźnicki P, Scheurig-Muenkler C, Kroencke TJ, Schwarz F. Optimal Conspicuity of Liver Metastases in Virtual Monochromatic Imaging Reconstructions on a Novel Photon-Counting Detector CT—Effect of keV Settings and BMI. Diagnostics. 2022;12(5):1231. doi:10.3390/diagnostics12051231.

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Figure 3. (A): Axial 70 keV reconstruction as well as VNC and iodine maps of a left renal mass in a portal venous CT scan of the abdomen. The lesion shows elevated HU in 70 keV (75 HU), VNC values of 66 HU (B) and 13 HU for iodine map CT values (C). (D,E): Contrast-enhanced ultrasound confirmed that there was no contrast medium uptake. (F–H): Example of a renal mass without solid components and elevated CT values in iodine maps in comparison to the first patient (52 HU) and similar values in 70 keV reconstructions (86 HU) compared to the confirmed renal cyst (A). Contrast-enhanced ultrasound confirmed a contrast enhancement (green arrow in (I,J)) and histopathology revealed the diagnosis of a renal cell carcinoma.

Protocol

Key Results

Source:
Becker J, Feitelson L-M, Risch F, Canalini L, Kaufmann D, Wudy R, Jehs B, Haerting M, Wollny C, Scheurig-Muenkler C, et al. Spectral Differentiation of Hyperdense Non-Vascular and Vascular Renal Lesions Without Solid Components in Contrast-Enhanced Photon-Counting Detector CT Scans—A Pilot Study. Diagnostics. 2025;15(1):79. https://doi.org/10.3390/diagnostics15010079

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Figure 4. Increased peripheral pulmonary artery visibility with ultra-high-resolution photon-counting CT. UHR-PCD-CTPA at IQ50 (A) and IQ25 (B) vs. EID-CTPA (C). Representative measurements of the minimal distance of the last discernible pulmonary artery branch to the pleura are shown (orange line, in mm). CTPA, CT pulmonary angiography; EID, energy-integrating detector; IQ, image quality index; PCD, photon-counting detector; UHR, ultra-high resolution

Source: Pannenbecker P, Rüth C, Grunz JP, et al. Increasing pulmonary artery visibility and diagnostic confidence with ultra-high resolution photon-counting detector CT pulmonary angiography. European Radiology. 2026.

Protocol

Comparison protocol (reference EID-CT)

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Figure 1. Visualization of the workflow followed in this study, including CT scanning, VMI generation, SPR estimation using the Hünemohr method (Hünemohr et al 2014), and a proton plan was created on the phantom. Additionally, the three assessments, phantom size-, traversed tissue type-, and proton energy-dependency are shown with the quantification of proton range, defined as the range at the 80% distal fall-off (R80) per proton spot, to assess range differences. Abbreviations: SPR—stopping-power ratio, DECT—dual-energy computed tomography, PCCT—photon-counting CT.

Source:
Lustermans D, Fonseca GP, Vilches-Freixas G, et al. Evaluation of proton range differences in photon-counting and dual-energy computed tomography across imaging doses and anthropomorphic phantom sizes. Physics in Medicine & Biology. 2026;71:065008.

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Key Results

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Fig. 1. Patient 9 PCD-CT reconstructions. A) Virtual monoenergetic image of 70 keV (VMI70) without iterative metal artifact reduction (iMAR); B) VMI70 with iMAR; C) Relative electron density (RED) image with iMAR. All images shown in the abdomen window (CT values between −125 and 225 HU). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Source: Lamaj E, Wohlfahrt P, Wilke L, et al. Photon-counting detector computed tomography in treatment planning of head-and-neck cancer. Physics and Imaging in Radiation Oncology. 2026;39:100995.

Protocol

Lamaj E, Wohlfahrt P, Wilke L, et al. Photon-counting detector computed tomography in treatment planning of head-and-neck cancer. Physics and Imaging in Radiation Oncology. 2026;39:100995.

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Figure 4. Patient with right-sided breast tumor (arrow) of no special type, G2, ER+/PR+/HER2-, visualized in breast MRI at initial diagnosis with T1w-subtraction after contrast administration (a) and fat-saturated T2w sequence (b). Photon-counting detector computed tomography with monoenergetic reconstruction (c, e) and iodine map (d, f) shows the tumor at initial tumor staging before NAST (c, d) and with a marked decline of tumor size after NAST (e, f). ER, Estrogen receptor; HER2, Human epidermal growth factor receptor; MRI, Magnetic resonance imaging; NAST, Neoadjuvant systemic therapy; PR, Progesterone receptor

Source: Source: Neubauer et al., European Radiology Experimental, 2025.

Protocol

Neubauer C, Nattenmüller J, Bamberg F, Windfuhr-Blum M, Neubauer J. Breast cancer assessment under neoadjuvant systemic therapy using thoracic photon-counting detector computed tomography in prone position: a pilot study. Eur Radiol Exp. 2025;9:41. doi: 10.1186/s41747-025-00576-z.

Courtesy of Al‑Ahli Hospital, Doha, Qatar. College of Medicine, QU Health, Qatar University, Doha, Qatar

April 13, 2026

Abstract
Small bowel ischemia remains difficult to diagnose early, especially when caused by extrinsic mechanical compression rather than vascular occlusion. Photon counting Computed Tomography (PCCT) allows iodine-based perfusion assessment with significantly improved spectral resolution.

Case presentation:
A 55-year-old woman with multiple comorbidities presented with acute severe lower abdominal pain and vomiting. Conventional imaging revealed a closed-loop small bowel obstruction without definitive evidence of ischemia. PCCT iodine mapping demonstrated a sharply demarcated segment of absent iodine enhancement in a distal ileal loop, indicating loss of perfusion in that segment. Urgent exploratory laparotomy identified a dense fibrous uterine band causing complete obstruction and an ischemic 40 cm ileal loop, which required resection with primary anastomosis.

Conclusion:
PCCT iodine mapping enabled early identification of bowel ischemia when standard CT was nondiagnostic. This case highlights PCCT’s growing value in emergency abdominal imaging.

Keywords: Fibrotic bad, Bowel Ischemia, Iodine Mapping, Photon Counting CT

Introduction

Small bowel ischemia is a life-threatening condition with reported mortality rates exceeding 50% when diagnosis is delayed. Early symptoms are nonspecific, and laboratory values such as leukocytosis, lactate, and CRP may remain normal until late stages, limiting clinical detection. [1] Conventional CT is the first line modality, yet its early-stage diagnostic sensitivity remains limited, sometimes as low as 64%, particularly before mucosal necrosis or pneumatosis develop. [1]

Dual energy CT (DECT) introduced iodine-based perfusion mapping, improving sensitivity in early ischemia. [2] However, DECT detectors are still energy integrating and subject to noise and reduced spectral precision.

Photon counting CT (PCCT) represents a major technological advancement. PCCT directly counts individual X-Ray photons and sorts them by energy, enabling higher spatial resolution, reduced electronic noise, and more accurate iodine quantification. [3] This makes PCCT particularly useful for detecting subtle perfusion changes, including early ischemia.

Fibrotic uterine origin bands represent an exceptionally rare etiology of small bowel obstruction and ischemia. Pelvic adhesions occur in more than 50% of women following Caesarean delivery. [5] Yet reports of uterine fibrotic bands producing closed loop ischemia are extremely scarce.

This case demonstrates how PCCT iodine maps identified critical ischemia despite standard images appearing inconclusive.

Clinical Case Study 1

A 55-year-old woman presented to the Emergency Department with acute, severe abdominal pain that had begun earlier that morning. The pain was continuous and predominantly localized in the lower abdomen, without radiation. She reported two episodes of vomiting and one bowel movement on the day of presentation, with no associated diarrhea. There was no history of fever, dysuria, hematuria, or other urinary symptoms. She described experiencing a similar but self-limiting episode of abdominal pain approximately two months earlier, which had resolved without medical intervention.

The patient had multiple chronic comorbidities, including type 2 diabetes mellitus, ischemic heart disease status post percutaneous coronary intervention, hypertension, dyslipidemia, depression, and overweight. She was a lifelong non-smoker. Her regular medications included insulin, ezetimibe/atorvastatin, acetylsalicylic acid, bisoprolol, and evolocumab. She had a surgical history of a cesarean section and a laparoscopic sleeve gastrectomy.

On clinical examination, the patient was alert but in moderate distress due to pain. She was hemodynamically stable, with no signs of shock. Abdominal examination revealed generalized guarding and central abdominal tenderness, with a firm lower abdomen more pronounced on the right side. Laboratory investigations showed potassium of 3.2 mmol/L, creatinine of 51 µmol/L, urea of 2.7 mmol/L, white blood cell count of 12.9 × 10⁹/L, hemoglobin of 13.4 g/dL, C-reactive protein of 1.5 mg/L, and random blood glucose of 159 mg/dL.

Initial non-contrast CT of the abdomen demonstrated mildly distended, fluid-filled distal ileal loops in the pelvis, measuring up to 2.2 cm, with mild mucosal thickening and associated mesenteric congestion. These findings raised concern for early vascular compromise or a developing small bowel obstruction. A small volume of pelvic free fluid was also noted (Fig. 1).

Fig.1: Coronal CT scan (without contrast) showed a fibrotic band extending from the fundus of uterus upward to the site of transitional zone (blue arrow), with focal segment of distal small bowel with early ischemic changes (yellow arrow).

Contrast-enhanced CT abdomen and pelvis with oral and intra-venous contrast revealed increased free intraperitoneal fluid. Oral contrast limited to the proximal small bowel, which appeared normal. A distal small bowel loop in the left lower abdomen showing significant wall edema and poor enhancement on arterial and venous phases. Marked mesenteric congestion around the affected loop. Fibrotic band extending from the fundus of uterus, up to the site of transitional zone. No pneumatosis or portal venous gas were noted. Patent superior mesenteric artery and superior mesenteric vein. Indeterminate transition point.

These findings were equivocal for bowel ischemia. The impression was closed-loop small bowel obstruction with suspected vascular compromise, likely secondary to adhesions, with progressive features concerning for bowel ischemia. Fig. (2)

Fig 2: Coronal CT scan (oral and IV contrast) showed a fibrotic band (yellow arrow) extending from the fundus
of uterus (blue arrow) upward to the site of transitional zone.

Fig 2: Sagittal CT scan (oral and IV contrast) showed a fibrotic band extending from the fundus of uterus
upward to the site of transitional zone.

PCCT Iodine Mapping revealed a 30–50 cm segment of distal ileum with complete absence of iodine enhancement, with a sharply defined cutoff compared to adjacent normally enhanced loops. This pattern strongly suggested severe perfusion failure despite nondiagnostic conventional CT findings.

Fig. 4: Axial PCCT scan (left) (oral and IV contrast) iodine mapping showed a normal mucosal iodine uptake
(yellow arrow). Axial conventional CT scan (right) (oral and IV contrast) showed faint normal mucosal contrast uptake
(yellow arrow).

Fig. 5a: Comparative axial images between iodine mapping image and conventional CT scan image.	Fig 5b: Yellow arrow showed focal segment of small bowel devoted from iodine /contrast uptake, blue arrow showed normal mucosal enhancement.
Fig.6a: Comparative coronal images between iodine mapping image and conventional CT scan image	Fig. 6b: Blue arrow showed focal segment of small bowel devoted from iodine /contrast uptake, yellow arrow showed normal mucosal enhancement.
Fig. 7a: Comparative sagittal images between iodine mapping image and conventional CT scan image	Fig. 7b: Yellow arrow showed focal segment of small bowel devoted from iodine /contrast uptake, blue arrow showed normal mucosal enhancement.

The patient underwent an urgent exploratory laparotomy, which revealed a large volume of serous peritoneal fluid and an ischemic loop of small bowel centrally located within the peritoneal cavity.

A dense fibrous band extending from the right posterior uterine wall to the posterior abdominal wall near the right iliac fossa was identified, causing complete small bowel obstruction.

The fibrous band was divided and excised. The compromised small bowel segment measured approximately 40 cm and was located about 1 meter proximal to the ileocecal junction. Despite repeated application of warm saline and observation for 25 minutes, there was no meaningful improvement in perfusion.

A resection of the non-viable segment was therefore performed, followed by side-to-side anastomosis using a linear stapler. The staple line was reinforced with a second layer of sutures. A pelvic drain was placed. The procedure was completed without intraoperative complications.

The patient showed gradual improvement postoperatively. Her nasogastric tube and Foley catheter were removed on postoperative day 1. She passed flatus on postoperative day 2 and had her first bowel movement on day 3.

During recovery, she developed a chest infection, which was evaluated and treated by pulmonology, then she was discharged on postoperative day 6 in stable condition.

Gross examination of the band revealed an irregular, firm tissue fragment measuring 1.5 x 1 x 0.5 cm. Microscopical examination revealed a vascularized fibrous tissue band.

Discussion

Small bowel ischemia continues to be one of the most challenging abdominal emergencies to diagnose early. Clinical presentation is often nonspecific, and laboratory markers remain limited in sensitivity. Conventional CT, although essential, frequently lacks sensitivity in early stages.

PCCT provides significant advantages due to its ability to detect subtle enhancement differences and quantify iodine concentration with high precision. Compared to DECT, PCCT offers superior energy resolution, reduced noise, and improved contrast to noise ratios, contributing to better visualization of bowel wall perfusion abnormalities.

PCCT images appeared inconclusive, iodine maps revealed a complete lack of enhancement in a diseased segment, providing diagnostic clarity. This timely detection enabled urgent surgical intervention, preventing perforation and further complications.

Fibrotic bands arising from the uterus are exceptionally uncommon. Although pelvic adhesions after Caesarean delivery are common, fibrotic uterine bands producing strangulating obstruction are sparsely documented.

Conclusion

PCCT iodine mapping enabled early recognition of small bowel ischemia secondary to a rare uterine fibrotic band. When conventional CT is equivocal, PCCT offers critical diagnostic insight by precisely evaluating bowel perfusion.

References

1. Menke J. Diagnostic accuracy of multidetector CT in acute mesenteric ischemia. Radiology. 2010;256(1):93–101.
2. Giraud R, Hetzel J, Bader H, et al. Assessment of small bowel ischemia using dual-energy CT iodine concentration. Diagn Interv Imaging. 2025;106(4):126–134.
3. Schwarz F et al. Photon-counting CT: abdominal applications. Br J Radiol. 2024.
4. Shaheen NH et al. Photon-counting CT for diagnosis of bowel infarction. Radiol Case Rep. 2022;17(5):1674–1677.
5. Attard JA, MacLean AR. Adhesive small bowel obstruction. Can J Surg. 2007;50(4):291–300.

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Figure 2. (a) A 86-year-old female who presented with abdominal pain. Reconstructed iodine quantification map of the axial CT image shows the left kidney with renal cyst. For homogeneous lesions, one ROI was placed in the interior of the renal lesion, as large as possible to cover the entire lesion (yellow arrow pointing to the ROI shown as yellow circle). (b) A 64-year-old female presented for RCC staging. A reconstructed iodine quantification map of the axial CT image shows the right kidney with renal neoplasm. For heterogeneous lesions, after the placement of the first ROI (yellow arrow pointing to the ROI shown as yellow circle), a secondary ROI (yellow star marking the ROI shown as yellow circle) was placed on the area of the highest conspicuity of iodine concentration. (CT: Computed tomography, RCC: Renal cell carcinoma, ROI: Region of interest).

Source: Tóth et al., Journal of Clinical Imaging Science, 2024

Protocol

Tóth A, Chamberlin JH, Mendez S, Varga-Szemes A, Hardie AD. Iodine quantification of renal lesions: Preliminary results using spectral-based material extraction on photon-counting CT. J Clin Imaging Sci. 2024;14:7. doi:10.25259/JCIS_1_2024

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Figure 3. Representative abdominal PVP scans from both a photon-counting detector CT (PCCT) and an energy-integrating detector CT (EID-CT), illustrating comparable image quality (IQ). Image A and B were rated as moderate and image D and E as good by both observers. Image C and F are the 55 keV reconstructions of image B and E respectively but were not assessed subjectively.

Protocol

Hoeijmakers EJI, Stammen L, Wildberger JE, et al. PCD-CT enables contrast media reduction in abdominal imaging compared to an individualized kV-adapted contrast media injection protocol on EID-CT. Eur J Radiol. 2024;179:111680.

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Figure 4. PCCT images of the pancreas with a superior mesenteric artery encasing PDAC in arterial (A–C) and portal venous (D–F) contrast phase. A and D are polyenergetic reconstructions. B and E are monoenergetic reconstructions at 40 keV. C and F are monoenergetic reconstructions at 70 keV.

Source: Woeltjen et al., European Journal of Radiology, 2024

Protocol

Woeltjen MM, Niehoff JH, Roggel R, et al. Pancreatic cancer in photon-counting CT: Low keV virtual monoenergetic images improve tumor conspicuity. Eur J Radiol. 2024;173:111374.

Jingyi Liu, MD*; Prof. Liang Zhu, MD*; Xi Zhao, MD**; Prof. Feng Feng, MD*

* Department of Radiology, Peking Union Medical College, Beijing, P. R. China** Siemens Healthineers, China

October 24, 2025

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History

A 47-year-old male patient, complaining of persistent upper abdominal pain for the past month, presented himself to the hospital for a check-up. An initial contrast-enhanced CT examination was performed on a conventional energy-integrating detector (EID) CT. This revealed an ill-defined hypo-enhancing mass in the pancreatic body, accompanied by distal pancreatic atrophy, dilation of the main pancreatic duct, splenic vein occlusion and collateral vessel formation. Two critical diagnostic concerns emerged: (1) heterogeneous attenuation within the adjacent main pancreatic duct raising suspicion of an intraductal tumor spread; (2) a ~5 mm hypoattenuating lesion in the hepatic segment IV, exhibiting indistinct margins and equivocal enhancement, raised concerns about a potential metastasis. With informed consent, another contrast-enhanced CT scan was performed three weeks later using an ultra-high resolution (UHR) mode with a photon-counting detector (PCD) CT, NAEOTOM Alpha, for further evaluation.

Diagnosis

Virtual monoenergetic images (VMI), displayed at 50 keV, revealed a distinctly delineated tumor with clear margins (39 × 24 mm in axial plane; 24 mm height in coronal view) in the pancreatic body, causing notably encasement of the splenic artery and occlusion of the splenic vein. Thickening and enhancement of the left celiac ganglion, not shown in previous EID CT, were seen as suspicious of a metastasis. Both prior imaging ambiguities were clearly resolved – the fluid attenuation within the main pancreatic duct was homogeneous, therefore ruling out intraductal tumor spread, and the hepatic lesion in segment IV was non-enhancing with a sharp delineation characterizing a cyst. A pancreatic ductal adenocarcinoma with perineural invasion (metastasis of the left celiac ganglion) was suggested and subsequently confirmed by pathological analysis after a successful radical distal pancreatectomy with splenectomy and a partial portal vein reconstruction. The patient recovered uneventfully.

Fig. 1: Axial images acquired during the arterial (Figs. 1a & 1b, EID at 1 mm, PCD at 0.4 mm) and venous phases (Figs. 1c & 1d, 3 mm) show a comparison of CT findings in the pancreas in EID (Figs. 1a & 1c) and PCD CT images (Figs. 1b & 1d). The fluid attenuation within the main pancreatic duct (arrows) adjacent to the tumor appears heterogeneous in EID CT images, however, clearly homogeneous in PCD CT images, ruling out the suspicion of an intraductal tumor spread. The tumor is distinctly delineated with clear margins in the PCD CT images (dotted arrows). Note the improved contrast in PCD CT images using VMIs displayed at 50 keV. 

Fig. 2: A hypoattenuating lesion in the hepatic segment IV, exhibiting indistinct margins and equivocal enhancement in an EID CT image (Fig. 2a, arrow), is clearly characterized as a non-enhancing, sharply delineated cyst in a PCD CT image (Fig. 2b, arrow). Both images are reconstructed at 1 mm, displayed at same window settings. The image noise is notably less in the PCD CT image.

Fig. 3: Thickening and enhancement of the left celiac ganglion, not shown in an EID CT image (Fig. 3a, arrow, 1 mm), is clearly seen in a PCD CT image (Fig. 3b, arrow, 0.4 mm), indicating a metastasis. It is also confirmed by pathological analysis after surgery. Both images are displayed at same window settings. Note the improved contrast in the PCD CT image using a VMI displayed at 50 keV. 

Fig. 4: cVRT images show a distinctly delineated tumor in the pancreatic body (Fig. 4a, arrow), causing notably encasement of the splenic artery (Fig. 4c, arrow), and occlusion of the splenic vein (Fig. 4d, arrow). The left celiac ganglion (Fig. 4b, arrow), thickened and enhanced, is confirmed as a metastasis by pathological analysis after surgery. Images reconstructed at 0.2 mm with a sharp kernel of Bv48 are used to create these cVRT images.

Comments

Accurate preoperative imaging is crucial in pancreatic cancer, yet conventional EID CT often struggles to delineate tumor boundaries and assess adjacent structures – particularly in hypo- or isoattenuating lesions – leading to potential misjudgments in resectability. [1]

PCD CT offers significant technical advances, including improved spatial resolution, reduced image noise and intrinsic spectral imaging. [2,3] These features enhance tumor conspicuity and allow improved visualization of both vascular and neural invasion. Emerging evidence has suggested that PCD CT outperforms conventional EID CT in abdominal imaging, supporting its growing value in preoperative assessment and surgical planning. [4,5].

In this case, these advantages translated into clear clinical impact – PCD CT not only improved tumor conspicuity and delineation of peripancreatic neural invasion, but also confidently resolved two critical diagnostic ambiguities: the suspected intraductal tumor spread and the potential hepatic metastasis, either of which could have altered surgical management.

These benefits were achieved through the use of an UHR scan mode, in which small sub-pixels are defined by electric fields rather than physical separations and are read out separately to increase the spatial resolution with improved geometrical dose efficiency of the detector. Simultaneously, spectral information was acquired, allowing for increased image contrast by displaying VMI at low keV (50 keV in this case). This unique combination provides improved image sharpness and contrast-to-noise ratio, helping the characterization of small lesions and anatomical details, especially in soft tissue. These UHR images are also optimized for in-depth three-dimensional image rendering, using cinematic volume rendering technique (cVRT), facilitating communication with the clinicians. It is also worth noting that a Flash mode (pitch of 2.35) with a collimation of 96 x 0.2 mm is performed to achieve a fast acquisition of the arterial phase (2.8 s), using the advantage of dual source CT scanning, further improving the visualization of vascular details.

This case highlights how the combination of ultra-high spatial resolution with low-keV spectral imaging can translate into actionable diagnostic confidence, enabling not only accurate local staging in pancreatic cancer but also better-informed surgical strategies through enhanced visualization of critical anatomical details.

Examination Protocol

Images: Courtesy of Department of Radiology, Peking Union Medical College, Beijing, P. R. China